Below is normal example that is generally given for loss of simultaneity in relativity

A person (A) is on platform. Another person (B) is travelling in train (moving left to right). When person A is right at middle of moving train (outside), lightning strikes at both the ends.

  • A sees lighting strike at both ends as simultaneous

  • B doesn’t see both the events to be simultaneous. Strike on the right is seen to be before left

There are couple of questions I am struggling with:

  • Typical explanation given is since B is moving towards right & light from right side is coming towards person, it will meet person B first and hence lighting on right will appear to B to happen before. So is this loss of simultaneity real or just because light takes more time to travel from left side. You can potentially have events which are simultaneously but light from them need not reach observe in same time.

  • If light didn’t have same velocity in all frame of reference and behaved like other velocities what will B see? both the events simultaneous.? If yes why.?

  • 1
    $\begingroup$ Let it also be noted that if when lightning strikes both ends of the train it also illuminates clocks that are located at each opposite ends of the train, the two flash images of the clock readings, when reaching B, will also confirm to B that the lightning struck the front of the train first. Understand how this occurs, and you will be on your way to understanding SR and simultaneity. $\endgroup$ – Sean Dec 6 '17 at 17:27
  • $\begingroup$ This animation provides a decent visual depiction of not only the relativity of simultaneity but also of the physical consequences of time dilation and length contraction associated with it -- youtube.com/watch?v=C2VMO7pcWhg $\endgroup$ – JM1 Dec 17 '17 at 4:47

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