*This preview shows
page 1. Sign up
to
view the full content.*

**Unformatted text preview: **hat the two events are spacelike separated, and, hence, acausal. They happen in a diﬀerent order in the two diﬀerent
frames. In the friends frame, the door closes and then hits the front. In the runner’s frame, when the pole hits the front, the door to the barn is still open. We
can show this rigorously using the formulae for Lorentz transformations. In the
friend’s frame the events happen
Barn door closes: (t1 , x1 ) = (0, 0)
Pole hits front: (t2 , x2 ) = (3.75 m, 15 m) (13) In the runners frame, these events happen as
¯¯
Barn door closes: (t1 , x1 ) = (0, 0)
¯¯
Pole hits front: (t2 , x2 ) = (−13.75 m, 20 m) (14) i.e. the barn door is still open when the pole hits the front in the runner’s frame.
Of course, we can ask what happens in the runner’s frame once the pole front hits
the barn. Let’s assume it can come to immediate rest. It takes ﬁnite time for
the front of the pole to communicate the stop” message to the back of the pole.
Assuming the pole is not completely r...

View
Full
Document