Question

If I am travelling 1mph below the speed of light past a stationary observer, and throw a ball at 50mph (relative to me), what would the observer see? Would the ball move 49mph faster than the speed of light relative to the observer?

Answer 1

An observer would see the ball travelling at pretty much the same speed as you. Moving clocks run slow. Although in your reference frame the ball would appear to move away quite quickly, in the observers frame the separation between you and the ball would grow very slowly.

Answer 2

When talking about such high speed one has to take into account relativistic effects. The idea behind relativity is that velocities are meaningless unless you give a reference. If i sit in a train, I view my seat as not moving, but to someone standing next to the train tracks sees my chair and I zooming by at quite a high speed.

Here is where things get weird. According to the theory of relativity ALL observers, no matter how fast they are going, see the SAME speed of light. So you travailing 1mph less than the speed of light would still measure the same speed of light as someone standing still. This can only occur if time slows down for the person traveling very fast.

So the person standing still would see the ball only go slightly faster than you but still going below the speed of light. But because time has slowed down for you, you would see the ball travel away at 50mph

Answer 3

What if you place a phone call to earth, at say, 0.7c, since radio waves travel at the speed of light, you should still be able to make the call. Would you sound like you were speaking really slowly?

Answer 4

Yes you would, well you have the right idea at least.

The light waves transmitted by the phone call would be stretched out if you were moving away from earth, and they would be squished together if you were moving towards earth. It's almost the same idea as the Doppler effect with sound.

When you hear a firetruck's siren coming toward you, the sound waves squish together and a higher pitched noise is heard. When the truck moves away the opposite happens and a lower pinched noise is heard. Same idea with light but instead of pitch changing, color changes.

Light waves from an object moving towards earth have higher energy light waves, they get bluer. Objects moving away appear redder. This is called red shifting or blue shifting. Astronomers use this effect to study many astronomical effects.

Answer 5

so if some is sending a live video from close to a black hole...the whole video will be red...did i get it right ?

Answer 6

Yes but that is due to Gravitational red shifting. Gravity in this case is pulling on the light waves causing them to stretch out.