# Simply, what is a Wormhole?

I know it must be a little annoying to have someone ask for a simple explanation of something that isn't simple, but I've been trying to find out in various ways and nothing seems to explain exactly what a wormhole is. Sort of, not just how does it work but also how does it occur and what is it? Again this may be asking for the impossible but if I could get it in very, very Laymen's terms that would be great :)

DaveC426913
Gold Member
I know it must be a little annoying to have someone ask for a simple explanation of something that isn't simple, but I've been trying to find out in various ways and nothing seems to explain exactly what a wormhole is. Sort of, not just how does it work but also how does it occur and what is it? Again this may be asking for the impossible but if I could get it in very, very Laymen's terms that would be great :)

There's no need for us to write out the basics here when it's already available. Have you checked wiki?
http://en.wikipedia.org/wiki/Wormhole
It would be better to read up on it, then come back with specific questions. That's commonly how we handle these kinds of 'what is x?' questions.

BTW, the more formal term is Einstein-Rosen bridge.

I know it must be a little annoying to have someone ask for a simple explanation of something that isn't simple, but I've been trying to find out in various ways and nothing seems to explain exactly what a wormhole is. Sort of, not just how does it work but also how does it occur and what is it? Again this may be asking for the impossible but if I could get it in very, very Laymen's terms that would be great :)

You might want to check out this Wormhole FAQ.

DaveC426913 said:
BTW, the more formal term is Einstein-Rosen bridge.

Actually, the term "Einstein-Rosen bridge" is not synonymous with "wormhole". An Einstein-Rosen bridge is a particular type of wormhole. It is the non-traversable so-called maximally extended Schwarzschild solution to the Einstein equations. Basically, it's a wormhole with a black hole at either end.

Okay, well if the wiki page is all the 'basics' I definitely didn't understand much of it. Perhaps I need a crash course in physics. I'll try and ask more specifically.
So as far as I understand, a traversable wormhole (if they can even exist) would enable you to travel faster than light speed because of the curvature of spacetime. . does this mean that the inside of a wormhole does not exist in spacetime, perhaps outside of the universe in some way? And if so does that not completely disable any object, that exists in space and time, to transfer its existence into this wormhole at all (without some catastrophic effect)?
But I guess my main question is, even if you can travel faster than light in this way, how does that enable you to travel backwards in time or reverse time in anyway, or any definition/perception of time. Surely that's completely impossible?
And if my questions are already flawed or don't make sense please explain why. Thank you :)

DaveC426913
Gold Member
So as far as I understand, a traversable wormhole (if they can even exist) would enable you to travel faster than light speed because of the curvature of spacetime.
No, it does not allow you to travel faster than light; it merely shortens the distance between A and B. You still traverse that distance conventionally.

No, it does not allow you to travel faster than light; it merely shortens the distance between A and B. You still traverse that distance conventionally.

Okay, you don't technically move faster than light, but you arrive at B before light travelling outside the wormhole, but across the same distance? So, have you not still travelled to B faster than light? In our universe? Like teleportation? Why is it that some Physicists think this would enable you to time travel?

DaveC426913
Gold Member
Okay, you don't technically move faster than light, but you arrive at B before light travelling outside the wormhole, but across the same distance? So, have you not still travelled to B faster than light? In our universe?
Yes. The distinction is that it does not violate relativity. Relativity means that your speed locally cannot reach or exceed c.

Why is it that some Physicists think this would enable you to time travel?
Time travel follows directly and inevitably from wormhole traversal (as soon as you have the latter, you automatically have the former), though I can't recall right now exactly how to explain it.

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Nabeshin
Time travel follows directly and inevitably from wormhole traversal (as soon as you have the latter, you automatically have the former), though I can't recall right now exactly how to explain it.

The basic idea is as follows: Imagine you have two mouths of a wormhole, A and B, and that there is initially no time delay between them. Now, move one of the mouths of the wormhole,say B, near a black hole or some other such object to induce time dilation there. After a period of time, a large time delay will develop between the two mouths. All one needs to do is wait until this time delay is larger than the light-travel time between the locations of the two mouths. Now, if you jump in the wormhole at mouth A and emerge at mouth B, you can speed back to A and arrive before you even jumped in!

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Right. Aren't the implications of this all far too complex to even seriously consider? How can we know that this time dilation wouldn't affect the entire wormhole not just one mouth? How could it ever even be physically possible to move a wormhole at all, let alone maintain it near extreme forces or near light speed? Surely you can't even transfer into a spaceless space, because you are of space? So even if you can keep it open can it really be traversable? And with that theory of quantum mechanics could this not be actually an entirely different universe/dimension? So if you think about it, you can't arrive before you even jumped in, but before another you in another dimension/universe jumped in? And what is the reasoning in the theory that microscopic ones occur naturally all the time?
Basically what is the meaning of everything ever please?

Nabeshin
Basically what is the meaning of everything ever please?

Well that's a big question :)

I suggest if anyone wants to see a little bit about how 'classical' wormhole theory works you read Visser's treatise: Lorentzian Wormholes https://www.amazon.com/dp/1563966530/?tag=pfamazon01-20 .

A lot of the calculations are done assuming some kind of naive approximation of quantum gravity. I'll leave it to you to decide whether or not the results are compelling enough to warrant serious merit. At any rate, I think it's a great read regardless.

DaveC426913
Gold Member
Right. Aren't the implications of this all far too complex to even seriously consider? How can we know that this time dilation wouldn't affect the entire wormhole not just one mouth? How could it ever even be physically possible to move a wormhole at all, let alone maintain it near extreme forces or near light speed? Surely you can't even transfer into a spaceless space, because you are of space? So even if you can keep it open can it really be traversable? And with that theory of quantum mechanics could this not be actually an entirely different universe/dimension? So if you think about it, you can't arrive before you even jumped in, but before another you in another dimension/universe jumped in? And what is the reasoning in the theory that microscopic ones occur naturally all the time?
Basically what is the meaning of everything ever please?
Yep. All good questions. It's really science fiction at this time - even going so far as to rely on types of matter and/or energy not known to exist.

Threads have been locked for being far less science-fictiony than this one.

Well that's a big question :)

I suggest if anyone wants to see a little bit about how 'classical' wormhole theory works you read Visser's treatise: Lorentzian Wormholes https://www.amazon.com/dp/1563966530/?tag=pfamazon01-20 .

:) I know, and I'm not sure I'd even want to find out if I could.
Just wanted to get the idea of this whole theory for a piece of fiction I'm writing, but I know that it's a seriously considered theory and I don't like making mistakes (even in fiction). If I continue to this for further research then I'll definitely check out your recommendation, thank you.

Yep. All good questions. It's really science fiction at this time - even going so far as to rely on types of matter and/or energy not known to exist.

Threads have been locked for being far less science-fictiony than this one.

Ha, have they? Oh well, thanks, as long as there are no definite established answers I think I can be happy with what I've learnt so far.

You've all been helpful, I hope I'm not misusing this site in any way! :)

HarryRool's Wormhole FAQ was really interesting to read.

Having gone through all that, it seems to me the a wormhole could almost be said to be the geometric inverse of a 3-sphere, at least with respect to how hypothetical light pulses interact with them.
A light pulse emanating from a point in a 3-sphere diverges to "infinity", reaching a maximum radius, and then converges again, albeit at the antipode.
Whereas a light pulse from infinity converges on a wormhole, reaching a minimum radius, emanates from the other side and diverges to infinity again, albeit a different infinity.

Also, here's a great video simulating a flight through a wormhole:

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I suggest if anyone wants to see a little bit about how 'classical' wormhole theory works you read Visser's treatise: Lorentzian Wormholes https://www.amazon.com/dp/1563966530/?tag=pfamazon01-20 .

I looked at the Visser book once. If you're not at least a graduate student in physics with advanced calculus and differential geometry under your belt, you probably don't have much of a chance of understanding it. It's way over my head at least. Also, it's like 16 years old.

:) Just wanted to get the idea of this whole theory for a piece of fiction I'm writing, but I know that it's a seriously considered theory and I don't like making mistakes (even in fiction). If I continue to this for further research then I'll definitely check out your recommendation, thank you.

I think that a better choice for you would be a pop physics title that came out a couple of years ago, The Physics of Stargates -- Parallel Universes, Time Travel, and the Enigma of Wormhole Physics by Enrico Rodrigo. It's by the same guy who produced the Wormhole FAQ that I mentioned.

One of the Amazon reviewers for this book seems to be a screenwriter who used it to make his screenplay more believable.

I looked at the Visser book once. If you're not at least a graduate student in physics with advanced calculus and differential geometry under your belt, you probably don't have much of a chance of understanding it. It's way over my head at least. Also, it's like 16 years old.

Well, classical general relativity is old now

Understand the concept of wormhole by taking an example of an apple and a worm . Consider the apple has four faces with face 1 opposite to face 3 and ... . Now the worm wants to go from face 1 to face 3 . It can either go 1 to 3 by travelling to 2 or 4 and reach to 3 or , it can dig a hole inside the apple and reach to 3 .
This explanation is very basic , just to get the starting clue of what is wormhole. In order to understand what actually wormhole is , you must have good knowledge of SPACE-TIME reference frames .
I hope this helps .

Nabeshin
I looked at the Visser book once. If you're not at least a graduate student in physics with advanced calculus and differential geometry under your belt, you probably don't have much of a chance of understanding it. It's way over my head at least. Also, it's like 16 years old.

I think that a better choice for you would be a pop physics title that came out a couple of years ago, The Physics of Stargates -- Parallel Universes, Time Travel, and the Enigma of Wormhole Physics by Enrico Rodrigo. It's by the same guy who produced the Wormhole FAQ that I mentioned.

One of the Amazon reviewers for this book seems to be a screenwriter who used it to make his screenplay more believable.

Yes, Visser's book certainly has a higher entrance threshold than a popular science text. I'd say undergrad level GR and some knowledge of field theory, at the minimum. But a lot of it is heuristic anyways, so I don't think it's too bad if one has this and is willing to put in the effort. I don't really know of any other way to really learn about wormholes other than reading papers (and the field hasn't progressed too much since Visser wrote his book).

Of course if one doesn't have the preparation or time to invest in such an endeavor, popular books (or the FAQ you mention) are a good substitute. However this usually comes at the disadvantage of having to take a lot of things for granted, and pushing analogies sometimes farther than is correct. It is somewhat like trying to discuss modern cosmology when all you know about is the balloon analogy.