The author (giving away the answer in the next line) clearly expects you to correct for time dilation:
The author (giving away the answer in the next line) clearly expects you to correct for time dilation:
and most of you obliged him.
But what logic say:
- the observer knows nothing about space-time invariance, time is the same in all frames, and the answer is 75 min.
- he knows all about relativity, and he computes that the flashes were simultaneous in S’, and the answer is zero!
- He is a bit confused, and thinks that he had better correct for time dilation.
What I think: the author of the question wanted to point out the connection with the Lorentz transformation for time:
with x = Lproper, and got carried away.