Suppose that you were able to build a spaceship that would a

Suppose that you were able to build a spaceship that would allow you to travel extremely close to the speed of light. Calculations show that you could fly to the center of the Milky Way (Distance = 30,000 light years), observe the super-massive black hole at the center and return in 20 years. Explain what would happen. Your clock on board the spaceship would run slow compared to the clocks on Earth. You would go on the trip but when you returned home you would find that 60,000 years had gone past on the Earth. This is because you are traveling at virtually the speed of light and it takes light 60,000 years to get to the center of the Galaxy and back again. You could travel this distance because throughout the trip you would be moving in slow motion. For you on the ship, just blinking your eyes might take years. Although you would return only 20 years older, you would likely be insane from being frozen in this super-slow motion state for 60,000 years. Your clock on board the spaceship would run slow compared to the clocks on Earth. But when you returned home you would find that only 20 years went by on the Earth as well. This is because it is nonsense that you would barely age but the Earth would be 60,000 years older. The reason that you can travel to the center of the Galaxy and back in 20 years is because your spaceship would be warping space-time. Everyone on Earth would agree that this is happening and during your journey, Earthlings would also measure the distance to the center of the Galaxy to be 10 light years. This would revert to its normal distance as soon as your trip was over and you stopped warping space-time. Your clock on board the spaceship would run slow compared to the clocks on Earth. You would go on the trip but when you returned home you would find that 60,000 years had gone past on the Earth. This is because you are traveling at virtually the speed of light and it takes light 60,000 years to get to the center of the Galaxy and back again. You could travel this distance because you would find that the speed of light is much larger when on board your ship. This means that Earthlings would say you are traveling much faster than the speed of light. But because you measure the speed of light to be greater, you would say that you traveled less than the speed of light. Your clock on board the spaceship would run slow compared to the clocks on Earth. You would go on the trip but when you returned home you would find that 60,000 years had gone past on the Earth. This is because you are traveling at virtually the speed of light and it takes light 60,000 years to get to the center of the Galaxy and back again. You could travel this distance because you would find that Earth\'s meter sticks shrink compared to yours. Inside your ship you would measure the center of the Galaxy to be only 10 light years away.

Solution

The last option is correct. Your clock on board the spaceship would run slow compared to the clocks on Earth. You would do on the trip but when you return home you would find that 60000 years had gone past on the Earth. This is because you are traveling at virutally the speed of light and it takes light 60000 years to get to the centre of the Galaxy and back again. You could travel this distance because you would measure the centre of the Galaxy to be only 10 light years away.