Post by Flying Monkeys on Jan 2, 2018 14:42:09 GMT
Imagine you are on a spaceship which is 24 light-hours from Earth. That is, light takes 24 hours to travel from Earth to your ship.
You are looking at Earth through a telescope and, of course, what you are seeing happened on Earth 24 hours ago.
Then you hit the thrusters and head back to Earth at (or close to) the speed of light, so it takes you 24 hours to get there.
During that period, 24 hours of time has passed on Earth, so 24 hours of light is sent out from Earth.
Now, when you started, there was already 24 hours of light between you and Earth, so during your journey, 48 hours' worth of light will have passed through your telescope.
So:
1. 24 hours has passed on Earth.
2. 24 hours has passed on your ship.
3. 48 hours has passed through your telescope.
So what I am seeing through the telescope will be a load of people moving at 2x their normal speed, like fast forwarding a film.
Hence, as I move towards something, it appears to be more quickly. (And as I move away from something, it will appear to be moving more slowly, to the extent that if I travel away from them at the speed of light, they will appear motionless.)
Question:
If someone is standing on Earth and looking at me waving at them through my ship's window, will I appear to be waving at normal speed, faster than normal, or slower than normal? (Note, this is imaginary, it has nothing to do with them being able to see me, it is just asking what speed time appears to be passing on the ship to an observer on Earth.)
You are looking at Earth through a telescope and, of course, what you are seeing happened on Earth 24 hours ago.
Then you hit the thrusters and head back to Earth at (or close to) the speed of light, so it takes you 24 hours to get there.
During that period, 24 hours of time has passed on Earth, so 24 hours of light is sent out from Earth.
Now, when you started, there was already 24 hours of light between you and Earth, so during your journey, 48 hours' worth of light will have passed through your telescope.
So:
1. 24 hours has passed on Earth.
2. 24 hours has passed on your ship.
3. 48 hours has passed through your telescope.
So what I am seeing through the telescope will be a load of people moving at 2x their normal speed, like fast forwarding a film.
Hence, as I move towards something, it appears to be more quickly. (And as I move away from something, it will appear to be moving more slowly, to the extent that if I travel away from them at the speed of light, they will appear motionless.)
Question:
If someone is standing on Earth and looking at me waving at them through my ship's window, will I appear to be waving at normal speed, faster than normal, or slower than normal? (Note, this is imaginary, it has nothing to do with them being able to see me, it is just asking what speed time appears to be passing on the ship to an observer on Earth.)
