19. An astronaut traveling with a speed v = 0.90c holds a meterstick in his hand. If he measures its length, he will obtain a value of
(A) 1.0 m,
(B) 2.5 m,
(C) 0.10 m,
(D) 0.50 m,
(E) 3.80 m.

1. 題目解析在這道題目中，考慮到相...