Can you explain the whole traveling faster than the speed of light causes time to slow down thing? to me it seems to contridect relitivity... ( I prob won't get it though)
If the space ship time slowed down relitive to earth wouldn't earths time slow down relative to the space ship? I know earth has a greater mass and would be less affected bu the ship's launch but still...
That is a tricky one.
You know if you are traveling at 50 mph and a car passes you doing 60 mph, that car's speed, relative to you, is 10mph.
Well, no matter how fast you're moving, light always appears to travel at the same speed. So technically, if you were traveling at half the speed of light, a light beam traveling next to you should appear to be traveling at half it's normal speed, but it won't.
The reason is, traveling at half the speed of light, time is also affecting you at half the rate, so the light wave would still appear to be traveling at normal speed.
If you were traveling at half the speed of light, and left earth for 1 year, when you got back, 2 years would have passed.
What's amazing is that we have proven this experimentally. Cesium-atom clocks (accurate to billionths of a second) put on satellites (specifically, GPS) have to be recalibrated on a regular basis because they beat at different rates than they do on Earth because of the speed differential.
You can't travel faster than light. If it were possible to travel faster, light would travel faster. However, at the speed of light, if you could achieve it, time would basically stop for you. 1 second for you would be millions of years on Earth.
Books have been written about this, so my 2-paragraph layman's explanation really fails to do it justice, but that's the jist. Where logic would have us expect to see a relativistic change in the speed of light, the change actually occurs in the passage of time, making light's speed appear constant regardless of the speed of the observer.