In Alan's frame of reference ...
In Beth's frame of reference ...
Beth (and her tape deck) are at the center of the railroad car. Alan, the tracks, and the landscape whizz by to the left at speed v. Alan stands by the railroad track. There are two loose wires on the track. Beth stands on a railroad car which moves at speed v to the right relative to Alan.
Just as Alan passes Beth, sparks occur simultaneously at both ends of the railroad car.
The railroad car comes to a halt a short distance down the track. Beth grabs her tape deck and hops off the car onto the ground. She and Alan walk towards each other. They meet.
Copyright © Michael Richmond. This work is licensed under a Creative Commons License.