Question

Albert and Emmy are looking to purchase some new spaceships. They pick out two identical single-seat space racers and take them out to space for a test drive. After flying around for a while, they decide to do some experiments. As Albert flies past Emmy at a very high but constant velocity, Emmy measures the length of Albert's ship, and compares it to the length of her own ship.

A.) Emmy Observes that Alberts ship is (shorter, longer, or the same length) as her ship

At the same time,

B.) Albert Observes that Emmy's ship is (shorter, longer, or the same length) as his

I thought that they would both be the same length, but I was incorrect. Please explain.

Answer 1

They both will see other's spaceship as shorter than theirs. Emmy will observe that Albert ship is shorter than her ship. And Albert will observe Emmy's so to be shorter than his ship. The reason is length contraction: the length of moving object appear shorter than its length at rest.

For Emmy, Albert is in motion and she herself is at rest, so by length contraction she observed that Albert's ship is shorter than her ship.

For Albert, Emmy is in motion and he himself is at rest, again by length contraction he will observe that Emmy's ship is shorter than his ship.