Re: The relativity of simultaneity



kenseto ha escrito:
On Jul 24, 5:20 pm, rvall...@xxxxxxxxx wrote:
kenseto ha escrito:



On Jul 23, 7:04 pm, rvall...@xxxxxxxxx wrote:
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On Jul 21, 10:43 am, rvall...@xxxxxxxxx wrote:
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On Jul 18, 6:51 pm, rvall...@xxxxxxxxx wrote:
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On Jul 17, 6:29 pm, rvall...@xxxxxxxxx wrote:
kenseto ha escrito:

On Jul 17, 9:54�am, PD <TheDraperFam...@xxxxxxxxxx> wrote:
On Jul 17, 8:34�am, kenseto <kens...@xxxxxxxxxxx> wrote:

On Jul 15, 7:58�pm, bill <cosmo...@xxxxxxxxxxxxxxx> wrote:

Regarding Einstein�s train gedanken depiction of the Relativity of
Simultaneity.

In �Relativity the Special and General Theory� Einstein points out
that from the stationary observer�s point of view (M) flash B (toward
which the train is moving) will reach the passenger before flash A.

This assertion of Einstein is wrong. Why? Because it is based on
closing velocities between the light fronts from A and B and the train
observer M'. Closing velocities as perceived by the track observer (M)
has no effect on the propagation of light fronts in the train. Closing
velocities is not observed by the train observer M'. The speed of
light from different directions in the M' frame is isotropic. What
this mean is that the SR concept of relativity of simultaneity (RoS)
is based on a false premise. This also mean that any SR paradox (such
as the pole and the barn paradox) that uses RoS to resolve will remain
a paradox.
If the track observer wants to determine if the flashes from A and B
will arrival will arrive at M' simultaneously he uses the LT as
follows:
A and B are at equal distance of 0.5L from M'.
The contracted length of 0.5L is equal to 0.5L/gamma.
Therefore the arrival time (according to the train clock) of the
flashes from A and B is equal to 0.5L/c*gamma.

This means that according to the LT the flashes will arrive at the
train observer simultaneously. This also means that the SR concept of
RoS is bogus. Note that the LT does not use the closing velcities as
perceived by the track observer to determine the simultaneity of
events in the train frame.

Ken has been corrected on each and every one of the mistakes in this
post numerous times.

Hey idiot there is no mistake in what I said. Using closing velocities
to determine the arrival time of the light fronts from A and B is
wrong. Besides it violates the isotropy of the speed of light in the
train frame. You are stupid.

Maybe this can help. Closing velocity between two moving entities is
not a relativistic invariant (same in all frames), it is frame
dependent. c-v depends on v. For the stationary frame (observer M) it
is c-v, for the moving frame (observer M’ in the train frame) it is c
in both senses (because v is zero in this case), without violating any
speed of light isotropy in the train frame. Don’t confuse closing
velocity (c-v) between the light ray and the moving M’ with light
velocity (c) (the two entities measured in the same frame, the
stationary or the moving one). See my response to Androcles in this
same thread.

There is no confusion on my part. Closing speed is indeed observer
dependent. But the track observer cannot use his observed closing
speeds to determine if the events in the train frame is simultaneous.
The train observer must make this determination by himself. In the
train frame the speed of light is isotropic and therefore he does not
observe any closing speed between him and the light fronts. Therefore
if the strikes occur simultaneously at equal distance then he will
observe them to be simultaneous.

Read again Einstein’s text and be careful determining which are the
events considered simultaneous or not respect the two different
frames. The events are {two strokes of lightning A and B which are
simultaneous with reference to the railway embankment}(I put
Einstein’s word between { }). Observer M in the embankment will see
the two light rays arriving to him simultaneously by definition of the
experiment. But now we have a third event (the simultaneous arriving
of the two light ray to M) that must be present in all frames. This
excludes completely the possibility that the two light rays meet at
the centre point M’ in the moving train frame at the same time, as you
are suggesting.

I suggested no such thing. Here's what I suggested.

Read your point 8. [The train observer must also sees the strikes to
be simultaneous]. Then you are saying that the rays arrive
simultaneously to M’.> From the track frame's point of view:
1. The strikes occur at equal distance of 0.5L m from him.
2. The speed of light in the track frame is isotropic.
3. Einstein stipulated that the track observer sees the flashes to be
simultaneous.

Einstein stipulated that the flashes ARE simultaneous for the track
frame (primary fact). And then, as a consequence of the stipulated
position M in the centre, and the constant and isotropic light speed,
the light rays arrive simultaneously to M, that is an event that must
be present in ANY frame.> 4. From items 1,2 and 3 the track observer determined that the flashes
occur simultaneously to begin with.

The flashes are simultaneous in the track frame by definition of the
experiment. Then, as a consequence, the observer at M MUST see the
light rays arriving simultaneously to him, an event that must be
present in ALL frames.> 5. The track observer says: The speed of light is isotropic in the
train frame.

The speed of light is isotropic in all frames by Einstein’s second
postulate.> 6. The track observer said: The flashes occur at equal distance of
0.5L/gamma from the strikes.

False. The track observer doesn’t use any gamma. For him the light
rays are at equal distance from M’ ONLY at the starting instant of the
light rays (unique one when M’ coincides with M), and the equal
distance is 0.5L (not 0.5L/gamma). After this instant, the distances
from the light rays to M’ become different, owed to the different
closing velocities (c-v) and (c+v).

These assertions are bogus. Why? Because it contradicts with the
measured isotropy of the speed of light in the train frame. M' cannot
claim the isotropy of the speed of light and at the same time claims
that he is moving wrt the light fronts at (c+v) and
(c-v).

Vacuum light speed is isotropic c in all frames, by postulate and
experiment. I don’t understand what contradiction are you talking
about. Observer at M’ considers himself at rest in the train frame
(v=0), and for him the closing velocities are c-0=c+0=c (the isotropic
c).

Exactly M' measures the speed of light to be isotropic and thus he
does not see any closing velocity.

Wrong deduction. You have no reason at all to say that M’ [does not
see any closing velocity]. In the train frame simply the closing
velocities between the light rays and M’ and the isotropic c have the
same value, as I put to you very clear in my last comment.> But RoS insists that M' sees the
front  flash before the rear flash. This means that the front flash
takes less transit time to reach the train observer than the transit
time that required for the rear flash to reach the train observer.

Wrong deduction again. In the train frame the transit time for both
light rays to reach M’ is exactly the same, running the same distance
at the same velocity c. Yes, M’ sees the front flash before the rear
flash, what implies that the front flash occurs BEFORE the rear flash.
The delay between the flashes is the same delay between the arriving
rays to M’.> Since both flashes were generated simultaneously at equal distance
from the strikes,

Yes, equal distance in both frames, BUT NOT SIMULTANEOSLY in both
frames. The  flashes were generated simultaneously ONLY IN THE
EMBANKMENT FRAME.> this means that the speed of light is anisotropic
according to RoS. Such RoS assertion is in direct conflict with the
measured isotropy of the speed of light in the train.

You are the one making the wrong deduction about light speed being
anisotropic according to RoS, owed to your primary error supposing the
flashes simultaneous in both frames.

No I didn't make any wrong deduction. I said that the track observer
concluded that the flashes were simultaneous to begin with.
The flashes are simultaneous for the track observer by definition of
the experiment. This is the primary fact. It is not a consequence of
what he sees, but the contrary is the true. As a consequence of the
primary fact, the track observer sees the two light rays arriving to
him simultaneously, in agreement with the isotropic light speed in all
frames.
Thereefore
these same flashes will occur simultaneously TO BEGIN WITH for the
train observer.
This is your primary error. I will repeat here what Einstein writes
(between { }):

{Are two events (e.g. the two strokes of lightning A and B which are
simultaneous with reference to the railway embankment also
simultaneous relatively to the train? We shall show directly that the
answer must be in the negative.}
Relativity, The Special and the General Theories, 1916, Part I: The
Special Theory of Relativity, Incise 9: The Relativity of
Simultaneity. (Almost at the beginning).

You are supposing true (as part of the definition of the experiment)
precisely what Einstein showed false in his writing. And when you find
a contradiction, you claim it is a SR one, being really only YOUR
contradiction.

(Skipping the rest)

RVHG (Rafael Valls Hidalgo-Gato)
.

Relevant Pages

  • Re: The relativity of simultaneity
    ... which the train is moving) will reach the passenger before flash A. ... Closing velocities as perceived by the track observer ... light from different directions in the M' frame is isotropic. ... the two light rays arriving to him simultaneously by definition of the ...
    (sci.physics.relativity)
  • Re: The relativity of simultaneity
    ... which the train is moving) will reach the passenger before flash A. ... Closing velocities as perceived by the track observer ... light from different directions in the M' frame is isotropic. ... this mean is that the SR concept of relativity of simultaneity (RoS) ...
    (sci.physics.relativity)
  • Re: The relativity of simultaneity
    ... which the train is moving) will reach the passenger before flash A. ... Closing velocities as perceived by the track observer ... light from different directions in the M' frame is isotropic. ... the two light rays arriving to him simultaneously by definition of the ...
    (sci.physics.relativity)
  • Re: The relativity of simultaneity
    ... which the train is moving) will reach the passenger before flash A. ... Closing velocities as perceived by the track observer ... light from different directions in the M' frame is isotropic. ... this mean is that the SR concept of relativity of simultaneity (RoS) ...
    (sci.physics.relativity)
  • Re: The relativity of simultaneity
    ... which the train is moving) will reach the passenger before flash A. ... Closing velocities as perceived by the track observer ... light from different directions in the M' frame is isotropic. ... this mean is that the SR concept of relativity of simultaneity (RoS) ...
    (sci.physics.relativity)
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