# Tag Info

## New answers tagged galaxies

1

The other answers seems to answer most of your questions, but I think one confusion remains: The speed of light as a maximum speed in the Universe (which is not the case). First off, redshift doesn't go to infinity for objects receding at $v = c$. We easily see galaxies recede at superluminal velocities. In fact, this is the case for all galaxies with a ...

1

Heather is right and it is not much more complex than that. Except you might need to follow the math to understand it. Dodelson certainly has the math. Light goes at c. Period. If you want to find the geodesics of light you set the metric ds^2 = 0. But space itself expands, and it can expand at any spee, it is not a particle or wave or object, it is just ...

1

The problem with the assumptions in your second paragraph is that space is moving, not the galaxies. Space itself can travel faster than the speed of light - that is not forbidden by general relativity. The speed of light as a constant therefore still holds, removing the implications you bring up. As an analogy, imagine you have a coordinate grid, and you ...

0

Well, I'm no expert, but I think part of the problem is that the definition of a galaxy is somewhat shaky. This article (which references this paper) has the definition, "A galaxy is a gravitationally bound collection of stars whose properties cannot be explained by a combination of baryons and Newton’s laws of gravity." So I suppose that we can't ...

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