Texts: A spaceship, S, is flying in a straight line with a constant speed v = 0.6c over the antenna on the roof of an observation post, P. According to the clocks at observation post P, it took 0.4 μs for S to travel across the antenna. How long did it take for S to travel across the antenna according to clocks onboard S? How long is the spaceship according to P? The time of flight over the antenna, as measured by S, a) is the proper time, b) is not the proper time.