I understand the fundamental functioning of a wormhole, just take a sheet of paper representing space time, and then fold it to make a hole with a pencil, so there you go, you have a faster passage to the other side of the sheet. However, what I don’t understand is how exactly space-time folds to allow for this passage. I always thought that space was something flat that has leveling according to the mass of stars and planets, so how exactly is it folded up allowing it to pass through a wormhole?
In: Physics
Wormholes are purely theoretical. The maths works for them, but there’s no evidence that the physics works.
Imagine having to find a path between two points on a piece of apper. There may be a whole number of different paths you could take (an infinite number), but given any two paths you can always turn one into the other by nudging it bit by bit.
The idea behind a wormhole would be that there could be paths where that isn’t possible; say if there is a hole in the middle of the paper; you can’t nudge a path that goes around one side into a path that goes around the other side.
And this leads to some interesting results; there are some maths/physics things that don’t change between paths where you nudge one into the other, but might get a different result if you take a path that goes the other side of a hole.
So with our wormhole, there may be two regions of spacetime that are connected via two separate sets of paths (“normally” and “through the wormhole”) and that could be interesting as it could mess with causality, leading to time travel and so on.
But there is no evidence that spacetime is disjointed in this way. It appears to be more like the piece of paper without the hole.
The problem with the “folding a piece of paper” analogy for wormholes is that the paper is a 2-d surface being folded in a larger 3-d space. Whereas spacetime is a 4-d “surface” that isn’t (as far as we know) embedded in some higher dimensional space. So it doesn’t necessarily make sense to talk about “folding” spacetime and trying to join different bits together.
Space is flat, at least the part around here is. However, that’s like standing in a parking lot and determining the Earth is flat. There could be places in the mountains or the ocean where there are deep channels that connect one place to another place.
On a small scale, humans make these, they are called tunnels.
The tunnels humans make are 3D, just like the mountains, because the Universe is very, very flat around here. It could also be that the Universe has more than 3 spatial directions, many string theories depend on this. Perhaps around here, three are flat and all the rest are tightly curled at a sub-atomic scale. In some other place, our three flat ones might have a different shape and other dimensions might be flat. If that’s a thing, and you can go to one of those places (for cause one of them to form) then you might find exceptions where a small movement in a new dimension brings you to a place that’s far away in our regular 3. The line between physics theory and science fiction is thin in this area.
Current experiments indicate space is “flat”, but none of these experiments are precise enough yet to truly rule that it is. They just indicate a high likelihood it is. Even an extremely slight curve to spacetime would change the nature of our universe drastically from flat, to positive curve or negative curve.
Wormholes are still purely theoretically to our knowledge. As in we haven’t actually found any yet. Or at least any that we are aware are wormholes (lookin’ at you black holes!).
The theory behind them is that they provide a shorter path between two points. Similar to drilling a tunnel through a hill instead of walking around it. Except you aren’t really drilling through anything, you are just decreasing the distance between two points compared to the distance involved using a different path. The paper-pencile metaphor is one of the best ways to visualize it.
From my understanding, Spacetime is a 4D geometry. Pretend a 2D plane is the 3D World we live in, fold it in 4D (represented by the 2D plane in 3D) and you have your shorter distance.
To take it down a dimension with 1D bring a straight line like a string, each end is far away from the other end but in 1D you can’t shorten the distance. Now imagine bending the string on a flat surface, bringing the two ends next to each other. Now their distance is much closer.
I hope that makes sense!
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