At the beginning of his 1905 paper 'On the Electrodynamics of Moving Bodies' Einstein defined the synchronization between two clocks using light signals, and on this basis formulates the following theorems(adsbygoogle = window.adsbygoogle || []).push({});

1. If the clock at B synchronizes with the clock at A, the clock at A synchronizes with the clock at B.

2. If the clock at A synchronizes with the clock at B and also with the clock at C, the clocks at B and C also synchronize with each other.

Furthermore, he assumes the following postulate holds true:

Any ray of light moves in the 'stationary' system of co-ordinates with

the determined velocity c, whether the ray be emitted by a stationary or

by a moving body.

So if a clock A at rest at the origin of the stationary system sends out a light signal with a timestamp t_A to a clock C at rest at location x in the stationary system, and this time stamp is found to synchronize with clock C (t_C = t_A +x/c), then the same timestamp t_B=t_A sent out by a clock B in motion at the origin of the stationary frame should, as per the above postulate, also synchronize with clock C.

However, this appears to contradict the Lorentz transformation, where a moving clock does not synchronize with a distant clock in the stationary system even if it synchronizes with a co-located stationary clock. How is this contradiction explained?

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# Speed of light postulate and clock synchronization

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