Strona 35 z 212

Now in reality (considered with reference to the railway

embankment) he is hastening towards the beam of light coming from

B, whilst he is riding on ahead of the beam of light coming from

A. Hence the observer will see the beam of light emitted from B

earlier than he will see that emitted from A. Observers who take

the railway train as their reference-body must therefore come to

the conclusion that the lightning flash B took place earlier than

the lightning flash A. We thus arrive at the important result:

Events which are simultaneous with reference to the embankment

are not simultaneous with respect to the train, and vice versa

(relativity of simultaneity). Every reference-body (co-ordinate

system) has its own particular time; unless we are told the

reference-body to which the statement of time refers, there is no

meaning in a statement of the time of an event.