Simultaneity question (1 Viewer)

[yskloisky]

Jason and Kylie are sitting at the northern and southern ends respectively of a train carriage travelling north at a high speed. Each holds a torch that they turn on and off. Harold is standing on a platform beside the train. As the midpoint of the carriage passes Harold, he observes simultaneous light flashes from both Jason and Kylie. Which one of the following statements is true?

A. To an observer inside the carriage, located at its midpoint, Jason and Kylie turned on their torches at the same time.
B. To an observer inside the carriage, located at its midpoint, Jason turned on his torch before Kylie.
C. To an observer inside the carriage, located at the midpoint, Kylie turned on her torch before Jason.
D. It does not make any sense to ask in which order Jason and Kylie turned on their torches, because Einstein showed that time is relative.

No matter how I look at it, the answer should be B (if Kylie is at the rear and the observer is moving away from Kylie), but instead the correct answer is C. Please help.

 

[leehuan]

Disclaimer: When I analysed relativity of simultaneity in the HSC I analysed it by thinking about how the light travelled within it's frame of reference.

The train is travelling north, and Kylie is at the south. The torch is turned on when the MIDPOINT of the train reaches Harold. At this point, Jason is now travelling AWAY from Harold, whereas Kylie is still travelling towards.

When the light ray comes out of their torches, it will bend towards the northerly direction (c is constant in all frames of references). If Jason's light ray is bent north, it's only getting further away from Harold. Whereas if KYLIE's light ray is bent north, it's actually doing the opposite and getting closer.