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Jerbearrrrrr
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I am having problems with this presentation of the train thought experiment. I actually think it's incorrect, but I'm not sure.
From Ray D'Inverno's book:
--
Imagine a train
travelling along a straight track with velocity v relative to an observer A on
the bank of the track. In the train, B is an observer situated at the centre of
one of the carriages. We assume that there are two electrical devices on the
track which are the length of the carriage apart and equidistant from A.
When the carriage containing B goes over these devices, they fire and activate
two light sources situated at each end of the carriage (Fig. 2.13). From the
configuration, it is clear that A will judge that the two events, when the light
sources first switch on, occur simultaneously. However, B is traveling
towards the light emanating from light source 2 and away from the light
emanating from light source 1. Since the speed of light is a constant, B will see
the light from source 2 before seeing the light from source 1, and so will
conclude that one light source comes on before the other.
[PLAIN]http://img144.imageshack.us/img144/2363/traing.jpg
--
- two sources of light (one on each end of train)
- B sits in the middle of train
- A sits on the platform (with same x-coord as B when the lights fire off)
- B sees the light first
Is it me, or is this a really bad treatment of the problem? The two lights that fire off at the same time...you can't really say something like that before simultaneity is understood surely.
My main problem is - B should see both flashes at the same time, if we reverse the situation (train stationary, A moving backwards).
I guess the author is saying "A sees the light flashes hit B at different times"?
If I am wrong (which I probably am), can someone explain what B observes and why?
Cheers
From Ray D'Inverno's book:
--
Imagine a train
travelling along a straight track with velocity v relative to an observer A on
the bank of the track. In the train, B is an observer situated at the centre of
one of the carriages. We assume that there are two electrical devices on the
track which are the length of the carriage apart and equidistant from A.
When the carriage containing B goes over these devices, they fire and activate
two light sources situated at each end of the carriage (Fig. 2.13). From the
configuration, it is clear that A will judge that the two events, when the light
sources first switch on, occur simultaneously. However, B is traveling
towards the light emanating from light source 2 and away from the light
emanating from light source 1. Since the speed of light is a constant, B will see
the light from source 2 before seeing the light from source 1, and so will
conclude that one light source comes on before the other.
[PLAIN]http://img144.imageshack.us/img144/2363/traing.jpg
--
- two sources of light (one on each end of train)
- B sits in the middle of train
- A sits on the platform (with same x-coord as B when the lights fire off)
- B sees the light first
Is it me, or is this a really bad treatment of the problem? The two lights that fire off at the same time...you can't really say something like that before simultaneity is understood surely.
My main problem is - B should see both flashes at the same time, if we reverse the situation (train stationary, A moving backwards).
I guess the author is saying "A sees the light flashes hit B at different times"?
If I am wrong (which I probably am), can someone explain what B observes and why?
Cheers
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