Ok so in Einstein's thought experiment with the train, everything makes sense except...
Einstein is stating that an event doesn't happen until someone SEES it. But isn't there a difference between SEEING an event happen and the event happening regardless of whether someone sees it or not...
Homework Statement
Spaceship with proper length 100m is moving at 0.2c in +x direction. In the back and front of the spaceship is a light source.
a. When the light in the back is turned on, how long will it take for the light to reach the front of the spaceship?
b. How about the light in...