Question

A person is watching a rocket with a astronaut inside move by at a speed near the speed of light. Which of the following statement is true?

• A. The length of the rocket is greater from the person's perspective than from the astronaut's perspective
• B. The length of the rocket is the same from the perspective of the person and the astronaut
• C. The length of the rocket is greater from the perspective of the astronaut than from the perspective of the person
• D. The person's length is greater, from his own perspective, as the rocket flies by, than it was before the rocket flew by
• E. The astronaut's length is greater, from his own perspective, as he flies by the person, than it was before he flew by the person

Answer 1

Answer: (C)

The length of the rocket is greater from the perspective of the astronaut than from the perspective of the person

Length of the moving rocket as seen by the person in rest frame $L=L_o\sqrt{1-v^2/c^2}$ $⟹L<L_o$

where $L_o$ is the rest length of the rocket as seen by the astronaut in moving frame.

Thus length of the rocket is greater from the astronaut's perspective than from the person's perspective.