Re: The relativity of simultaneity

On Jul 23, 7:04 pm, rvall...@xxxxxxxxx wrote:
kenseto ha escrito:



On Jul 21, 10:43 am, rvall...@xxxxxxxxx wrote:
kenseto ha escrito:

On Jul 18, 6:51 pm, rvall...@xxxxxxxxx wrote:
kenseto ha escrito:

On Jul 17, 6:29 pm, rvall...@xxxxxxxxx wrote:
kenseto ha escrito:

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

On Jul 15, 7:58�pm, bill <cosmo...@xxxxxxxxxxxxxxxx> 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. 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.
Since both flashes were generated simultaneously at equal distance
from the strikes, 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.

Observer M (at rest in the embankment frame) is the one
considering M’ moving at some not zero v velocity, and different
closing velocities (c-v) and (c+v) with the light rays. You are mixing
(incorrectly) an M observation with an M’ one. Of course, you arrive
to a contradiction, but it is only your one.

No I didn't mix anything. The closing velocities as seen by M has no
effect on the isotropy of the speed of light in the train. But RoS use
them anyway to arrive at the bogus assertion that the train observer
actually sees the front flash before the rear flash. This bogus
assertion leads to the bogus concept of RoS.



Your deduction that the track
observer considers the light rays always at the same distance from M’
is incorrect.

No it is not incorrect. Please watch the following video:
http://www.youtube.com/watch?v=wteiuxyqtoM
You will note that as the light spheres expand they will meet at an
infinite number of locations at equal distance from the origins of the
flashes. The track observer is located at one of these locations and
the train observer is at a different location but he will maintain the
same distance from the origins of the flashes.

It is totally incorrect. The distances that the track observer sees
between the light rays and the moving with v velocity M’ are inversely
proportional to the different closing velocities (c-v) and (c+v).

Your statement is totally incorrect. What the track observer sees as
closing velocities has avbsolute no effect on the isotropy of the
speed of light in the train. Beside the train must make his own
determine whether the strikes are simultaneous as follows:
1. The speed of light in his frame is isotropic.
2. He is at equal distance from the strikes.
3. It was determined that the strikes were simultaneous to begin with.
4. Therefore the train observer must also sees the strikes to be
simutlaneous.

Ken Seto

As a
consequence, ray B arrives to M’ before ray A arrives to M’. As I
noted you more than one time before (without any comment from your
part yet), two light rays running in opposite senses over the same
right line can meet simultaneously only at a single point, no matter
what frame are you using to describe the movement. In our case this
point is M in the embankment frame (by definition of the experiment),
excluding totally that the rays can meet also simultaneously at a
different M’ point as you are (incorrectly) claiming. The event of the
light rays arriving simultaneously to M’ simply doesn’t exist at all
in any frame, including of course the train one.
Even if in the train frame the points A and B (where the flashes
originate) are at the same distance from M’, that doesn’t imply that
the flashes were simultaneous in the train frame (your primary error,
as I had notice to you more than one time).

Ah....if the flashes were not simultaneous to begin with then the
track observer will not be able to see the flashes arriving at him
simultaneously. Why? Because the track observer is at equal distance
from the strikes and the speed of light in the track frame is
isotropic. It appear that it is you who made the error.

Ken Seto


I can’t see the video yet owed to local technical problems in my
computer. Anyway, a video shows only what his creator thinks it must
do. I am guessing that he shares with you the wrong idea about the two
flashes A and B being a single simultaneous event present in all
frames (or perhaps you are simply interpreting bad the video).
Absolute simultaneity can refer only to things occurring at the- Hide quoted text -

- Show quoted text -...

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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 ...
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  • Re: The relativity of simultaneity
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  • Re: The relativity of simultaneity
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