# Special relativity and causality, which event actually happens?

In Revolutions in Twentieth Century Physics, David Griffith's introduces the relativity of simultaneity with a thought experiment akin to the "Train and platform" problem wherein the outcome is that two observers (one on a moving train car and the other on a stationary platform) differ in their observation of whether a flash of light (initiated at the moment both observers pass one another) hits the rear and front of the train car simultaneously or at different points in time.

I follow the thought experiment and the logic of the explanation, however when modifying the experiment as follows I loose myself and cannot reconcile what the outcome would be and why:

• If we add a condition that if light strikes the rear and front ends simultaneously, the observer on the train car (A) lives and if it strikes each end at a different time, observer A dies, would observer A live or die?

• From the perspective of the observer A, light would strike both ends simultaneously and he should continue to riding the train, however from the perspective of the observer on the platform he should die.

What would the "real" outcome be and how would we reconcile it theoretically?

• Alice is facing north. Bob is facing south. A light beam is fired in a random direction. If the light beam hits a target to their left, they die. The beam hits a target. Alice says "Oh, no! That target is on our left! We're doomed!". Bob says "Wrong! That target is on our right! We get to live!". What would be the real outcome and how would we reconcile it theoretically? Commented Apr 2, 2018 at 14:28