How fast is gravity?
z@z
:: = Tom Van Flandern in http://www.deja.com/=dnc/getdoc.xp?AN=616385205
:: LIGO is only a gravitational
:: wave detector, not a gravimeter able to detect gravity or
:: gravitational force variations. [...] you seem to have confused
:: changes in gravitational force with gravitational waves. These
:: two concepts are nothing alike. It is undisputed that
:: gravitational waves, if these [...] exist, must propagate at
:: lightspeed. However, gravitational waves are often confused
:: with changes in gravitational fields (force variations) [...]
:
: This seems somewhat obtuse.
On the contrary. Tom's exposition is clear and sound.
: If we assume gravity consists
: of a single field, and waves propagate through that field at
: the speed c, then surely this same field cannot propagate
: disturbances instantaneously.
Non sequitur. There is no apriori reason why changes in the "field"
itself should propagate at the same speed as "waves" through the
"field". In the case of Coulomb fields and electromagnetic radiation,
the "waves" do not even propagate through the "field".
The introduction of retardation at c in the electrostatic field
is not only a pure ad-hoc-hypothesis in Maxwell's theory but even
inconsistent with the derivation of electromagnetic radiation.
:: The "speed of gravity", which is the same as the speed of
:: propagation of force variations, ...
:
: But surely in any field that supports waves of a characteristic
: speed the propagation of "force variations" must occur at that
: same speed. The same applies in all sorts of contexts. For example,
: in fluid media there are acoustic waves and the medium also has
: the ability to communicate static forces, but a change in the static
: forces can't propagate faster than the acoustic propagation speed.
That's obviously wrong. Water is an almost incompressible fluid with
an acoustic propagation speed of around 1.5 km/s. But the effects of
a big enough earthquake on the seabed at a depth of 7.5 km don't need
5 seconds to propagate to the surface.
A better example for recognizing that physical effects propagating
faster than the waves themselves must be involved consistutes the
case of surface waves of water.
: If you stand in the path of a supersonic fighter approaching you
: at Mach 2, you will never even feel the slightest breeze or
: elevation in pressure (let alone hear any sound) until it hits you.
If we replace the supersonic fighter by a huge meteorite, then we will
feel not only a slight breeze before it hits us.
: For example, changes in electrostatic forces are communicated at
: the speed of light.
The evidence is rather in favour of instantaneous communication.
http://www.deja.com/=dnc/getdoc.xp?AN=614676790
: We have the example of
: electromagnetism, in which the field of a moving charge points
: to the charge's present position, even though we understand that
: changes in the force are propagated at the speed of light. See,
: for example, Rindler's "Essential Relativity", chapter 6.3, where
: he derives the field of a uniformly moving charge, and comments
: "It is interesting to note that the electric field ... is directed
: away from the point where the charge is AT THAT INSTANT, though
: (because of the finite speed of propagation of all effects) it
: cannot be DUE to the position of the charge at that instant."
There may be special cases (e.g. a uniformly moving charge) where it
is actually possible to show that SUBTLETIES in our official theories
(rather than subtleties in Nature herself) CONSPIRE to DISGUISE the
effect of propagation delays. "Not-disguised" propagation delays
however violate momentum conservation.
(Such a Bohrian language is also used in the faq)
http://www.deja.com/=dnc/getdoc.xp?AN=538880440
:: In the above, you are describing changes in gravitational fields, or
:: force variations. Such changes may indeed rise and fall in strength in
:: "wave-like" fashion. Nonetheless, they are not the "disturbances of
:: space-time" referred to as gravitational waves. They are just force
:: cycles.
:
: So you distinguish between "disturbances of spacetime" and the
: "force" of gravity?
I suppose that Tom distinguishes between "disturbances of space-time"
referred to as gravitational waves and "disturbances of space-time"
referred to as gravitational fields.
Wolfgang Gottfried G.
http://members.lol.li/twostone/E/physics1.html
Joe Fischer
: : = Darrin Moss in http://www.deja.com/=dnc/getdoc.xp?AN=616661662: :: In the above, you are describing changes in gravitational fields, or
: :: force variations. Such changes may indeed rise and fall in strength in
: :: "wave-like" fashion. Nonetheless, they are not the "disturbances of
: :: space-time" referred to as gravitational waves. They are just force
: :: cycles.
: :
: : So you distinguish between "disturbances of spacetime" and the
: : "force" of gravity?
: I suppose that Tom distinguishes between "disturbances of space-time"
: referred to as gravitational waves and "disturbances of space-time"
: referred to as gravitational fields.
: Wolfgang Gottfried G.
All this, without mention of "geometry". Ants on
a stretching rubber band do not need to move to get closer
together or farther apart.
I say this without knowing positively what the
mechanism of gravitation is, but I think it is foolish
to count on a medium or particle stream to _absolutely_
be needed to be the mechanism of gravity.
And this is the futility in Tom's argument, he,
and we, do not know what the mechanism is, and he, and
we, do not know that anything "propagates".
Even the existence of gravitational radiation,
as Tom mentioned, is still speculative to some degree.
More could be meaningful said in four words,
"we do not know".
Joe Fischer
--
3
3
Jwrrock
mechanism of gravitation is, but I think it is foolish
to count on a medium or particle stream to _absolutely_
be needed to be the mechanism of gravity.
And this is the futility in Tom's argument, he,
and we, do not know what the mechanism is, and he, and
we, do not know that anything "propagates".
Even the existence of gravitational radiation,
as Tom mentioned, is still speculative to some degree."
Well said, Joe. An entirely new approach is needed.
Tom Van Flandern
Darri...@onlinesales.com (Darrin Moss) writes:
>> [tvf]: It is undisputed that gravitational waves, if
>> these...exist, must propagate at lightspeed. However,
>> gravitational waves are often confused with changes in
>> gravitational fields (force variations)...
> [dm]: This seems somewhat obtuse. If we assume gravity consists
> of a single field, and waves propagate through that field at
> the speed c, then surely this same field cannot propagate
> disturbances instantaneously.
This mixes concepts. Lets separate them.
(1) Gravitational waves: A source mass does not emit gravitational waves
unless it is accelerated by something else. If it does accelerate, then it
may disturb the "space-time" it travels through (which is *not* its own
field). If it does disturb "space-time", that would be a gravitational wave.
Such a wave is far too weak to affect any other astrophysical body, and so
obviously is not related to the source mass's own gravitational field.
(2) Changes in gravitational fields: These are not waves. They can take
any form, progressive, periodic, discrete pulses -- whatever the source mass
does. As the source mass moves, it causes its own gravitational field to
move with it. Thinking of changes in gravitational fields as "waves" is not
useful because they are simply changes in the distribution of potential
energy, and have no wave properties. If they did, two source masses would
produce interference patterns in their fields.
Suppose for the sake of argument that changes in a gravitational field
were periodic so as to produce a wave-like phenomenon. When a gravimeter
detects such a periodic field change, as happens every day in laboratories,
that is clearly not a detection of a "gravitational wave". No detector built
to date has yet detected the phenomenon that GR calls "gravitational waves".
> [dm]: A field that supports waves at a characteristic speed must
> respond to changes locally, and the local coupling transmits
> effects at the characteristic speed.
You trapped yourself into a verbal dilemma when you said "field". Fields
can affect the underlying "space-time" medium, but they are not that medium;
and only the medium supports waves. Waves in the space-time medium have a
characteristic speed of c. At shorter wavelengths, they are called
"electromagnetic waves".
Changes in gravitational fields are not wave-like in character, even if
periodic.
> If LIGO were to find gravitational waves, this would surely lend
> strong support to the field theory of GR, and according to GR
> it's clear that ALL gravitational effects propagate at c.
Because gravitational waves are not waves in the field, detection of
them has no obvious implications for field theory. Changes in gravitational
fields are trivial to create, to detect, and to measure; so that happened
long ago. If gravitational waves are detected in the future, that would
merely confirm that the medium for propagation of electromagnetic phenomena
does exist -- something that is not disputed by any theory to my knowledge.
So, while interesting, it will not help us discriminate among competing
theories.
>> [tvf]: The "speed of gravity", which is the same as the speed
>> of propagation of force variations...
> [dm]: But surely in any field that supports waves of a
> characteristic speed the propagation of "force variations" must
> occur at that same speed.
Gravitational fields are not a medium, and do not support waves, to the
best of current knowledge. If a source mass moves, the field moves too.
Observations show no delay in the field.
If you are thinking that a source mass acceleration sets off a wave of
field change that propagates outward at the speed of light, welcome to the
shocking world of reality: Binary pulsars confirm what solar system data has
long hinted at. Gravitational fields update much faster than even a linear
extrapolation of each star's previous position and velocity over one
light-time would permit. For details, see figure 3 and table I of my paper,
"The speed of gravity -- What the experiments say", in one of these
locations:
[1] MetaRes.Bull., v. 6, #4, pp. 49-62 (1997/12/15).
[2] Phys.Lett.A, v. 250, #1-3, pp. 1-11 (1998/12/21).
Follow-up: Phys.Lett.A, v. 262, pp. 261-263 (1999/11/01).
[3] Infinite Energy, v. 5, #27, pp. 50-58 (1999/Sept.&Oct.).
[4] Dolphin web site:
<http://www.ldolphin.org/vanFlandern/gravityspeed.html>.
[5] German version:
<http://www.omicron-research.com/RecDocD/introD.htm>.
English version (for downloading):
<http://www.omicron-research.com/RecDocE/introE.html>
> [dm]: This same kind of confusion often arises when people claim
> to have achieved faster-than-light transmission of Mozart
> recordings, or some such, but invariably it turns out that all
> they have done is built a filter with numerator dynamics, so the
> output signal "leads" the input. A bright chimp can design a
> filter like that, but it obviously doesn't represent faster-
> than-light communication.
Understood. However, we are here dealing with a phenomenon that not only
propagates much faster than light, but does so in forward time, not in
reverse time as special relativity requires. If we could engineer a
gravitational shielding device, we would have no difficulty sending a
gravitational Morse code at superluminal speeds.
During the past ten years, it has been solidly established in the
journals that do not exclude this subject matter (e.g., Galilean
Electrodynamics, Apeiron, and Physics Essays, among others) that Lorentzian
relativity (LR) agrees with the eleven independent experiments testing all
aspects of special relativity (SR) at least as well as SR does. [See "What
the Global Positioning System tells us about relativity", in "Open Questions
in Relativistic Physics", F. Selleri, ed., Apeiron, Montreal, pp. 81-90
(1998); also available at <http://metaresearch.org>.] In fact, the
historical record shows that Michelson, DeSitter, Sagnac, and Ives all
claimed to have falsified SR (in favor of LR) with their experiments. Both
versions of the relativity of motion, LR and SR, are based on Poincare's
relativity principle. Both are based on Lorentz's coordinate
transformations. They differ primarily in that SR claims the equivalence of
all inertial frames by insisting that the Lorentz transformations apply
reciprocally between both frames; whereas LR gives special status to the
local gravity field as a preferred frame.
Without a full exposition of the differences, as this applies to ftl
propagation, SR has a proof that it's impossible, and LR does not. The
finding of any phenomenon that does propagate faster than light in forward
time does not "violate the laws of physics". It falsifies SR in favor of LR.
GR is mathematically untouched by this change because LR and SR are based on
the same math -- the Lorentz transformations. However, the accepted
*interpretation* of GR would change because ftl propagation is no longer
forbidden.
> [dm]: I think a field that communicates "forces" instantaneously
> but propagates waves at a fixed finite speed would be very hard
> to rationalize, and we've certainly never observed such a thing.
A field that communicates "forces" instantaneously is precisely what all
relevant experiments observe, as reported in the aforementioned paper. The
field propagates no waves, so the attribute you question does not arise.
> [dm]: For example, changes in electrostatic forces are
> communicated at the speed of light.
A similar dilemma arises for electrostatic forces. The hypothetical
carrying agents, "virtual photons", are misnamed because they have no
properties in common with real photons. For an experimental result that
flatly contradicts your assertion about the speed of electrostatic forces,
see "Electromagnetic mass and the inertial properties of nuclei", C.W.
Sherwin and R.D. Rawcliffe, Report I-92 of March 14, 1960 of the
Consolidated Science Laboratory, Univ. of Illinois, Urbana; obtainable from
U.S. Department of Commerce's Clearinghouse for Scientific and Technical
Information, document AD 625706. See description in Heretical Verities, T.E.
Phipps, Jr., Classic Non-fiction Library, Urbana, pp. 273-282 (1986):
Charges respond to each other's instantaneous positions, and not to the
"left-behind potential hill" following an acceleration.
>> [tvf]: The "speed of gravity"... is constrained by experiments
>> to be >much faster than the speed of light....
> [dm]: It is? I would have to dispute that. It sounds like the
> "experiments" you have in mind are evaluations of the directions
> of force between relatively moving objects, and your rationale
> is that if the force points in the direction of the distant
> object's instantaneous position (with respect to the rest frame
> of the observer), then the force is propagating instantaneously,
> but surely that's well-known to be false. We have the example of
> electromagnetism, in which the field of a moving charge points
> to the charge's present position, even though we understand that
> changes in the force are propagated at the speed of light.
Two of the experiments have a different character, unrelated to force
directions. The Walker-Dual experiment is a direct speed measurement. See
W.D. Walker and J. Dual, "Superluminal propagation speed of longitudinally
oscillating electrical fields", abstract #72 in: "Causality and Locality in
Modern Physics and Astronomy: Open Questions and Possible Solutions", ed. S.
Jeffers, York University, North York, 1997. A web version of the paper is
available at <xxx.lanl.gov/abs/gr-qc/9706082>. The experimental design is
described at <http://www.ndt.net/library/www_cd96/eth/exp_3.htm>. The other
experiment, D.M. Greenberger and A.W. Overhauser, "The role of gravity in
quantum theory", Sci.Amer. 242 (May), pp. 66-76, 1980, finds a violation of
the weak equivalence principle -- the geometric interpretation of gravity.
For the other four experiments, let's define our terms more carefully.
Let's speak of the direction of the 3-space acceleration of the target body,
rather than "force". The 3-space acceleration of a target body is a change
of its momentum. Unless we intend to create momentum changes ex nihilo,
thereby leaving the domain of physics, changes of target momentum must
represent exchanges of momentum with the source of gravity, even if the
"field" is an intermediary in the process. In both cases, for gravitational
and electrostatic fields, the direction of the momentum in the target's
frame of reference is indeed the instantaneous direction of the source.
However, the effective direction is necessarily modified by the motion of
the target, in the amount of aberration, arctan (v/V), where v is the
transverse speed of the target and V is the propagation speed of the
momentum change. (Momentum is mass times velocity.) If measured aberration
is nearly zero compared to stellar aberration = arctan (v/c), it follows
that V >> c. The speed of gravity must be much faster than the speed of
light.
The only cause we have to doubt this is SR, which proves that such high
speeds are impossible in forward time. However, if LR replaces SR, not much
else changes, but that proof vanishes.
> [dm]: See, for example, Rindler's "Essential Relativity",
> chapter 6.3, where he derives the field of a uniformly moving
> charge, and comments "It is interesting to note that the
> electric field ... is directed away from the point where the
> charge is AT THAT INSTANT, though (because of the finite speed
> of propagation of all effects) it cannot be DUE to the position
> of the charge at that instant."
This interpretation assumes a propagation speed of c. We now know
better, both theoretically and experimentally. The Sherwin-Rawcliffe
experiment cited above shows that a frequently-taught notion about
electrostatics is wrong. Supposedly, the force between charges is toward
their instantaneous positions as long as the motion is linear, but shows
retardation when one of the charges is accelerated. The cited experiment
shows no delay even when a charge is accelerated.
> [dm]: So you distinguish between "disturbances of spacetime" and
> the "force" of gravity? Sounds like the basic source of
> confusion here is that you have in mind two very different
> phenomena, both of which you refer to as "gravity".
That nomenclature is not of my making. The confusion was introduced by
the terminology "gravitational waves", referring to space-time disturbances,
the same phenomenon as electromagnetic waves (except for wavelength). The
equally inappropriate terminology "virtual photons" causes the same kind of
confusion.
> [dm]: One consists of disturbances of spacetime (as in general
> relativity) and the other consists of "forces", which presumably
> you do NOT regard as disturbances in spacetime. You're really
> talking about two completely separate and (as far as I can tell)
> unrelated phenomena.
"Disturbances of spacetime" are gravitational waves, the part of GR not
yet established. The part that is established, dealing with gravitational
forces and field changes, works fine to first order in the potential. These
two things are clearly different and largely unrelated phenomena.
> [dm]: They certainly can't both be characteristics of a single
> field law. If LIGO detects waves, I think you will have to
> declare them to be not gravitational, or else declare your
> instantaneous forces to be not gravitational, or else give up
> your instantaneous forces.
The "speed of gravity" has been a discussion point for nearly 200 years.
Laplace's 1807 paper made the earliest extant estimate of the speed of
gravity: at least 10 million times the speed of light. All relevant modern
experiments, without exception, agree that it must be much faster than
light.
Gravitational waves propagate at speed c, period -- the same as all
other disturbances of the "space-time medium". They make no changes in the
gravitational field, and they play no role in the gravitational acceleration
of astrophysical bodies. The fact that a confusion of these important
distinctions has been allowed to languish for so long is hardly any fault of
yours. But I trust you can see the paradoxes that arise if one tries to
seriously maintain that gravitational waves are just changes in
gravitational fields. To recap, let GW = gravitational waves, and GF =
changes in gravitational forces:
GW are hypothetical and ultra weak; GF are real and strong.
GW require a quadrupole moment. So they emanate from orbiting bodies
of significant mass (which lose momentum), not from the source of gravity.
GF emanate from the source of gravity, and do not require significant mass
in the target body.
GW cause orbits to decay; propagation delay for GF would causes
orbits to expand.
GW propagate at speed c; GF propagate with speed at least 20 billion
c.
-|Tom|-
Tom Van Flandern - Washington, DC - <http://metaresearch.org>
Meta Research fosters astronomy research on ideas not otherwise
supported solely because they conflict with mainstream theories
Mark Fergerson
<snip>
> Two of the experiments have a different character, unrelated to force
> directions. The Walker-Dual experiment is a direct speed measurement. See
> W.D. Walker and J. Dual, "Superluminal propagation speed of longitudinally
> oscillating electrical fields", abstract #72 in: "Causality and Locality in
> Modern Physics and Astronomy: Open Questions and Possible Solutions", ed. S.
> Jeffers, York University, North York, 1997. A web version of the paper is
> available at <xxx.lanl.gov/abs/gr-qc/9706082>. The experimental design is
> described at <http://www.ndt.net/library/www_cd96/eth/exp_3.htm>. The other
> experiment, D.M. Greenberger and A.W. Overhauser, "The role of gravity in
> quantum theory", Sci.Amer. 242 (May), pp. 66-76, 1980, finds a violation of
> the weak equivalence principle -- the geometric interpretation of gravity.
The link http://www.ndt.net/library/www_cd96/eth/exp_3.htm
terminates at
http://www.ndt.net/library/library.php3 which isn't much help. Please
elaborate?
> For the other four experiments, let's define our terms more carefully.
> Let's speak of the direction of the 3-space acceleration of the target body,
> rather than "force". The 3-space acceleration of a target body is a change
> of its momentum. Unless we intend to create momentum changes ex nihilo,
There are those who claim it is possible to transfer momentum to and
from the vacuum itself; the famed "reactionless" drive of golden age
SF. The "source of gravity" in these ideas is apparently the
self-energy of the vacuum.
<snip>
> GW are hypothetical and ultra weak; GF are real and strong.
> GW require a quadrupole moment. So they emanate from orbiting bodies
> of significant mass (which lose momentum), not from the source of gravity.
> GF emanate from the source of gravity, and do not require significant mass
> in the target body.
> GW cause orbits to decay; propagation delay for GF would causes
> orbits to expand.
> GW propagate at speed c; GF propagate with speed at least 20 billion
> c.
Hm. Robert L. Forward used to mess around with a dingus he
eventually patented, the Rotating Gravity Gradiometer; a gross
mechanical device comprising masses at the ends of motor-driven
cruciform arms linked by strain gauges. The gauges showed the relative
direction of the nearest gravitating mass, and could "see" a
basketball-sized object at a few meters. A driven version (signal
applied to the piezoelectric strain elements) could be phase-locked to
another, remote, detector. What was he demonstrating, GW or GF?
AFAIK he never did propagation delay measurements, alas.
Mark L. Fergerson
Joe Fischer
: This is a response to Darrin Moss's thoughtful questions.
:[snip]
: Understood. However, we are here dealing with a phenomenon that not only
: propagates much faster than light, but does so in forward time, not in
: reverse time as special relativity requires.
I understand that nothing propagates much faster than
light. I also understand nothing propagates in geometric
gravity. Forward and reverse time is beyond this discussion.
: If we could engineer a
: gravitational shielding device, we would have no difficulty sending a
: gravitational Morse code at superluminal speeds.
If we could grow wings, we could fly. What I don't
understand is why FTL is so important, why FTL garners so
much interest, why educated people even mention FTL, it
is even more impossible that a gravitational shielding
device. If nothing propagates in gravitation, what is
to shield?
This is a pretty good article, except for apparent
fetishes of FTL travel, FTL communication, FTL gravity
propagation.
I pray that you live a thousand years, but even
if you do, you will never see any of these things, they
are SCIENCE FICTION!
:[snip]
: For the other four experiments, let's define our terms more carefully.
: Let's speak of the direction of the 3-space acceleration of the target body,
: rather than "force". The 3-space acceleration of a target body is a change
: of its momentum.
Both 3-space acceleration and momentum are Newtonian
concepts. Einstein tried to make gravity conserve globally,
but apparently was unsuccessful in that.
: Unless we intend to create momentum changes ex nihilo,
: thereby leaving the domain of physics, changes of target momentum must
: represent exchanges of momentum with the source of gravity, even if the
: "field" is an intermediary in the process.
This statement reveals logic completely engrossed
in Newtonian concepts. Gravitational effects are identical
to inertial effects, because they _are_ inertial effects,
objects in inertial motion do not accelerate, objects in
freefall or orbit are in inertial motion in General Relativity,
I apologize if this goes to any newsgroup other than relativity.
: In both cases, for gravitational
: and electrostatic fields, the direction of the momentum in the target's
: frame of reference is indeed the instantaneous direction of the source.
: However, the effective direction is necessarily modified by the motion of
: the target, in the amount of aberration, arctan (v/V), where v is the
: transverse speed of the target and V is the propagation speed of the
: momentum change. (Momentum is mass times velocity.) If measured aberration
: is nearly zero compared to stellar aberration = arctan (v/c), it follows
: that V >> c. The speed of gravity must be much faster than the speed of
: light.
Unless there is no speed of gravity, unless gravity
is geometric, unless there is no acceleration in inertial
motion, unless nothing propagates in gravity, unless gravity
is not Newtonian in Euclidean space, unless apparent gravity
effects do not result from "forces".
: The only cause we have to doubt this is SR, which proves that such high
: speeds are impossible in forward time. However, if LR replaces SR, not much
: else changes, but that proof vanishes.
And now Tom appeals to the ether gods to show us
A sign that General Relativity is wrong, while giving
Lorentz Ether Theory the stature of relativity, it is now
Lorentz Relativity against Special Relativity.
LET will replace SR when pigs fly. It is frustrating
to see so much good in an article and then be subjected to
the fossilized ether theory being elevated to equality with SR.
What is not mentioned, is that experimental evidence
overwhelming demonstrates that _ALL_ theories of gravity
that require "forces" to produce freefall (inertial motion)
are doomed to failure, advanced gravity theory requires
General Relativity concepts.
Jim Carr
>[snip]
: Understood. However, we are here dealing with a phenomenon that not only
: propagates much faster than light, but does so in forward time, not in
: reverse time as special relativity requires.
In article <390c3d14$1...@news.iglou.com>
joe...@iglou.com (Joe Fischer) writes:
>
> I understand that nothing propagates much faster than
>light. I also understand nothing propagates in geometric
>gravity. Forward and reverse time is beyond this discussion.
Do either of you understand that this cross-post is off-topic
and that followups should be set to sci.physics.relativity, or
that the 'distinction' TvF was describing (between gravity and
GR vis-a-vis "propagation time") is fully documented in the
Relativity FAQ and references therein?
Carry on. And note followups.
--
James A. Carr <j...@scri.fsu.edu> | "The half of knowledge is knowing
http://www.scri.fsu.edu/~jac/ | where to find knowledge" - Anon.
Supercomputer Computations Res. Inst. | Motto over the entrance to Dodd
Florida State, Tallahassee FL 32306 | Hall, former library at FSCW.
JimJast
Long time no see :-). When I read "Speed of Gravity" it reminded me immediately
our discussions long time ago (10 years?). I see that I failed miserably when I
tried to convince you using GR where there is no gravitational force, that
there is no problem with binary systems spinning out of control. Since you are
apparently still not convinced I try again, this time to explain why there is
no problem with them spinning out of control even in Newtonian Approximation
(since you seem to like it better):
When you use Newtonian Approximation instead of GR (which of course is right
thing to do as long as space is not too much curved, velocities of matter are
much less than c, and ... "speed of gravity" is c :-) (you wouldn't seriously
believe that it might be something else in the relativistic world, would you?)
then you have to apply the math of Newtonian approximation. Your problem got
created by dropping from "gravitational force" the component that depends on
velocity of the "source of gravitational force". That such a component exists
follows from the fact that the same Coulomb law describes both "gravitational
force" and force between electric charges so if there is such a component in
electricity (and it is) it must be in gravity since the math is identical in
both cases.
To make life easier I write that component in a form that shows clearly why you
don't need to worry (I write vectors in square brackets and scalars without
brackets):
component_of_gravitational_force_due_to_velocity_of_source =
= (G M m/(c r^2)([v] - 3([e].[v])[e])
where G is gravitational constant, M is mass of the "source of gravitational
force", m is mass of the target of "gravitational force projectiles", [v] is
velocity of the "source of gravitational force" at the retarded position, c is
speed of light, and [e] is a unit vector pointing from the target to the
retarded position of the "source of gravitational force".
As you may see, since [v] is perpendicular to [e] the dot product vanishes and
the correction to the "gravitational force", GMm/r^2, that points at the
visible (retarded) position equals the same "gravitational force" times v/c in
direction of [v], and therefore it is a drag that prevents violation of
conservation of angular momentum (ain't nature smart?). You might have also
ignored the component of "gravitational force" that is due to acceleration of
the "source of gravitational force" but since we already prevented our binary
system from spinning out of control (as well as any planet or moon) we may stop
here.
-- Jim
AMW
Joe Fischer wrote:
> If we could grow wings, we could fly. What I don't
> understand is why FTL is so important, why FTL garners so
> much interest, why educated people even mention FTL, it
> is even more impossible that a gravitational shielding
> device. If nothing propagates in gravitation, what is
> to shield?
Some work on the more exotic aspects of General Relativity
indicate no known reason that FTL travel is impossible, just
very difficult to do. The basic reason that had been given
is the violation of the energy conditions. However, those
conditions are themselves assumptions of what realistic
stress energy tensors would look like, and at present are
looking rather shaky. Whether there actually is a limitation
or not is almost beside the point. The thing is, we don't know
why, or even if, it is impossible.
You assume it is, and people such as Chris Van Dem Broek, Matt
Visser, et.al. are wasting their time. I disagree. The fruits
of their efforts, which would not be started if they agreed
with you, will give us a better insight into how the universe
works. Even if they are able to show why it is impossible,
that is something more than we have now.
And if you are wrong, and FTL is possible, then we can get
off this rock and out into the rest of the galaxy. That would
certainly increase the chances of survival of our species.
In short, while the probability of success may appear very
small, the potential rewards make such a line of inquiry
highly attractive, and the risk at this stage of the game
negligible. Blind acceptance of the impossibility of FTL
travel answers nothing, and is not the way science is done.
Ben
Gerry Quinn
>Some work on the more exotic aspects of General Relativity
>indicate no known reason that FTL travel is impossible, just
>very difficult to do. The basic reason that had been given
>is the violation of the energy conditions. However, those
>conditions are themselves assumptions of what realistic
>stress energy tensors would look like, and at present are
>looking rather shaky. Whether there actually is a limitation
>or not is almost beside the point. The thing is, we don't know
>why, or even if, it is impossible.
>
These fantasies all depend on negative energy, and all theory suggests
that such energy is always associated with enough positive energy to
cancel its effects.
The thermodynamic arguments against the time travel that would be
possible if FTL travel were possible are at least as strong.
>You assume it is, and people such as Chris Van Dem Broek, Matt
>Visser, et.al. are wasting their time. I disagree. The fruits
>of their efforts, which would not be started if they agreed
>with you, will give us a better insight into how the universe
>works. Even if they are able to show why it is impossible,
>that is something more than we have now.
>
The only reason any of this nonsense is taken seriously is because of
the excessively symmetry and observer-centred approach of relativistic
theories starting with SR. A more realistic approach based on Lorentz's
theory makes it obvious that the reason for the principle of relativity
is that the fundamental particles of all mass-energy travel at exactly c
through a flat background space. Consequently, theories about
aggregates of such particles travelling faster than c are simply
rubbish.
- Gerry Quinn
Jonathan Silverlight
>
>
>Joe Fischer wrote:
>
>> If we could grow wings, we could fly. What I don't
>> understand is why FTL is so important, why FTL garners so
>> much interest, why educated people even mention FTL, it
>> is even more impossible that a gravitational shielding
>> device. If nothing propagates in gravitation, what is
>> to shield?
>
>indicate no known reason that FTL travel is impossible, just
>very difficult to do. The basic reason that had been given
>is the violation of the energy conditions.
I was under the impression that FTL led to violation of causality. Not
so?
Tom Van Flandern
> When I read "Speed of Gravity" it reminded me immediately our
> discussions long time ago (10 years?). I see that I failed
> miserably when I tried to convince you using GR where there is
> no gravitational force, that there is no problem with binary
> systems spinning out of control.
My paper, “The speed of gravity – What the experiments say" in
Phys.Lett.A, v. 250, pp. 1-22 (1998) is primarily about GR, not Newtonian
gravity. I recommend you read it so you can better appreciate what the
issues are, and what the experimental evidence has to say about them.
As for binary pulsars, I described what they tell us about this question
in figure 3 and table I of my paper. Are you aware that no experiment
whatever gives a speed of gravity anywhere near lightspeed, directly or
indirectly? Shouldn’t experiments be the ultimate arbiters of correct
physics versus personal beliefs?
> I try again, this time to explain why there is no problem with
> them spinning out of control even in Newtonian Approximation ...
You are disagreeing not just with me, but with most professional
relativists, when you claim there is no problem for Newtonian gravity
propagating at the speed of light. It is well known to relativists that the
speed of Newtonian gravity must be infinite. See Misner, Thorne, and
Wheeler's "Gravitation", chapter 7, p. 177 (1973) for a plain statement to
that effect. Anyone who has written a computer program to numerically
integrate orbits has had the opportunity to learn that, if gravity is slower
than instantaneous, orbits spiral.
> When you use Newtonian Approximation instead of GR (which of
> course is right thing to do as long as space is not too much
> curved, ...
Space is not curved in GR. "Space-time" is curved. "Space-time" is a
mathematical entity, and does not consist of space plus time. For example, a
string stretched between any two points along the Earth's orbit describes a
straight line through space. The Earth's orbit is obviously curved relative
to the string. That cannot be caused by space curvature or the string would
curve as much as the orbit.
Similar remarks apply to the paths of light beams (the “null geodesics”
of GR). These are slightly curved near source masses. Yet a taut rope would
experience no such curvature. Indeed, we measure curvature relative to
non-curved coordinate grid lines, which are like a network of taut ropes.
> ... velocities of matter are much less than c, and ... "speed of
> gravity" is c :-) (you wouldn't seriously believe that it might
> be something else in the relativistic world, would you?)
I am sorry you are unfamiliar with Lorentzian relativity (LR). The speed
of light is no speed limit in LR. Yet LR is based on Poincare's relativity
principle and the Lorentz transformations, just as SR is. You should not be
surprised that a relativity theory can have ftl propagation in forward time,
if you know the history of relativity before Einstein.
> Your problem got created by dropping from "gravitational force"
> the component that depends on velocity of the "source of
> gravitational force".
Suppose the source has no velocity? But if you simply mean "relative
velocity", then that is what causes aberration, the subject of my paper,
which I certainly did include. If one includes lightspeed aberration for
gravity, that makes orbits spiral "out of control", to use your phrase.
> That such a component exists follows from the fact that the same
> Coulomb law describes both "gravitational force" and force
> between electric charges so if there is such a component in
> electricity (and it is) it must be in gravity since the math is
> identical in both cases.
"Retarded potentials" in electrodynamics also ignore aberration, as I
discussed in “Reply to comment on: ‘The speed of gravity’”, Phys.Lett.A, v.
262, pp. 261-263 (1999). This is another way of saying that the propagation
speed of "virtual photons" is taken as infinite in electrodynamics. Both the
Walker-Dual experiment and the Sherwin-Rawcliffe experiment (cited
previously) show that electrostatic forces cannot be propagated as slowly as
the speed of light. When belief and experiment conflict, which should
govern?
> As you may see, since [v] is perpendicular to [e] the dot
> product vanishes
If [e] points toward the retarded position, it cannot be orthogonal to
[v] or the force would not be central. So your term does not vanish.
Aberration (the effect of retardation) can only legitimately be included
once, not twice. When propagation delay (the same thing as aberration, just
viewed from another frame of reference) is added to equations of motion,
orbits spiral. Period. Nothing remains to cancel this spiraling. The proof?
The Poynting-Robertson effect shows that when a force really does propagate
at the speed of light, as in the case of solar radiation pressure, it really
does cause orbits to spiral.
> and therefore it is a drag that prevents violation of
> conservation of angular momentum (ain't nature smart?)
If nature were somehow “smart” enough to conserve angular momentum on
its own by canceling forces that would violate that conservation, then tidal
forces, which violate angular momentum conservation, could not exist. That
is obviously not the case.
I am sorry if all this upsets your beliefs. But to make progress, we
must each subordinate our personal beliefs and biases to the outcome of
nature's experiments. That is what my papers are about. When new evidence
arrives, do we choose to revise our previous opinions to remain in accord
with the results of valid tests of reality, or to dictate to nature what
must be true according to our beliefs? -|Tom|-
Joe Fischer
: <a...@nospam.stanford.slac.edu> writes
There are a lot of confused minds mixing different
issues here. No measurement has ever been made supporting
anything like FTL. I would call it "getting there before
you begin the trip", which is definitely a violation of causality.
But at high percentages of c, greater distances are
covered, so that it appears that an object can travel more
than one light year in one year.
But this does us no good at all, it is just a math
exercise.
Tom Van Flandern
> I was under the impression that FTL led to violation of
> causality. Not so?
Short answer: Not so.
Slightly longer answer: FTL is forbidden only in special relativity
(SR). FTL is allowed in Lorentzian relativity (LR). Eleven independent
experiments test various aspects of SR and LR, the theories of the
relativity of motion. All 11 are clearly consistent with LR, and arguably
consistent with SR also. But the demonstration of a true FTL signal in
forward time would immediately falsify SR, but leave LR intact. Gravity
might be an example of just that.
But even without this discussion of the speed of gravity, FTL cannot
become a violation of causality until LR has been falsified in favor of SR.
That definitely has not yet happened. -|Tom|-
Gerry Quinn
>Jonathan Silverlight <jsi...@merseia.demon.co.uk> writes:
>
>> I was under the impression that FTL led to violation of
>> causality. Not so?
>
> Short answer: Not so.
>
> Slightly longer answer: FTL is forbidden only in special relativity
>(SR). FTL is allowed in Lorentzian relativity (LR). Eleven independent
>experiments test various aspects of SR and LR, the theories of the
>relativity of motion. All 11 are clearly consistent with LR, and arguably
>consistent with SR also. But the demonstration of a true FTL signal in
>forward time would immediately falsify SR, but leave LR intact. Gravity
>might be an example of just that.
>
I do not believe it would leave Lorentzian relativity intact. The
principle of relativity in Lorentzian relativity is not fundamental, but
is instead a consequence of the fundamental particles of all mass-energy
travelling at a universal speed of c (that is to say, being massless).
If they travelled at multiple speeds, you could not make a time machine,
but it is clear that numerous violations of physics as currently known
would occur.
So any FTL process, which would equate to a PoR violation, would have to
be restricted to some currently unknown force. I'm inclined to think
that a world in which such a force could be manipulated would be a
strange one in which our current notions of thermodynamics would be
strongly violated.
> But even without this discussion of the speed of gravity, FTL cannot
>become a violation of causality until LR has been falsified in favor of SR.
>That definitely has not yet happened. -|Tom|-
>
No FTL is why Lorentzian relativity works. In a sense, it says it even
more strongly than SR.
- Gerry Quinn
Asimov
Re: How fast is gravity? (02 May 00 06:07:32)
JF> There are a lot of confused minds mixing different
JF> issues here. No measurement has ever been made supporting
JF> anything like FTL. I would call it "getting there before
JF> you begin the trip", which is definitely a violation of causality.
JF> But at high percentages of c, greater distances are
JF> covered, so that it appears that an object can travel more
JF> than one light year in one year.
JF> But this does us no good at all, it is just a math
JF> exercise.
I question the assumption that all information must travel at c.
Quantum entanglement has demonstrated that it isn't necessarily so.
I think the same could be said of information carried by gravitation.
I feel causality is just a philosophical artifice to help keep us sane.
I might be wrong...
... ...and THAT is how we know the Earth is banana-shaped.
--
| Return Address: asi...@mnetREMOVE-THIS.axess.com
| Standard disclaimer: The views of this user are strictly her/his own.
| Signature auto-added at gateway.
Tom Van Flandern
>> [tvf]: the demonstration of a true FTL signal in forward time
>> would immediately falsify SR, but leave LR intact. Gravity
>> might be an example of just that.
> [gq]: I do not believe it would leave Lorentzian relativity
> intact. The principle of relativity in Lorentzian relativity is
> not fundamental, but is instead a consequence of the fundamental
> particles of all mass-energy traveling at a universal speed of c
> (that is to say, being massless). If they traveled at multiple
> speeds, you could not make a time machine, but it is clear that
> numerous violations of physics as currently known would occur.
Physicists have sought such a violation of currently known physics by
either version of the relativity of motion (SR or LR) for nearly a century
now. Many have been reported, but none have survived scrutiny. I notice you
likewise do not mention any specific violation, probably sensing (correctly)
that any such example can be explained by LR also.
See, for example, Amer.J.Phys. 41, 1068-1077 (1973). Summarizing: ** No
experimental difference, predicted or realized, yet exists between the
Lorentzian “ether” form of relativity and Einstein’s special relativity. The
former has clock retardation, the latter has time dilation; but both have
the same Lorentz transformations. The only possible experimental difference
between the two theories may lie in a one-way experiment that is not a
direct measurement of the speed of light. The latter would require
synchronized clocks from start to finish, and that synchronization cannot be
slow clock transport since this would yield the same synchronization as the
Einstein convention. It may be that no experimental difference is possible.
**
The principle of relativity has to do with the relativity of all motion.
It does not relate directly to lightspeed. Your thinking is focused on the
SR interpretation of reality, in which time and space change, thereby
setting limits to speed. But you may find, as many have before you, that LR
can explain reality in as satisfying a way without any changes to time or
space, and therefore without need of universal speed limits.
> [gq]: So any FTL process, which would equate to a PoR violation,
> would have to be restricted to some currently unknown force.
> I'm inclined to think that a world in which such a force could
> be manipulated would be a strange one in which our current
> notions of thermodynamics would be strongly violated.
When time is not changed, exceeding lightspeed is no more dramatic than
a propeller plane exceeding the sound barrier (e.g., with a gravity assist).
A few papers have developed thermodynamic consequences of models based
on LR, and these are very attractive in that they explain much. However, the
first step of the process is to get rid of all the SR corollaries in one’s
thinking. Minkowski diagrams have their place, but are just a confusion
factor for fundamental thinking if nothing happens to time, but only to
individual clocks.
>> [tvf]: But even without this discussion of the speed of
>> gravity, FTL cannot become a violation of causality until LR
>> has been falsified in favor of SR. That definitely has not yet
>> happened.
> [gq]: -No FTL- is why Lorentzian relativity works. In a sense,
> it says it even more strongly than SR.
In LR, the first thing that changes is the velocity addition rule. Once
that is gone, lightspeed is relegated to a property of a particular medium,
but no longer has controlling significance to all of physics. I recommend:
R. Mansouri and R.U. Sexl, “A test theory of special relativity: I.
Simultaneity and clock synchronization”, Gen.Rel.&Grav. 8, 497-513 (1977).
This lays out the equations of LR (called the “test theory”), and allows one
to begin to develop new intuitions about how physics works in this
alternative relativity model. IMO, it is worth the time investment. -|Tom|-
Bob May
and time going backwards. The diagrams explain everything in a very
nice and graphic method what going faster than light does and how it
seems to be going backwards in time.
--
Bob May
Don't subscribe to ACCESS1 for your webserver for the low prices. The
service has
been lousy and has been poor for the last year. Bob May
JimJast
near lightspeed, directly or indirectly?
But also no experiment whatever gives a speed of gravity anywhere near _any_
speed, directly or indirectly because "gravitational force" turned out to be
not a physical entity but only a mathematical fiction.
You seem to miss an important point: both variants of Newtonian gravity, with
high velocity and with low don't agree with experiments.
I agree that approximation with infinite speed gives better fit to the
experiments. E.g. in a simple case of bending the light rays it gives only 50%
error while the one with speed c gives no bending whatsoever. But the error of
50% is not such a big advantage over 100% error if it requires an application
of a non physical fudge element of infinite speed.
Most people think that a theory that gives 50% error should be replaced by one
that gives 0% error anyway and it has been done by replacing both mentioned
theories by GR. However for small velocities both are about the same good
(which is my point) and the one with c does not produce outrageous effects like
error being of order of v/c. It is still of order of (v/c)^2 as I wanted to
turn your attention to in the previous message.
> You are disagreeing not just with me, but with most professional >
relativists, when you claim there is no problem for Newtonian gravity >
propagating at the speed of light. It is well known to relativists that the >
speed of Newtonian gravity must be infinite. See Misner, Thorne, and >
Wheeler's "Gravitation", chapter 7, p. 177 (1973) for a plain statement > to
that effect.
You are talking about people who believe that the universe is expending and are
prompting us to believe in it as well, since in their opinion only faith can
make one believe that, for the lack of some decent math or physics supporting
the idea. Some of them (or all) also believe in existence of supernatural
beings as one may find from the last couple of pages of the book that you
mentioned. So I happen to disagree with them already on a few accounts. I might
on one more.
> Space is not curved in GR. "Space-time" is curved. "Space-time" is a >
mathematical entity, and does not consist of space plus time. For > example, a
string stretched between any two points along the Earth's > orbit describes a
straight line through space. The Earth's orbit is > obviously curved relative
to the string. That cannot be caused by space > curvature or the string would
curve as much as the orbit.
Not so. The only difference between GR and Newtonian Gravity is the curved
space in GR (not curved spacetime). It is not so obvious that the spacetime is
curved also, or at least there is no evidence that it is. Misner, Thorne, and
Wheeler's insist that it is curved "inside the matter" because it can't be
curved in vacuum or we have to throw GR out of the
window. Those relativists maintain that being in universe we are "inside the
matter". It sounds like magic to me. They insist on it but don't deliver any
evidence except faith so I leave the question of curvature of the spacetime
undecided. In my opinion it is flat everywhere. "Inside matter" and outside.
So we don't know if spacetime is curved but we know that space is. It has of
course nothing to do with orbits of planets. They would look the same in
perfectly flat space with possible exception of Mercury, because of its
velocity and proximity to the sun around which there is a noticeable bump in
space. Slightly more space than Euclidean geometry would allow. Those orbits
are of course not straight lines in space but "straight" in spacetime in which
time is a little bit crooked too, running at different rates in different
places (as seen from gravitational and cosmological redshifts), compensating
for that curvature of space to keep e.g. spacetime flat (if it is flat).
> Similar remarks apply to the paths of light beams (the "null geodesics" > of
GR). These are slightly curved near source masses. Yet a taut rope > would
experience no such curvature. Indeed, we measure curvature > relative to
non-curved coordinate grid lines, which are like a network of > taut ropes.
Not so neither. Light rays in vacuum (e.g. in a tube with vacuum) are our
standard of "straight line". We see that space around sun is curved because
when the sun leaves the place (figuratively speaking) the rays of light change
their paths. Those straight lines are different when the sun is there and when
it is not there. And since when the sun is not there the space is
(approximately) flat it must be bend when the sun is there. It is rather simple
logic.
> If [e] points toward the retarded position, it cannot be orthogonal to [v] >
or the force would not be central. So your term does not vanish.
v/c vanishes. (v/c)^2 might stay. One wouldn't expect much more from Newtonian
gravity. Besides, we still have components of "gravitational force" due to
acceleration and also "(gravito)magnetic field" (since the target moves also)
to reduce the error even further. Zero error happens to be outside of reach of
Newtonian gravity anyway (with c or without).
> Nothing remains to cancel this spiraling. The proof? The > Poynting-Robertson
effect shows that when a force really does > propagate at the speed of light,
as in the case of solar radiation > pressure, it really does cause orbits to
spiral.
Of course: Newtonian gravity fails while the same method in electrodynamics
gives true results. But isn't it why we use GR instead Newtonian Approximation
for gravity if we need exact results? Does it mean you propose not to use
Newtonian Approximation ever (even in civil engineering)?
> I am sorry if all this upsets your beliefs.
Why would it? I agreed right form the beginning that Newtonian Gravity is not
exact. I just wanted to point to the fact that even with speed being c it is
not as bad as you are presenting it. In particular, for small velocities, it
doesn't produce errors of order of v/c which I thought was your concern but
only (v/c)^2. The errors follow from the fact that there is no curvature of
space in Newtonian Gravity while it is in the real world (and observable). The
infinite speed does not help a lot. Some other fudge factors might be more
appropriate. But why to bother if we have GR that does not have all those
problems?
-- Jim
Tom Van Flandern
where it is much more active. Please send follow-ups there.
Jim Carr should take note that the FAQ is extremely out of date on this
subject, which is why it keeps coming up for new discussions. Very little of
the material in this thread is covered by the FAQ.
jim...@aol.com (JimJast) writes:
>> [tvf]: Are you aware that no experiment whatever gives a speed
>> of gravity anywhere near lightspeed, directly or indirectly?
> [jj]: But also no experiment whatever gives a speed of gravity
> anywhere near _any_ speed, directly or indirectly because
> "gravitational force" turned out to be not a physical entity but
> only a mathematical fiction.
Without disputing this arguable concept, let's focus on 3-space
gravitational acceleration of the target body instead of "gravitational
force". Then experiments showing that the acceleration is toward the
instantaneous gravity source instead of the retarded source set a lower
limit to the speed of gravity that is much faster than light -- unless
additional ad hoc assumptions are made about GR.
> [jj]: You seem to miss an important point: both variants of
> Newtonian gravity, with high velocity and with low don't agree
> with experiments. I agree that approximation with infinite speed
> gives better fit to the experiments. E.g. in a simple case of
> bending the light rays it gives only 50% error while the one
> with speed c gives no bending whatsoever. But the error of 50%
> is not such a big advantage over 100% error if it requires an
> application of a non physical fudge element of infinite speed.
These tiny differences between Newtonian gravity and GR are of order
(v/c)^2 and of no importance here. The speed of light, c, appears
legitimately in GR in connection with the permittivity and permeability of
the space-time medium. That usage has nothing to do with the speed of
gravity. If a finite speed of gravity is inserted into Newtonian or GR
equations of motion, either theory deviates from reality at the level (v/c),
many orders of magnitude grater than the difference between the two
theories.
> [jj]: Most people think that a theory that gives 50% error
> should be replaced by one that gives 0% error anyway and it has
> been done by replacing both mentioned theories by GR. However
> for small velocities both are about the same good (which is my
> point) and the one with c does not produce outrageous effects
> like error being of order of v/c. It is still of order of
> (v/c)^2 as I wanted to turn your attention to in the previous
> message.
Please direct your attention to the effect of a propagation delay
resulting from speed c, as occurs in the Poynting-Robertson effect for the
force of solar radiation pressure. For gravity, that would be huge, and is
the only effect that matters in this discussion.
> [jj]: You are talking about people who believe that the universe
> is expending and are prompting us to believe in it as well ...
We are clearly in much better agreement about cosmology.
>> [tvf]: the paths of light beams (the "null geodesics" of GR)
>> .... are slightly curved near source masses. Yet a taut rope
>> would experience no such curvature. Indeed, we measure
>> curvature relative to non-curved coordinate grid lines, which
>> are like a network of taut ropes.
> [jj]: So we don't know if spacetime is curved but we know that
> space is. ... Light rays in vacuum ... are our standard of
> "straight line". We see that space around sun is curved because
> when the sun leaves the place (figuratively speaking) the rays
> of light change their paths. Those straight lines are different
> when the sun is there and when it is not there. And since when
> the sun is not there the space is (approximately) flat it must
> be bend when the sun is there. It is rather simple logic.
What is the logic that leads you to prefer space being bent versus the
light beam being bent? From this experiment alone, either interpretation
seems applicable. How could you tell the difference?
Remember, GR has two interpretations. In one, the curvature tensor
represents curved spacetime. In the other, it represents density of the
"spacetime medium", and light slows and bends by refraction. In either
interpretation, the light rays bend by twice as much as in Newtonian
gravity.
I gave you my argument that space is not really bent. We can stretch a
rope taut past the Sun. If space were bent, the rope would have to follow
bent space. If the light beams bend as they pass the Sun, then their paths
will curve relative to the rope, which will have no such bend.
Another point: If space were bent, the curvature would be independent of
the speed of the light beam, body, or rope passing through it. Only if
"space-time" (not just space) is bent can you get a bend that depends on
speed. Sorry, but I don't see the simplicity of your logic. :-( -|Tom|-
Gerry Quinn
> Without disputing this arguable concept, let's focus on 3-space
>gravitational acceleration of the target body instead of "gravitational
>force". Then experiments showing that the acceleration is toward the
>instantaneous gravity source instead of the retarded source set a lower
>limit to the speed of gravity that is much faster than light -- unless
>additional ad hoc assumptions are made about GR.
>
Do you accept that the same argument would imply that the electrostatic
force between two charged spheres "has a speed faster than light"? Or
do you assert that the orbits of two spheres of opposite charge would be
unstable?
>
> Please direct your attention to the effect of a propagation delay
>resulting from speed c, as occurs in the Poynting-Robertson effect for the
>force of solar radiation pressure. For gravity, that would be huge, and is
>the only effect that matters in this discussion.
>
That would be the pressure of the retarded solar radiation associated
with increased entropy. Like gravitational radiation, it travels at c.
It seems you must believe that even in electrostatics / electromagnetism
there are two forces with different properties. Perhaps you could
elaborate on the implications of your ideas for these better understood
- or at least better tested - phenomena, then we could more easily
assess the validity of your thoughts on gravitation.
- Gerry Quinn
Steve Carlip
> Without disputing this arguable concept, let's focus on 3-space
> gravitational acceleration of the target body instead of "gravitational
> force". Then experiments showing that the acceleration is toward the
> instantaneous gravity source instead of the retarded source set a lower
> limit to the speed of gravity that is much faster than light -- unless
> additional ad hoc assumptions are made about GR.
The required ``additional ad hoc assumptions about general relativity''
are the following:
1. The field equations of general relativity give the correct description
of gravitation.
2. The way to find out what the field equations predict about the motion
of an object is to put in an initial configuration and to then solve the
equations (typically either in a systematic approximation or by using
numerical methods) to find the configuration at later times.
Point 1 means, unambiguously, that no gravitational effect propagates
faster than light. For arbitrary small deviations from a fixed spacetime
geometry, the proof is trivial. To make this universal---to drop the
requirement of looking only at small deviations---takes a bit more
work, but it is not too hard.
Point 2, when carried out, shows that there are ``compensating terms''
that nearly (but not exactly) cancel the effects of aberration.
That's all there is to it. The only reason for any dispute is that Van
Flandern does not understand the Einstein field equations very well,
and therefore rejects (with no particular evidence) some rather straight-
forward proofs of their consequences.
Steve Carlip
Steven B. Harris
writes:
>It seems you must believe that even in electrostatics /
electromagnetism
>there are two forces with different properties. Perhaps you could
>elaborate on the implications of your ideas for these better
understood
>- or at least better tested - phenomena, then we could more easily
>assess the validity of your thoughts on gravitation.
>
>- Gerry Quinn
In a sense, virtual and real particles do have different properties.
The force "transmitted" by virtual particles does not point to the
retarded position of the source, but instead to the instantaneous
position of it. For real particles carrying momentum and energy
(information, in the classic sense), however, the momentum/force vector
is toward the retarded position (ie, there is aberation in the force
and momentum transfer direction, and for any kind of information
tranfer). This is a little weird, and certainly counterintuitive the
first time you hear about it. Yet, it's all necessary to conserve
momentum: if the field is static and is not itself storing or carrying
momentum, then the objects originating the field at all times must have
all momentum. Which is to say: Newton's third law suffers if the force
vectors from static fields don't point at instantaneous positions.
However, Tom Van Flandern has never really been able to deal with all
this. As you say quite rightly, one should deal with it in EM before
fussing about gravity.
Ali
Steven B. Harris <sbha...@ix.netcom.com> wrote in message
news:8f5i6f$n72$1...@slb6.atl.mindspring.net...
The resolution of it is in the representation of the objects as the same:
regular selfsupporting arangement of instantaneous collision events; the
same as the virtual objects, which are without the regularity and the
selfsupporting characteristic following from it. In this case all the
interactions through the field will comprise from identical elements:
atractions, joining of the virtual particles and the relative to the
direction of progression of the particle - real object - direction of
collision progressions in it will mark the differences between the different
fields: electrostatic, magnetic, electromagnetic and gravitational.
A clue is provided to which is which by the possibility of variations.
The relative direction of change regularity is parallel with the progression
of the object: 2 possibilities - forward of reverce. Electrostatic fields
have two different possibilities + or -.
Perpendicular to the direction of progression gives similar but unlimited
variants (plus it is perpendicular to the electrostatic) - magnetic fields.
The two regularities could coexist - electromagnetic.
No real distinction in the direction of progression and the direction of
change regularity - like it is too large or perfectly simmetrical - just the
gravity left.
A quite remarkable coincidence of this representation to the reality that it
results in the exact number and character of observed fields - together with
the perfectly good fit of the regular arangement inside of particles to the
observed rest masses of stable isotops. Hm...
--
Aladar
http://www2.3dresearch.com/~alistolmar
Joe Fischer
: In a sense, virtual and real particles do have different properties.
: The force "transmitted" by virtual particles does not point to the
: retarded position of the source, but instead to the instantaneous
: position of it. For real particles carrying momentum and energy
: (information, in the classic sense), however, the momentum/force vector
: is toward the retarded position (ie, there is aberation in the force
: and momentum transfer direction, and for any kind of information
: tranfer).
Why are you mentioning this in a gravity thread,
without identifying Newtonian gravitation as your model.
: This is a little weird, and certainly counterintuitive the
: first time you hear about it. Yet, it's all necessary to conserve
: momentum: if the field is static and is not itself storing or carrying
: momentum, then the objects originating the field at all times must have
: all momentum. Which is to say: Newton's third law suffers if the force
: vectors from static fields don't point at instantaneous positions.
: However, Tom Van Flandern has never really been able to deal with all
: this. As you say quite rightly, one should deal with it in EM before
: fussing about gravity.
Tom knows celestial mechanics, and knows no delays
are included in calculations for propagation.
Frankly, I think his weird insistance that gravity
propagates Billions and Billions times the speed of light
is a concession to the apparent general consensus of the
scientific community that gravity is an "attractive" force
mediated by "fields" of particles or other mediums.
I think those that know General Relativity best
will back me up in stating that there is no evidence that
the mechanism of gravitation is propagated particles or
other mediums. While the question still stands, it is
quite contradictory to say "gravitational forces" cause
inertial motion freefall.
Threads like this are actually a lot of noise,
and could be all signal, if the model of gravitation
and mechanics is mentioned in the subject line, or at
the top of the article.
Joe Fischer
Jim Graber
Steve Carlip <car...@dirac.ucdavis.edu> wrote:
>
> Point 2, when carried out, shows that there are ``compensating terms''
> that nearly (but not exactly) cancel the effects of aberration.
>
I note that the accelerating Kinnersley photon rocket does not emit
gravitational radiation, whereas a charged accelerating photon rocket
would emit electromagnetic radiation. Also apparently GR compensates
for most or all of second order aberration (i.e., the aberration due to
acceleration) as well as the first order aberration (i.e. the aberration
due to velocity). (reference quote above and Carlip astro-ph/9909087)
This suggests that gravitational radiation should be proportional to
jerk ( ie the third time derivative of position) rather than
acceleration (the second time derivative of position).
Is this true? If not, what is the relation of
gravitational radiation to acceleration and jerk?
Thanks. Jim Graber
Sent via Deja.com http://www.deja.com/
Before you buy.
Gerry Quinn
>In <GrbR4.10861$sB3....@news.indigo.ie> ger...@indigo.ie (Gerry Quinn)
>writes:
>
>>It seems you must believe that even in electrostatics /
>electromagnetism
>>there are two forces with different properties. Perhaps you could
>>elaborate on the implications of your ideas for these better
>understood
>>- or at least better tested - phenomena, then we could more easily
>>assess the validity of your thoughts on gravitation.
>>
>>- Gerry Quinn
>
>
>The force "transmitted" by virtual particles does not point to the
>retarded position of the source, but instead to the instantaneous
>position of it. For real particles carrying momentum and energy
>(information, in the classic sense), however, the momentum/force vector
>is toward the retarded position (ie, there is aberation in the force
>and momentum transfer direction, and for any kind of information
>first time you hear about it. Yet, it's all necessary to conserve
>momentum: if the field is static and is not itself storing or carrying
>momentum, then the objects originating the field at all times must have
>all momentum. Which is to say: Newton's third law suffers if the force
>vectors from static fields don't point at instantaneous positions.
>However, Tom Van Flandern has never really been able to deal with all
>this. As you say quite rightly, one should deal with it in EM before
>fussing about gravity.
>
My intuition on this one is to think of the advanced and retarded
effects of gravity to be equal, so long as there is no change in
entropy. (With no change in entropy, there is no reason for any
physical model to be assymetric with respect to the direction of time.)
Thus we are attracted in two directions - towards the Sun as it was
eight minutes ago, and towards the Sun as it will be eight minutes from
now. The sum of these attractions points squarely at the Sun.
If I understand things correctly (and I admit I do not yet understand
them all that well) the virtual particles you talk about above, like the
photons in the physics faq, are actually the sum of advanced and
retarded virtual particles.
And as for photons, so for gravitons, even if these don't seem to be
mathematically well-behaved so far...
- Gerry Quinn
Steven B. Harris
writes:
> I think those that know General Relativity best
>will back me up in stating that there is no evidence that
>the mechanism of gravitation is propagated particles or
>other mediums.
No evidence? You mean, other than the fact that all other known
forces are propagated by fields which must be quantized for the most
accurate theories (ie, by particles), but which looked otherwise, on
first view?
There is such a thing as induction, you know. Fool me once, shame on
you. Fool me the same way four times straight, shame on me.
Joe Fischer
: > I think those that know General Relativity best
: >the mechanism of gravitation is propagated particles or
: >other mediums.
:
: No evidence?
Right, that means all experiments to date fit
the concepts of freefall is inertial motion, support
the Principle of Equivalence, and verify complex geometry
of a mathematical mapping of space-time.
: You mean, other than the fact that all other known
: forces are propagated by fields which must be quantized for the most
: accurate theories (ie, by particles), but which looked otherwise, on
: first view?
Physics can't be done on "it must be so because
---all other known forces are like that----"
If you haven't noticed, gravity _is_ different!
And as far as I know, all quantum physics other than QED
is close range, please tell me if that is not true.
: There is such a thing as induction, you know. Fool me once, shame on
: you. Fool me the same way four times straight, shame on me.
Gravity keeps fooling everybody. Deduce all you
want, evidence for propagation or medium has to be physical.
Are you aware that freefall in General Relativity is
inertial motion, and General Relativity is accepted as best.
Will you state that propagated particles or a
medium are needed for inertial motion? Please don't,
things are goofy enough as it is.
I really need somebody to comment on this, many
readers are most comfortable with Newtonian concepts,
and some elaboration on freefall and inertial motion
versus acceleration would help a lot of people.
Joe Fischer
Steve Carlip
> This suggests that gravitational radiation should be proportional
> to jerk ( ie the third time derivative of position) rather than
> acceleration (the second time derivative of position).
Not quite, but close. The power of emitted gravitational radiation
depends on the third time derivative of the mass quadrupole
moment. For point particles, the quadrupole moment looks like
a sum of terms of the form mr^2. So its third derivative has one
piece that looks like jerk, and another that looks like velocity times
acceleration.
If you look at the end of section 3 of my Phys. Lett. A paper, there's
a slightly more elaborate analysis.
Steve Carlip
Jwrrock
Are you aware that freefall in General Relativity is
inertial motion, and General Relativity is accepted as best.
Will you state that propagated particles or a
medium are needed for inertial motion? Please don't,
things are goofy enough as it is.
I really need somebody to comment on this, many
readers are most comfortable with Newtonian concepts,
and some elaboration on freefall and inertial motion
versus acceleration would help a lot of people.
Joe Fischer
One thing puzzles me, Joe. In an ordinary inertial state there is no time
dilation. But in inertial motion in freefall, clocks are dilated by the
gravitational field...indicating, at least to me, that a force, or forces are
interacting. It would seem to me that gravity is accelerating the mass and
inertial resistance is limiting it...both forces in equilibrium...no force
felt. Isn't that in accordance with the equivalence principle?
Jim R
Joe Fischer
: Joe Fischer writes:
: I really need somebody to comment on this, many
: readers are most comfortable with Newtonian concepts,
: and some elaboration on freefall and inertial motion
: versus acceleration would help a lot of people.
: One thing puzzles me, Joe. In an ordinary inertial state there is no time
: dilation. But in inertial motion in freefall, clocks are dilated by the
: gravitational field...
I don't think you will find a reference for that,
the SO-CALLED time dilation experiments were done with
devices at each end of a 30 meter tower (a little less
than 30 meters, actually).
The tower was on the surface of Earth, and could
just as well have been in an accelerating elevator in
deep space.
There was no time dilation, there was simply a
difference between sent frequency and received frequency,
and this has been misconstrued to mean time dilation.
: indicating, at least to me, that a force, or forces are
: interacting. It would seem to me that gravity is accelerating the mass and
: inertial resistance is limiting it...both forces in equilibrium...no force
: felt. Isn't that in accordance with the equivalence principle?
: Jim R
No, that isn't the PoE, that is Newtonian gravitation.
There really needs to be some thought given to other possible
mechanisms for gravitation than forces acting at a distance,
as steel bars or cables the 5,000 miles thick would not hold
the Earth in orbit against centrifugal force, so how can any
unconnected particles or tenuous medium do so?
You can get all the force discussions you want in
sci.physics where Newtonian gravitation is accepted, but
in a relativity newsgroup, after 85 years of success of
General Relativity, things that agree with GR should be
explored.
In fact, it is the "too good to be true" forces
in equilibrium that pointed the way to the PoE. Inertia
provides the effect of gravitation, but it is not the
mechanism, gravity needs more than relativity, it needs
a real physical process as the mechanism.
And this mechanism must be a process of matter.
Joe Fischer
Tom Van Flandern
> Do you accept that the same argument would imply that the
> electrostatic force between two charged spheres "has a speed
> faster than light"?
Yes, of course. Direct experimental evidence, such as the
Sherwin-Rawcliffe experiment, confirms that conclusion. The force carriers,
“virtual photons”, are a misnomer because they have no properties in common
with real photons.
> It seems you must believe that even in electrostatics /
> electromagnetism there are two forces with different properties.
Would you equate electrostatic force with electromagnetic radiation
pressure? I don’t think so. There are obviously two different forces
involved, with next to nothing in common. Electrostatic force involves
“virtual photons” as force carriers, and is consistent in *every* observable
way with faster-than-light propagation speed. Radiation pressure involves
real photons traveling at the speed of light, and obeys all the laws of
physics, such as displaying aberration appropriate for propagation speed =
light speed. Electrostatic forces affect charges and only charges, radiation
pressure pays no attention to charge. Etc.
If we are agreed about these basic facts about E-M, then perhaps we are
prepared to recognize that gravity may also exhibit two different types of
force. From my perspective, the only “new” part of this (i.e., not out of
someone else’s textbook) is my suggestion that gravitational waves and
electromagnetic waves are disturbances of the same medium. That is pretty
much straight from Occam’s Razor: Why multiply hypotheses, or wave media,
unnecessarily? Are there supposed to be two different media to space, one
for E-M waves and one for gravitational waves?
> My intuition on this one is to think of the advanced and
> retarded effects of gravity to be equal, so long as there is no
> change in entropy. (With no change in entropy, there is no
> reason for any physical model to be asymmetric with respect to
> the direction of time.) Thus we are attracted in two directions
> -- towards the Sun as it was eight minutes ago, and towards the
> Sun as it will be eight minutes from now. The sum of these
> attractions points squarely at the Sun.
Despite the popularity of such ideas among non-physicists, it is a
violation of the causality principle for any effect to precede its cause.
And as for entropy, a generalized definition (crudely, entropy = disorder)
shows that entropy always increases during E-M interactions unless work is
done; and entropy always decreases during gravitational interactions unless
work (e.g., a supernova) is done. This preserves the net entropy of the
universe and keeps infinitely-old-universe models viable. But it is also
getting far from the topic here. -|Tom|-
Tom Van Flandern
> In a sense, virtual and real particles do have different
> properties. The force "transmitted" by virtual particles does
> not point to the retarded position of the source, but instead to
> the instantaneous position of it. For real particles carrying
> momentum and energy (information, in the classic sense),
> however, the momentum/force vector is toward the retarded
> position (ie, there is aberration in the force and momentum
> transfer direction, and for any kind of information transfer).
> This is a little weird, and certainly counterintuitive the first
> time you hear about it.
Nice description. So far, so good.
> Yet, it's all necessary to conserve momentum: if the field is
> static and is not itself storing or carrying momentum, then the
> objects originating the field at all times must have all
> momentum. Which is to say: Newton's third law suffers if the
> force vectors from static fields don't point at instantaneous
> positions. However, Tom Van Flandern has never really been able
> to deal with all this. As you say quite rightly, one should deal
> with it in EM before fussing about gravity.
In this respect, EM and gravity seem to behave the same to me. Real
waves or wavicles propagate at speed c, virtual entities propagate at speeds
so fast they must be approximated as infinite speeds. I’m not aware of any
problems I have dealing with this.
OTOH, your paragraph just above seems vague and garbled to me. Perhaps
you might be kind enough to try again, and inject some of the clarity of
your previous paragraph into the one above.
One point in particular: Nature doesn’t guaranty momentum conservation.
Tidal forces and radiation pressure are examples of forces that have no such
conservation. Tides arise from virtual particles, and nature apparently has
no way to differentiate between a tidal force and a gravitational force. So
why does it conserve momentum for the latter but not the former?
I conclude that enforced conservation of angular momentum seems highly
implausible. By contrast, ftl propagation of gravity explains what happens
with both tides and gravitation because it makes ordinary gravity a central
force and tides a non-central force. How do you explain this
behavior? -|Tom|-
Steven B. Harris
<t...@mindspring.com> writes:
>>
> One point in particular: Nature doesn’t guaranty momentum
conservation.
>Tidal forces and radiation pressure are examples of forces that have
no such
>conservation.
What makes you think that?
Tides arise from virtual particles, and nature apparently has
>no way to differentiate between a tidal force and a gravitational
>force. So why does it conserve momentum for the latter but not the
>former?
Simple answer: it doesn't. Your premise is wrong.
The time has some, the Walrus said, to talk to many things--
Of shoes and ships and sailing wax, and cabbages and kings
Of why the sea is boiling hot, and whether pigs have wings....
> I conclude that enforced conservation of angular momentum seems
>highly implausible.
Conclude all you like.
>By contrast, ftl propagation of gravity explains what happens
>with both tides and gravitation because it makes ordinary gravity a
central
>force and tides a non-central force. How do you explain this
>behavior? -|Tom|-
What behavior? Tides are a central force in the fame of the
primary. They only change when you more your reference frame to the
accelerated vicinity in which the tide is felt. The forces that turn
the central force of tides into a radial force are basically the
centrifugal forces that appear in rotating reference frames.
Gerry Quinn
I would consider the electrostatic and electromagnetic forces to be two
aspects of the same force. And that classical wave theories of both
light and gravity are obsolete, even though proponents of the latter do
not seem to know it yet.
But let's say for the sake of argument that electrostatic force is FTL.
Do you think it can be used to send signals? Or that the equivalent
gravitational effect can? These "instantaneous" forces are pretty
nebulous, no?
>> My intuition on this one is to think of the advanced and
>> retarded effects of gravity to be equal, so long as there is no
>> change in entropy. (With no change in entropy, there is no
>> reason for any physical model to be asymmetric with respect to
>> the direction of time.) Thus we are attracted in two directions
>> -- towards the Sun as it was eight minutes ago, and towards the
>> Sun as it will be eight minutes from now. The sum of these
>> attractions points squarely at the Sun.
>
> Despite the popularity of such ideas among non-physicists, it is a
>violation of the causality principle for any effect to precede its cause.
When there is no entropy change, one might as well say that the cause of
the Earth's position today is its motion tomorrow as well as its motion
yesterday. Causality and time's arrow depend on entropy.
>And as for entropy, a generalized definition (crudely, entropy = disorder)
>shows that entropy always increases during E-M interactions unless work is
>done; and entropy always decreases during gravitational interactions unless
>work (e.g., a supernova) is done. This preserves the net entropy of the
>universe and keeps infinitely-old-universe models viable. But it is also
>getting far from the topic here. -|Tom|-
>
In the first instance, you seem to be confusing heat and work. In fact
entropy is constant in reversible reactions (where free energy is
transformed without degradation). In the case of a supernova, some work
is done, but much is 'wasted' as heat, and so entropy increases.
Secondly, consider two objects that fall together under gravitational
attraction and stick. Clearly one object exists where two did before,
but that object is hot and its particles have considerable random
thermal motion. Entropy has increased. A crude definition of entropy as
macroscopic disorder doesn't wash.
Electricity suppliers often use gravitational interactions to store
energy. No thermodynamic peculiarities are observed in pumped water
storage as distinct from other types.
There are some seeming paradoxes related to black holes that bother some
people, but these are based on taking general relativity seriously as a
realistic description of nature, and pretending that matter falling into
a black hole somehow disappears. We don't have to assume that.
- Gerry Quinn
Ali
Tom Van Flandern <t...@mindspring.com> wrote in message
news:8fb110$1m5$1...@nntp9.atl.mindspring.net...
> ger...@indigo.ie (Gerry Quinn) writes:
>
> > Do you accept that the same argument would imply that the
> > electrostatic force between two charged spheres "has a speed
> > faster than light"?
>
> Yes, of course. Direct experimental evidence, such as the
> Sherwin-Rawcliffe experiment, confirms that conclusion. The force
carriers,
> "virtual photons", are a misnomer because they have no properties in
common
> with real photons.
Only one - basic - property is missing: the virtual photons or spontaineous
collision events do not self-sustain the regular collision chain - like the
photon does. Never reach a full phase, leak it's own time, but in the brief
period of their existence they act like the normal full collision chain
bodies: attract each other, join together if they get too close. Real chains
extend from body to body, comprised by these attraction elements of virtual
photons.
Force carriers? I would call them love birds - it has more meaning, closer
to the reality...
>
> > It seems you must believe that even in electrostatics /
> > electromagnetism there are two forces with different properties.
>
> Would you equate electrostatic force with electromagnetic radiation
> pressure? I don't think so. There are obviously two different forces
> involved, with next to nothing in common. Electrostatic force involves
> "virtual photons" as force carriers, and is consistent in *every*
observable
> way with faster-than-light propagation speed. Radiation pressure involves
> real photons traveling at the speed of light, and obeys all the laws of
> physics, such as displaying aberration appropriate for propagation speed =
> light speed. Electrostatic forces affect charges and only charges,
radiation
> pressure pays no attention to charge. Etc.
>
Correct. The main finding here: the photon is the full phase object and as
such it has to propagate through the medium - of colliding elements - with
the exact progression speed of collision event probabilities to be
self-sustaining. (Only a very small edge is obtained from the feedback,
deformation of the basis.) The two perpendicular co-existing regularity
makes it easier to achieve, more of the available spontaineous collisions
will fit into the regularity required and self-preserved.
(But what do you mean under force?)
> If we are agreed about these basic facts about E-M, then perhaps we
are
> prepared to recognize that gravity may also exhibit two different types of
> force.
Do you know Newton's description?
> From my perspective, the only "new" part of this (i.e., not out of
> someone else's textbook) is my suggestion that gravitational waves and
> electromagnetic waves are disturbances of the same medium. That is pretty
> much straight from Occam's Razor: Why multiply hypotheses, or wave media,
> unnecessarily? Are there supposed to be two different media to space, one
> for E-M waves and one for gravitational waves?
No. And what you call "force" through the field for each field types -
electrostatic, magnetic, electro-magnetic and gravitational - between two
bodies with the characteristic property of generating such fields -
comprosed of the ankered in the bodies chains of attraction moments of
virtual photons, connecting the bodies in each other's fields. The strength
of "force" is defined by the collision event number (for gravity - mass)
involved in the characteristic regularity for the given field of the given
bodies.
>
> > My intuition on this one is to think of the advanced and
> > retarded effects of gravity to be equal, so long as there is no
> > change in entropy. (With no change in entropy, there is no
> > reason for any physical model to be asymmetric with respect to
> > the direction of time.) Thus we are attracted in two directions
> > -- towards the Sun as it was eight minutes ago, and towards the
> > Sun as it will be eight minutes from now. The sum of these
> > attractions points squarely at the Sun.
>
> Despite the popularity of such ideas among non-physicists, it is a
> violation of the causality principle for any effect to precede its cause.
<...>
> -|Tom|-
>
>
> Tom Van Flandern - Washington, DC - <http://metaresearch.org>
> Meta Research fosters astronomy research on ideas not otherwise
> supported solely because they conflict with mainstream theories
>
>
You should think about my description.
The resolution of it is in the representation of the objects as the same:
regular selfsupporting arangement of instantaneous collision events; the
same as the virtual objects, which are without the regularity and the
selfsupporting characteristic following from it. In this case all the
interactions through the field will comprise from identical elements:
atractions, joining of the virtual particles and the relative to the
direction of progression [progression - measured as temperature at large]
of the particle - real object - direction of
collision progressions in it will mark the differences between the different
fields: electrostatic, magnetic, electromagnetic and gravitational.
A clue is provided to which is which by the possibility of variations.
The relative direction of change regularity is parallel with the progression
of the object: 2 possibilities - forward or reverse. Electrostatic fields
Jwrrock
<: One thing puzzles me, Joe. In an ordinary inertial state there is no time
: dilation. But in inertial motion in freefall, clocks are dilated by the
: gravitational field...
I don't think you will find a reference for that,
the SO-CALLED time dilation experiments were done with
devices at each end of a 30 meter tower (a little less
than 30 meters, actually).>
Actually an experiment was done several years ago in which a rocket carrying an
atomic clock was sent almost straight up. In freefall the clock ran slower than
an identical earth-based clock. It would seem that the acceleration affected
the clock even though it was not *felt*.
I would have to look it up to give you the particulars on it but I'm sure some
here would have knowledge of it.
Regards,
Jim R
Joe Fischer
: > One point in particular: Nature doesn’t guaranty momentum
: >conservation.
: >Tidal forces and radiation pressure are examples of forces that have
: >no such conservation.
:
: What makes you think that?
He was trained to think "tidal forces" are a gradient
in some imaginary "field".
In reality, what is called tidal forces is merely
objects following different worldlines, in inertial motion,
and the so-called tidal forces are proportional to the
inertial mass of the object times a value that can be
assigned to the difference in 4-velocity.
: Tides arise from virtual particles, and nature apparently has
: >no way to differentiate between a tidal force and a gravitational
: >force. So why does it conserve momentum for the latter but not the
: >former?
:
: Simple answer: it doesn't. Your premise is wrong.
And he called your article "garbled". :-)
: The time has some, the Walrus said, to talk to many things--
: Of shoes and ships and sailing wax, and cabbages and kings
: Of why the sea is boiling hot, and whether pigs have wings....
On second thought.........:-)
: > I conclude that enforced conservation of angular momentum seems
: >highly implausible.
:
: Conclude all you like.
There must be a conclusion of Euclidean space or
some other nonsensical coordinate system in there some place.
: >By contrast, ftl propagation of gravity explains what happens
: >with both tides and gravitation because it makes ordinary gravity a
: >central force and tides a non-central force. How do you explain this
: >behavior? -|Tom|-
: What behavior? Tides are a central force in the fame of the
: primary. They only change when you more your reference frame to the
: accelerated vicinity in which the tide is felt. The forces that turn
: the central force of tides into a radial force are basically the
: centrifugal forces that appear in rotating reference frames.
Am I in the wrong newsgroup? :-)
Joe Fischer
Jim Carr
... note followups ...
Joe Fischer writes:
:
: One thing puzzles me, Joe. In an ordinary inertial state there is no time
: dilation. But in inertial motion in freefall, clocks are dilated by the
: gravitational field...
In article <20000510124721...@ng-ch1.aol.com>
jwr...@aol.com (Jwrrock) writes:
>
> I don't think you will find a reference for that,
>the SO-CALLED time dilation experiments were done with
>devices at each end of a 30 meter tower (a little less
>than 30 meters, actually).>
The Relativity FAQ contains references for a subset of a wide
variety of "time dilation" experiments, both those appropriate
to SR alone and those where GR must be included.
>Actually an experiment was done several years ago in which a rocket carrying an
>atomic clock was sent almost straight up. In freefall the clock ran slower than
>an identical earth-based clock. It would seem that the acceleration affected
>the clock even though it was not *felt*.
>
>I would have to look it up to give you the particulars on it but I'm sure some
>here would have knowledge of it.
Look in the Relativity FAQ.
--
James A. Carr <j...@scri.fsu.edu> | "The half of knowledge is knowing
http://www.scri.fsu.edu/~jac/ | where to find knowledge" - Anon.
Supercomputer Computations Res. Inst. | Motto over the entrance to Dodd
Florida State, Tallahassee FL 32306 | Hall, former library at FSCW.
Paul Schlyter
Tom Van Flandern <t...@mindspring.com> wrote:
> One point in particular: Nature doesn't guaranty momentum conservation.
> Tidal forces and radiation pressure are examples of forces that have
> apparently has no way to differentiate between a tidal force and a
> gravitational force. So why does it conserve momentum for the latter
> but not the former?
When friction is involved, momentum isn't conserved -- and this is
valid for both gravitational and tidal forces. BTW tidal forces are
really nothing but gravitational forces: differentiate the gravity
force and you'll get the tidal force. Didn't you know that? Or are
you just trying to confuse the issue?
--
----------------------------------------------------------------
Paul Schlyter, Swedish Amateur Astronomer's Society (SAAF)
Grev Turegatan 40, S-114 38 Stockholm, SWEDEN
e-mail: pausch at saaf dot se or paul.schlyter at ausys dot se
WWW: http://hotel04.ausys.se/pausch http://welcome.to/pausch
Steve Carlip
> One point in particular: Nature doesn't guaranty momentum
> conservation. Tidal forces and radiation pressure are examples
> of forces that have no such conservation.
Tom, you don't *really* believe that momentum isn't conserved
in tidal interactions, do you?
Steve Carlip
G=EMC^2 Glazier
Jim Graber
Steve Carlip <car...@dirac.ucdavis.edu> wrote:
> Not quite, but close. The power of emitted gravitational radiation
> depends on the third time derivative of the mass quadrupole
> moment. For point particles, the quadrupole moment looks like
> a sum of terms of the form mr^2. So its third derivative has one
> piece that looks like jerk, and another that looks like velocity times
> acceleration.
Thanks for your very helpful reply. I did some simple calculations based
on your explanation. The results suggest to me that the jerk terms do
not contribute to the radiated power and hence only the velocity times
acceleration terms contribute, at least to leading order. Is this
true, or have my calculations (below) been too simplistic once again.
To ease the ascii, let D = d/dt.
Then gravitational radiation power is proportional to D^3(mr^2), which
=s 6m D(r) D^2(r) + 2 m r D^3(r).
This is the velocity times acceleration term and the jerk term
you mention. The problem is the r in the jerk term. It seems to imply
that radiated power increases with distance, which doesn't seem right.
So lets look at this a little more closely.
let r = j t^3 + a t^2 + v t + p
(j=jerk; a=acceleration; v=velocity; p= position).
Now compute D^3(mr^2). First drop m or set m=1.
Result is 120 j^2 t^3 + 120 a j t^2 + 24 a^2 t + 48 j v t
+12 j p + 12 a v.
To get instantaneous value, set t=0.
result is 12 j p + 12 a v.
(Again jerk times position plus acceleration times velocity.
But translation invariance implies we can also set p =0.
Therefore the jerk term drops out and only the acceleration times
velocity term contributes.
Comments or corrections, please? Thanks. Jim Graber
Tom Van Flandern
>> [tvf]: Nature doesn't guaranty momentum conservation. Tidal
>> forces and radiation pressure are examples of forces that have
>> no such conservation.
> [sbh]: What makes you think that?
Sorry, I didn't know there was anyone in this discussion unfamiliar with
this because it is standard, non-controversial astronomy. The
non-conservation of orbital momentum from radiation pressure is called "the
Poynting-Robertson effect", and is described in many textbooks. See one such
description on p. 440 of "The Astronomy and Astrophysics Encyclopedia", ed.
S.P. Maran, Van Nostrand Reinhold (1992).
The same reference also has lots of material on tidal friction. In
brief, when one body (e.g., the Moon) pulls on another non-rigid body of
finite radius (e.g., the Earth), the attraction on the near-side exceeds the
attraction on the far-side, resulting in a "tidal bulge" toward the source
of gravity (Moon). The force from that bulge would remain radial, and
orbital momentum would remain conserved, if the target body (Earth) were
non-rotating.
But the real Earth rotates. Elastic forces within the Earth drag the
tidal bulge ahead in the direction of rotation faster than the changing
gravity field can compensate ("tidal friction"). The result is that the
Earth's pull back on the Moon has a non-radial component from the leading
bulge that accelerates the Moon, causing its orbit to spiral away from
Earth. Computations of the magnitude of this mechanism agree rather well
with the size of the observed spiraling effect in the Moon's actual orbit.
The dilemma for us here is that this force from Earth's tidal bulge on
the Moon is non-radial and non-conservative (i.e., it changes the Moon's
orbital momentum). Yet to nature, it looks identical to aberration -- an
offset of the center of force of Earth's gravity from the radial direction.
How can nature compensate for this effect in the case of ordinary gravity,
but not for tidal bulges? The Moon has no way to know why the force it feels
is non-radial, only that it is. -|Tom|-
Tom Van Flandern
> [gq]: let's say for the sake of argument that electrostatic
> force is FTL. Do you think it can be used to send signals? Or
> that the equivalent gravitational effect can? These
> "instantaneous" forces are pretty nebulous, no?
Yes, I think electrostatic force variations certainly can be used to
send ftl signals, because their propagation speeds are ftl in forward time,
and therefore have no causality violations. This is fully in accord with,
and allowed by, Lorentzian relativity. Moreover, the Walker-Dual experiment
(previously cited) comes very close to demonstrating an actual electrostatic
signal sent ftl. -|Tom|-
Tom Van Flandern
>> [tvf]: One point in particular: Nature doesn't guaranty
>> [orbital] momentum conservation.
> [ps]: If all forces involved are central, momentum conservation
> is guaranteed.
Of course. But my examples were of non-central forces.
>> [tvf]: Tidal forces and radiation pressure are examples of
>> forces that have no such conservation. Tides arise from virtual
>> particles, and nature apparently has no way to differentiate
>> between a tidal force and a gravitational force. So why does it
>> conserve momentum for the latter but not the former?
> [ps]: When friction is involved, momentum isn't conserved - and
> this is valid for both gravitational and tidal forces.
Of course. If we look at a whole, enclosed system, momentum is always
conserved because it cannot disappear or reappear from the universe. But our
discussion was about orbital angular momentum only. That can and does
change. The sink for it (e.g., the rotation of the Earth) does not
participate in the dynamical system under discussion, so its momentum is
irrelevant here.
> [ps]: BTW tidal forces are really nothing but gravitational
> forces: differentiate the gravity force and you'll get the tidal
> force. Didn't you know that? Or are you just trying to confuse
> the issue?
Tidal forces are so-named because they are distinguishable from
gravitational forces, and have different properties. The one that is
relevant here is that gravitational forces are central and tidal forces are
not.
Your point about differentiating is beyond my comprehension.
Differentiate gravitational potential and you get gravitational force. But
no one would confuse potential and force. For example, the former affects
clock rates, the latter does not. Surely you weren't arguing that a function
and its derivative are equivalent! ??? So I have no idea what you were
trying to argue. -|Tom|-
Tom Van Flandern
>> [tvf]: One point in particular: Nature doesn't guaranty
>> momentum conservation. Tidal forces and radiation pressure are
>> examples of forces that have no such conservation.
> [sc]: Tom, you don't *really* believe that momentum isn't
> conserved in tidal interactions, do you?
We were discussing orbital angular momentum, which is certainly not
conserved. The fact that total momentum is conserved in the rotations of
bodies is irrelevant to our discussion. I trust you were not simply trying
to deflect attention from the substance of my previous message.
Your proposed solution to the "speed of gravity" dilemma uses "slow"
propagation speeds (c), and therefore creates non-central forces. As I see
it, you have no way to escape this dilemma within the laws of physics. Your
solution restores momentum conservation by mathematical decree, declaring
that the effective direction of force application is (nearly) central, as
required to agree with observations. Mathematically, of course, one can do
almost anything. But if there is any physics behind making this momentum
violation disappear, it has escaped me.
Indeed, the example of tidal forces illustrates the physical problem you
face very well. A finite propagation speed of gravity from Earth to Moon, or
a tidal force raised on Earth and acting on the Moon, would both present the
Moon with an essentially identical non-central force. You adopt mathematics
that cancels the non-central component of gravitational force, but does not
cancel the non-central component of tidal force. This is inconsistent.
Please explain. -|Tom|-
me...@cars3.uchicago.edu
>sbha...@ix.netcom.com(Steven B. Harris) writes:
>
>>> forces and radiation pressure are examples of forces that have
>>> no such conservation.
>
>
>
>brief, when one body (e.g., the Moon) pulls on another non-rigid body of
>finite radius (e.g., the Earth), the attraction on the near-side exceeds the
>attraction on the far-side, resulting in a "tidal bulge" toward the source
>of gravity (Moon). The force from that bulge would remain radial, and
>orbital momentum would remain conserved, if the target body (Earth) were
>non-rotating.
>
> But the real Earth rotates. Elastic forces within the Earth drag the
>tidal bulge ahead in the direction of rotation faster than the changing
>gravity field can compensate ("tidal friction"). The result is that the
>Earth's pull back on the Moon has a non-radial component from the leading
>bulge that accelerates the Moon, causing its orbit to spiral away from
>Earth. Computations of the magnitude of this mechanism agree rather well
>with the size of the observed spiraling effect in the Moon's actual orbit.
>
> The dilemma for us here is that this force from Earth's tidal bulge on
>the Moon is non-radial and non-conservative (i.e., it changes the Moon's
>orbital momentum).
There is no dilemma. The angular momentum of the systme is conserved.
Nobody, ever, said that the angular momentum of the Earth alone, or
the Moon alone needs to be conserved. The full angular mommentum of
the system consists of
1) The orbital angular momentum.
2) The rotational angular momentum of the Earth.
3) The rotational angular momentum of the Moon.
All of this is covered perfectly well by standard mechanics. What's
your problem?
Mati Meron | "When you argue with a fool,
me...@cars.uchicago.edu | chances are he is doing just the same"
Gerry Quinn
>ger...@indigo.ie (Gerry Quinn) writes:
>
>> [gq]: let's say for the sake of argument that electrostatic
>> force is FTL. Do you think it can be used to send signals? Or
>> that the equivalent gravitational effect can? These
>> "instantaneous" forces are pretty nebulous, no?
>
> Yes, I think electrostatic force variations certainly can be used to
>send ftl signals, because their propagation speeds are ftl in forward time,
>and therefore have no causality violations. This is fully in accord with,
>and allowed by, Lorentzian relativity. Moreover, the Walker-Dual experiment
>(previously cited) comes very close to demonstrating an actual electrostatic
>signal sent ftl. -|Tom|-
>
If such transmission is demonstrated, you win, although since the
principle of relativity would be violated, Lorentzian relativity might
not be a very good term. FTL signals would allow us to determine our
absolute velocity.
I don't believe any such violation will be seen, myself. Because how do
you believe Lorentzian relativity actually works, if there is no such
limit? (The question cannot be dodged as it is in SR.) My own view is
that Lorentzian relativity proves that the fundamental particles of all
matter must be massless, travelling at c. Nor do I see any need to
invoke a fundamental arrow of time, since entropy can serve to explain
it.
- Gerry Quinn
Joe Fischer
: sbha...@ix.netcom.com(Steven B. Harris) writes:
: >> [tvf]: Nature doesn't guaranty momentum conservation. Tidal
: >> forces and radiation pressure are examples of forces that have
: >> no such conservation.
:
: > [sbh]: What makes you think that?
: Sorry, I didn't know there was anyone in this discussion unfamiliar with
: this because it is standard, non-controversial astronomy. The
: non-conservation of orbital momentum from radiation pressure is called "the
: Poynting-Robertson effect", and is described in many textbooks. See one such
: description on p. 440 of "The Astronomy and Astrophysics Encyclopedia", ed.
: S.P. Maran, Van Nostrand Reinhold (1992).
Sorry, but tidal effects, friction and forces
are not the same in General Relativity as they are in
Newtonian concepts, in GR, all "forces" are explained
for freemoving objects by geometry and complex kinematics,
the fact that GR experts talk about "forces" is a mystery
to me.
It has all the markings of people thinking they
know General Relativity and gravity, and they only know
Newtonian gravitation and mechanics in Euclidean space.
Joe Fischer
Jan Panteltje
> Yes, I think electrostatic force variations certainly can be used to
>send ftl signals, because their propagation speeds are ftl in forward time,
Then I could buid a ftl transmitter on my desk right here, with the equipment
I have.
And so could anyone else.
It has not been shown.
What in the world is your idea of 'electrostatic forces'?
Jan
Paul Stowe
Well Jan. you'll notice that Mr. Van Flandern has never explained the
mathematical flaw in Feynman's or Griffth's resolution to the retarded
position problem of coulombic force. Nor, to my knowledge, has anyone
else. If this analysis is valid, the it would not matter, both
infinite speed AND c are valid solutions to the issue centrally
pointing Coulombic forces.
Paul Stowe
JimJast
> Your proposed solution to the "speed of gravity" dilemma uses "slow"
>propagation speeds (c), and therefore creates non-central forces.
>
[jj]
Why do you keep saying that retarded potential will produce a non-central
force. According to the rules of calculus the acceleration got from the
retarded potential has a component directed toward retarded position (that you
might have in mind) but also one directed perpendicularly to that direction,
parallel the movement of the source of potential, and total of those two
components gives central force, at least with (v/c)^2 accuracy (which you
yourself said is negligible, and this parallel component is v/c of the first
one for uniform motion so accuracy is 100% for uniform motion). So why are you
neglecting this other component?
I don't think you neglected to get acquainted with the solutions that you could
find in the literature, or you could even do them yourself (which supposedly is
a lot of work, but might be instructive), so it is kind of a puzzle to me.
-- Jim
Jim Carr
Steve Carlip <car...@dirac.ucdavis.edu> writes:
}
} [tvf]:
} >One point in particular: Nature doesn't guaranty
} > momentum conservation. Tidal forces and radiation pressure are
} > examples of forces that have no such conservation.
}
} Tom, you don't *really* believe that momentum isn't
} conserved in tidal interactions, do you?
In article <8fiicq$uj6$1...@slb7.atl.mindspring.net>
"Tom Van Flandern" <t...@mindspring.com> writes:
>
> We were discussing orbital angular momentum, which is certainly not
>conserved.
But that is not what you said. You didn't even say angular. You
only said "momentum" and you stated it as a *particular* point as
if it were a well-established physical fact.
>The fact that total momentum is conserved in the rotations of
>bodies is irrelevant to our discussion. I trust you were not simply trying
>to deflect attention from the substance of my previous message.
The substance of your "message" above was a false assertion made
as if it were fact. That assertion could only serve to confuse
and mislead less informed individuals reading this in the physics
or astro newsgroups, so it was quite appropriate for Carlip to
make that observation for their benefit.
Jim Carr
pau...@saafNOSPAM.se (Paul Schlyter) writes:
}
} [tvf]:
} > Tidal forces and radiation pressure are examples of
} > forces that have no such conservation. Tides arise from virtual
} > particles, and nature apparently has no way to differentiate
} > between a tidal force and a gravitational force. So why does it
} > conserve momentum for the latter but not the former?
}
} When friction is involved, momentum isn't conserved - and
} this is valid for both gravitational and tidal forces.
In article <8fiics$pq4$1...@slb2.atl.mindspring.net>
"Tom Van Flandern" <t...@mindspring.com> writes:
>
> Of course. If we look at a whole, enclosed system, momentum is always
>conserved because it cannot disappear or reappear from the universe.
Since your second sentence is correct, why did you write "of course"
in response to a statement that is in contradiction to it? Frictional
forces dissipate kinetic energy, but they do not fail to conserve
momentum. A totally inelastic collision is a good example.
>But our
>discussion was about orbital angular momentum only. That can and does
>change.
Of course, but that is no excuse for reinforcing flawed statements
such as the one above or not noting the status of angular momentum
or momentum conservation as distinct from an arbitrary subset of them.
Jim Carr
... note followups ...
In article <8fii5a$sm5$1...@slb6.atl.mindspring.net>
"Tom Van Flandern" <t...@mindspring.com> writes:
>
... to sbha...@ix.netcom.com(Steven B. Harris) ...
>
>The dilemma for us here is that this force from Earth's tidal bulge on
>the Moon is non-radial and non-conservative (i.e., it changes the Moon's
>orbital momentum).
That "i.e." is *not* the definition of "non-conservative" used in
physics nor is it the gravitational force that is responsible for
the dissipation of energy in the bulk of the earth.
Paul Schlyter
Tom Van Flandern <t...@mindspring.com> wrote:
> ger...@indigo.ie (Gerry Quinn) writes:
>
>> [gq]: let's say for the sake of argument that electrostatic
>> force is FTL. Do you think it can be used to send signals? Or
>> that the equivalent gravitational effect can? These
>> "instantaneous" forces are pretty nebulous, no?
>
> send ftl signals, because their propagation speeds are ftl in forward time,
> and allowed by, Lorentzian relativity. Moreover, the Walker-Dual experiment
> (previously cited) comes very close to demonstrating an actual electrostatic
> signal sent ftl. -|Tom|-
electrostatic force variations? It ought to be much easier to do
this than to build an "FTL gravity transmitter", don't you think so?
In your place I would be very eager to build such a device and prove
to the world that I was right. I mean, if you succeed in becoming
the first person to demonstrate transmission of messages FTL, you'll
become one of the icons in the history of science. And you'd
probably have no more problems getting funds for what you'd want
to do. What about it, Tom - wouldn't this be something?
I can only see one reason to hesitate trying to do this: fear
of being wrong, and have this demonstrated to the world.
Paul Schlyter
>
>>> [tvf]: One point in particular: Nature doesn't guaranty
>
>> [ps]: If all forces involved are central, momentum conservation
>> is guaranteed.
>
> Of course. But my examples were of non-central forces.
bodies involved in tidal interaction all were either rigid bodies, or
frictionless fluid bodies (e.g. balls of supercooled helium), then
momentum would be conserved.
>>> [tvf]: Tidal forces and radiation pressure are examples of
>>> forces that have no such conservation. Tides arise from virtual
>>> particles, and nature apparently has no way to differentiate
>>> between a tidal force and a gravitational force. So why does it
>>> conserve momentum for the latter but not the former?
>
>> this is valid for both gravitational and tidal forces.
>
> discussion was about orbital angular momentum only. That can and does
> participate in the dynamical system under discussion, so its momentum is
> irrelevant here.
participates in the dynamical system!
But even if you include the Earth's rotation, momentum won't be
conserved because of friction, which will generate heat which is
radiated away out from the system. So only about half the energy
lost when the Earth slows its rotation is transferred to the Moon and
lifting its orbit: the other half is radiated away as heat.
>> [ps]: BTW tidal forces are really nothing but gravitational
>> forces: differentiate the gravity force and you'll get the tidal
>> force. Didn't you know that? Or are you just trying to confuse
>> the issue?
>
> Tidal forces are so-named because they are distinguishable from
> gravitational forces, and have different properties. The one that is
> relevant here is that gravitational forces are central and tidal forces are
> not.
forces.
> Your point about differentiating is beyond my comprehension.
at the USNO? Did you forget what you then knew?
> Differentiate gravitational potential and you get gravitational force.
Differentiate gravitational potential and you get gravitational
get tidal force.
Gravitational potential is measured in Nm/kg, or Joules per kilogram.
The gravitational potential is proportional to the inverse of the
distance to the gravitating body.
Gravitational force, the derivative of gravitational potential, is
measured in N/kg, or Newtons per kilogram. Since 1 N = 1 kg m/s^2
this means N/kg also can be expressed as m/s^2. The gravitational
forcel is proportional to the inverse of the square of the distance
to the gravitating body.
Tidal force, the derivative of gravitational force, is measured in
N/kg m, or Newtons per kilogram per meter. Since 1 N = 1 kg m/s^2
this means N/kg m also can be expressed as 1/s^2. The tidal force
is proportional to the inverse of the cube of the distance to the
gravitating body.
> But no one would confuse potential and force.
> For example, the former affects clock rates, the latter does not.
> Surely you weren't arguing that a function and its derivative are
> equivalent! ??? So I have no idea what you were trying to argue. -|Tom|-
(except the sole case of f(x)=exp(x), where the derivative indeed
equals the function -- but that doesn't apply here).
But you seem to want to argue that a tidal force is a force. It isn't,
instead it's the derivative of a force. The popular concept of this
is that gravitation and tidal forces both are forces.
Where does such a misconception lead?
Well, let's compare an ocean with a human body (the latter consists
of some 75% of water): both are subject to the same gravitational
force from the Sun, therefore both follows the same orbit around the
Sun. OK?
Next, consider tidal forces: an ocean is subject to significant tides
due to the tidal forces. Likewise, the homan body too must be
subject to considerable tides, right? (this "argument" is often
brough up by astrologers as an "explanation" to why humans should be
affected by planets). OK? No, it's not OK: since tides aren't forces
but derivatives of forces, the size of the object subject to the
tides matter: even though there are significant tides in the oceans,
you won't find any noticeable tides in the human body, or in your
bathtub - these objects are just too small for that.
Again consider the relation potential - force - tides:
The gravitational potential - zero at infinite distance - is
proportional to the inverse of the distance to the gravitating body.
Derive something proportional to 1/x, and you'll get something proportional
to 1/x^2:
The gravitational force is proportional to the inverse of the square
of the distance to the gravitating body.
Derive something proportional to 1/x^2, and you'll get something proportional
to 1/x^3:
The tidal "force" is proportional to the inverse of the cube of the
distance to the gravitating body.
Do you understand better now why the tidal force is the derivative
of the gravitational force ???
Joe Fischer
: ... note followups ...
It seems odd you are scrounging for articles in
sci.physics.relativity and sending them to sci.physics. :-)
: pau...@saafNOSPAM.se (Paul Schlyter) writes:
: } [tvf]:
: } > Tidal forces and radiation pressure are examples of
: } > forces that have no such conservation. Tides arise from virtual
: } > particles, and nature apparently has no way to differentiate
: } > between a tidal force and a gravitational force. So why does it
: } > conserve momentum for the latter but not the former?
: }
: } When friction is involved, momentum isn't conserved - and
: } this is valid for both gravitational and tidal forces.
: In article <8fiics$pq4$1...@slb2.atl.mindspring.net>
: "Tom Van Flandern" <t...@mindspring.com> writes:
: > Of course. If we look at a whole, enclosed system, momentum is always
: >conserved because it cannot disappear or reappear from the universe.
:
: Since your second sentence is correct, why did you write "of course"
: in response to a statement that is in contradiction to it? Frictional
: forces dissipate kinetic energy, but they do not fail to conserve
: momentum. A totally inelastic collision is a good example.
Only in Euclidean space, and if gravity is present,
with Newtonian gravitation.
: >But our
: >discussion was about orbital angular momentum only. That can and does
: >change.
:
: Of course, but that is no excuse for reinforcing flawed statements
: such as the one above or not noting the status of angular momentum
: or momentum conservation as distinct from an arbitrary subset of them.
You must have liked it, you added sci.physics
as a followup. :-)
At a time when readers in sci.physics.relativity
are asking for a dictionary of terms and the models and
theories they are compatible with, involving Newton's
pet theory is not going to make things more clear.
The whole idea of "speed of gravity" is not
resolvable in the absence of proof of something propagating.
Joe Fischer
Jim Carr
... off-topic newsgroup snipped ...
Jim Carr (j...@dirac.scri.fsu.edu) wrote:
|
| ... note followups ...
In article <391d9242$1...@news.iglou.com>
grav...@iglou.com (Joe Fischer) writes:
>
> It seems odd you are scrounging for articles in
>sci.physics.relativity and sending them to sci.physics. :-)
Your smiley is noted and ignored. I read the article in sci.physics,
which was among the two lead newsgroups in the cross-post, and my
comments did not concern relativity theory -- hence the restricted
followups.
| } When friction is involved, momentum isn't conserved - and
| } this is valid for both gravitational and tidal forces.
|
| In article <8fiics$pq4$1...@slb2.atl.mindspring.net>
| "Tom Van Flandern" <t...@mindspring.com> writes:
| > Of course. If we look at a whole, enclosed system, momentum is always
| >conserved because it cannot disappear or reappear from the universe.
|
| Since your second sentence is correct, why did you write "of course"
| in response to a statement that is in contradiction to it? Frictional
| forces dissipate kinetic energy, but they do not fail to conserve
| momentum. A totally inelastic collision is a good example.
>Only in Euclidean space, and if gravity is present,
>with Newtonian gravitation.
False.
| >But our
| >discussion was about orbital angular momentum only. That can and does
| >change.
|
| Of course, but that is no excuse for reinforcing flawed statements
| such as the one above or not noting the status of angular momentum
| or momentum conservation as distinct from an arbitrary subset of them.
>You must have liked it, you added sci.physics
>as a followup. :-)
False. The TVF article was posted to sci.physics and sci.astro
as well as a newsgroup irrelevant to the point made here.
z@z
:: = Tom Van Flandern
:: Yes, I think electrostatic force variations certainly can be used to
:: send ftl signals, because their propagation speeds are ftl in forward time,
:: and therefore have no causality violations. This is fully in accord with,
:: and allowed by, Lorentzian relativity. Moreover, the Walker-Dual experiment
:: (previously cited) comes very close to demonstrating an actual electrostatic
:: signal sent ftl. -|Tom|-
:
: When do you plan to build an "FTL radio transmitter" based on
: electrostatic force variations? It ought to be much easier to do
: this than to build an "FTL gravity transmitter", don't you think so?
What kind of sense does it make to transmit information over
a few meters instantaneously? Electromagnetic radiation needs
10 nanoseconds for 3 meters. The big advantage of electromagnetic
radiation over instantaneous (i.e. nothing propagates) electrostatic
effects is the possibility to direct and redirect (e.g. by mirrors)
radiation.
Electrostatic forces however decrease in all directions with the
inverse distance square law.
Two quotes from Heinrich Hertz:
"The total force may be split up into the electrostatic part
and the electromagnetic part; there is no doubt that at shorter
distances the former, at greater distances the latter,
preponderates and settles the direction of the total force."
"Since the interferences undoubtedly change sign after 2.8 m in the
neighborhood of the primary oscillation, we might conclude that the
electrostatic force which here predominates is propagated with
infinite velocity."
http://www.deja.com/=dnc/getdoc.xp?AN=532021977
That most (or even all?) experiments, when interpreted directy, are
inconsistent with a propagation at c of electroststatic forces is
normally accepted. But a direct result of an experiment can almost
always be explained away by further assumptions.
: In your place I would be very eager to build such a device and prove
: to the world that I was right. I mean, if you succeed in becoming
: the first person to demonstrate transmission of messages FTL, you'll
: become one of the icons in the history of science. And you'd
: probably have no more problems getting funds for what you'd want
: to do. What about it, Tom - wouldn't this be something?
It has already been shown that electrostatic effects of constant
oscillations are in phase with the source. Logical reasoning is enough
to conclude, that the effects at a distance are also in phase with the
source if the signal is not constant but represents information.
So the experimental result of FTL transmission can only have an
impact if it will be "officially" recognized and published.
: I can only see one reason to hesitate trying to do this: fear
: of being wrong, and have this demonstrated to the world.
On the contrary, I do not exclude that the experiment has already been
performed but that its result is kept quiet, because it is almost
impossible to explain it by an ad-hoc-hypothesis within the orthodox
view.
Consistent logical reasoning clearly shows that the assumption of
electostatic forces propagating at the same speed as electromagnetic
radiation is refuted both on theoretical and experimental grounds.
Wolfgang Gottfried G.
Two of my previous posts of this thread:
http://www.deja.com/=dnc/getdoc.xp?AN=617250979
http://www.deja.com/=dnc/getdoc.xp?AN=617635057
Paul Schlyter
> : = Paul Schlyter
> :: = Tom Van Flandern
>
> :: Yes, I think electrostatic force variations certainly can be used to
> :: send ftl signals, because their propagation speeds are ftl in forward time,
> :: and therefore have no causality violations. This is fully in accord with,
> :: and allowed by, Lorentzian relativity. Moreover, the Walker-Dual experiment
> :: (previously cited) comes very close to demonstrating an actual electrostatic
> :: signal sent ftl. -|Tom|-
> :
> : When do you plan to build an "FTL radio transmitter" based on
> : electrostatic force variations? It ought to be much easier to do
> : this than to build an "FTL gravity transmitter", don't you think so?
>
> What kind of sense does it make to transmit information over
> a few meters instantaneously?
work. The time delay of a transmission at lightspeed over a few meters
is of course negligble, so there's very little practical application of
such an FTL transmitter, if it can be built.
> Electromagnetic radiation needs
> 10 nanoseconds for 3 meters. The big advantage of electromagnetic
> radiation over instantaneous (i.e. nothing propagates) electrostatic
> effects is the possibility to direct and redirect (e.g. by mirrors)
> radiation.
>
> Electrostatic forces however decrease in all directions with the
> inverse distance square law.
> : In your place I would be very eager to build such a device and prove
> : to the world that I was right. I mean, if you succeed in becoming
> : the first person to demonstrate transmission of messages FTL, you'll
> : become one of the icons in the history of science. And you'd
> : probably have no more problems getting funds for what you'd want
> : to do. What about it, Tom - wouldn't this be something?
>
> It has already been shown that electrostatic effects of constant
> oscillations are in phase with the source. Logical reasoning is enough
> to conclude, that the effects at a distance are also in phase with the
> source if the signal is not constant but represents information.
>
> So the experimental result of FTL transmission can only have an
> impact if it will be "officially" recognized and published.
actually can be transmitted FTL, and not merely that the "oscillations
are in phase" in some simple case.
> : I can only see one reason to hesitate trying to do this: fear
> : of being wrong, and have this demonstrated to the world.
>
> On the contrary, I do not exclude that the experiment has already been
> performed but that its result is kept quiet, because it is almost
> impossible to explain it by an ad-hoc-hypothesis within the orthodox
> view.
keep quiet about it this time, don't you think so?
> Consistent logical reasoning clearly shows that the assumption of
> electostatic forces propagating at the same speed as electromagnetic
> radiation is refuted both on theoretical and experimental grounds.
as massive as body B, then A also falls twice as fast as B (Aristotle).
However, the experiments by Galileo Galilei showed that the "consistent
logic" failed in this case.
If you're making a controversial claim in physics, and if you want to
be taken seriously, you cannot just refer to "consistent logic" or
"experiments already performed but kept secret" - you'll have to do
the experiment and have it published in a peer-reviewed journal!
Jim Carr
... note followups to the one newsgroup where this is topical ...
: = Paul Schlyter
:: = Tom Van Flandern
::
:: Yes, I think electrostatic force variations certainly can be used to
:: send ftl signals, because their propagation speeds are ftl in forward time,
:: and therefore have no causality violations. This is fully in accord with,
:: and allowed by, Lorentzian relativity. Moreover, the Walker-Dual experiment
:: (previously cited) comes very close to demonstrating an actual electrostatic
:: signal sent ftl. -|Tom|-
:
: When do you plan to build an "FTL radio transmitter" based on
: electrostatic force variations? It ought to be much easier to do
: this than to build an "FTL gravity transmitter", don't you think so?
In article <8flv9d$a8a$1...@pollux.ip-plus.net>
"z@z" <z...@z.lol.li> writes:
>
>What kind of sense does it make to transmit information over
>a few meters instantaneously?
What kind of sense does it make to even claim you can "transmit
information" with something that never varies?
>Electromagnetic radiation needs 10 nanoseconds for 3 meters.
He said "electrostatic". That doesn't need to go anywhere because
it has always been there. Always.
>Electrostatic forces however decrease in all directions with the
>inverse distance square law.
They also don't change with time.
srp
>
> Electrostatic forces however decrease in all directions with the
> inverse distance square law.
>
>
> "The total force may be split up into the electrostatic part
> and the electromagnetic part; there is no doubt that at shorter
> distances the former, at greater distances the latter,
> preponderates and settles the direction of the total force."
I wonder on what basis he could assert such a conclusion, considering
that magnetostatic interaction decreases in all directions with
the inverse distance cube law, which means that any electromagnetic
event will have the inverse cube effect dominate at short range
while at greater distances the inverse square effect is bound to
dominate, and very quickly at that.
André Michaud
Service de Recherche Pédagogique http://www.microtec.net/srp/
Bruce Sterling Woodcock
"Paul Schlyter" <pau...@saafNOSPAM.se> wrote in message
news:8fmanj$q1t$1...@merope.saaf.se...
> > :: = Tom Van Flandern
> >
> > :: Yes, I think electrostatic force variations certainly can be used
to
> > :: send ftl signals, because their propagation speeds are ftl in forward
time,
> > :: and therefore have no causality violations. This is fully in accord
with,
> > :: and allowed by, Lorentzian relativity. Moreover, the Walker-Dual
experiment
> > :: (previously cited) comes very close to demonstrating an actual
electrostatic
> > :: signal sent ftl. -|Tom|-
> > :
> > : When do you plan to build an "FTL radio transmitter" based on
> > : electrostatic force variations? It ought to be much easier to do
> > : this than to build an "FTL gravity transmitter", don't you think so?
> >
> > a few meters instantaneously?
>
> work. The time delay of a transmission at lightspeed over a few meters
> is of course negligble, so there's very little practical application of
> such an FTL transmitter, if it can be built.
I don't understand why you guys are still arguing. You do realize that
FTL transmission has been demonstrated, right? It's just controversial
if actual "information" can be transmitted arbitrarily or not. So far
trying to propogate "changes" in the field has been unable to exceed
lightspeed.
Bruce
Tom Van Flandern
>> [tvf]: Yes, I think electrostatic force variations certainly
>> can be used to send ftl signals, because their propagation
>> speeds are ftl in forward time, and therefore have no causality
>> violations. This is fully in accord with, and allowed by,
>> Lorentzian relativity. Moreover, the Walker-Dual experiment
>> (previously cited) comes very close to demonstrating an actual
>> electrostatic signal sent ftl.
> [gq]: If such transmission is demonstrated, you win, although
> since the principle of relativity would be violated, Lorentzian
> relativity might not be a very good term.
Lorentzian relativity is based on the principle of relativity, which was
much discussed in the late 19th century and was popularized by Poincare
about 1899. Neither the relativity principle nor the Lorentz transformations
were original to Einstein. Only reciprocity (i.e., the equivalence of all
inertial frames) was original in SR. And frame reciprocity just happens to
be the only aspect of SR that has no experimental support in any of the 11
independent tests bearing on SR.
> FTL signals would allow us to determine our absolute velocity.
We can determine our absolute velocity now, relative to the microwave
background rest frame. But the principle of relativity only insists that all
velocities are relative to something else. The microwave rest frame is
considered a preferred frame of convenience, not of necessity.
Exactly the same remark applies to Lorentzian relativity, wherein the
local gravity field plays the role of a preferred frame of convenience, but
not of necessity. You will be hard-pressed to find any objection to that
arrangement that does not also apply to SR and the microwave background
frame as well.
In short, there are no “absolute velocities” in LR. But there are frames
relative to which physics becomes simpler. The GPS system has already
strongly demonstrated the truth of that reality. The Earth-centered-inertial
(ECI) frame makes the physics of GPS so simple that, after a pre-launch
clock rate adjustment, relativity can be forgotten completely. By contrast,
using SR, the instantaneous co-moving inertial frames of the GPS satellites
and receivers all require unique clock corrections for each clock pair at
each moment of time!
> [gq]: I don't believe any such violation will be seen, myself.
> Because how do you believe Lorentzian relativity actually works,
> if there is no such limit?
That’s easy to explain. Nothing ever happens to space or time in LR.
Gravitational potential or motion relative to the local gravity field causes
clocks to slow their rates. This is the same type of slowing experienced by
a pendulum clock when the temperature increases -- an effect on clocks, but
not on time itself.
As the speed of light is approached, an electromagnetic clock’s rate
approaches zero. If the speed of light is exceeded, its rate may even
reverse and start backwards. It’s still a clock running backwards as time
moves forward, so no problems with causality can arise even in principle.
Exceeding the speed of light is likewise easy to achieve in principle.
Using electromagnetic forces or thrusts is analogous to using a propeller
plane to exceed the speed of sound -- it can’t be done without the aid of
some other force not limited by the speed of sound. Likewise, exceeding the
speed of light requires using a force not limited to the speed of light.
Gravity is an example of such a force.
> [gq]: My own view is that Lorentzian relativity proves that the
> fundamental particles of all matter must be massless, traveling
> at c. Nor do I see any need to invoke a fundamental arrow of
> time, since entropy can serve to explain it.
You might be pleasantly surprised to see how easily the universe can be
understood in classical physics terms once the universal speed limit is
lifted. For just a glimpse at how much simpler physics can become, look at
the first chapter or two of my book, “Dark Matter, Missing Planets and New
Comets” (North Atlantic Books, 2nd edition 1999, see reviews and other
information at <http://metaresearch.org>). -|Tom|-
Tom Van Flandern
> [lengthy discussion of tidal “forces” omitted]
To bring the discussion back on topic: The Earth’s gravitational force
on the Moon has a non-central component due to tidal friction. To the Moon,
the offset of the direction of that force is indistinguishable from the
offset of the direction of Earth’s gravitational force due to aberration. So
if gravitational aberration were to exist after all because gravity
propagates at lightspeed, but is cancelled by a velocity-dependent force
provided by nature to conserve angular momentum, then nature must also
cancel tidal friction. However, that is contrary to observations. But how
could the Moon possibly tell the difference? How could it know when to
ignore a non-central force component, and when to respond to it? -|Tom|-
Tom Van Flandern
>> [tvf]: electrostatic force variations certainly can be used to
>> send ftl signals, because their propagation speeds are ftl in
>> forward time ...
> jp]: Then I could build a ftl transmitter on my desk right here,
> with the equipment I have. And so could anyone else. It has not
> been shown. What in the world is your idea of 'electrostatic
> forces'?
When you say “build a transmitter”, I suspect you might be confusing
“electrostatic” with “electromagnetic”. In reality, it would be quite
challenging to create a field of positive or negative charge that could be
detected at a great distance, then modulate it in some way, and finally
measure its propagation speed.
The best design I know of is the Walker-Dual experiment, which is
described at <http://www.ifm.mavt.ethz.ch/research/exp-3.html>. That may
give you some idea of the technological hurdles involved. -|Tom|-
Tom Van Flandern
> [jj]: Why do you keep saying that retarded potential will
> produce a non-central force. According to the rules of calculus
> the acceleration got from the retarded potential has a component
> directed toward retarded position (that you might have in mind)
> but also one directed perpendicularly to that direction,
> parallel the movement of the source of potential ...
> So why are you neglecting this other component?
This is a good question. Think about the force of radiation pressure,
produced when, say, solar photons propagate to a balloon satellite and
produce a repulsive force. That force is directed exactly in line with the
light-time-retarded position of the Sun. There is no component perpendicular
to that direction of the type you describe. The same is true of the force
from impact of arrows, bowling balls, sound waves, etc. The direction of the
force is toward the position of the source retarded by the propagation time
from source to target. This applies to all types of force that propagate at
speeds up to and including the speed of light.
The only exceptions are electrostatic and gravitational forces. Why
should these be exceptions to the expectations dictated by simple geometry?
And where does that extra force perpendicular to the retarded direction
originate? The answer is that, for most of the 20th century, it was believed
that ftl propagation in forward time was impossible, and therefore that the
speed of propagation of electrostatic and gravitational forces must be
lightspeed. But that made the acceleration equations wrong because angular
momentum was continually added or subtracted. Not knowing how else to deal
with this circumstance, angular momentum conservation was invoked (because
observations said it was required), which mathematically created a
fictitious force along the target velocity vector that cancelled the
transverse acceleration caused by propagation delay (aberration). To this
day, there is no known physical justification for this angular momentum
conservation. But few have questioned it.
Now, in the year 2000, we know this whole, convoluted line of reasoning
was based on a wrong assumption -- that nothing could propagate ftl in
forward time. Lorentzian relativity (LR) allows that, and LR is
experimentally viable. If we reset to the time before SR was accepted, and
re-examine all the knowledge obtained subsequently, today we would simply
conclude that electrostatic and gravitational forces propagate ftl, thereby
explaining everything that needs explaining. No more twins or EPR paradoxes,
Copenhagen school, “no deep reality”, obstacles to unification and
quantization -- physics gets simple and orderly again. And that’s not all
bad. :-) -|Tom|-
JimJast
>The same is true of the force
>from impact of arrows, bowling balls, sound waves, etc. The direction of the
>force is toward the position of the source retarded by the propagation time
>from source to target.
[jj]
That's the mistake you are making.
What you said is not true. Arrow is a good example. Think about it as shot at
you from a passing car. If it were shot directly toward you, it would never hit
you. It would pass you because it has the component of the velocity equal to
the velocity of the car. To hit you it has to be shot into direction of the
point behind you (from the point of view of the car) and so if it hit you it
would point with its other end to the direction of the actual position of the
car, and not to the retarded position as you maintain it would. It is even
better visible if you were a moving target because then the arrow is moving in
frame "at rest" along its axis. You would have also an impression that the
arrow came from the actual, and not retarded position, becase you would see it
pointing at that direction after hitting you (being shot at the point in front
of you while you were moving).
Gerry Quinn
>ger...@indigo.ie (Gerry Quinn) writes:
>> FTL signals would allow us to determine our absolute velocity.
>
> We can determine our absolute velocity now, relative to the microwave
>background rest frame. But the principle of relativity only insists that all
>velocities are relative to something else. The microwave rest frame is
>considered a preferred frame of convenience, not of necessity.
>
And in LR it would be considered to be the most reasonable candidate for
the absolute frame, since it is in any case the only candidate that can
be agreed upon (at least in this part of the universe) unless the
principle of relativity is found to be violated in some way. However,
there is no direct argument I am aware of as to why the microwave
background should not itself have an absolute velocity. Maybe a
cosmological argument for this will be found sometime.
> Exactly the same remark applies to Lorentzian relativity, wherein the
>local gravity field plays the role of a preferred frame of convenience, but
>not of necessity. You will be hard-pressed to find any objection to that
>arrangement that does not also apply to SR and the microwave background
>frame as well.
>
> In short, there are no “absolute velocities” in LR. But there are frames
>relative to which physics becomes simpler. The GPS system has already
>strongly demonstrated the truth of that reality. The Earth-centered-inertial
>(ECI) frame makes the physics of GPS so simple that, after a pre-launch
>clock rate adjustment, relativity can be forgotten completely. By contrast,
>using SR, the instantaneous co-moving inertial frames of the GPS satellites
>and receivers all require unique clock corrections for each clock pair at
>each moment of time!
>
In LR there is a frame in which clocks run fastest. FTL communication
would allow us to determine this frame, which is the unique absolute
frame.
>> [gq]: I don't believe any such violation will be seen, myself.
>> Because how do you believe Lorentzian relativity actually works,
>> if there is no such limit?
>
> That’s easy to explain. Nothing ever happens to space or time in LR.
>Gravitational potential or motion relative to the local gravity field causes
>clocks to slow their rates. This is the same type of slowing experienced by
>a pendulum clock when the temperature increases -- an effect on clocks, but
>not on time itself.
>
> As the speed of light is approached, an electromagnetic clock’s rate
>approaches zero. If the speed of light is exceeded, its rate may even
>reverse and start backwards. It’s still a clock running backwards as time
>moves forward, so no problems with causality can arise even in principle.
>
Let's say the clock is a candle with stripes painted on it. As it
exceeds the speed of light it starts to grow longer. No problems with
causality, you say?
> Exceeding the speed of light is likewise easy to achieve in principle.
>Using electromagnetic forces or thrusts is analogous to using a propeller
>plane to exceed the speed of sound -- it can’t be done without the aid of
>some other force not limited by the speed of sound. Likewise, exceeding the
>speed of light requires using a force not limited to the speed of light.
>Gravity is an example of such a force.
>
Again, it seems to me that the existence of any force leading
to low-energy violations of the principle of relativity would be
incompatible with the observed universal obedience to this principle.
The absolute frame would be physically distinguishable, and this in turn
should lead to some observable effects on simple dynamic systems.
(Violations at very high energy are a different matter, we might see
those yet.)
- Gerry Quinn
>> [gq]: My own view is that Lorentzian relativity proves that the
>> fundamental particles of all matter must be massless, traveling
>> at c. Nor do I see any need to invoke a fundamental arrow of
>> time, since entropy can serve to explain it.
>
> You might be pleasantly surprised to see how easily the universe can be
>understood in classical physics terms once the universal speed limit is
>lifted. For just a glimpse at how much simpler physics can become, look at
>the first chapter or two of my book, “Dark Matter, Missing Planets and New
>Comets” (North Atlantic Books, 2nd edition 1999, see reviews and other
>information at <http://metaresearch.org>). -|Tom|-
Jan Panteltje
>
>>> [tvf]: electrostatic force variations certainly can be used to
>>> send ftl signals, because their propagation speeds are ftl in
>>> forward time ...
>
>> jp]: Then I could build a ftl transmitter on my desk right here,
>> with the equipment I have. And so could anyone else. It has not
>> been shown. What in the world is your idea of 'electrostatic
>> forces'?
>
> When you say “build a transmitter”, I suspect you might be confusing
>“electrostatic” with “electromagnetic”. In reality, it would be quite
>challenging to create a field of positive or negative charge that could be
>detected at a great distance, then modulate it in some way, and finally
>measure its propagation speed.
and one way light speed measurements to be done in the lab.
>
> The best design I know of is the Walker-Dual experiment, which is
>described at <http://www.ifm.mavt.ethz.ch/research/exp-3.html>. That may
>give you some idea of the technological hurdles involved. -|Tom|-
>
Tom, that is about GRAVITY NOT about electrostatic charge (I looked it up).
The link is also very old, you published it before, and there are no results.
Aleksandr Timofeev
>
> To bring the discussion back on topic: The Earth’s gravitational
> force on the Moon has a non-central component due to tidal friction.
> To the Moon, the offset of the direction of that force is
> indistinguishable from the offset of the direction of Earth’s
> gravitational force due to aberration. So if gravitational aberration
> were to exist after all because gravity propagates at lightspeed,
> but is cancelled by a velocity-dependent force provided by nature to
> conserve angular momentum, then nature must also cancel tidal
> friction. However, that is contrary to observations. But how could
> the Moon possibly tell the difference? How could it know when to
> ignore a non-central force component, and when to respond to it?
From my point of view in the given controversy of a property of
stationary and non-stationary processes and systems mix up in the
implicit form.
For clear understanding and overcoming of these problems it is
necessary to have the answers to the following problems:
1. What can you tell about properties of a stationary physical
dynamic systems?
2. What is a stationary process?
3. What is a stationary (time-independent) motion in a physical
system?
4. What is a unsettled (time-dependent) motion in a physical
system?
5. Can you indicate the elementary examples of a stationary
physical systems, inside which there is stationary
(time-independent) dynamic process?
6. What renders influence in a stationary physical systems
a transfer rate of energy on resultant motion in a system?
---
Aleksandr Timofeev
http://www.deja.com/=dnc/getdoc.xp?AN=621526710
http://www.friends-partners.org/~russeds/unknown/astrochem/
Sent via Deja.com http://www.deja.com/
Before you buy.
Asimov
Re: How fast is gravity? (14 May 00 23:51:16)
"VF> You might be pleasantly surprised to see how easily the universe
"VF> can be understood in classical physics terms once the universal speed
"VF> limit is lifted.
I'm sympathetic to this notion (and for trying to sell your book) but
what concrete proof presenty exists of your assertions? It really always
boils down to putting things in concrete... <g>
... 299,792,458 km/sec, eh? OK, what's the speed of DARK?
--
| Return Address: asi...@mnetREMOVE-THIS.axess.com
| Standard disclaimer: The views of this user are strictly her/his own.
| Signature auto-added at gateway.
Paul Schlyter
Bruce Sterling Woodcock <sirb...@ix.netcom.com> wrote:
> "Paul Schlyter" <pau...@saafNOSPAM.se> wrote in message
> news:8fmanj$q1t$1...@merope.saaf.se...
>> In article <8flv9d$a8a$1...@pollux.ip-plus.net>, z@z <z...@z.lol.li> wrote:
>>
>>>: = Paul Schlyter
>>>:
>>>: electrostatic force variations? It ought to be much easier to do
>>>: this than to build an "FTL gravity transmitter", don't you think so?
>>>
>>> What kind of sense does it make to transmit information over
>>> a few meters instantaneously?
>>
>> In this case it's just to demonstrate that it works -- or that it doesn't
>> work. The time delay of a transmission at lightspeed over a few meters
>> is of course negligble, so there's very little practical application of
>> such an FTL transmitter, if it can be built.
>
> I don't understand why you guys are still arguing. You do realize that
> FTL transmission has been demonstrated, right?
kept secret"? Well, if you want to demonstrate something, you cannot keep
it secret. Or are you referring to some experiment which actually has been
documented? If so, please name the place and date of the experiment, the
name of the experimenter(s), the journal and issue where it's been published,
and the names, dates and places of other experimenters who have verified
this experiment.
> It's just controversial if actual "information" can be transmitted
> arbitrarily or not.
> So far trying to propogate "changes" in the field has been unable to exceed
> lightspeed.
And the discussion is about this: whether actual information can be transmitted
FTL or not - through gravity, or by electrostatic fields, or in some other way.
Relativity says it cannot be done - Tom van Flandern says it can be done, if we
can overcome some practical difficulties.
Paul Schlyter
differential of the gravity force?
In the future, please remember that if you differentiate something proportional
to 1/X^2, you'll end up with something proportional to 1/X^3. And, as you
already know, the gravity force is proportional to 1/r^2 while the tidal "force"
is proportional to 1/r^3....
> To bring the discussion back on topic: The Earth's gravitational force
> on the Moon has a non-central component due to tidal friction. To the Moon,
> the offset of the direction of that force is indistinguishable from the
> offset of the direction of Earth's gravitational force due to aberration.
> So if gravitational aberration were to exist after all because gravity
> propagates at lightspeed, but is cancelled by a velocity-dependent force
> provided by nature to conserve angular momentum, then nature must also
> cancel tidal friction.
1. Friction and gravitation aren't the same thing.
2. The tidal friction actually moves gravitating matter (mostly the oceans,
but also the Earht's crust a bit) to some other place compared to where it
would have been in the absence of friction. If matter is redistributed, this
surely affects the gravitational field around the matter, right? Now, the tides
work on a time scale of hours, while light propagates from the Earth to the Moon
in about 1.3 seconds. And the amount of the lunar secular acceleration, due
to the tides, is still not known with particularly high precision -- perhaps
to within 10% or so, but not more. I *don't* think one can, with such imprecise
knowledge of the secular acceleration, tell whether the tidal component of the
Earth-Moon gravitation acts towards the acutal or the aberrated position of
the Earth's tidal bulge.
> However, that is contrary to observations. But how could the Moon possibly
> tell the difference? How could it know when to ignore a non-central force
> component, and when to respond to it?
while gravity propagating at c doesn't. But the Moon doesn't really need
to "know" this, since it's all in the gravitational field surrounding the
Earth: the Moon just responds to this field.
Once again, the answers to your question are in the field equations of GR.
Yes, it requires some work to understand these properly, however if you really
do want to know, there's no shortcut: you'll have to work your way through
these equations.
And if you don't want to know -- why are you asking these questions?
Steve Carlip
> In article <8f9r4g$4v9$1...@mark.ucdavis.edu>,
> Steve Carlip <car...@dirac.ucdavis.edu> wrote:
>> Not quite, but close. The power of emitted gravitational radiation
>> depends on the third time derivative of the mass quadrupole
>> moment. For point particles, the quadrupole moment looks like
>> a sum of terms of the form mr^2. So its third derivative has one
>> piece that looks like jerk, and another that looks like velocity times
>> acceleration.
[...]
> Then gravitational radiation power is proportional to D^3(mr^2),
which =s 6m D(r) D^2(r) + 2 m r D^3(r).
> This is the velocity times acceleration term and the jerk term you
> mention. The problem is the r in the jerk term. It seems to imply
> that radiated power increases with distance, which doesn't seem
> right.
First, r here is distance to the center of mass of the radiating system,
not to the observer. So the factor of r isn't so unreasonable. Second,
the relevant quadrupole moment isn't really quite mr^2. You actually
have a tensor with a term Q_{ij} = m r_i r_j for each particle in the
system (r_i are the three coordinates of the particle relative to the
center of mass). To get the power emitted, you have to first sum over
particles, then subtract a multiple of the identity to make Q_{ij}
traceless, then take the third derivative, then take the square as a
matrix, then take the trace of the result.
If you want to see how this is done for some simple examples (two
masses on a spring and a binary star system), you might look at
chapter 9 of Schutz's _A First Course in General Relativity_. (You
don't actually need to know much GR to follow the computations of
radiated power.)
Steve Carlip
z@z
:: = Wolfgang G. in http://www.deja.com/=dnc/getdoc.xp?AN=623203938
:: So the experimental result of FTL transmission can only have an
:: impact if it will be "officially" recognized and published.
:
: Well, that would be the purpose of such an experiment: show that information
: actually can be transmitted FTL, and not merely that the "oscillations
: are in phase" in some simple case.
There are two possibilities: either the electrostatic effects of constant
oscillations are everywere (more or less) in phase with the source or
they are not. Both electomagnetic radiation (propagating at c) and wire
waves (propagating at around 0.66 c) are not everywhere in phase with the
source. If such a source oscillates at 10^8 Hertz, then the wire waves
are only at distances 2m, 4m, 6m, ... and electromagnetic radiation at
distances 3m, 6m, 9m, ... in phase with the source.
Now let us suppose that the electostatic actions at a distance of such
constant oscillations are actually EVERYWHERE in phase with their source
and nothing at all can be detected propagating at c.
Without the introduction of an ad-hoc-hypothesis having nothing to do
with Maxwell's equations, we must conclude from the experimental results
concerning constant signals that also variable signals are transmitted
instantaneously.
If electrostatic effects actually propagated at c as officially assumed,
then the action of the charge of the oscillating source ( ) would propagate
like e.m. radiation.
( ) 1) propagation at c
0 (+)
(-) +
1 (+) - +
(-) + - +
2 (+) - + - +
Such an outcome is excluded by the experiments which are in agreement
with instantaneous effects:
( ) 2) instantaneous effects
0 (+) + + + + + +
(-) - - - - - -
1 (+) + + + + + +
(-) - - - - - -
2 (+) + + + + + +
The introduction of the hypothesis that no information can be transmitted
faster than light leads to a rather strange outcome.
0 (+) 3) "instantaneous effects" propagating at c
(-) -
1 (+) + +
(-) - - -
2 (+) + + + +
What does happen if we emit after two normal cycles an inverted cycle?
0 (+)
(-) -
1 (+) + +
(-) - - -
2 (+) + + + +
(+) ? ? ? ? ?
3 (-) ? ? ? ? ? ?
:: Consistent logical reasoning clearly shows that the assumption of
:: electostatic forces propagating at the same speed as electromagnetic
:: radiation is refuted both on theoretical and experimental grounds.
: If you're making a controversial claim in physics, and if you want to
: be taken seriously, you cannot just refer to "consistent logic" or
: "experiments already performed but kept secret" - you'll have to do
: the experiment and have it published in a peer-reviewed journal!
The majority of the so-called "experimental facts" are based on MUCH MUCH
more questionable "logical reasonings" (and ad-hoc-hypotheses) than the
experimental fact of instantaneous actions at a distance allowing FTL
transmission of information.
Anyway, such an experiment is certainly not difficult to do, at least if
interference is used in order to determine time differences of signals
propagating both as electrostatic forces and in wires. Does anybody know
experimentalists who are able and willing to perform such an experiment
with signals containing information?
Wolfgang Gottfried G.
Simple propagation speed (thought)experiment:
http://www.deja.com/=dnc/getdoc.xp?AN=614676790
http://www.deja.com/=dnc/getdoc.xp?AN=616067444
Paul Schlyter
> : = Paul Schlyter
> :: = Wolfgang G. in http://www.deja.com/=dnc/getdoc.xp?AN=623203938
>
> :: So the experimental result of FTL transmission can only have an
> :: impact if it will be "officially" recognized and published.
> :
> : Well, that would be the purpose of such an experiment: show that information
> : actually can be transmitted FTL, and not merely that the "oscillations
> : are in phase" in some simple case.
>
> There are two possibilities: either the electrostatic effects of constant
> oscillations are everywere (more or less) in phase with the source or
> they are not.
> : If you're making a controversial claim in physics, and if you want to
> : be taken seriously, you cannot just refer to "consistent logic" or
> : "experiments already performed but kept secret" - you'll have to do
> : the experiment and have it published in a peer-reviewed journal!
>
> The majority of the so-called "experimental facts" are based on MUCH MUCH
> more questionable "logical reasonings" (and ad-hoc-hypotheses) than the
> experimental fact of instantaneous actions at a distance allowing FTL
> transmission of information.
>
> Anyway, such an experiment is certainly not difficult to do,
> at least if interference is used in order to determine time differences
> of signals propagating both as electrostatic forces and in wires. Does
> anybody know experimentalists who are able and willing to perform such
> an experiment with signals containing information?
very willing to do such an experiment: if Tom is right, the
experiment will succeed. The only reason to not want to do this
experiment is to try to avoid the embarassment of being wrong.
Paul Stowe
writes:
>In article <8frqd5$rt4$1...@pollux.ip-plus.net>, z@z <z...@z.lol.li> wrote:
>
>> : = Paul Schlyter
>> :: = Wolfgang G. in http://www.deja.com/=dnc/getdoc.xp?AN=623203938
>>
>> :: So the experimental result of FTL transmission can only have an
>> :: impact if it will be "officially" recognized and published.
>> :
>> : Well, that would be the purpose of such an experiment: show that
>> : information actually can be transmitted FTL, and not merely that
>> : the "oscillations are in phase" in some simple case.
>>
>> There are two possibilities: either the electrostatic effects of
>> constant oscillations are everywere (more or less) in phase with
>> the source or they are not.
>
>[ snip ]
velocity of FTL signals, wasn't it? If so, see "Faster than Light"
Scientific American August 1993 starting on page 52.
Paul Stowe
Jan Panteltje
>:: = Wolfgang G. in http://www.deja.com/=dnc/getdoc.xp?AN=623203938
>
>:: So the experimental result of FTL transmission can only have an
>:: impact if it will be "officially" recognized and published.
>:
>: Well, that would be the purpose of such an experiment: show that information
>: actually can be transmitted FTL, and not merely that the "oscillations
>: are in phase" in some simple case.
>
>There are two possibilities: either the electrostatic effects of constant
>oscillations are everywere (more or less) in phase with the source or
>: be taken seriously, you cannot just refer to "consistent logic" or
>: "experiments already performed but kept secret" - you'll have to do
>: the experiment and have it published in a peer-reviewed journal!
>
>The majority of the so-called "experimental facts" are based on MUCH MUCH
>more questionable "logical reasonings" (and ad-hoc-hypotheses) than the
>experimental fact of instantaneous actions at a distance allowing FTL
>transmission of information.
>
>interference is used in order to determine time differences of signals
>propagating both as electrostatic forces and in wires. Does anybody know
>experimentalists who are able and willing to perform such an experiment
>with signals containing information?
>
>
>
>
>Simple propagation speed (thought)experiment:
>http://www.deja.com/=dnc/getdoc.xp?AN=614676790
>http://www.deja.com/=dnc/getdoc.xp?AN=616067444
>
How / what does your experiment look like.
I still do not have a clue about that.
Jan
Tom Van Flandern
>> [tvf]: it would be quite challenging to create a field of
>> positive or negative charge that could be detected at a great
>> distance, then modulate it in some way, and finally measure its
>> propagation speed.
> [jp]: Even if done at a short distance it would allow 'syncing
> clocks' and one way light speed measurements to be done in the
> lab.
The shorter the distance, the shorter the modulation wavelength must be
so that each cycle can be timed with the necessary precision. The speed of
light, for example, is a foot per nanosecond.
>> [tvf]: The best design I know of is the Walker-Dual experiment
> [jp]: that is about GRAVITY NOT about electrostatic charge ...
> The link is also very old, you published it before, and there
> are no results.
The preliminary results were reported at a 1997 meeting, with abstract
by W.D. Walker and J. Dual published in "Superluminal propagation speed of
longitudinally oscillating electrical fields", abstract #72 in: "Causality
and Locality in Modern Physics and Astronomy: Open Questions and Possible
Solutions", ed. S. Jeffers, York University, North York, 1997. The results
were in-phase ftl signals. But given the importance of these results, the
reviewers thought the systematic errors needed better controls. The last I
heard, the experimental design was being modified to provide those controls.
Whatever these experimenters might find should be of enormous interest
to all physicists -- whether they find signals propagating ftl, or have the
first experimental detection of an electric or gravitational signal
propagating at lightspeed or less. It is unfortunate that their preliminary
results have not been more widely published purely because they happened to
see less signal propagation delay than lightspeed propagation would allow.
In that connection, the theoretical paper on LANL is still of considerable
interest at <xxx.lanl.gov/abs/gr-qc/9706082>.
Of course, the basic principle of detecting field variations from an
oscillating source is the same for fields from mass or charge. -|Tom|-
Tom Van Flandern
>> [tvf]: The microwave rest frame is considered a preferred frame
>> of convenience, not of necessity.
> [gq]: And in LR it would be considered to be the most reasonable
> candidate for the absolute frame, since it is in any case the
> only candidate that can be agreed upon (at least in this part of
> the universe) unless the principle of relativity is found to be
> violated in some way.
That is very much in line with 19th century thinking about the nature of
the “aether”. Physics has come a long way since then. We now know that every
local gravity field plays the role of a local “preferred frame” in
Lorentzian relativity (LR). This is an observational result. The best way
proposed so far to understand it theoretically is to conclude that the
“light-carrying medium” is not impervious to gravity, but in fact does
respond to gravity and becomes more concentrated (denser) near large masses.
That requires that light waves propagating through this medium will
experience refraction effects because of the density changes. It so happens
that these predicted refraction effects are exactly the observed
light-bending, gravitational redshift, and radar time delay effects, as
Eddington already showed in his 1920 book (previously cited).
The principle of relativity merely states that all motion is relative.
That remains true when the standard for rest is the local gravity field. LR
uses the principle of relativity. It does not violate it.
> [gq]: In LR there is a frame in which clocks run fastest. FTL
> communication would allow us to determine this frame, which is
> the unique absolute frame.
What is the frame where gravitational potential goes to zero? Or what is
the absolute frame for measuring the speed of sound waves? If your answer
for the latter is “the local standard of rest”, note that it is different at
every latitude on Earth. And as every pilot who has flown the jet stream
knows, “local rest” can have a high speed relative to “neighboring rest”.
LR always has a local frame in which clocks run fastest. But it has no
such universal frame. Even the “microwave background” has been proposed to
be a local intergalactic “fog” by proponents of alternatives to the Big
Bang. Some observational evidence supports that possibility, and none
refutes it. Given that the microwave frame is not suitable, what would you
then propose for your “universal standard of rest”?
>> [tvf]: As the speed of light is approached, an electromagnetic
>> clock’s rate approaches zero. If the speed of light is
>> exceeded, its rate may even reverse and start backwards. It’s
>> still a clock running backwards as time moves forward, so no
>> problems with causality can arise even in principle.
> [gq]: Let's say the clock is a candle with stripes painted on
> it. As it exceeds the speed of light it starts to grow longer.
> No problems with causality, you say?
No, that’s an SR prediction, because time itself reverses direction in
SR. In LR, nothing happens to time, so the candle simply burns out. The only
reason an E-M-based clock reverses in LR is because the propagation of
electrons slows as the effective density of the medium increases. Electron
propagation would cease at lightspeed. And electron propagation could (in
principle) reverse if the clock went faster than lightspeed. But these
effects take place in forward time advancing at a uniform rate for all
frames. -|Tom|-
Tom Van Flandern
>> [tvf] The same is true of the force from impact of arrows,
>> bowling balls, sound waves, etc. The direction of the
>> force is toward the position of the source retarded by the
>> propagation time from source to target.
> [jj]: What you said is not true. Arrow is a good example. Think
> about it as shot at you from a passing car. If it were shot
> directly toward you, it would never hit you. It would pass you
> because it has the component of the velocity equal to the
> velocity of the car.
Remember, there is no such thing as “absolute motion”. It’s all
relative. Only two frames matter here, the frame of the source of the arrow,
and the frame of its target. The source considers itself at rest and only
the target as moving, and the arrow must be fired in a direction that leads
the target because of arrow propagation delay.
The target considers itself at rest and the source moving, and therefore
sees the arrow approaching from the retarded position of the source, not its
current position. The angle between the two directions is called
“aberration” and is the same as the “lead angle” in the source frame.
> [jj]: It is even better visible if you were a moving target
> because then the arrow is moving in frame "at rest" along its
> axis. You would have also an impression that the arrow came from
> the actual, and not retarded position, because you would see it
> pointing at that direction after hitting you (being shot at the
> point in front of you while you were moving).
Consider the archer’s frame, which we will later identify with the Sun.
Now add a passing train as the target, which we will later identify with the
Earth. Note the path of the arrow shot from the archer’s bow as it passes
through an open window on the near side of the train and out another window
on the far side.
First, we can neglect any sideways speed shared by the source and
target, such as the solar system’s motion around the galaxy. All motion is
relative, and the arrow’s path can be described completely in terms of the
relative speeds of train, archer and arrow.
From the archer’s rest frame, the arrow always moves radially away from
the archer. It never curves or changes direction. Yet the archer sees it fly
through a forward window on the passing train, and exit a more rearward
window, because the train moved while the arrow transited the cabin.
From the train’s perspective, the train is at rest and the archer is
passing by. The arrow’s path is always linear, coming from the direction of
the archer when he shot the arrow (his “retarded” position), and continuing
along the same straight line from a forward window on one side to a rearward
window on the other side of the cabin.
By the time the arrow transits the cabin, the archer has appeared to
move on as seen from the train, and is no longer on the line of the arrow’s
flight. Moreover, if the arrow were to strike the cabin, part of its
momentum would go toward reducing the relative passing speed between train
and archer.
This example is used to illustrate the concepts of “propagation delay”
and “aberration”, and their equivalence. The only other aspect to this worth
mentioning is that, from the train’s perspective, a snapshot would show the
orientation of the arrow to be still in line with the present location of
the archer and not in-line with the arrow’s own motion. That is because the
relative speed of train and archer affects the arrow’s flight path, but not
its orientation.
Applying this to Sun and Earth, since the orientation of gravitons is
irrelevant, we see that gravitational force from the Sun must tend to
increase the relative speed between Earth and Sun, just as the arrow would
decrease it. This is only because gravity is attractive, whereas arrows are
repulsive. The direction of the momentum transfer is always necessarily
toward the retarded position of the source.
So if gravity propagated at the speed of light, gravity would change the
Earth’s mean orbital velocity, just as solar radiation pressure changes it
for dust particles or balloon satellites. -|Tom|-
Tom Van Flandern
> what concrete proof presently exists of your assertions?
I try not to make assertions, but only to draw conclusions from
observations, experiments, and deductive reasoning. But sometimes I don’t
repeat enough of the prior discussion and references, so some conclusions
might appear to be assertions.
Regarding the speed of gravity, my Physics Letters A paper summarizes
all six experiments that have anything to contribute to our knowledge of
that matter, and all six imply gravity speeds strongly ftl.
Regarding the possibility of ftl propagation in principle, my GPS paper
tabulates all 11 independent experiments that test any aspect of SR, and
concludes that none of them distinguishes SR from LR. The only difference
between SR and LR is in frame reciprocity. No experiment demonstrates SR’s
frame reciprocity. Without frame reciprocity, SR becomes LR, and the proof
that nothing can propagate ftl in forward time ceases to exist.
Do you wish me to repeat either of these citations? Do you see an error
in either paper? Are these the “assertions” you were asking about? -|Tom|-
Tom Van Flandern
> [ps]: the discussion is about this: whether actual information
> can be transmitted FTL or not - through gravity, or by
> electrostatic fields, or in some other way. Relativity says it
> cannot be done - Tom van Flandern says it can be done, if we can
> overcome some practical difficulties.
Correction. Special relativity (SR) says it cannot be done. The other
relativistic theory of motion, Lorentzian relativity (LR), says it can be
done. Hundreds of physicists and several new journals have been saying that
for several years now. While I appreciate the attribution to me, it is
undeserved.
>> [tvf]: To bring the discussion back on topic: The Earth's
>> gravitational force on the Moon has a non-central component due
>> to tidal friction. To the Moon, the offset of the direction of
>> that force is indistinguishable from the offset of the
>> direction of Earth's gravitational force due to aberration.
> [ps]: Why? Just because you say so?
I said this because, to the Moon, both these forces manifest themselves
as 3-space accelerations of the Moon in a direction offset from the radial
to the Earth’s center of mass. I thought I was making a logical deduction
from the cited observational and experimental facts. If you disagree, just
cite some manifestation distinguishing the two forces that is available to
the Moon so it can choose to ignore aberration but respond to the tidal
component of Earth’s gravity.
I really don’t see how the Moon could possibly tell the difference, so I
posed this as a reasoned conclusion. If you do see how the Moon can
distinguish the two, just say so, and if you have a physically reasonable
mechanism, that blows my conclusion away.
>> [tvf]: So if gravitational aberration were to exist after all
>> because gravity propagates at lightspeed, but is cancelled by a
>> velocity-dependent force provided by nature to conserve angular
>> momentum, then nature must also cancel tidal friction.
> [ps]: Why? Just because you say so?
This also was the conclusion line of a logical syllogism. The only way
to show such a conclusion wrong is to show that one of its premises is
erroneous or that the reasoning is invalid.
Is the claim I just made true because I say so? No, it’s true because
those are the rules of logical reasoning. I trust you had a course in logic
in college.
So the premises of my last few syllogisms are: (1) The tidal component
of Earth’s gravity produces a non-central force component that accelerates
the Moon in a transverse direction because it is non-central. (2)
Propagation delay produces a non-central force component to ordinary gravity
that should also cause the Moon to accelerate in the transverse direction
because it is non-central, but does not. Therefore, something must
distinguish these two cases because the Moon responds differently to each.
According to relativists in this discussion, GR requires that the Moon
conserve orbital angular momentum when gravitational forces act. This
requirement creates a velocity-dependent counter-force that cancels the
effect of propagation delay, making the ordinary gravitational force of
Earth on Moon pretty closely central.
My objections are: (A) If this mythical counter-force existed, it would
cancel the tidal component of gravitational force too, because there is no
way the Moon could tell which was which. (The Moon simply receives
instructions to accelerate in some direction, central or non-central.) (B)
This mythical counter-force is a deus ex machina.
My explanation for why the two gravitational forces on the Moon do not
behave the same is that the ordinary gravitational force is actually central
because its propagation speed has no detectable delay. This explanation
overcomes objections (A) and (B), and introduces no new objections --
except, apparently, that people have to adjust their thinking about what GR
really means for physics.
> [ps]: 1. Friction and gravitation aren't the same thing.
Agreed. But the frictional component of Earth’s gravitational pull on
the Moon is gravitation.
> [ps]: I *don't* think one can, with such imprecise knowledge of
> the secular acceleration, tell whether the tidal component of
> the Earth-Moon gravitation acts towards the actual or the
> aberrated position of the Earth's tidal bulge.
The “aberrated position of the Earth’s bulge” did not enter this
discussion. I was comparing two forces: (1) The tidal component of Earth’s
gravitational force on the Moon manifests itself as a non-central
gravitational force acting on the Moon. (2) The Earth’s ordinary gravity
acting on the Moon likewise manifests itself as a non-central gravitational
force if it has aberration.
Both of these forces appear to the Moon as non-central forces that
potentially induce the Moon to spiral outward in its orbit. If we had only
the Moon to go by, you are right that we couldn’t tell yet if part of its
secular acceleration were due to aberration and part to tides. But GR makes
a specific claim that gravitational aberration is cancelled to conserve
orbital angular momentum.
I dispute that claim, and raised the Moon as a counter-example. (This is
actually Dennis McCarthy’s clever example.) If there were a mechanism in
nature to conserve angular momentum, then how can the Moon know to respond
to one type of non-central gravitational force (the tidal one), but ignore
the other type of non-central gravitational force (the aberrated one)? Why
does it enforce orbital angular momentum conservation in one case, but not
in the other? How can it possibly know the difference so it can behave
differently in the two cases?
> [ps]: The Moon "knows" this because the tides redistribute
> matter in the Earth, while gravity propagating at c doesn't.
> But the Moon doesn't really need to "know" this, since it's all
> in the gravitational field surrounding the Earth: the Moon just
> responds to this field.
Here we approach the heart of the matter. In mathematics, one can simply
say “orbital angular momentum is conserved in this case, and not in that
case”, and it is so! No physical reasonability is required. But in physics,
a physical reason is required. Real bodies don’t obey field equations, they
respond to forces. If two forces are otherwise indistinguishable, it is not
physically reasonable to write equations that require the Moon to respond to
them in completely different ways. -|Tom|-
Joe Fischer
: Correction. Special relativity (SR) says it cannot be done. The other
: relativistic theory of motion, Lorentzian relativity (LR), says it can be
: done. Hundreds of physicists and several new journals have been saying that
: for several years now. While I appreciate the attribution to me, it is
: undeserved.
Can you provide a reference for Lorentz Ether Theory
being called "relativity theory" in any textbook, or is this
just some kind of delusion?
If a medium pervading space had anything to do
with physics, it is unlikely that relativity would be
what it is today, "space" would be like a checkerboard.
Joe Fischer
Jan Panteltje
>
>
>Tom Van Flandern - Washington, DC - <http://metaresearch.org>
>Meta Research fosters astronomy research on ideas not otherwise
>supported solely because they conflict with mainstream theories
>
>
>
I will start by looking up the preprint.
More later.
Thank you for the exaustive responce.
Sometimes I do not know what to think of all this.
Also I would like to hear Mr Carlips opinion.
Funny, do not even know what an electron really is...
Jan
Chris Hillman
On Wed, 17 May 2000, Tom Van Flandern wrote:
> I try not to make assertions, but only to draw conclusions from
> observations, experiments, and deductive reasoning. But sometimes I
> don’t repeat enough of the prior discussion and references, so some
> conclusions might appear to be assertions.
Actually, -I- think the biggest problem with this approach is that TVF
forgot to learn gtr before he started making claims about what he calls
"gtr" which make him look really silly!
http://www.math.washington.edu/Relativity/reading.html
> Regarding the speed of gravity, my Physics Letters A paper summarizes
> all six experiments that have anything to contribute to our knowledge of
> that matter, and all six imply gravity speeds strongly ftl.
Repeating that ten million times still won't make it true :-/
http://xxx.lanl.gov/abs/gr-qc/990908
http://www.math.washington.edu/~hillman/PUB/debate
> Do you wish me to repeat either of these citations? Do you see an
> error in either paper?
Speaking for myself, I'd say that TVF's claims are either wrong, or "not
even wrong". In recent posts he seems to be sticking to the latter
category :-(
Chris Hillman
Home Page: http://www.math.washington.edu/~hillman/personal.html
Chris Hillman
On Wed, 17 May 2000, Tom Van Flandern wrote:
> The principle of relativity merely states that all motion is
> relative.
Funny... everyone else seems to think it means covariance wrt the Lorentz
group (at the level of tangent spaces, in the context of gtr and more
complicated relativistic gravitation theories).
> That remains true when the standard for rest is the local gravity
> field.
I liked the bit about sending signals FTL using "force variations" in an
-electrostatic- field...
Anyway, even bystanders who don't have -any- mathematical or physical
background have probably noticed the same thing I have: I've been reading
and posting here for several years, and I haven't previously seen -any-
concensus, until now, when people who seemingly can't agree on anything
else (like Gerry and I) seem to agree that TVF is talking marlarkey :-/
Actually, it -is- kind of amusing to watch TVF in action: he's sort of a
master of the wild and wacky mathematical -faux pas-. I think he's the
Gracie Allen of physics :-)
(Gracie Allen played a not very bright but endearing character in a very
early TV series [B. C., IIRC!] who never realizes how utterly bizaire her
every utterance sounds to ordinary mortals.)
Chris Hillman
On Wed, 17 May 2000, Tom Van Flandern wrote:
> Hundreds of physicists and several new journals have been saying that
[FTL communication?]
> for several years now.
So, what, ABC polled the membership of the APS? "One out of five
physicists say chlorox gets your clothes cleaner than clean!" :-)
Would one of those "new journals" be Galilean Electrodynamics? :-/ And do
"journals" say things? Like, "Phys. Lett A" calls a press conference, and
there stands their press spokesperson, it cannot do otherwise, reading a
carefully worded statement of disinformation, and then deflecting tough
questions from angry reporters who sense that someone is trying to mislead
them? :-)
> This also was the conclusion line of a logical syllogism. The only
> way to show such a conclusion wrong is to show that one of its
> premises is erroneous or that the reasoning is invalid.
Green is red, and red is blue, therefore green is--- blue! :-)
Anyone can dress up nonsense to look like "logical reasoning", but nobody
here seems to be fooled into thinking that it amounts to a mound of
elephant doo, which I have to admit I found a bit surprising... shame on
me! :-/
Interesting that it is probably the very fact that TVF abjures mathematics
in his posts which has made it so easy for everyone here (apparently) to
see how silly his "reasoning" is :-) If he dressed it up in impressive
sounding mathematical language, he'd probably be taken more seriously by
at least some people without much mathematical background :-/
Bill Nelson
: Remember, there is no such thing as "absolute motion". It's all
: relative. Only two frames matter here, the frame of the source of the arrow,
: and the frame of its target. The source considers itself at rest and only
: the target as moving, and the arrow must be fired in a direction that leads
: the target because of arrow propagation delay.
... rest deleted ..
All of this is immaterial - as it assumes that gravity acts like a single
arrow.
A more realistic model would be an infinite number of archers shooting an
infinite number of arrows at the moving target. In other words, there
would be arrows at the target all the time. It doesn't matter if they
are moving 1 inch per year or 10 times the speed of light.
To the target (Earth), there is this fixed bunch of archers (Sun) shooting
immense numbers of arrows at it.
I don't see how "aberation", or any of your other concepts, fits this.
--
Bill Nelson (bi...@peak.org)
Jan Panteltje
I think they make a few mistakes.
What they want to do, I think, is measure the difference in phase as they move
away from the vibrating rod.
Normal way to do that, is move away, while comparing the phase with that of the
source.
Now here practical problems come in.
You cannot use the phase of the exiting oscillator, you would have to take it via
a detector from the sending rod itself.
Also the 2 rods (sending and receiving) are so close these form a coupled system.
The first thing they think to solve by using a fixed position and then an AM
modulated (varying strength) source.
Then (and here is the error I think), they state that by measuring the difference
in phase of the sidebands of the received AM signal, they can say something about
the absolute phase shift, due to the 'group delay'.
Now this would only be true if the 'medium' in between had some frequency dependent
properties.
I know of no such thing with gravity, and gravity waves (an whole another subject
it seems), have not even been show to exists yet?
Looking at EM waves (as an analogy) shows that in a vacuum the group delay
difference does not do much?
We can receive signals from Pioneer 10 (bit further away then 2.5 cm) without
problems.
The signals are not (the waveform is not) distorted due to group delay differences
in the used band.
If using a non vacuum medium, like for example a cable or glass fiber, yes, then you
have a different situation.
So their experiment should really give no change as the result, which it does.
Interesting would be what happened when inserting materials between transmitter and
receiver. maybe some things could be found to change with a medium in between?
The one's garbage is the others PhD?
If I was to referee on this, I would say, nice setup, but try again with 2
interferometers, one on the sending vibrating bar, one on the receiver, and
then slowly move away..
Lots of practical problems.
Well, time can prove me wrong, for sure, but I am not holding my breath for this.
Regards
Jan
Gerry Quinn
>ger...@indigo.ie (Gerry Quinn) writes:
>
>>> [tvf]: The microwave rest frame is considered a preferred frame
>>> of convenience, not of necessity.
>
>> [gq]: And in LR it would be considered to be the most reasonable
>> candidate for the absolute frame, since it is in any case the
>> only candidate that can be agreed upon (at least in this part of
>> the universe) unless the principle of relativity is found to be
>> violated in some way.
>
> That is very much in line with 19th century thinking about the nature of
>the “aether”. Physics has come a long way since then. We now know that every
>local gravity field plays the role of a local “preferred frame” in
>Lorentzian relativity (LR). This is an observational result. The best way
>proposed so far to understand it theoretically is to conclude that the
>“light-carrying medium” is not impervious to gravity, but in fact does
>respond to gravity and becomes more concentrated (denser) near large masses.
>That requires that light waves propagating through this medium will
>experience refraction effects because of the density changes. It so happens
>that these predicted refraction effects are exactly the observed
>light-bending, gravitational redshift, and radar time delay effects, as
>Eddington already showed in his 1920 book (previously cited).
>
That's sort of correct except of course that a simple refraction model
is only valid in static situations. The force of gravity also depends
on the relative motion of the gravitating entities. (This is why GR is
full of horrible matrices.)
However, when I talk about "Lorentzian relativity" I refer to a model in
which space is globally flat and gravity is a _force_. In this
interpretation there is no direct necessity for the concept of local
inertial frames.
> The principle of relativity merely states that all motion is relative.
>That remains true when the standard for rest is the local gravity field. LR
>uses the principle of relativity. It does not violate it.
>
>> [gq]: In LR there is a frame in which clocks run fastest. FTL
>> communication would allow us to determine this frame, which is
>> the unique absolute frame.
>
> What is the frame where gravitational potential goes to zero? Or what is
>the absolute frame for measuring the speed of sound waves? If your answer
>for the latter is “the local standard of rest”, note that it is different at
>every latitude on Earth. And as every pilot who has flown the jet stream
>knows, “local rest” can have a high speed relative to “neighboring rest”.
>
> LR always has a local frame in which clocks run fastest. But it has no
>such universal frame. Even the “microwave background” has been proposed to
>be a local intergalactic “fog” by proponents of alternatives to the Big
>Bang. Some observational evidence supports that possibility, and none
>refutes it. Given that the microwave frame is not suitable, what would you
>then propose for your “universal standard of rest”?
>
What I said - the frame in which time runs fastest. FTL might offer
means of extending the radius of the observable universe, but even
assuming that it does not, and that the observable universe is in a
region of the entire universe such that we are affected by
a constantly-sloping gravitational potential that we cannot detect, it
makes no difference really. We could not detect the absolute frame in
these circumstances, but its detectability is not important.
>>> [tvf]: As the speed of light is approached, an electromagnetic
>>> clock’s rate approaches zero. If the speed of light is
>>> exceeded, its rate may even reverse and start backwards. It’s
>>> still a clock running backwards as time moves forward, so no
>>> problems with causality can arise even in principle.
>
>> [gq]: Let's say the clock is a candle with stripes painted on
>> it. As it exceeds the speed of light it starts to grow longer.
>> No problems with causality, you say?
>
> No, that’s an SR prediction, because time itself reverses direction in
>SR. In LR, nothing happens to time, so the candle simply burns out. The only
>reason an E-M-based clock reverses in LR is because the propagation of
>electrons slows as the effective density of the medium increases. Electron
>propagation would cease at lightspeed. And electron propagation could (in
>principle) reverse if the clock went faster than lightspeed. But these
>effects take place in forward time advancing at a uniform rate for all
>frames. -|Tom|-
>
I'll let the SRians have their say on this one, but I think they might
tell you that the clock would read imaginary time. What they think they
mean by that, and how such a candle would look, I have no clue, nor do I
know what distinction you are drawing in the above paragraph.
- Gerry Quinn
Asimov
"VF> Do you wish me to repeat either of these citations? Do you see an
"VF> error in either paper? Are these the assertions you were asking
"VF> about?
No need to repeat anything, just a small brief "meat & potatoes"
summary. Pehaps suggest some simple experiments or gedanken to
illustrate the principles. Nothing too complicated wot! <g>
... Essay: Describe the universe in 500 words or less & name 2 examples.
Paul Schlyter
> Interesting that it is probably the very fact that TVF abjures
> mathematics in his posts which has made it so easy for everyone here
> (apparently) to see how silly his "reasoning" is :-)
gravitational force is the derivative of the gravitational potential.
Too bad he didn't want to go one step further and agree that the
tidal "force" is the derivative of the gravitational force....
Paul Schlyter
Tom Van Flandern <t...@mindspring.com> wrote:
> pau...@saafNOSPAM.se (Paul Schlyter) writes:
>
>> [ps]: the discussion is about this: whether actual information
>> can be transmitted FTL or not - through gravity, or by
>> electrostatic fields, or in some other way. Relativity says it
>> cannot be done - Tom van Flandern says it can be done, if we can
>> overcome some practical difficulties.
>
> Correction. Special relativity (SR) says it cannot be done. The other
> relativistic theory of motion, Lorentzian relativity (LR), says it can
> be done. Hundreds of physicists and several new journals have been
> saying that for several years now. While I appreciate the attribution
> to me, it is undeserved.
Why do you ignore General Relativity (GR)? Since GR currently is our
best theory of gravitation, it seems unwise to ignore it here. And
according to those who know GR, the "speed of gravity" can never be
larger than the speed of light in GR.
>>> [tvf]: To bring the discussion back on topic: The Earth's
>>> gravitational force on the Moon has a non-central component due
>>> to tidal friction. To the Moon, the offset of the direction of
>>> that force is indistinguishable from the offset of the
>>> direction of Earth's gravitational force due to aberration.
>
>> [ps]: Why? Just because you say so?
>
> I said this because, to the Moon, both these forces manifest
> themselves as 3-space accelerations of the Moon in a direction
> offset from the radial to the Earth's center of mass.
No....
1. There is no such offset due to aberration. In Newtonian gravity
there's no offset because gravity is assumed to propagate instantly.
And in GR there's no such offset either, because of those
"cancellation terms" which Steve Carlip and others have described to
you a number of times.
2. The offset terms due to the tides are there because the tidally
disturbed Earth is no longer radially symmetric. ANY body which
deviates from a sphere will have an "offset from a central force"
in its gravity. This is valid not just for the tides but for
the Earth's flattening as well.
> I thought I was making a logical deduction from the cited
> observational and experimental facts.
Too bad you twisted your logic.
> If you disagree, just cite some manifestation distinguishing the
> two forces that is available to the Moon so it can choose to
> ignore aberration but respond to the tidal component of Earth's
> gravity.
One of them is due to an actual redistribution of mass, while the
other is due to just your fantasy. There is no aberration in
the gravitation.
> I really don’t see how the Moon could possibly tell the difference, so
> I posed this as a reasoned conclusion. If you do see how the Moon can
> distinguish the two, just say so, and if you have a physically
> reasonable mechanism, that blows my conclusion away.
Why should the Moon be affected by a non-existent force?
>>> [tvf]: So if gravitational aberration were to exist after all
>>> because gravity propagates at lightspeed, but is cancelled by a
>>> velocity-dependent force provided by nature to conserve angular
>>> momentum, then nature must also cancel tidal friction.
>
>> [ps]: Why? Just because you say so?
>
> This also was the conclusion line of a logical syllogism. The only way
> to show such a conclusion wrong is to show that one of its premises is
> erroneous or that the reasoning is invalid.
>
> Is the claim I just made true because I say so? No, it’s true because
> those are the rules of logical reasoning. I trust you had a course in
> logic in college.
And so did Aristotle, one of the worlds greatest philosophers. So
why don't you quote Aristotle too? Why don't you claim the Earth
is stationary in absolute terms? Why don't you claim body A always
falls X times faster than body B of body A is X times more massive
than body B? These are quite logical conclusions -- at least if you
ignore empirical evidence, as Aristotle did.
> So the premises of my last few syllogisms are: (1) The tidal component
> of Earth's gravity produces a non-central force component that
> accelerates the Moon in a transverse direction because it is non-central.
And this non-central force is due to an actual redistribution of
mass.
> (2) Propagation delay produces a non-central force component to ordinary
> gravity that should also cause the Moon to accelerate in the transverse
> direction because it is non-central, but does not.
True -- and that's because gravity doesn't work according to your
simple-minded Newtonian logic. The answer here is to be found by
digesting the field equations of GR -- but you don't seem to want
to bother doing that.
> Therefore, something must distinguish these two cases because the Moon
> responds differently to each.
Indeed!
(1) is due to an actual redistribution of mass
(2) is due to your misconception of how gravity should work.
> According to relativists in this discussion, GR requires that the Moon
> conserve orbital angular momentum when gravitational forces act. This
> requirement creates a velocity-dependent counter-force that cancels the
> effect of propagation delay, making the ordinary gravitational force of
> Earth on Moon pretty closely central.
>
> My objections are: (A) If this mythical counter-force existed, it would
> cancel the tidal component of gravitational force too, because there is
> no way the Moon could tell which was which. (The Moon simply receives
> instructions to accelerate in some direction, central or non-central.)
If this was the case, then redistribution of matter would not affect
the gravity field at all, and gravity and matter would become unrelated.
Is that really what you want to propose?
> (B) This mythical counter-force is a deus ex machina.
It's needed to explain observed properties of gravity....
> My explanation for why the two gravitational forces on the Moon do not
> behave the same is that the ordinary gravitational force is actually
> central because its propagation speed has no detectable delay.
I.e. you're actually proposing Newtonian mechanics and rejecting GR.
> This explanation overcomes objections (A) and (B), and introduces no
> new objections --
Are you really unaware that GR predicts many phenomena better
than Newtonian mechanics?
> except, apparently, that people have to adjust their thinking about
> what GR really means for physics.
Are you really unaware that you're really rejecting GR and proposing
Newtonian mechanics as a replacement?
>> [ps]: 1. Friction and gravitation aren't the same thing.
>
> Agreed. But the frictional component of Earth's gravitational pull on
> the Moon is gravitation.
No. It causes changes in gravitation because it redistributes
matter -- but it's not gravitation by itself as you here claim.
>> [ps]: I *don't* think one can, with such imprecise knowledge of
>> the secular acceleration, tell whether the tidal component of
>> the Earth-Moon gravitation acts towards the actual or the
>> aberrated position of the Earth's tidal bulge.
>
> The "aberrated position of the Earth's bulge" did not enter this
> discussion. I was comparing two forces: (1) The tidal component of
> Earth's gravitational force on the Moon manifests itself as a
> non-central gravitational force acting on the Moon.
That's because the tidally disturbed Earth isn't spherical. Did you
forget your celestial mechanics classes? OK, they were probably a
long time ago, but....
> (2) The Earth's ordinary gravity acting on the Moon likewise
> manifests itself as a non-central gravitational force if it has
> aberration.
..."if it has aberration" .... but what if it has no aberration?
> Both of these forces appear to the Moon as non-central forces that
> potentially induce the Moon to spiral outward in its orbit. If we
> had only the Moon to go by, you are right that we couldn’t tell yet
> if part of its secular acceleration were due to aberration and part
> to tides.
Correect -- that is if gravity has aberration. But it hasn't....
> But GR makes a specific claim that gravitational aberration
> is cancelled to conserve orbital angular momentum.
Yes.
> I dispute that claim,
In what way?
(1) Are you claiming gravity has aberration ?
or
(2) Are you proposing to reject GR in favor of Newtonian mechanics?
> and raised the Moon as a counter-example. (This is actually Dennis
> McCarthy’s clever example.) If there were a mechanism in nature to
> conserve angular momentum, then how can the Moon know to respond
> to one type of non-central gravitational force (the tidal one),
> but ignore the other type of non-central gravitational force
> (the aberrated one)?
Because the other one isn't a gravitational force.
> Why does it enforce orbital angular momentum conservation in one
> case, but not in the other? How can it possibly know the difference
> so it can behave differently in the two cases?
Do you really want to know? Really really? If so, the answer can
be found by digesting the field equations of GR. Have fun!
If not: why do you bother to ask?
>> [ps]: The Moon "knows" this because the tides redistribute
>> matter in the Earth, while gravity propagating at c doesn't.
>> But the Moon doesn't really need to "know" this, since it's all
>> in the gravitational field surrounding the Earth: the Moon just
>> responds to this field.
>
> Here we approach the heart of the matter. In mathematics, one can
> simply say "orbital angular momentum is conserved in this case, and
> not in that case", and it is so! No physical reasonability is required.
> But in physics, a physical reason is required. Real bodies don’t obey
> field equations,
They don't? Did you find experimental evidence for a deviation
from this? If not, why are you so sure about this?
> they respond to forces. If two forces are otherwise indistinguishable,
> it is not physically reasonable to write equations that require the
> Moon to respond to them in completely different ways. -|Tom|-
If you want to view this from the point of GR, your main illusion
here is your assumption of the existence of a gravitational force.
In GR there are no gravitational forces, but only accelerations
due to a curved space-time.
So re-ask your question, from this perspective, and then find the
answer from the field equations of GR. You cannot really understand
GR without actually learning it (although you've been trying hard for
many years now...)
Standeven
Bill Nelson <bi...@spock.peak.org> wrote in message
news:8fvqp6$45$1...@bashir.peak.org...
Imagine water molecules instead of arrows. Then the stream of water
will not experience any aberration due to the motion of the target,
even though the molecules are not moving infinitely fast.
More to the point, the force will point between the incident and
reflected stream of water, neither of which experiences aberration.
So the force will point at a fixed angle to the current location of
the water gun, regardless of how the target is moving relative to it.
JimJast
> Applying this to Sun and Earth, since the orientation of gravitons is
>irrelevant, we see that gravitational force from the Sun must tend to
>increase the relative speed between Earth and Sun, just as the arrow would
>decrease it.
[jj]
What "gravitons"? Until now I was under impression that you were talking about
retarded Newtonian gravitational potential and the direction of its gradient
(which incidentally happens point to the same direction as the arrow that you
mentioned even if from point of view of the target the arrow flies partly
sideways). I happen to know nothing about "gravitons" and their properties. You
should defind them first. But it you do, shouldn't you rather define them in a
way that their movement with reasonable speed agrees with the observations,
than to give them properties contradicting the observations and then complain
that they can't have reasonable speed? If they have to move faster than c for
gravity to work as it does, and they can't move faster than c for other
reasons, shouldn't therefore the conclusion be that they don't exist at all and
that we may finally return to the good old GR and forget about "speed of
gravitational force" which in GR has no sense anyway for the reason that in GR
gravitational force does not act at distance and so the question from which
direction it comes is moot?
If you however consider just a Newtonian potential, and keep the source of it
at rest (since, as you agree, it is irrelevent who moves) it is obvious that
its gradient will allways point to actual position of the source regardless of
the movement of the target. If you start moving the source in a "medium" at
rest, carying that potential with certain speed, you are bound to re-invent
relativity and may finally decide that gravity is not made out of small balls
("gravitons") moving with speed of light (which BTW is your conclusion right
now anyway).
-- Jim