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Challenge: topology

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X-Phy

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Jan 7, 2012, 11:58:40 AM1/7/12
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The idea have been emitted that space-time wouldn't be prior but sort
of an emergent concept. This concept has also been reworked in
various geometrical guises, in addition to the historical one that led
to relativity, special and general. The equations of physics
themselves harbor a strange paradox: interaction at a distance isn't
allowed while they contain derivatives, linking causally neighboring
points. There is no way to get rid of this link, even when
postulating that interaction must occur at a same point, since that
implies defining velocities, again through derivatives. Even far
fetched considerations, as Wheeler pointed out, all of physical laws
can be traced back to a single theorem in topology: boundaries have no
boundary, entail first the definition of a topology, that is, which
point is near to which point. So the very foundation of physics, yet
often unrealized, is subsumed in topology.

In the realm of mathematics, topology is easily defined in terms of
sets. The concept of neighbor can even be made quantitative through
spaces of numbers, which are then used to built more elaborated
structures, like precisely Riemannian manifolds. But there is nothing
in physics inducing a topology. Which phenomenon, principle, law
makes that one point is near to this one but
not to that other one? Anyway, what is a point? If there are no
points but only events, what makes that one event is near to this one
but not to that other one? Or what is the physical nature of the
space and time tag of an event?

--
X-Phy

dlzc

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Jan 7, 2012, 1:39:56 PM1/7/12
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Dear X-Phy:

On Jan 7, 9:58 am, X-Phy <xphysic...@gmail.com> wrote:
> The idea have been emitted that space-time wouldn't be
> prior but sort of an emergent concept.

Excellent seed for a discussion. Thank you.

I disagree with "emergent" in the usual context, for this issue. I
would choose mass and spacetime as properties of *the population*,
Universe. Meaningless in quantum interactions, but meaningful
"relative to something else".

All I can "contribute", but I expect to love the discussion.

> This concept has also been reworked in various
> geometrical guises, in addition to the historical one that
> led to relativity, special and general.  The equations of
> physics themselves harbor a strange paradox: interaction
> at a distance isn't allowed while they contain derivatives,
> linking causally neighboring points.  There is no way to
> get rid of this link, even when postulating that interaction
> must occur at a same point, since that implies defining
> velocities, again through derivatives.  Even far fetched
> considerations, as Wheeler pointed out, all of physical
> laws can be traced back to a single theorem in topology:
> boundaries have no boundary, entail first the definition of
> a topology, that is, which point is near to which point.
> So the very foundation of physics, yet often unrealized,
> is subsumed in topology.
>
> In the realm of mathematics, topology is easily defined
> in terms of sets.  The concept of neighbor can even be
> made quantitative through spaces of numbers, which
> are then used to built more elaborated structures, like
> precisely Riemannian manifolds.  But there is nothing
> in physics inducing a topology.  Which phenomenon,
> principle, law makes that one point is near to this one
> but not to that other one?

Conservation of momentum in a multi-body system.

> Anyway, what is a point?

A feature of a mathematical model impressed on spacetime.

> If there are no points but only events, what makes that
> one event is near to this one but not to that other one?

See "point" above.

> Or what is the physical nature of the space and time
> tag of an event?

Jargon I don't know. Out and watching.

David A. Smith

ben6993

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Jan 7, 2012, 4:37:14 PM1/7/12
to
I see the metric of space as emergent, but I won't write anything
detailed here about the Rasch method (as an example of a method of
constructing a space metric) as I have written it before. I see mass
as emergent as two counter-rotating gyroscopic actions in the same
body can, I suspect, reduce the mass, particularly if the two
gyroscopes are in two different and orthogonal sets of 4D. Both
orthogonal to the laboratory space where an elementary particle is a
point. I think that the up quark with its two gyroscopes works this
way and causes it to be lighter than a down quark which only has the
one gyroscope, while a neutrino has four gyroscopic actions virtually
eliminating its the mass.

What I see as not emergent is the spin state space and its contents.
That is like a cosmos. But that cosmos contains, for an elementary
particle, a motion at speed c. For bosons that is a linear speed c
and for fermions it is a rotational speed c. Motions at speed c makes
elementary particles appear as points to us through relativistic
effects, and makes them no-touch objects requiring interaction via
fields. It also means that the particles cannot form an aether and so
the space metric has no easy place to stick on secure coordinates.
The metric presumably emerges out of interactions between particles.

Ben Smith,
not a physicist

mpc755

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Jan 7, 2012, 5:57:39 PM1/7/12
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The rate at which an atomic clock ticks is a physical process
determined by the physical state of the space in which it exists.

Time is not a dimension.

harald

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Jan 9, 2012, 3:43:44 AM1/9/12
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"mpc755" <mpc...@gmail.com> wrote in message
news:43b3ac95-a131-47f7...@o14g2000vbo.googlegroups.com...
Indeed time is not a spatial dimension; it's a measure for the progress of
physical processes (usually by the count of standard process cycles).

Cl.Massé

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Jan 14, 2012, 5:40:55 PM1/14/12
to
On 7 jan, 19:39, dlzc <dl...@cox.net> wrote:

> > In the realm of mathematics, topology is easily defined
> > in terms of sets.  The concept of neighbor can even be
> > made quantitative through spaces of numbers, which
> > are then used to built more elaborated structures, like
> > precisely Riemannian manifolds.  But there is nothing
> > in physics inducing a topology.  Which phenomenon,
> > principle, law makes that one point is near to this one
> > but not to that other one?
>
> Conservation of momentum in a multi-body system.

The conservation of momentum is the consequence of the homogeneity of
space. It requires more than simple topology.

What I mean is, for example, a photon come from another galaxy. How
does it know that it is near an electron on earth, so as to be
absorbed by it? Of course, we can say there is an em field at a
point, but how does it know that the electron is in the vicinity of
that point?

--
X-Phy

glen herrmannsfeldt

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Jan 14, 2012, 10:42:58 PM1/14/12
to
Cl.Massé <clm...@online.fr> wrote:

(snip)

> The conservation of momentum is the consequence of the homogeneity of
> space. It requires more than simple topology.

> What I mean is, for example, a photon come from another galaxy. How
> does it know that it is near an electron on earth, so as to be
> absorbed by it? Of course, we can say there is an em field at a
> point, but how does it know that the electron is in the vicinity of
> that point?

What does 'in the vicinity' mean? Close enough, relative to the wavelength.

My always favorite example is the neutron cross-section, which for
some nuclides is much larger than the nuclear diameter for slow
(long wavelength) neutrons. If the wave function has enough amplitude
at the nucleus, it can get absorbed.

Otherwise, if you use path integrals, the photon wave function has to
explore all the possible places where an electron might be available
to absorb it. It then has to choose, with the appropriate amplitude,
which of the possible electrons will absorb that photon.

-- glen

dlzc

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Jan 15, 2012, 4:34:31 PM1/15/12
to
Dear Cl.Massé:

On Jan 14, 3:40 pm, Cl.Massé <clma...@online.fr> wrote:
> On 7 jan, 19:39,dlzc<dl...@cox.net> wrote:
>
> > > In the realm of mathematics, topology is easily defined
> > > in terms of sets.  The concept of neighbor can even be
> > > made quantitative through spaces of numbers, which
> > > are then used to built more elaborated structures, like
> > > precisely Riemannian manifolds.  But there is nothing
> > > in physics inducing a topology.  Which phenomenon,
> > > principle, law makes that one point is near to this one
> > > but not to that other one?
>
> > Conservation of momentum in a multi-body system.
>
> The conservation of momentum is the consequence of the
> homogeneity of space.  It requires more than simple
> topology.

I disagree. The time portion is homogeneous, because physics is the
same everywhere. The space portion unfolds as a result of CoM, so it
too is homogeneous.

> What I mean is, for example, a photon come from another
> galaxy.  How does it know that it is near an electron on
> earth, so as to be absorbed by it?

Because it is always in its own *here*, it made the entire journey, as
if it had just now been emitted. In QM, a real propagating photon is
a series of virtual photons. Each virtual photon arose locally, just
as the electron in your example is local.

> Of course, we can say there is an em field at a point, but how
> does it know that the electron is in the vicinity of that point?

Maxwell has a photon packet as an EM field. How could they not "know"
of each other?

David A. Smith

X-Phy

unread,
Jan 17, 2012, 10:52:58 AM1/17/12
to
On 15 jan, 04:42, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote:

> > The conservation of momentum is the consequence of the homogeneity of
> > space.  It requires more than simple topology.
> > What I mean is, for example, a photon come from another galaxy.  How
> > does it know that it is near an electron on earth, so as to be
> > absorbed by it?  Of course, we can say there is an em field at a
> > point, but how does it know that the electron is in the vicinity of
> > that point?
>
> What does 'in the vicinity' mean? Close enough, relative to the wavelength.

It means that, in a near point in time, the wave will propagate to the
electron. (a trajectory or path is a continuous map.)

It is not about quantum mechanical babble, it is about basic space
time. In this context, quantum mechanics is merely wave mechanics,
and classical mechanics also applies.

> My always favorite example is the neutron cross-section, which for
> some nuclides is much larger than the nuclear diameter for slow
> (long wavelength) neutrons. If the wave function has enough amplitude
> at the nucleus, it can get absorbed.

That's much more than topology. For those who aren't familiar with
it, here a short reminding:

If X is a set, a topology of X is a collection of its subsets called
open sets, and that have these properties:
- X and the empty set are open sets.
- The union of any number, including infinite, of open sets is an open
set.
- The intersection of a finite number of open sets is an open set.

A neighborhood of an element x of X is a subset of X that contains at
least one open set to which x belongs.

An example is R with the collection of all its open intervals and
their unions. It is called the usual topology.

A map X -> Y is continuous iff the inverse image of any open set in Y
is an open set in X.

If the open set in Y get smaller and smaller, the open set in X do
too. Thus a continuous map, as it were, conserves the vicinity, which
itself is rather loosely defined.

A homeomorphism X -> Y is a continuous map that has an inverse which
is continuous. It is sort of an isomorphism of topologies.

> Otherwise, if you use path integrals, the photon wave function has to
> explore all the possible places where an electron might be available
> to absorb it. It then has to choose, with the appropriate amplitude,
> which of the possible electrons will absorb that photon.

We don't need paths integral, which is a much elaborated, and
correlatively useless concept. To think about topology, the Huygens
principle is way enough, and the paths integral can be derived from
it.

--
X-Phy

X-Phy

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Jan 19, 2012, 9:13:31 AM1/19/12
to
On 17 jan, 16:52, X-Phy <xphysic...@gmail.com> wrote:

> We don't need paths integral, which is a much elaborated, and
> correlatively useless concept.  To think about topology, the Huygens
> principle is way enough, and the paths integral can be derived from
> it.

The original Huygens principle can be cast in a mathematical form, the
Huygens-Fresnel principle.

Heuristically, the derivation is as follow:

As the wave equation is linear, the wave can be written as a sum of
delta functions, which evolve separately during a small time interval.
Then everything is superposed again, and that gives a solution of the
equation. It is as if every point of space radiates in every
direction to the same distance, and then all the spherical wave fronts
are added, taking the phase into account. This is the explanation of
the Huygens principle. Now after many of those steps, and letting the
time interval tend to zero, every possible path is covered, since the
points of arrival become the points of departure in any direction.
The phase evolution is given by the action, according to usual
physics. The path integral is obtained by taking all the paths
between two given points.

--
X-Phy

dlzc

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Jan 19, 2012, 1:38:53 PM1/19/12
to
Dear X-Phy:

On Jan 19, 7:13 am, X-Phy <xphysic...@gmail.com> wrote:
> On 17 jan, 16:52, X-Phy <xphysic...@gmail.com> wrote:
>
> > We don't need paths integral, which is a much
> > elaborated, and correlatively useless concept.  To think
> > about topology, the Huygens principle is way enough,
> > and the paths integral can be derived from it.
>
> The original Huygens principle can be cast in a
> mathematical form, the Huygens-Fresnel principle.
>
> Heuristically, the derivation is as follow:
>
> As the wave equation is linear, the wave can be written
> as a sum of delta functions, which evolve separately
> during a small time interval. Then everything is
> superposed again, and that gives a solution of the
> equation.  It is as if every point of space radiates in
> every direction to the same distance, and then all the
> spherical wave fronts are added, taking the phase into
> account.  This is the explanation of the Huygens
> principle.

Still requires FTL propagation, just as the "path integral" method you
turn your nose up at.

> Now after many of those steps, and letting the time
> interval tend to zero, every possible path is covered,
> since the points of arrival become the points of
> departure in any direction. The phase evolution is
> given by the action, according to usual physics.  The
> path integral is obtained by taking all the paths
> between two given points.

... And does not yield any new information (IMO), and presupposes the
"methodology" that magically yields c as maximum for statistical
systems. With no handle on underlying mechanism.

David A. Smith

harald

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Jan 20, 2012, 3:52:34 AM1/20/12
to

"dlzc" <dl...@cox.net> wrote in message
news:84555712-be24-459b...@p13g2000yqd.googlegroups.com...
> Dear X-Phy:
>
> On Jan 19, 7:13 am, X-Phy <xphysic...@gmail.com> wrote:
>> On 17 jan, 16:52, X-Phy <xphysic...@gmail.com> wrote:
>>
>> > We don't need paths integral, which is a much
>> > elaborated, and correlatively useless concept. To think
>> > about topology, the Huygens principle is way enough,
>> > and the paths integral can be derived from it.
>>
>> The original Huygens principle can be cast in a
>> mathematical form, the Huygens-Fresnel principle.
>>
>> Heuristically, the derivation is as follow:
>>
>> As the wave equation is linear, the wave can be written
>> as a sum of delta functions, which evolve separately
>> during a small time interval. Then everything is
>> superposed again, and that gives a solution of the
>> equation. It is as if every point of space radiates in
>> every direction to the same distance, and then all the
>> spherical wave fronts are added, taking the phase into
>> account. This is the explanation of the Huygens
>> principle.
>
> Still requires FTL propagation, just as the "path integral" method you
> turn your nose up at.

That is, if Bell was right ...

>> Now after many of those steps, and letting the time
>> interval tend to zero, every possible path is covered,
>> since the points of arrival become the points of
>> departure in any direction. The phase evolution is
>> given by the action, according to usual physics. The
>> path integral is obtained by taking all the paths
>> between two given points.
>
> ... And does not yield any new information (IMO), and presupposes the
> "methodology" that magically yields c as maximum for statistical
> systems. With no handle on underlying mechanism.

Indeed, the path integral has no corresponding physical model that I know of
(at least not one that makes any sense).

dlzc

unread,
Jan 20, 2012, 1:26:32 PM1/20/12
to
Dear harald:
The method described above, requires FTL communication. No reference
to Bell. All wavefronts, everywhere, add up to a local propagation
speed of c (max).

> >> Now after many of those steps, and letting the time
> >> interval tend to zero, every possible path is covered,
> >> since the points of arrival become the points of
> >> departure in any direction.  The phase evolution is
> >> given by the action, according to usual physics. The
> >> path integral is obtained by taking all the paths
> >> between two given points.
>
> > ... And does not yield any new information (IMO), and
> > presupposes the "methodology" that magically yields
> > c as maximum for statistical systems.  With no handle
> > on underlying mechanism.
>
> Indeed, the path integral has no corresponding physical
> model that I know of (at least not one that makes any
> sense).

Exactly the same for Huygens then. It is mechanism supported entirely
by no different magic.

If you desire a "physical model" to dull your senses so that you can
ignore the magic, that is fine.

Suppose that we are comprised of particles falling from an event
horizon towards a central singularity (with other than a Schwarzchild
metric, so that we can end up in an infinitely diffuse future).
Suppose that our individual particles are interacting with both the
past and future of other "neighboring" particles (including our own).
In this "web of lies", photons (and other c-limited particles) are the
carriers of all forces, and the "necessary magic" or "physical model"
is entirely described by the gestalt that defines the space we travel
though. Namely, the system of all matter and energy.

You should appreciate that it is entirely classical... no reference to
quantum behaviors at all.

David A. Smith

harald

unread,
Jan 23, 2012, 5:12:08 AM1/23/12
to

"dlzc" <dl...@cox.net> wrote in message
news:14cfee0a-335c-4ab1...@e8g2000yqd.googlegroups.com...
Perhaps the description is unclear, I admit that I skipped over it as I know
the Huygens principle: it is based on a propagation speed of c.

>> >> Now after many of those steps, and letting the time
>> >> interval tend to zero, every possible path is covered,
>> >> since the points of arrival become the points of
>> >> departure in any direction. The phase evolution is
>> >> given by the action, according to usual physics. The
>> >> path integral is obtained by taking all the paths
>> >> between two given points.
>>
>> > ... And does not yield any new information (IMO), and
>> > presupposes the "methodology" that magically yields
>> > c as maximum for statistical systems. With no handle
>> > on underlying mechanism.
>>
>> Indeed, the path integral has no corresponding physical
>> model that I know of (at least not one that makes any
>> sense).
>
> Exactly the same for Huygens then. It is mechanism supported entirely
> by no different magic.

Huygens made plausible assumptions of how a wave propagates.

> If you desire a "physical model" to dull your senses so that you can
> ignore the magic, that is fine.

I desire a physical model as safeguard against pure nonsense.

> Suppose that we are comprised of particles falling from an event
> horizon towards a central singularity (with other than a Schwarzchild
> metric, so that we can end up in an infinitely diffuse future).
> Suppose that our individual particles are interacting with both the
> past and future of other "neighboring" particles (including our own).
> In this "web of lies", photons (and other c-limited particles) are the
> carriers of all forces, and the "necessary magic" or "physical model"
> is entirely described by the gestalt that defines the space we travel
> though. Namely, the system of all matter and energy.
>
> You should appreciate that it is entirely classical... no reference to
> quantum behaviors at all.

"Interacting with the future" is very strong magic and certainly not
classical.

dlzc

unread,
Jan 23, 2012, 11:11:13 AM1/23/12
to
Dear harald:

On Jan 23, 3:12 am, "harald" <h...@swissonline.ch> wrote:
> "dlzc" <dl...@cox.net> wrote in message
> news:14cfee0a-335c-4ab1...@e8g2000yqd.googlegroups.com...
> > On Jan 20, 1:52 am, "harald" <h...@swissonline.ch> wrote:
> >> "dlzc" <dl...@cox.net> wrote in message
> >> > Still requires FTL propagation, just as the "path
> >> > integral" method you turn your nose up at.
>
> >> That is, if Bell was right ...
>
> > The method described above, requires FTL communication.
> > No reference to Bell.  All wavefronts, everywhere, add up to
> > a local propagation speed of c (max).
>
> Perhaps the description is unclear, I admit that I skipped over
> it as I know the Huygens principle: it is based on a
> propagation speed of c.

... with a very stiff medium, aka "instantaneous signaling".

...
> > Suppose that we are comprised of particles falling from
> > an event horizon towards a central singularity (with other
> > than a Schwarzchild metric, so that we can end up in
> > an infinitely diffuse future). Suppose that our individual
> > particles are interacting with both the past and future
> > of other "neighboring" particles (including our own).
> > In this "web of lies", photons (and other c-limited
> > particles) are the carriers of all forces, and the
> > "necessary magic" or "physical model" is entirely
> > described by the gestalt that defines the space we
> > travel though.  Namely, the system of all matter and
> > energy.
>
> > You should appreciate that it is entirely classical...
> > no reference to quantum behaviors at all.
>
> "Interacting with the future" is very strong magic and
> certainly not classical.

Yes, actually it is. Interior solution of a black hole using only
classical GR, Kruskal metric I believe.

David A. Smith

X-Phy

unread,
Jan 28, 2012, 9:32:52 AM1/28/12
to
On 23 jan, 11:12, "harald" <h...@swissonline.ch> wrote:

> Perhaps the description is unclear, I admit that I skipped over it as I know
> the Huygens principle: it is based on a propagation speed of c.

It can be used to derive the law of refraction. It applies with
inhomogenous wave speed too.

--
X-Phy

X-Phy

unread,
Jan 28, 2012, 9:32:48 AM1/28/12
to
On 19 jan, 19:38, dlzc <dl...@cox.net> wrote:

> > As the wave equation is linear, the wave can be written
> > as a sum of delta functions, which evolve separately
> > during a small time interval.  Then everything is
> > superposed again, and that gives a solution of the
> > equation.  It is as if every point of space radiates in
> > every direction to the same distance, and then all the
> > spherical wave fronts are added, taking the phase into
> > account.  This is the explanation of the Huygens
> > principle.
>
> Still requires FTL propagation, just as the "path integral" method you
> turn your nose up at.

The weight of a path that propagates FTL is zero, since the action is
infinite.

> > Now after many of those steps, and letting the time
> > interval tend to zero, every possible path is covered,
> > since the points of arrival become the points of
> > departure in any direction.  The phase evolution is
> > given by the action, according to usual physics.  The
> > path integral is obtained by taking all the paths
> > between two given points.
>
>  ... And does not yield any new information (IMO), and presupposes the
> "methodology" that magically yields c as maximum for statistical
> systems.  With no handle on underlying mechanism.

c is conventionally the speed of light, and so defines the distance
unit from the time unit. That gives a geometry to space, it is the
gist of special relativity. What is required is the continuity of a
path, which is a topological issue.

--
X-Phy

harald

unread,
Feb 1, 2012, 3:47:11 AM2/1/12
to

"dlzc" <dl...@cox.net> wrote in message
news:7a93e9b3-c4f5-45a0...@o20g2000yqh.googlegroups.com...
> Dear harald:
>
> On Jan 23, 3:12 am, "harald" <h...@swissonline.ch> wrote:
>> "dlzc" <dl...@cox.net> wrote in message
>> news:14cfee0a-335c-4ab1...@e8g2000yqd.googlegroups.com...
>> > On Jan 20, 1:52 am, "harald" <h...@swissonline.ch> wrote:
>> >> "dlzc" <dl...@cox.net> wrote in message
>> >> > Still requires FTL propagation, just as the "path
>> >> > integral" method you turn your nose up at.
>>
>> >> That is, if Bell was right ...
>>
>> > The method described above, requires FTL communication.
>> > No reference to Bell. All wavefronts, everywhere, add up to
>> > a local propagation speed of c (max).
>>
>> Perhaps the description is unclear, I admit that I skipped over
>> it as I know the Huygens principle: it is based on a
>> propagation speed of c.
>
> ... with a very stiff medium, aka "instantaneous signaling".

??? The Huygens principle has no "instantaneous signaling"; instead it uses
propagation at speed c, just as for example Einstein applied it for his
final calculation of the gravitational bending of light.

> ...
>> > Suppose that we are comprised of particles falling from
>> > an event horizon towards a central singularity (with other
>> > than a Schwarzchild metric, so that we can end up in
>> > an infinitely diffuse future). Suppose that our individual
>> > particles are interacting with both the past and future
>> > of other "neighboring" particles (including our own).
>> > In this "web of lies", photons (and other c-limited
>> > particles) are the carriers of all forces, and the
>> > "necessary magic" or "physical model" is entirely
>> > described by the gestalt that defines the space we
>> > travel though. Namely, the system of all matter and
>> > energy.
>>
>> > You should appreciate that it is entirely classical...
>> > no reference to quantum behaviors at all.
>>
>> "Interacting with the future" is very strong magic and
>> certainly not classical.
>
> Yes, actually it is. Interior solution of a black hole using only
> classical GR, Kruskal metric I believe.

I don't call GR "classical" physics but that doesn't matter: GR certainly
doesn't allow interaction with the future. Perhaps you are referring to a
modern variant of GR?

Harald

dlzc

unread,
Feb 1, 2012, 1:18:02 PM2/1/12
to
Dear harald:

On Feb 1, 1:47 am, "harald" <h...@swissonline.ch> wrote:
> "dlzc" <dl...@cox.net> wrote in message
>
> news:7a93e9b3-c4f5-45a0...@o20g2000yqh.googlegroups.com...
...
> >> Perhaps the description is unclear, I admit that I skipped over
> >> it as I know the Huygens principle: it is based on a
> >> propagation speed of c.
>
> > ... with a very stiff medium, aka "instantaneous signaling".
>
> ??? The Huygens principle has no "instantaneous signaling";

Then we can stop going back and forth about who understands what. It
does, I cannot convince you, we can move on.

...
> > Yes, actually it is.  Interior solution of a black hole using only
> > classical GR, Kruskal metric I believe.
>
> I don't call GR "classical" physics but that doesn't matter:

GR treats the Universe as infinitely divisible, so that all physics
must stay constant below the scale of molecules... which it clearly
does not. So it is *classical*, in that differentiation and
integration can occur at all scales.

> GR certainly doesn't allow interaction with the future. Perhaps
> you are referring to a modern variant of GR?

Eddington and Kruskal are not all that "modern", are they?

David A. Smith

harald

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Feb 2, 2012, 5:52:28 AM2/2/12
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"dlzc" <dl...@cox.net> wrote in message
news:64713c00-c5af-4e4a...@p13g2000yqd.googlegroups.com...
> Dear harald:
>
> On Feb 1, 1:47 am, "harald" <h...@swissonline.ch> wrote:
>> "dlzc" <dl...@cox.net> wrote in message
>>
>> news:7a93e9b3-c4f5-45a0...@o20g2000yqh.googlegroups.com...
> ...
>> >> Perhaps the description is unclear, I admit that I skipped over
>> >> it as I know the Huygens principle: it is based on a
>> >> propagation speed of c.
>>
>> > ... with a very stiff medium, aka "instantaneous signaling".
>>
>> ??? The Huygens principle has no "instantaneous signaling";
>
> Then we can stop going back and forth about who understands what. It
> does, I cannot convince you, we can move on.

I can only guess why you did not attempt to convince me with the help of a
reference such as this one:
http://en.wikipedia.org/wiki/Huygens%E2%80%93Fresnel_principle

or the one to which I already referred (p.198-199 of the English text):
http://www.alberteinstein.info/gallery/gtext3.html

> ...
>> > Yes, actually it is. Interior solution of a black hole using only
>> > [..] GR, Kruskal metric I believe.
>> [..]
>> GR certainly doesn't allow interaction with the future. Perhaps
>> you are referring to a modern variant of GR?
>
> Eddington and Kruskal are not all that "modern", are they?

According to the abovementioned overview of GR, does it allow interaction
with the future? It relies on measurements with "systems of reference" that
use ordinary clocks which, I think, only interact with the present.
Causality is an important feature of relativity theory.

Harald

dlzc

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Feb 2, 2012, 1:30:10 PM2/2/12
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Dear harald:

On Feb 2, 3:52 am, "harald" <h...@swissonline.ch> wrote:
> "dlzc" <dl...@cox.net> wrote in message
>
> news:64713c00-c5af-4e4a...@p13g2000yqd.googlegroups.com...
> >> > Yes, actually it is. Interior solution of a black
> >> > hole using only [..] GR, Kruskal metric I believe.
> >> [..]
> >> GR certainly doesn't allow interaction with the
> >> future. Perhaps you are referring to a modern
> >> variant of GR?
>
> > Eddington and Kruskal are not all that "modern",
> > are they?
>
> According to the abovementioned overview of GR,
> does it allow interaction with the future?

I did not reference "abovementioned". One day I can find references
to it, and then when I need to...

> It relies on measurements with "systems of
> reference" that use ordinary clocks which, I think,
> only interact with the present.

... have not verified the "stability" of these links...
http://arxiv.org/pdf/0903.4717.pdf
http://www.sciencedaily.com/releases/2010/04/100406172648.htm
http://www.einstein-online.info/spotlights/changing_places

> Causality is an important feature of relativity theory.

Exterior geometrical concerns do not apply to interior solutions. It
irritates me when "flatlanders" simply refuse to let go of their
assertions of what "must" apply across an event horizon, without even
blinking an eye.

David A. Smith

harald

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Feb 3, 2012, 7:16:55 AM2/3/12
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"dlzc" <dl...@cox.net> wrote in message
news:ca5ac4c4-9164-401f...@b10g2000pbd.googlegroups.com...
> Dear harald:
>
> On Feb 2, 3:52 am, "harald" <h...@swissonline.ch> wrote:
>> "dlzc" <dl...@cox.net> wrote in message
>>
>> news:64713c00-c5af-4e4a...@p13g2000yqd.googlegroups.com...
>> >> > Yes, actually it is. Interior solution of a black
>> >> > hole using only [..] GR, Kruskal metric I believe.
>> >> [..]
>> >> GR certainly doesn't allow interaction with the
>> >> future. Perhaps you are referring to a modern
>> >> variant of GR?
>>
>> > Eddington and Kruskal are not all that "modern",
>> > are they?
>>
>> According to the abovementioned overview of GR,
>> does it allow interaction with the future?
>
> I did not reference "abovementioned". One day I can find references
> to it, and then when I need to...
>
>> It relies on measurements with "systems of
>> reference" that use ordinary clocks which, I think,
>> only interact with the present.
>
> ... have not verified the "stability" of these links...
> http://arxiv.org/pdf/0903.4717.pdf
> http://www.sciencedaily.com/releases/2010/04/100406172648.htm
> http://www.einstein-online.info/spotlights/changing_places

The links work. Interesting, thanks! :-)

However, a quick scan through those references didn't show me anything about
interaction of particles with the future. Perhaps you can pinpoint one of
those places?

>> Causality is an important feature of relativity theory.
>
> Exterior geometrical concerns do not apply to interior solutions. [..]

Not "concerns" but the theoretical foundations of the theory.

dlzc

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Feb 3, 2012, 1:31:17 PM2/3/12
to
As I said, one day I find a suitable link, and the next day I cannot.

> >> Causality is an important feature of relativity theory.
>
> > Exterior geometrical concerns do not apply to interior
> > solutions. [..]
>
> Not "concerns" but the theoretical foundations of the theory.

Does an event horizon have a center in this Universe?

David A. Smith

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