Re: Contraction of Length Measurements in SR? No, not possible.
Dirk Van de moortel
"GSS" <gurchar...@yahoo.com> wrote in message news:1142707562.4...@j33g2000cwa.googlegroups.com...
> Friends,
> In a separate thread titled 'Is length contraction of a rod real or
> perspective???', it is being argued that the length contraction of a
> rod observed by moving observers is only apparent and not real. The
> analysis given below shows that this apparent contraction actually does
> not affect the length measurements in any way.
>
> Coordinate Systems:
> The cardinal idea responsible for the invention of coordinate systems
> by Descartes consists of the assumption that to each real number there
> corresponds a unique point on a straight line. We choose a straight
> line X and a point O on it, which we call the origin. We choose a point
> A and call the length of the line segment OA, the unit length. Next we
> pick up any point P on this line X, as shown in the figure and take the
> ratio of the lengths of the line segments OP and OA. Let this ratio
> OP/OA be equal to x. The number x is called the coordinate of P.
>
> .....O...........A..................................P.............> X
>
> The association of the set of points P on coordinate line X with the
> set of real numbers x, constitutes a coordinate system of the
> one-dimensional SPACE, once the notion of certain 'unit length' OA has
> been defined.
>
> Therefore, when we say that the coordinate of point P is x, it implies
> that the ratio OP/OA be equal to x. The distance OP or the length of
> line segment OP is associated with the coordinate x as
>
> OP = x.OA
> = x times unit length OA
> If OA is defined to be 1 meter then
> OP = x meters
>
> Now let us consider a pole of length L and a small standard rod of unit
> length Lu as shown below such that the pole is laid parallel to X-axis
> of a suitable coordinate system K0.
>
> ___ Lu
> ______________________________ L
>
> Suppose the unit length Lu is of one meter. Then to determine the
> length L of the pole in meters, we have to carry out a measurement
> process something like the one illustrated below. [For the sake of
> argument we may assume that this measurement process is automated and
> keeps getting repeated all the time.]
>
> ___1
> ______________________________ L
>
> ___2
> ______________________________ L
>
> ___3
> ______________________________ L
>
> ___4
> ______________________________ L
>
> ___5
> ______________________________ L
>
> ___6
> ______________________________ L
>
> ___7
> ______________________________ L
>
> ___8
> ______________________________ L
>
> ___9
> ______________________________ L
>
> ___10
> ______________________________ L
>
>
>
> This measurement shows that the length L of the pole is 10 meters. This
> can also be expressed as the ratio of L/Lu .
>
> L/Lu = 10
>
> or, L = 10 Lu = 10 meters.
>
> Now let us imagine that this pole is observed from some far away
> location from where the objects appear to be much smaller in size. Even
> from this far away location the measured length of the pole is still
> found to be 10 meters.
>
> Next let us imagine that this pole is being observed from inertial
> reference frames K1, K2, K3 etc in relative uniform motion along X-axis
> of K0. For all observers in relative uniform motion wrt the pole, the
> lengths L and Lu will *appear* to be shorter (say L' and Lu') by their
> respective gamma factors. But the length of the pole measured with the
> standard meter rod is still found to be 10 meters since the ratio of
> the apparent lengths L' and Lu' is still the same L'/Lu' =10.
Not 10 meters, but 10 "accented meters"
>
> Therefore it can be safely concluded that the length of a 10 m pole
> measured with a standard meter rod as per SI standards, will be found
> to be the same 10 m when observed from any inertial reference frame K1,
> K2, K3 etc. in relative uniform motion.
It will not be the same 10 m. It will observed to be 10 m'
(accented meters).
>
> This shows that the assertion of SR regarding length contraction of
> physical objects when observed from reference frames in relative
> uniform motion is *wrong* and just a facade.
No, it shows something else.
Exercise: what does it show?
Dirk Vdm
GSS
.....O...........A..................................P.............> X
..... Lu
.............................. L
Suppose the unit length Lu is of one meter. Then to determine the
length L of the pole in meters, we have to carry out a measurement
process something like the one illustrated below. [For the sake of
argument we may assume that this measurement process is automated and
keeps getting repeated all the time.]
..... 1
.............................. L
..... 2
.............................. L
..... 3
.............................. L
..... 4
.............................. L
..... 5
.............................. L
..... 6
.............................. L
This measurement shows that the length L of the pole is 6 meters. This
can also be expressed as the ratio of L/Lu .
L/Lu = 6
or, L = 6 Lu = 6 meters.
Now let us imagine that this pole is observed from some far away
location from where the objects appear to be much smaller in size. Even
from this far away location the measured length of the pole is still
found to be 6 meters.
Next let us imagine that this pole is being observed from inertial
reference frames K1, K2, K3 etc in relative uniform motion along X-axis
of K0. For all observers in relative uniform motion wrt the pole, the
lengths L and Lu will *appear* to be shorter (say L' and Lu') by their
respective gamma factors. But the length of the pole measured with the
standard meter rod is still found to be 6 meters since the ratio of the
apparent lengths L' and Lu' is still the same L'/Lu' =6.
Therefore it can be safely concluded that the length of a 6 m pole
measured with a standard meter rod as per SI standards, will be found
to be the same 6 m when observed from any inertial reference frame K1,
K2, K3 etc. in relative uniform motion.
This shows that the assertion of SR regarding contraction of length
measurements of physical objects when observed from reference frames in
relative uniform motion is *wrong* and just a facade.
GSS
Sam Wormley
Space Interferometry Mission as a Test of Lorentz Length Contraction
http://renshaw.teleinc.com/papers/simiee2/simiee2.stm
Abstract--A basic tenet of special relativity is the concept of
length contraction seen by an observer in motion. Lorentz
contraction, which changes the apparent location of a light source,
combines with aberration, which changes the apparent direction to the
source, producing a variety of effects. While aberration has been
confirmed, Lorentz contraction has never been tested directly, due to
the generally negligible size of the effect. As the earth orbits the
sun, Lorentz contraction offsets the apparent position of a distant
source by as much as 18 micro-arcseconds (mas) per degree of
separation. This offset is in addition to that caused by aberration.
The Space Interferometry Mission, due for launch in 2005, promises a
resolution of +/- 1 mas in a field of view of one degree, allowing
for the first time the direct confirmation of Lorentz length
contraction, one-hundred years after the introduction of
Einstein's special theory of relativity in 1905.
Space Interferometry Mission
http://planetquest.jpl.nasa.gov/SIM/sim_index.cfm
GSS
I corrected the original illustration because
it was not showing properly.
As far as accented meters is concerned, I consider the standard meter
as the 'standard' as per SI standards. It is not possible to regard it
as changeable as per apparent observations and still consider it as a
'standard'.
GSS
Dirk Van de moortel
"GSS" <gurchar...@yahoo.com> wrote in message news:1142709657....@i39g2000cwa.googlegroups.com...
> Sorry, Dirk Vdm
> I corrected the original illustration because
> it was not showing properly.
> As far as accented meters is concerned, I consider the standard meter
> as the 'standard' as per SI standards.
And first you call it Lu and a bit later you call it Lu'.
> It is not possible to regard it
> as changeable as per apparent observations and still consider it as a
> 'standard'.
But first you call it Lu and a bit later you call it Lu'.
Now, make the exercise I gave you:
It does not show
"that the assertion of SR regarding length contraction of
physical objects when observed from reference frames
in relative uniform motion is *wrong* and just a facade."
It shows something else.
Hexenmeister
"Dirk Van de moortel" <dirkvand...@ThankS-NO-SperM.hotmail.com> wrote
in message news:5QYSf.323513$xe4.10...@phobos.telenet-ops.be...
| Exercise: what does it show?
|
| Dirk Vdm
It shows your religion has lost another convert, fucking stupid alt.moron!
It shows reason has triumphed over stupidity, alt.local.village.idiot!
It shows all your trolling was in vain, dumbest cunt.
ROFLMAO! Gloat, gloat.
Androcles.
Hexenmeister
| ______________________________ L
|
| Suppose the unit length Lu is of one meter. Then to determine the
| length L of the pole in meters, we have to carry out a measurement
| process something like the one illustrated below. [For the sake of
| argument we may assume that this measurement process is automated and
| keeps getting repeated all the time.]
|
| ______________________________ L
|
| ___2
| ______________________________ L
|
| ___3
| ______________________________ L
|
| ___4
| ______________________________ L
|
| ___5
| ______________________________ L
|
| ___6
| ______________________________ L
|
| ___7
| ______________________________ L
|
| ___8
| ______________________________ L
|
| ___9
| ______________________________ L
|
| ___10
|
|
|
| This measurement shows that the length L of the pole is 10 meters. This
| can also be expressed as the ratio of L/Lu .
|
|
| or, L = 10 Lu = 10 meters.
|
| Now let us imagine that this pole is observed from some far away
| location from where the objects appear to be much smaller in size. Even
| from this far away location the measured length of the pole is still
|
| Next let us imagine that this pole is being observed from inertial
| reference frames K1, K2, K3 etc in relative uniform motion along X-axis
| of K0. For all observers in relative uniform motion wrt the pole, the
| lengths L and Lu will *appear* to be shorter (say L' and Lu') by their
| respective gamma factors. But the length of the pole measured with the
| the apparent lengths L' and Lu' is still the same L'/Lu' =10.
|
| Therefore it can be safely concluded that the length of a 10 m pole
| measured with a standard meter rod as per SI standards, will be found
| K2, K3 etc. in relative uniform motion.
|
| physical objects when observed from reference frames in relative
| uniform motion is *wrong* and just a facade.
|
Yep.
Androcles.
The Ghost In The Machine
> Friends,
> In a separate thread titled 'Is length contraction of a rod real or
> perspective???', it is being argued that the length contraction of a rod
> observed by moving observers is only apparent and not real. The analysis
> given below shows that this apparent contraction actually does not affect
> the length measurements in any way.
I'm not sure what a "length measurement" is in the context of a rod moving
by me; the best I can do is to affix two lights to the rod and measure the
time between light pulses generated by the rod (which leads to one
measurement), or affix two mirrors to the rod and measure the time between
light pulses generated by me (which leads to another).
Either way, one has to be very careful on how one performs the
measurement, as one is beset by two problems.
[1] The rod is moving, if the lights do not flash.
[2] The lights may or may not be synchronized if they flash. Light speed,
after all, is not infinite; this was known even in Galileo's time (and
Galileo came up with a surprisingly good figure for lightspeed even back
then; the main problem was that the distance to Jupiter was not quite
right).
A proper theoretical calculation using this space-time equivalence would
result in the following. Since you're already using O and A I'm going to
have to alter my notation a bit; let O be the non-moving observer, as
before, with coordinate system (x_O, t_O)_O; the moving rod will be M
in this variant, with coordinate system (x_M, t_M)_M; the relationship
will be the Lorentz, as hypothesized by SR:
x_M = (x_O - v * t_O)*g
t_M = (t_O - v * x_O/c^2)*g
and therefore
x_O = (x_M + v * t_M)*g
t_O = (t_M + v * x_M/c^2)*g
where g = 1/sqrt(1-v^2/c^2), as usual. This also means that
(x_O,t_O)_O = ( (x_O - v*t_O)*g, (t_O - v*x_O/c^2)*g)_M
(x_M,t_M)_M = ( (x_M + v*t_M)*g, (t_M + v*x_M)/c^2)*g)_O
If the lights are not flashing then one is essentially trying to measure
two events, with one event being (0,t_M)_M and the other being (L, t'_M)_M
for some values t_M and t'_M. For convenience we set t_M = 0; this
immediately yields t_O = 0 as well in the Lorentz.
For various reasons, however, t'_M is not necessarily zero without a lot
of work. If O allows the rod to pass over him, then t'_O is nonzero anyway
(it takes time for the second endpoint to move over the observer, after
all), and therefore trying to set t'_M = 0 is slightly pointless.
Since O is forever locked to his origin, one is essentially solving the
equation
x'_O = 0 with x'_M = L
This gives t'_M = -L/v and t'_O = (-L/v + v*L/c^2)*g
= (L/v)(-1 + v^2/c^2)*g = -L/(vg). Since v is ostensibly known the rod
has effectively shrunk in this measurement scenario.
If the lights *are* flashing then we are measuring two times from flash
events at (0,0)_M and (L,0)_M. This means t_M = t'_M = 0. However, t'_O
is *not* zero, but vgL/c^2. Since x'_O = gL O cannot observe this
directly but must wait abs(x'_O/c) = x'_O/c time units for the flash to
reach him (SR assumes lightspeed is c everywhere). Total time between
flashes is therefore (gL/c + vGL/c^2) = (gL/c)*(1+v/c) =
(L/c)*sqrt(1+v/c)/sqrt(1-v/c), and in this scenario the rod is now *longer*.
If we are using mirrors and a single (radar/lidar) flash from (0,0)_O
= (0,0)_M, then in M-space the flash to the far endpoint can be rendered
(L,L/c)_M = ( (L+vL/c)*g, L/c+vL/c^2)*g)_O. The time it takes O to see
the second flash is therefore simply twice the value (L/c + vL/c^2)*g =
(L/c)*sqrt(1+v/c)/sqrt(1-v/c) again.
Weird goings-on, to be sure.
It turns out that, if both rods are moving, both are contracted by the
same amount. One can observe the measurement method from a number of
spots and one will still get the same result; the problem is that the
measurement is being conducted from the *stationary* rod's reference frame.
This is valid but problematic in establishing what the length of the rod
is in the *moving* reference frame.
>
> This shows that the assertion of SR regarding contraction of length
> measurements of physical objects when observed from reference frames in
> relative uniform motion is *wrong* and just a facade.
No, it simply means that your measurement is not doing what you seem to
think it is doing.
>
> GSS
--
#191, ewi...@earthlink.net
It's still legal to go .sigless.
Hexenmeister
"The Ghost In The Machine" <ewi...@earthlink.net> wrote in message
news:pan.2006.03.18....@earthlink.net...
| On Sat, 18 Mar 2006 11:04:46 -0800, GSS wrote:
|
| > Friends,
| > In a separate thread titled 'Is length contraction of a rod real or
| > perspective???', it is being argued that the length contraction of a rod
| > observed by moving observers is only apparent and not real. The analysis
| > given below shows that this apparent contraction actually does not
affect
| > the length measurements in any way.
|
| I'm not sure what a "length measurement" is in the context of a rod moving
| by me; the best I can do is to affix two lights to the rod and measure the
| time between light pulses generated by the rod (which leads to one
| measurement), or affix two mirrors to the rod and measure the time between
| light pulses generated by me (which leads to another).
You best isn't good enough. Your uncertainty is noted.
You are a fucking weird idiot.
Androcles.
Tom Roberts
> In a separate thread titled 'Is length contraction of a rod real or
> perspective???', it is being argued that the length contraction of a
> rod observed by moving observers is only apparent and not real.
That argument is purely linguistic, about the meanings of the words
"apparent" and "real". That most posters in the other thread do not
realize this does not change this fact.
> The
> analysis given below shows that this apparent contraction actually does
> not affect the length measurements in any way.
No. You do not understand how measurements are actually made, and made
an invalid assumption.
You are correct that all length measurements are actually ratios to a
standard meterstick.
> [...]
When an observer in frame A makes a measurement of a rod at rest in
frame B, where B moves relative to A along the rod's length, the
observer in A does _not_ take a ratio to a standard meterstick at rest
in frame B, she takes a ratio to a meterstick at rest in frame A.
Because the rod is moving, naturally the observer in A must mark both
ends _simultaneously_ in frame A (which requires assistants) and then
use a meterstick at rest in frame A to measure the length between the
marks. Ultimately it is the difference in simultaneity between frames A
and B that is the source of the length contraction (an observer at rest
in frame B would say that the observer in A marked the front of the rod
before the back end, so naturally the distance between marks in A is
shorter than the rod at rest in B).
Tom Roberts tjro...@lucent.com
GSS
...
> But first you call it Lu and a bit later you call it Lu'.
Let me repeat the relevant part of my post for clarification.
[Coordinate Systems:
The cardinal idea responsible for the invention of coordinate systems
by Descartes consists of the assumption that to each real number there
corresponds a unique point on a straight line. We choose a straight
line X and a point O on it, which we call the origin. We choose a point
A and call the length of the line segment OA, the unit length. Next we
pick up any point P on this line X, as shown in the figure and take the
ratio of the lengths of the line segments OP and OA. Let this ratio
OP/OA be equal to x. The number x is called the coordinate of P.
.....O...........A..................................P.............> X
The association of the set of points P on coordinate line X with the
set of real numbers x, constitutes a coordinate system of the
one-dimensional SPACE, once the notion of certain 'unit length' OA has
been defined.
Therefore, when we say that the coordinate of point P is x, it implies
that the ratio OP/OA be equal to x. The distance OP or the length of
line segment OP is associated with the coordinate x as
OP = x.OA
= x times unit length OA
If OA is defined to be 1 meter then
OP = x meters
Now let us consider a pole of length L and a small standard rod of unit
length Lu as shown below such that the pole is laid parallel to X-axis
of a suitable coordinate system K0.
..... Lu
.............................. L ]
Let us imagine that this pole is observed from some far away location
from where the objects *appear* to be much smaller in size say Lu' and
L'. Even from this far away location the measured length of the pole is
still found to be the same. Mind you here Lu' and L' are the apparently
reduced sizes because of the observation from a long distance. Lu' is
still the meter rod even though it *appears* to be smaller in size.
Similarly let us imagine that this pole is being observed from inertial
reference frames K1, K2, K3 etc in relative uniform motion along X-axis
of K0. For all observers in relative uniform motion wrt the pole, the
lengths L and Lu will *appear* to be shorter (say L' and Lu'). But the
length of the pole measured with the standard meter rod is still found
to be the same since this measurement just depicts the ratio of L' and
Lu'.
Here we are essentially talking about the *measurement reading* as per
standard notions.
> Now, make the exercise I gave you:
> It does not show
> "that the assertion of SR regarding length contraction of
> physical objects when observed from reference frames
> in relative uniform motion is *wrong* and just a facade."
> It shows something else.
> Exercise: what does it show?
No, it still shows that the assertions of SR regarding length
contraction of physical objects when observed from reference frames in
relative uniform motion is *wrong* and just a facade. Two prominent
justifications for this observation are :
(a) As shown above the coordinate x of a point P is just a *ratio* of
two length segments, namely OP and OA. In SR this *ratio* representing
the coordinate x is claimed to transform to x' in moving coordinate
system. This is logically and fundamentally *wrong*. Possibly under
certain situations, as for example while observing from a distance, the
length segments OP and OA might *appear* to be shorter but their ratio
just cannot change.
(b) The second postulate of SR depicts a fundamentally and logically
wrong assumption that the speed of light in vacuum is the same constant
c in all reference frames in relative uniform motion. This assumption
is built in to the following relation involving space-time interval dS,
(dS)^2 = (dx)^2 + (dy)^2 + (dz)^2 - (c.dt)^2
= (dx')^2 + (dy')^2 + (dz')^2 - (c.dt')^2
Just to comply with this wrong assumption, the notion of time as an
absolute measure of change has been sacrificed in SR, leading to wrong
notions of relative time and consequent wrong notions of length
contractions. This wrong assumption has given rise to such
fundamentally absurd convictions among SR followers that they really
believe that the time intervals *dt* of a standard atomic clock will be
seen to be *different* in each of the infinitely many reference frames
in relative motion!!
In my opinion it is a matter of shame on the collective intelligence of
Humanity that such absurd notions of SR are still lingering on in this
21st century. All that just for defending one wrong assumption!!!
GSS
Dirk Van de moortel
"GSS" <gurchar...@yahoo.com> wrote in message news:1142754751....@z34g2000cwc.googlegroups.com...
> Dirk Vdm wrote:
> ...
> > But first you call it Lu and a bit later you call it Lu'.
>
> Let me repeat the relevant part of my post for clarification.
There is no need to repeat it, so I snip it up to the point
where you went wrong.
[snip]
> Similarly let us imagine that this pole is being observed from inertial
> reference frames K1, K2, K3 etc in relative uniform motion along X-axis
> of K0. For all observers in relative uniform motion wrt the pole, the
> lengths L and Lu will *appear* to be shorter (say L' and Lu'). But the
> length of the pole measured with the standard meter rod is still found
> to be the same since this measurement just depicts the ratio of L' and
> Lu'.
So the length is not 10 meters, but 10 "accented-meters"
If you measure a thing that is moving with respect to yourself,
then you are supposed to compare with *your* measuring
rod, not with some rod that is flying with the object you are
measuring.
>
> Here we are essentially talking about the *measurement reading* as per
> standard notions.
In your scheme you first compare with Lu. Then you compare
with Lu'. That is not a standard.
>
> > Now, make the exercise I gave you:
> > It does not show
> > "that the assertion of SR regarding length contraction of
> > physical objects when observed from reference frames
> > in relative uniform motion is *wrong* and just a facade."
> > It shows something else.
> > Exercise: what does it show?
>
> No, it still shows that the assertions of SR regarding length
> contraction of physical objects when observed from reference frames in
> relative uniform motion is *wrong* and just a facade. Two prominent
> justifications for this observation are :
>
> (a) As shown above the coordinate x of a point P is just a *ratio* of
> two length segments, namely OP and OA. In SR this *ratio* representing
> the coordinate x is claimed to transform to x' in moving coordinate
> system.
And that x' is not the ratio of L'/Lu'.
> This is logically and fundamentally *wrong*.
Indeed, it is definitely logically and fundamentally *wrong*.
It is also not what SR says. I have seen many blatant
misconceptions of SR on this forum, but this must be the
most stupid one ever. My very sincere congratulations.
> Possibly under
> certain situations, as for example while observing from a distance, the
> length segments OP and OA might *appear* to be shorter but their ratio
> just cannot change.
>
> (b) The second postulate of SR depicts a fundamentally and logically
> wrong assumption that the speed of light in vacuum is the same constant
> c in all reference frames in relative uniform motion.
If you call something that is observed over and over during the
last 150 years "a fundamentally and logically wrong assumption",
that is of course your business. But since you seem to be such
an ignorant and arrogant imbecile, I will not bother attempting
to explain. Surely *that* you must understand.
>
> This assumption
> is built in to the following relation involving space-time interval dS,
>
> (dS)^2 = (dx)^2 + (dy)^2 + (dz)^2 - (c.dt)^2
> = (dx')^2 + (dy')^2 + (dz')^2 - (c.dt')^2
>
> Just to comply with this wrong assumption, the notion of time as an
> absolute measure of change has been sacrificed in SR, leading to wrong
> notions of relative time and consequent wrong notions of length
> contractions. This wrong assumption has given rise to such
> fundamentally absurd convictions among SR followers that they really
> believe that the time intervals *dt* of a standard atomic clock will be
> seen to be *different* in each of the infinitely many reference frames
> in relative motion!!
>
> In my opinion it is a matter of shame on the collective intelligence of
> Humanity that such absurd notions of SR are still lingering on in this
> 21st century. All that just for defending one wrong assumption!!!
You sound like Thomas Smid in disguise.
Dirk Vdm
oriel36
All you ever do is come here and imitate Newton but whereas Newton's
maneuvering is enjoyable up to a point,insofar as his lies and
misjudgements can be corrected,nothing useful comes from what you do.
Newton created the illusion that Keplerian orbital distances working
off mean Sun/Earth distances are valid when using a standard time -the
calendrically driven clockwork RA/dEC system.
"PHENOMENON IV.
That the fixed stars being at rest, the periodic times of the five
primary planets, and (whether of the sun about the earth, or) of the
earth about the sun, are in the sesquiplicate proportion of their mean
distances from the sun.
This proportion, first observed by Kepler, is now received by all
astronomers; for the periodic times are the same, and the dimensions of
the orbits are the same, whether the sun revolves about the earth, or
the earth about the sun. And as to the measures of the periodic times,
all astronomers are agreed about them. But for the dimensions of the
orbits, Kepler and Bullialdus, above all others, have determined them
from observations with the greatest accuracy; and the mean distances
corresponding to the periodic times differ but insensibly from those
which they have assigned, and for the most part fall in between them;
as we may see from the following table." NEWTON
The chopping and changing from 'times' to 'distances' looks great for
those who know no better but nothing Kepler wrote supports how Newton
forced his own geometry into valid astronomical perspectives .
In short,your are wasting valuable time and human effort on a 17th
century creation.
Hexenmeister
"Tom Roberts" <tjro...@lucent.com> wrote in message
news:Mh6Tf.2710$tN3....@newssvr27.news.prodigy.net...
| GSS wrote:
| > In a separate thread titled 'Is length contraction of a rod real or
| > perspective???', it is being argued that the length contraction of a
| > rod observed by moving observers is only apparent and not real.
|
| That argument is purely linguistic, about the meanings of the words
| "apparent" and "real".
Roberts is in Wonderland again.
`When I use a word,' Humpty Roberts said, in rather a scornful tone, `it
means just what I choose it to mean -- neither more nor less.'
`The question is,' said Alice, `whether you can make words mean so many
different things.'
`The question is,' said Humpty Roberts, `which is to be master -- that's
all.'
Alice was too much puzzled to say anything; so after a minute Humpty Roberts
began again. `They've a temper, some of them -- particularly verbs: they're
the proudest -- adjectives you can do anything with, but not verbs --
however, I can manage the whole lot of them! Impenetrability! That's what I
say!'
Androcles.
GSS
.....
> When an observer in frame A makes a measurement of a rod at rest in
> frame B, where B moves relative to A along the rod's length, the
> observer in A does _not_ take a ratio to a standard meterstick at rest
> in frame B, she takes a ratio to a meterstick at rest in frame A.
But why this complication?
The measurement of a rod L at rest in frame B can be easily automated
so that a robotic system can perform the precision measurement of the
rod with a standard meter stick. This automated robotic measurement
system can be remotely controlled and the whole measuring operation can
be video taped and viewed live from remote locations. If an observer in
frame A is in motion relative to frame B and wants to measure the
length of the rod L she can simply switch on the measuring system
remotely and observe the whole measuring operation on the TV screen.
With modern technology this appears to be quite a simple operation. Of
course this advantage of modern technology was not available to Albert
Einstein about 100 years ago.
> Because the rod is moving, naturally the observer in A must mark both
> ends _simultaneously_ in frame A (which requires assistants) and then
> use a meterstick at rest in frame A to measure the length between the
> marks. Ultimately it is the difference in simultaneity between frames A
> and B that is the source of the length contraction (an observer at rest
> in frame B would say that the observer in A marked the front of the rod
> before the back end, so naturally the distance between marks in A is
> shorter than the rod at rest in B).
Other than day dreaming, I don't think you can actually perform this
operation even with modern technology. Assume the rod is lying on the
ground and the observer A is flying in an aircraft. Kindly describe how
will she use a meterstick at rest in the aircraft and measure the
length of the rod on the ground.
GSS
Dirk Van de moortel
Dirk Van de moortel
You really *are* Thomas Smid, aren't you?
Dirk Vdm
Hexenmeister
|
| You really *are* Thomas Smid, aren't you?
You REALly *are* an alt.moron, alt.local.village idiot, alt.moron, aren't
you?
Don't worry. "Real" has nothing to do with it, stupid does.
Androcles.
Tom Roberts
> Tom Roberts wrote:
> .....
>> When an observer in frame A makes a measurement of a rod at rest in
>> frame B, where B moves relative to A along the rod's length, the
>> observer in A does _not_ take a ratio to a standard meterstick at rest
>> in frame B, she takes a ratio to a meterstick at rest in frame A.
>
> But why this complication?
This is not a "complication", it is a _simplification_ (the observer in
frame A controls the standard metersticks(s) used in the measurement).
And besides, it is what we mean by "measurement of length in frame A".
>> Because the rod is moving, naturally the observer in A must mark both
>> ends _simultaneously_ in frame A [...]
>
> Other than day dreaming, I don't think you can actually perform this
> operation even with modern technology.
We do it all the time for objects moving with velocities of a few tens
of meters/sec or less, using cameras. Yes, it has not been possible to
experimentally test this particular prediction of SR, due to technical
difficulties.
Tom Roberts tjro...@lucent.com
Hexenmeister
| GSS wrote:
| > Tom Roberts wrote:
| > .....
| >> When an observer in frame A makes a measurement of a rod at rest in
| >> frame B, where B moves relative to A along the rod's length, the
| >> observer in A does _not_ take a ratio to a standard meterstick at rest
| >> in frame B, she takes a ratio to a meterstick at rest in frame A.
| >
| > But why this complication?
|
| This is not a "complication",
Real has nothing to do with it.
| it is a _simplification_ (the observer in
| frame A controls the standard metersticks(s) used in the measurement).
| And besides, it is what we mean by "measurement of length in frame A".
And besides, real has nothing to do with it.
|
| >> Because the rod is moving, naturally the observer in A must mark both
| >> ends _simultaneously_ in frame A [...]
| >
| > Other than day dreaming, I don't think you can actually perform this
| > operation even with modern technology.
|
| We do it
No WE do not. Real has nothing to do with it.
Androcles.
Nicolaaas Vroom
"Sam Wormley" <swor...@mchsi.com> schreef in bericht
news:H%YSf.35334$oL.15374@attbi_s71...
>
> Space Interferometry Mission as a Test of Lorentz Length Contraction
> http://renshaw.teleinc.com/papers/simiee2/simiee2.stm
>
> Abstract--A basic tenet of special relativity is the concept of
> length contraction seen by an observer in motion.
This is a very interesting document, but it also raises certain issues.
1. IMO in the document two different "types" of length contraction
are discussed: Object length related and Distance related.
2. In figure 3 Length contraction of a moving train is discussed.
The observer is stationary or resting. (Object length related)
3. In Figure 1 the distance between telephone poles is discussed.
Observation point of view is the train, which has a speed v.
The background, the poles are "fixed".
In figure 5 length contaction based on the distance between stars
is discussed. Observation point of view is the Earth and is in motion.
The background, the stars are "fixed".
(Distance related)
4. At page 144 "Subtle is the Lord" by Abraham Pais is written:
"The question whether the Lorentz contraction does or does not
exist is confusing. It does not "really" exist in so far as it does not
exist
for an observer who moves with the rod; it "really" exists, however,
in the sense, that it can as a matter of principle be
demonstrated by a resting observer".
5. IMO what the SIM does is to demonstrate length contration
based on distance, in this particular case distance between stars.
That is not what is discussed in the above mentioned quotation
which discusses length contraction of an object.
Length Contraction based on the distance between the poles
and the distance between the stars, IMO if observed by a
moving observer, represents more a vissible illusion
and is not real and not physical related.
6. Above figure 3, in order to test length contraction of the train,
there is written: "that a different set of contacts is required".
I agree with that.
This is in agreement with the coments I made in the thread:
"Is length contraction of a rod real or perspective???"
which raises two issues with "relativity of simultaneity"
and a moving train. For an overview see:
http://users.pandora.be/nicvroom/simultaneity.htm#remarks2
Nicolaas Vroom
http://users.pandora.be/nicvroom/
PD
You'll note this procedure works ONLY if L is laying still on the
ground, so that you have the freedom to pick up Lu and move it around.
You'll note that this procedure breaks immediately if L is moving. This
means that this procedure must be modified somehow to accomodate moving
lengths.
And this is where the fun begins.
PD
PD
The Ghost In The Machine wrote:
> On Sat, 18 Mar 2006 11:04:46 -0800, GSS wrote:
>
> > Friends,
> > In a separate thread titled 'Is length contraction of a rod real or
> > perspective???', it is being argued that the length contraction of a rod
> > observed by moving observers is only apparent and not real. The analysis
> > given below shows that this apparent contraction actually does not affect
> > the length measurements in any way.
>
> I'm not sure what a "length measurement" is in the context of a rod moving
> by me; the best I can do is to affix two lights to the rod and measure the
> time between light pulses generated by the rod (which leads to one
> measurement), or affix two mirrors to the rod and measure the time between
> light pulses generated by me (which leads to another).
Neither of these is useful for measuring the length of a moving object.
a) You are relying on the lights affixed to the moving rod to be fired
simultaneously. However, what is simultaneous in the rod's frame will
not be simultaneous in your frame, and this would obviously alter the
measurement.
b) In the second case, while the light is propagating away from you,
the rod and its mirrors are moving, and so in your frame it is apparent
that light will be reflected from the rearmost mirror first, and again
this would obviously alter the measurement.
What you want is a way to take a picture of both ends of the rod
simultaneously, where simultaneity is defined in *your* frame, not the
rod's.
There are lots of practical ways to do this. Here's one. Assemble a
line of proximity sensors and fire them *all* simultaneously. The
boundary between adjacent sensors with one showing something nearby and
the next showing nothing nearby marks the end of the moving rod, and
there will be two such instances.
PD
The Ghost In The Machine
> The Ghost In The Machine wrote:
>> On Sat, 18 Mar 2006 11:04:46 -0800, GSS wrote:
>>
>> > Friends,
>> > In a separate thread titled 'Is length contraction of a rod real
>> > or
>> > perspective???', it is being argued that the length contraction of a
>> > rod observed by moving observers is only apparent and not real. The
>> > analysis given below shows that this apparent contraction actually
>> > does not affect the length measurements in any way.
>>
>> I'm not sure what a "length measurement" is in the context of a rod
>> moving by me; the best I can do is to affix two lights to the rod and
>> measure the time between light pulses generated by the rod (which leads
>> to one measurement), or affix two mirrors to the rod and measure the
>> time between light pulses generated by me (which leads to another).
>
> Neither of these is useful for measuring the length of a moving object.
> a) You are relying on the lights affixed to the moving rod to be fired
> simultaneously. However, what is simultaneous in the rod's frame will
> not be simultaneous in your frame, and this would obviously alter the
> measurement.
> b) In the second case, while the light is propagating away from you, the
> rod and its mirrors are moving, and so in your frame it is apparent that
> light will be reflected from the rearmost mirror first, and again this
> would obviously alter the measurement.
Both fair criticisms, and you're obviously aware of the problem in
measurement here.
> What you want is a way to take a picture of both ends of the rod
> simultaneously, where simultaneity is defined in *your* frame, not the
> rod's.
> There are lots of practical ways to do this. Here's one. Assemble a line
> of proximity sensors and fire them *all* simultaneously.
As defined in my frame, of course. This would yield a pair of events
(0,0)_O = (0,0)_A
(L',0)_O = (L,t)_A
for some value of L' and t (L is a constant here).
Since, by the Lorentz,
L = L'*g
t = (-vL'/c^2)*g
L' = L/g and O observes that the rod has shrunk (since g > 1).
> The boundary
> between adjacent sensors with one showing something nearby and the next
> showing nothing nearby marks the end of the moving rod, and there will
> be two such instances.
And the measurement would still be "wrong" -- but then, space and time
twist in very strange ways in SR and have to be properly accounted for.
[rest snipped for brevity]
Nicolaaas Vroom
"Nicolaaas Vroom" <nicolaa...@pandora.be> schreef in bericht
news:rfPUf.334145$Aa4.10...@phobos.telenet-ops.be...
>
> "Sam Wormley" <swor...@mchsi.com> schreef in bericht
> news:H%YSf.35334$oL.15374@attbi_s71...
>>
>> Space Interferometry Mission as a Test of Lorentz Length Contraction
>> http://renshaw.teleinc.com/papers/simiee2/simiee2.stm
>>
>> Abstract--A basic tenet of special relativity is the concept of
>> length contraction seen by an observer in motion.
>
> This is a very interesting document, but it also raises certain issues.
>
> 1. IMO in the document two different "types" of length contraction
> are discussed: Object length related and Distance related.
> based on distance, in this particular case distance between stars.
> That is not what is discussed in the above mentioned quotation
> which discusses length contraction of an object.
> Length Contraction based on the distance between the poles
> and the distance between the stars, IMO if observed by a
> moving observer, represents more a vissible illusion
> and is not real and not physical related.
> 6. Above figure 3, in order to test length contraction of the train,
> there is written: "that a different set of contacts is required".
> I agree with that.
> This is in agreement with the coments I made in the thread:
> "Is length contraction of a rod real or perspective???"
> which raises two issues with "relativity of simultaneity"
> and a moving train. For an overview see:
> http://users.pandora.be/nicvroom/simultaneity.htm#remarks2
>
> Nicolaas Vroom
> http://users.pandora.be/nicvroom/
>
In the above mentioned post I made some remarks
pointing out a difference between length contraction
of a physical object versus space i.e. the distance between two
objects.
IMO length contraction is only possible in the first case.
As such SIM, because it observes the position of stars,
what ever the explanation is, IMO it does not prove
length contraction.
Any comments ?
Nicolaas Vroom
Harry
"Nicolaaas Vroom" <nicolaa...@pandora.be> wrote in message
news:5KF3g.392387$MJ1.11...@phobos.telenet-ops.be...
From the Lorentz transformations: length contraction + conventional clock
recalibration results in reduced measured "stationary" distances as measured
from the moving system (note that without recalibration the effect will be
opposite, which is more intuitive). This happens by mathematical necessity,
for you can't expect that a shortened ruler will not affect measurements.
Harald
Tom Roberts
> I made some remarks
> pointing out a difference between length contraction
> of a physical object versus space i.e. the distance between two
> objects.
In SR such a distinction is of no consequence.
> IMO length contraction is only possible in the first case.
In a current-conducting wire, the length contraction between moving
electrons is important in the analysis using Maxwell's equations.
> As such SIM, because it observes the position of stars,
> what ever the explanation is, IMO it does not prove
> length contraction.
I don't know much about the Space Interferometry Mission, but I do note
that your link "explaining" it is to Curt Renshaw's website, not a NASA
website; he has displayed serious misconceptions about SR. He claims it
"will be launched" in 2005; the NASA/JPL website discusses prospects for
launch in 2011.
Tom Roberts
Nicolaaas Vroom
"Tom Roberts" <tjrobe...@sbcglobal.net> schreef in bericht
news:Lw34g.70361$H71....@newssvr13.news.prodigy.com...
> Nicolaaas Vroom wrote:
> > I made some remarks
> > pointing out a difference between length contraction
> > of a physical object versus space i.e. the distance between two
> > objects.
>
> In SR such a distinction is of no consequence.
Can you please explain in a little more detail
or give me an url which explains ?
The only thing that I can think of has to do with bending of light
around massive objects (The sun).
In that case the distance between a star close to the Sun
and a star further away seems to decrease, but that has nothing
to do with length contraction.
> > IMO length contraction is only possible in the first case.
>
> In a current-conducting wire, the length contraction between moving
> electrons is important in the analysis using Maxwell's equations.
I am not aware that Maxwell's equations have anything to with
the movement of individual electrons.
Is there anything written about this subject in the book Gravitation ?
The only thing I know that in two parallel wires when the currents
run in the same direction they attract (Biot et Savart)
and in opposite directions they repel.
> > As such SIM, because it observes the position of stars,
> > what ever the explanation is, IMO it does not prove
> > length contraction.
>
> I don't know much about the Space Interferometry Mission, but I do note
> that your link "explaining" it is to Curt Renshaw's website, not a NASA
> website; he has displayed serious misconceptions about SR.
Has this any effect if SIM is going to prove length contraction ?
> He claims it "will be launched" in 2005; the NASA/JPL website discusses
> prospects for launch in 2011.
>
>
> Tom Roberts
Nicolaas Vroom
http://users.pandora.be/nicvroom/
Tom Roberts
> "Tom Roberts" <tjrobe...@sbcglobal.net> schreef in bericht
> news:Lw34g.70361$H71....@newssvr13.news.prodigy.com...
>> Nicolaaas Vroom wrote:
>>> I made some remarks
>>> pointing out a difference between length contraction
>>> of a physical object versus space i.e. the distance between two
>>> objects.
>> In SR such a distinction is of no consequence.
>
> Can you please explain in a little more detail
> or give me an url which explains ?
Try: Taylor and Wheeler, _Spacetime_Physics_.
Here's a directly related example:
When you look at a building from directly in front, it appears to be
wider than when you look at it from a corner. This effect does not
affect the building itself, of course, and is purely due to your point
of view. And because this is purely a geometrical effect, it would not
matter if the front corners of the building were replaced with markers,
there being no object between them. Similarly in SR, "length
contraction" is purely a geometrical effect, an artifact of one's point
of view, and it does not matter if there is an object between the
endpoints, or if there are just markers with no object between.
>> In a current-conducting wire, the length contraction between moving
>> electrons is important in the analysis using Maxwell's equations.
>
> I am not aware that Maxwell's equations have anything to with
> the movement of individual electrons.
Maxwell's equations are the best _classical_ theory we have for the
behavior of electromagnetic phenomena in general, and the behavior of
charged particles in particular. I am discussing _non_quantum_
electrodynamics here.
> Is there anything written about this subject in the book Gravitation ?
Probably not. While MTW has a very wide compass, you really need an E&M
textbook, not a gravitation textbook. Or an SR textbook, as above.
Tom Roberts
Nicolaaas Vroom
> Nicolaaas Vroom wrote:
>> "Tom Roberts" <tjrobe...@sbcglobal.net> schreef in bericht
>> news:Lw34g.70361$H71....@newssvr13.news.prodigy.com...
>>> Nicolaaas Vroom wrote:
>>>> I made some remarks
>>>> pointing out a difference between length contraction
>>>> of a physical object versus space i.e. the distance between two
>>>> objects.
>>> In SR such a distinction is of no consequence.
>>
>> Can you please explain in a little more detail
>> or give me an url which explains ?
>
> Try: Taylor and Wheeler, _Spacetime_Physics_.
>
> Here's a directly related example:
> When you look at a building from directly in front, it appears to be wider
> than when you look at it from a corner. This effect does not affect the
> building itself, of course, and is purely due to your point of view. And
> because this is purely a geometrical effect, it would not matter if the
> front corners of the building were replaced with markers, there being no
> object between them. Similarly in SR, "length contraction" is purely a
> geometrical effect, an artifact of one's point of view, and it does not
> matter if there is an object between the endpoints, or if there are just
> markers with no object between.
Interesting point of view.
Consider your building with a height of 1 cm and a depth of 1 cm.
Now your building becomes a rail road track with a length l0.
Consider an observer at the centre of this building.
Place a firing device FD at both ends of the building.
Make the track longer
Place a train on the track with a length l0
left on the track.
The train has a speed v= 0.5c
The train moves from left to right.
When the front of the train hits the left FD a light is generated
but this light signal is ignored by the observer
At some moment in time the front of the train will hit the right FD.
and a light signal will be generated
At some moment in time the back of the train will hit the left FD etc.
Question will the observer see both lightsignals simultaneous ?
Nicolaas Vroom
http://users.pandora.be/nicvroom/
Nicolaaas Vroom
I was hoping that someone was going to answer this question
"leider" alas, noone does.
IMO accordingly to SR the observer should not see the two
lightsignals simultaneous.
And what should be the reason ?
Should it be a geometrical effect ?
Any way what does that mean ?
Is that the same as visible illusion ?
Or can you replace the word geometrical with mathematical ?
And if it is a geometrical effect does it help to add the words
Galilean or Euclidean ?
Only questions - no answers.
I still hope that some one is going to answer the first question.
At the same time maybe he or she can answer the following question.
Suppose the track is not a straight line but follows a big circle.
Suppose the observer is at the centre of this circle.
First the train is at rest.
Position two lights outside the track (from the observer
point of view) one lamp almost at the front FL of the train and one
almost at the back BL of the train such that from the observer
point both lamps are off.
The train starts to move slowly.
The observer sees the following:
1. Front Lamp off Back Lamp ON
2. FL ON BL ON
3. FL ON BL OFF
4. FL OFF BL OFF
Now the train has made one revolution.just before BL comes ON.
Question at a high speed is the following scenario possible
that in stead of 4 FL OFF BL OFF
the observer sees: 4. FL ON BL ON
for a very small period ?
This means the Back Lamp goes ON before the Front Lamp goes OFF
which is the end of one revolution.
Nicolaas Vroom