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I have a spaceship moving at very close to the speed of light. Inside are the captain and two crew members. The captain is positioned at the front of the spaceship with a clock and a light. One crew member is positioned at the back of the spaceship, a certain distance away from the light, with a mirror and a clock, and the other crew member is positioned at the top of the spaceship, directly above the light, the same distance away from the light as the other crew member, and also with a mirror and a clock. All the clocks are synchronized. The captain notes the time on his clock and then flashes the light. When the crew members at the back and top of the ship see the flash they note the time on their respective clocks. The light then reflects off of the mirrors and returns to the captain, and he notes the time/times.

When the three men compare notes, what do they find?

Did the crew members at the back and top of the spaceship see the flash of light at the same time?

Did the reflection from both mirrors reach the captain at the same time?

Now let's consider the viewpoint of a stationary observer, standing on a nearby planet.

To the observer, did the light reach the two crew members at the same time?

To the observer, did the light return to the captain at the same time?

Thanks in advance for any insight that you can offer.