View Full Version : Black Holes Eating Space-Time

2010-Nov-02, 09:39 PM
Just a question about black holes:
Are black holes literally consuming space-time, or just producing really strong bends in the space-time grid like any other massive object? By consuming space time, I mean will a spot infinitely far away, given enough time, eventually be consumed by the black hole (as if the infinite spot is tied to a rope, and the black hole is slowly but surely pulling in the rope). What I am leading to, is if black holes were consuming space time, then as the universe turns into black holes and white dwarfs, if there were enough black holes, perhaps could it overcome the expansion of space, and end up in a big crunch?

Ken G
2010-Nov-02, 09:58 PM
On large scales, mass has the same effect on spacetime whether it is spread out or concentrated in black holes. Black holes only do violent things to spacetime locally to the hole.

2010-Nov-03, 03:26 AM
you can think of any gravitational body as pulling on the "fabric" of space/time but unlike a real blanket it doesn't snap or even get tighter as you real it in.

The issue is there are many ways to conceptualise what is actually happening and you have to pick the best conceptualization for the question you are asking.

I doubt that the expansion of space would be effected if every massive body turned into a black hole. This is because at even nominal distances from a black hole space operates fairly normally. You've probably heard that if they sun suddenly changed to a black hole of the same mass the Earth's orbit would not change. Expansion is only measurable at a VERY large distance and at these distances the presence of black holes are pretty much distinguishable from a non black hole body of the same mass.

To take it further and expand on what Ken said. If we took Andromeda and replaced it with an equal mass black hole not much would change for the milky way. We'd have a great gravitational lens but until it got close, like in 5 billion years, we'd be ok and even then I'm not sure if the merger would be much worse then it is already going to be.