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Asked by anon-258116 on 30 Jun 2020.
Question: What's on the other side of a black hole
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Scott Lawrie answered on 29 Jun 2020: last edited 30 Jun 2020 12:58 pm
Black holes aren’t like a door in the wall: you don’t start on one side, go through the door and come out the other side. They’re actually three-dimensional like a ball, and no matter which way you fall into them, you always end up in the middle. There are all kinds of wierd and wonderful things that happen as you fall in, which you can research yourself, but what happens exactly in the middle is anyone’s guess: we just don’t know!
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Krishna Mooroogen answered on 30 Jun 2020:
Well, black holes aren’t really holes they are very dense leftover stuff from stars, this means there’s a lot of stuff crammed into a tiny space. The reason it looks black is that light isn’t fast enough (even though light is the fastest thing in the universe!) to escape the very high gravity. On Earth we have to make fast rockets (but nowhere near as fast as light) in order to escape the Earth – this is called escape velocity.
The reason in stories we talk about going through a black hole, comes from an idea that space can be bent due to high gravity. This is in essence Einstein’s theory of General relativity.
The idea goes, that if we bend space enough it could connect to very far places together. This is a bit tricky to imagine without a picture, but there are some nice videos on youtube about general relativity and hyperspace. -
Richard Fielder answered on 1 Jul 2020:
The future. An important point about relativity is that space and time aren’t separate, but rather there is a single 4-dimensional structure we call space-time. Just as it’s possible to rotate within 3-dimensional space so that you face in a different direction, it’s possible to rotate within 4-dimensional space-time. The spatial and timelike dimensions behave slightly differently, so we’re not able to simply turn on the spot and start travelling in time. But under certain extreme conditions, in particular very high velocity or very high gravitational fields, space and time dimensions can start getting rotated and mixed up.
It turns out that the event horizon of a black hole defines the point where space-time is effectively rotated by 90 degrees due to the strong gravitational field. The reason you can’t escape is that the centre of the black hole is no longer in front of you in a spatial dimension, but is rather in your future in the time dimension. The only way to change that is to cause a similar rotation in the dimensions to change it back again, which would require either a similarly large mass or travelling faster than light. As far as we know there is no way to produce either of those (you can’t create mass out of nowhere, and if you brought it with you you’d never cross the event horizon in the first place), which is why you can’t ever escape from a black hole.
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