Originally posted by woadman
It is commonly believed that all galaxies are moving away from each other..because the empty space between them is expanding. (Dark energy) So are we moving away from other galaxies FASTER than the speed of light? Einstein said that was a no-no.
Not all galaxies are moving apart. Andromeda and the Milky Way are on a collision course, due to start colliding in about 2 billion years or so.
But the thing about the speed of light, space itself does not have to obey that limit. That limit is only for matter being accelerated by some force, it does not get to the speed of light, instead starts warping time and space in a way that foreshortens the object moving close to c and time slows down in its own frame of reference.
If we can get spacecraft going at .99c we can effectively (at least for the travelers) go faster than c. That is to say, you might think you are going say 7 times the speed of light and a trip say 70 light years would only take ten years of ship time and the people inside would age only ten years. So if they do that exact trip, going out 70 light years, say spending 10 years on the planet orbiting the target star, when they get back to Earth, they will have aged 30 years but 150 years will be seen to have gone by on Earth.
So Earth men see the trip as not going faster than the speed of light but the people on board will have traveled in time to a future 120 years later than they otherwise would have seen.