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## Wormhole shortcuts

Imagine a traveller breaking down in the middle of the Australian outback, say 100 miles from Alice Springs. That’s much too far to walk, but being an enterprising guy he decides he can take a shortcut - instead of taking the route “as the crow flies”, he can instead get to Alice Springs direct “as the worm tunnels”. After all, the Earth’s surface is curved, so the direct route is quicker.

Sadly, of course, 100 miles is pretty much next-door compared to the size of the Earth, so the Earth’s curvature is pretty minimal at such a distance so our intrepid traveller would not actually save a tremendous amount of distance.

So this is the question I have about wormholes. Assuming that such things exist and are traversable as portrayed that Interstellar movie, would they save that much distance? In books and the like, the idea is always presented with a sheet of paper folded over 180 degrees, so there’s a short distance for the “wormhole” to travel.

Fine, except space appears to be very flat on a large scale - the paper is not folded. Suppose our Interstellar movie wormhole went only to the Andromeda galaxy - would it really be that much quicker, given that Andromeda is “pretty much next-door” to us compared to the size of the universe? Wouldn’t the universe being pretty flat rule out wormholes as shortcuts?

2. Originally Posted by Ufonaut99
Imagine a traveller breaking down in the middle of the Australian outback, say 100 miles from Alice Springs. That’s much too far to walk, but being an enterprising guy he decides he can take a shortcut - instead of taking the route “as the crow flies”, he can instead get to Alice Springs direct “as the worm tunnels”. After all, the Earth’s surface is curved, so the direct route is quicker.

Sadly, of course, 100 miles is pretty much next-door compared to the size of the Earth, so the Earth’s curvature is pretty minimal at such a distance so our intrepid traveller would not actually save a tremendous amount of distance.

So this is the question I have about wormholes. Assuming that such things exist and are traversable as portrayed that Interstellar movie, would they save that much distance? In books and the like, the idea is always presented with a sheet of paper folded over 180 degrees, so there’s a short distance for the “wormhole” to travel.

Fine, except space appears to be very flat on a large scale - the paper is not folded. Suppose our Interstellar movie wormhole went only to the Andromeda galaxy - would it really be that much quicker, given that Andromeda is “pretty much next-door” to us compared to the size of the universe? Wouldn’t the universe being pretty flat rule out wormholes as shortcuts?

There are so many theories about multiple varieties of wormholes, with no consensus on if or how they exist. We just don't have any solid data.

3. ine, except space appears to be very flat on a large scale - the paper is not folded. Suppose our Interstellar movie wormhole went only to the Andromeda galaxy - would it really be that much quicker, given that Andromeda is “pretty much next-door” to us compared to the size of the universe? Wouldn’t the universe being pretty flat rule out wormholes as shortcuts?
It may be flat overall, but there is plenty of local curvatures. It just balances out to flat.

4. Originally Posted by Noclevername
It may be flat overall, but there is plenty of local curvatures. It just balances out to flat.
Can you explain what you mean by “balancing out”? I’m not a physicist so it goes a bit over my head. Do you mean that there is negative curvature to balance the positive curvature around massive objects?

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5. Originally Posted by Jens
Can you explain what you mean by “balancing out”? I’m not a physicist so it goes a bit over my head. Do you mean that there is negative curvature to balance the positive curvature around massive objects?

Sent from my iPhone using Tapatalk
Some parts of space curve one way, some in another (due to gravitation, mainly) and given that it takes place roughly the same amount in all directions, it all adds up to about flat on large scales. It's like a textured wall (hate those things), there may be bumps but it's not a mountain range, it's a planar surface.

6. Originally Posted by Noclevername
Some parts of space curve one way, some in another (due to gravitation, mainly) and given that it takes place roughly the same amount in all directions, it all adds up to about flat on large scales. It's like a textured wall (hate those things), there may be bumps but it's not a mountain range, it's a planar surface.
I may be wrong about this, but when we say that the curvature is flat, I don't think we are talking about the curvature in a direction, but rather whether the universe is open (will undergo runaway inflation), or closed (so that it will recollapse), and that what we see seems to be very close to the critical density. Is that wrong?

7. Originally Posted by Ufonaut99
So this is the question I have about wormholes. Assuming that such things exist and are traversable as portrayed that Interstellar movie, would they save that much distance? In books and the like, the idea is always presented with a sheet of paper folded over 180 degrees, so there’s a short distance for the “wormhole” to travel.

Fine, except space appears to be very flat on a large scale - the paper is not folded. Suppose our Interstellar movie wormhole went only to the Andromeda galaxy - would it really be that much quicker, given that Andromeda is “pretty much next-door” to us compared to the size of the universe? Wouldn’t the universe being pretty flat rule out wormholes as shortcuts?
I may be wrong, because this is only something I have heard from other people, but although the universe appears to be flat in three dimensions, I think the argument is that, like the piece of paper that is flat in two dimensions but curved in three dimensions like the surface of the earth, there would be other dimensions, and so our universe could well be flat in the three dimensions that we see but curved in a higher dimension, and that the wormhole would allow you to cross that.

8. Originally Posted by Jens
I may be wrong about this, but when we say that the curvature is flat, I don't think we are talking about the curvature in a direction, but rather whether the universe is open (will undergo runaway inflation), or closed (so that it will recollapse), and that what we see seems to be very close to the critical density. Is that wrong?
Maybe. I interpreted "flat" as being like, as the OP said, curvature of space. But then I'm often wrong.

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Originally Posted by Noclevername
Originally Posted by Jens
I may be wrong, because this is only something I have heard from other people, but although the universe appears to be flat in three dimensions, I think the argument is that, like the piece of paper that is flat in two dimensions but curved in three dimensions like the surface of the earth, there would be other dimensions, and so our universe could well be flat in the three dimensions that we see but curved in a higher dimension, and that the wormhole would allow you to cross that.
Maybe. I interpreted "flat" as being like, as the OP said, curvature of space. But then I'm often wrong.
And I'm often wrong, too Taking the good old rubber-sheet analogy, locally mass like planets, stars, galaxies, etc make "dimples" in the sheet, so in a way I could see how we could "tunnel" through the dimple that we're in to get to somewhere a bit quicker. However, these dimples aren't that great nor deep, so we wouldn't save much.

On a larger scale, the rubber sheet extends out to (and presumably beyond) our observable universe. At this scale, the dimples are effectively too small to worry about - the sheet is to all intents and purposes flat, much as the surface of the earth is flat (around Alice Springs) if you ignore the small hollows. So my question is that at THIS scale, how would wormholes save you any appreciable distance?

10. Originally Posted by Ufonaut99
And I'm often wrong, too Taking the good old rubber-sheet analogy, locally mass like planets, stars, galaxies, etc make "dimples" in the sheet, so in a way I could see how we could "tunnel" through the dimple that we're in to get to somewhere a bit quicker. However, these dimples aren't that great nor deep, so we wouldn't save much.

On a larger scale, the rubber sheet extends out to (and presumably beyond) our observable universe. At this scale, the dimples are effectively too small to worry about - the sheet is to all intents and purposes flat, much as the surface of the earth is flat (around Alice Springs) if you ignore the small hollows. So my question is that at THIS scale, how would wormholes save you any appreciable distance?
The rubber sheet analogy does not correlate with the folded-paper analogy. You don't tunnel through a dimple.

11. Wormholes are not tunnels across space, but between spaces. They may take time to pass through (or may not, there's some argument about that) However, that transit time has no relation to how far apart the mouths of the tunnel are in normal space.

12. https://physics.stackexchange.com/qu...ugh-a-wormhole

Infinite-Exotic-Region Wormhole (exotic matter distributed throughout space) ~ 1 hour
Large-Exotic-Region Wormhole (exotic matter confined to large finite radius) >= 7 days
Medium-Exotic-Region Wormhole (exotic matter loosely restricted to throat) ~ 200 days
Small-Exotic-Region Wormhole (exotic matter closely restricted to throat) >= 0.7 seconds

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Originally Posted by Noclevername
The rubber sheet analogy does not correlate with the folded-paper analogy. You don't tunnel through a dimple.
Ah, that's interesting, so looks like I've misunderstood something. What I thought was, taking the rubber sheet analogy, Earth would cause a dimple, like :

rubber_sheet.jpg

This sheet is 20x20 squares, with the planet dead centre. Let's say each square, if the sheet was flat, would be 1 unit of length. So launching a rocket from the bottom of the dimple to the outer edge would have to follow the sheet, so have to cover a distance of, say, 20 units (since the squares near the planet are "stretched").

I always though wormholes were effectively "tunneling" from one part of the sheet directly to another part - in this case, a straight line from the bottom of the dimple up to the outer edge, so probably in this case being 15 units long.

So is that a wrong idea?

(ps, I appreciate that this assumes that space actually IS curved, and not just behaves as if curved. Actually, is this also important for whether wormholes are actually possible?)

14. Originally Posted by Ufonaut99
Ah, that's interesting, so looks like I've misunderstood something. What I thought was, taking the rubber sheet analogy, Earth would cause a dimple, like :

rubber_sheet.jpg

This sheet is 20x20 squares, with the planet dead centre. Let's say each square, if the sheet was flat, would be 1 unit of length. So launching a rocket from the bottom of the dimple to the outer edge would have to follow the sheet, so have to cover a distance of, say, 20 units (since the squares near the planet are "stretched").

I always though wormholes were effectively "tunneling" from one part of the sheet directly to another part - in this case, a straight line from the bottom of the dimple up to the outer edge, so probably in this case being 15 units long.

So is that a wrong idea?

(ps, I appreciate that this assumes that space actually IS curved, and not just behaves as if curved. Actually, is this also important for whether wormholes are actually possible?)
It's wrong in that wormholes are not lines. A line crosses space, a wormhole skips it altogether. The mouths of a wormhole are basically touching each other.

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Originally Posted by Noclevername
Thanks for the link. I'll have some reading to do ... but drats, will have to happen after work now !

16. Depending on the theory, some other estimates say it may take longer to travel through traversable wormholes than crossing physical light-years.

If traversable wormholes even exist. If wormholes themselves even exist.

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I'm not a fan of wormholes producing FTL travel but then I'm not a fan of FTL travel in general. Until/unless they can describe/explain the issues with causation I think it's fantasy. I suspect if we ever do find/create a transverseable wormhole then we will pop out the other end no quicker than the light distance between the ends. The trip may be shorter, but the external time will not be FTL.

Although that's just my opinion it is bad science to ignore the contradictions that a theory creates. FTL produces contradictions that are often conveniently ignored, even by scientists.

Of course, if I could get to my destination before I left it might solve my lateness issues.

18. Originally Posted by Bearded One

Of course, if I could get to my destination before I left it might solve my lateness issues.
Unless your trip takes longer than it would to cross the physical space. In which case you'd be even later!!

19. Originally Posted by Bearded One
I'm not a fan of wormholes producing FTL travel but then I'm not a fan of FTL travel in general. Until/unless they can describe/explain the issues with causation I think it's fantasy.
Personally, I'm a fan, but I agree with you that they are most likely fantasy. But then again, I'm also a fan of Harry Potter.

20. Originally Posted by Noclevername
Unless your trip takes longer than it would to cross the physical space. In which case you'd be even later!!
That could be an interesting premise for a story - takes longer but can get you from A to B without going through the intervening space. A story about slower hidden travel could be bit different at least.

21. The wormholes in Orion's Arm are consistent with theory, particularly so since they were revised by a physicist a few years ago; they do have issues with causality, but there is a whole subset of wormholes which do not have such issues, simply because of the geometry of space-time. Here is a diagram that should explain why this is so.
https://www.orionsarm.com/page/322
So long as both mouths of a wormhole stay outside each other's future light cone, no causality problems can occur.

22. Originally Posted by Van Rijn
That could be an interesting premise for a story - takes longer but can get you from A to B without going through the intervening space. A story about slower hidden travel could be bit different at least.
I recall some science fiction story where the idea was they went into something like "subspace" or a different dimension, where the speed of light was different than our's. Of course the hope was the speed of light was faster in that dimension, but it was in fact slower.

A little more seriously, yes, I like that idea, at least for a story. Imagine that travel through the wormhole is faster for those in the wormhole, but no faster for those outside of it. So one could travel to another planet quickly, by your perspective, but years would have passed in normal space. Would solve the paradox problem and give us interstellar travel.

23. Originally Posted by Swift
I recall some science fiction story where the idea was they went into something like "subspace" or a different dimension, where the speed of light was different than our's. Of course the hope was the speed of light was faster in that dimension, but it was in fact slower.

A little more seriously, yes, I like that idea, at least for a story. Imagine that travel through the wormhole is faster for those in the wormhole, but no faster for those outside of it. So one could travel to another planet quickly, by your perspective, but years would have passed in normal space. Would solve the paradox problem and give us interstellar travel.
(My Bold) I always assumed this to be the case anyhow?? This was always my understanding of how wormholes, warp-drive or any other FTL travel would work to eliminate causality paradoxes.

24. Originally Posted by cosmocrazy
(My Bold) I always assumed this to be the case anyhow?? This was always my understanding of how wormholes, warp-drive or any other FTL travel would work to eliminate causality paradoxes.
But that is rarely (never?) how they are depicted in fiction.

25. Originally Posted by cosmocrazy
(My Bold) I always assumed this to be the case anyhow?? This was always my understanding of how wormholes, warp-drive or any other FTL travel would work to eliminate causality paradoxes.
Most fictional FTL portrays the same time passage in normal space, as inside the wormhole/warp/hyperspace. Most popular SF (Star Trek, etc) is guilty of non-Einsteinian simultaneity. So commonly that most lay people assume it to be the case in theory, as well.

26. In my mind FTL is only ever going to be useful to the traveller, in that he/she can get somewhere much faster in their own time frame.

So for example, a signal is sent at the speed of light from an initial point (A) , the receiver is 5 light years away at point (B). At the same time the signal is sent from point A a traveller goes through a worm-hole instantaneously to point B. At the exact moment the traveller arrives at point B (back to the initial reference frame) the sent signal is received. The traveller never arrives before the signal. For the traveller no time has passed but for the initial reference frame 5 years has gone by.

Essentially the traveller steps out of the initial time frame then re-enters 5 years in the initial frame of reference's future.
Last edited by cosmocrazy; 2019-May-29 at 02:41 PM.

27. Originally Posted by Swift
But that is rarely (never?) how they are depicted in fiction.
Ah.. yes i see what you mean

28. Originally Posted by cosmocrazy
In my mind FTL is only ever going to be useful to the traveller, in that he/she can get somewhere much faster in their own time frame but all other relative time frames remain within the laws of physics.

So for example, a signal is sent from an initial point (A) at the speed of light the receiver is 5 light years away at point (B). At the same time the signal is sent from point A a traveller goes through a worm-hole instantaneously to point B. At the exact moment the traveller arrives at point B the initial signal is received. The traveller never arrives before the signal. For the traveller no time has passed but for the other reference frames 5 years has gone by.

Essentially the traveller steps out of the initial time frame then re-enters 5 years in his/her future.
So FTL would really be EAFAL: Exactly As Fast As Light.

29. Originally Posted by Noclevername
Most fictional FTL portrays the same time passage in normal space, as inside the wormhole/warp/hyperspace. Most popular SF (Star Trek, etc) is guilty of non-Einsteinian simultaneity. So commonly that most lay people assume it to be the case in theory, as well.