Train and Tunnel - Solution
Back to problem
- In the tunnel frame points A and D are simultaneous
so the train fits inside the tunnel exactly.
But in the train frame D is simultaneous with C and A is simultaneous
with B. So when the nose of the train emerges from the tunnel at D,
the tail is still at C, and when the tail finally enters the tunnel at A,
the nose is already at B, so the train is much longer than the tunnel
in the train frame.
As we can see from the space-time diagram, this is not a contradiction,
just two different ways of seeing the same reality.
(Please review the section on