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Video: The Hubble Ultra Deep Field in 3D

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Charles Johnson8/12/2009 2:46:06 pm PDT

How Can Galaxies Recede Faster than the Speed of Light?

As you look at galaxies further and further away, they appear to be moving faster and faster away from us. And it is possible that they could eventually appear to be moving away from us faster than the speed of light. At that point, light leaving the distant galaxy would never reach us.

When that happens, the distant galaxy would just fade away as the last of the photons reached Earth, and then we would never know it was ever there.

This sounds like it breaks Einstein’s theories, but it doesn’t. The galaxies themselves aren’t actually moving very quickly through space, it’s the space itself which is expanding away, and the galaxy is being carried along with it. As long as the galaxy doesn’t try to move quickly through space, no physical laws are broken.