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Author Topic: Are wormholes real?  (Read 13773 times)

Joshua Speelman

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Are wormholes real?
« on: 15/12/2010 13:30:03 »
Joshua Speelman  asked the Naked Scientists:
   
In science-fiction book and movies, the concept of faster than light travel is often portrayed by "space folding" or "wormholes".  

Are such things even hypothetically possible or are they just flights of fancy?

Joshua Speelman
Michigan, USA

What do you think?
« Last Edit: 15/12/2010 13:30:03 by _system »


 

Offline Bill S

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Are wormholes real?
« Reply #1 on: 15/12/2010 14:56:38 »
Hi, Joshua,

I am not a scientist, but I have a sort of interest in time travel, so I have done a bit of reading on this subject.  This extract from my notes may be of interest.


So much has been written about wormholes, both in science fiction and in popular science books that it is very easy to lose sight of the fact that a wormhole is actually a hypothetical topological feature.  No-one has ever seen a wormhole, or even found physical evidence of one.  Furthermore, although there is good evidence for the curvature of spacetime, in various scenarios, there is no actual physical evidence for the large scale “folding” of space that would permit the use of wormholes as the sort of shortcuts, illustrated in numerous popular science books. 

    Traversable wormholes are not ruled out by general relativity, and it could be that one of these might occur naturally.  However, by far the majority of the solutions of the equations of general relativity indicate that naturally occurring wormholes would be so short lived that their throats would snap shut before even light had time to pass through; so a theoretically traversable wormhole might be of absolutely no practical use, unless it could be modified in some way. 
Enter Kip Thorne, who demonstrated that a Lorentzian wormhole could be held open by the introduction of exotic matter – a theoretical substance which has negative energy density, and which may not be ruled out by general relativity.

So, all very hypothetical stuff, but great for science fiction, which I think is where it all started.
 

Offline graham.d

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« Reply #2 on: 16/12/2010 11:01:01 »
That's a good answer for a non-scientist, Bill.
 

Offline Don_1

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Are wormholes real?
« Reply #3 on: 16/12/2010 13:22:36 »
Until a wormhole is found, they can only be a hypothetical flight of fancy. The question is, would we recognise one if it were there? Could we actually detect a wormhole, if they do exist?
 

Offline Bill S

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« Reply #4 on: 16/12/2010 15:32:59 »
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Could we actually detect a wormhole, if they do exist?

"Cherchez le ver."
 

Offline yor_on

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« Reply #5 on: 17/12/2010 01:02:17 »
I don't think there are any stable wormholes. Maybe they can come to be some short instant but they should collapse immediately. the only way to keep one 'open' seems to be if you could 'coat' its 'inside' with something strong enough (a 'force') to stop it from collapsing on itself, I saw some such idea somewhere I'm sure?

Don't remember what they suggested using though, but whatever it was it made no sense as you should be crushed to smithereens trying to travel such a thing anyway.

If you think of how Einstein used the concept of 'geodesics' to present the idea of a 'wrinkled' 'SpaceTime' though :) Expending energy you can break loose from those 'geodesics' light takes and so shorten the journey. ´But looking at space 'naievly' that would not shorten the 'distance' from A to B, as it would seem as the shortest line anyway in a Newtonian 'space', as I understands it.
« Last Edit: 17/12/2010 09:34:12 by yor_on »
 

Offline Bill S

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« Reply #6 on: 17/12/2010 17:09:23 »
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Don't remember what they suggested using though

If I remember rightly it was Kip Thorne, responding to a question from Carl Sagan, who started it all.  His suggestion that exotic matter could be used to prop open these hypothetical wormholes has been taken up by others since. I think Thorne had grave doubts about the feasibility of all this, so perhaps he is a reluctant hero of the time travel revolution.
One thing that puzzles me is how one would get the exotic matter into (through) the wormhole if it was inclined to snap shut before light had time to pass through, which seems to be the prediction.   
 

Offline QuantumClue

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« Reply #7 on: 17/12/2010 18:35:21 »
I don't think there are any stable wormholes. Maybe they can come to be some short instant but they should collapse immediately. the only way to keep one 'open' seems to be if you could 'coat' its 'inside' with something strong enough (a 'force') to stop it from collapsing on itself, I saw some such idea somewhere I'm sure?

Don't remember what they suggested using though, but whatever it was it made no sense as you should be crushed to smithereens trying to travel such a thing anyway.

If you think of how Einstein used the concept of 'geodesics' to present the idea of a 'wrinkled' 'SpaceTime' though :) Expending energy you can break loose from those 'geodesics' light takes and so shorten the journey. ´But looking at space 'naievly' that would not shorten the 'distance' from A to B, as it would seem as the shortest line anyway in a Newtonian 'space', as I understands it.

To make a wormhole stable, we require exotic matter... this may come readily in black holes, however, we cannot make much of this in the lab. The closest we come to making this stuff, exists in the center of an interaction in the vacuum called the Casimir Effect.
 

Offline yor_on

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« Reply #8 on: 18/12/2010 16:53:57 »
To be honest I only know of one kind of matter myself, the one I meet everyday. I can't touch any 'anti matter' as it would transform, together with parts of me presumably, into rest products of positive energy as I understands it :) Exotic matter as seen inside a vacuum may exist, but I would rather call it a 'foam', or a 'fluid', or a 'field' myself. To me matter constitutes of what is 'touch able' by me. The baryonic kind if you like :) But there exist several definitions of what 'exotic matter' constitutes. 
 

Offline QuantumClue

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« Reply #9 on: 18/12/2010 18:14:24 »
Well, exotic matter is just like ordinaty matter except for one fundamental difference, and that is it is an antigravity substance. It's just as real and just as tangible as all other matter. Large amounts of it however are rare.
 

Offline peppercorn

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« Reply #10 on: 18/12/2010 19:59:50 »
Well, exotic matter is just like ordinaty matter except for one fundamental difference, and that is it is an antigravity substance. It's just as real and just as tangible as all other matter. Large amounts of it however are rare.

Has anyone actually found proof of Anti-gravity partials/material? Not so much rare as highly theoretical, surely?
 

Offline QuantumClue

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« Reply #11 on: 18/12/2010 20:57:48 »
Well, not to my knowledge. We can theoretically create some of this stuff. A very small portion of the Casimir force an interaction between two plates in a vacuum has a very small amount of exotic matter. So yes, we can make this stuff in the lab; we cannot harvest it though, to any practical needs however.
 

Offline Bill S

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« Reply #12 on: 18/12/2010 21:38:55 »
I thought the Casimir effect was due to interaction between virtual particles and the metal plates, but it's all a bit technical for me. 
Where does the exotic matter come into it?
 

Offline QuantumClue

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« Reply #13 on: 18/12/2010 22:03:05 »
I'll try and sum this up quickly then, as lay as I can make it.

The energy arising between two plates in the vacuum is an increasingly negative energy as the plate seperation is reduced.
 

Offline Bill S

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« Reply #14 on: 19/12/2010 20:03:44 »
Sorry,QC, I still don't see the link between negative energy and exotic matter. [:I]
 

Offline QuantumClue

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« Reply #15 on: 20/12/2010 11:12:01 »
I hate to state the obvious, but negative matter is a negative energy -Mc^2.
 

Offline peppercorn

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« Reply #16 on: 20/12/2010 12:06:20 »
So yes, we can make [exotic matter] in the lab; we cannot harvest it though, to any practical needs however.

Wikipedia, the bastion of all human knowledge ;), says the following about Exotic matter:
"[Exotic matter can be] Hypothetical particles which have "exotic" physical properties that would violate known laws of physics, such as a particle having a negative mass."

http://en.wikipedia.org/wiki/Exotic_matter

It lists other definitions of ExM, but this is the only one that comes close to fitting what you are describing.
« Last Edit: 20/12/2010 12:08:10 by peppercorn »
 

Offline imatfaal

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« Reply #17 on: 20/12/2010 14:13:36 »
QC - you're making a lot of leaps there.  Casimir effect is not normally viewed as proof of either negative energy nor negative mass which as p'corn (1,000 post congratulations) mentioned is still highly theoretical and thus fits the name exotic.  Casimir is generally seen as the ruling of out of larger wavelength sections of zero point energy fluctuations; thus causing an imbalance and an inward force.  There is a great demonstration here at Wolfram and a really good 'layman's' (some peoples favourite term of opprobruim at the moment) explanation here at  IOP (sign up required - but free)
 

Offline QuantumClue

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« Reply #18 on: 20/12/2010 15:16:14 »
Let's take a look shall we at what I said. If we go to wikipedia's article on the casimir effect, we actually have a small portion dedicated to wormholes:

''Exotic matter with negative energy density may be required to stabilize a wormhole.[20] Morris, Thorne and Yurtsever pointed out that the quantum mechanics of the Casimir effect can be used to produce a locally mass-negative region of space-time,[21]''

Which is what I have said.

http://en.wikipedia.org/wiki/Casimir_effect

The idea the energy is increasingly negative is not actually theoretical - it's a part of experimental fact. It is used in the hopeful harvest of large amounts of negative energy http://arxiv.org/ftp/physics/papers/0010/0010027.pdf
 

Offline imatfaal

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« Reply #19 on: 20/12/2010 16:31:38 »
QC - I hate to quibble on an off-topic note, but that is one unpublished paper and an aside on wikipedia.  I am not even saying you are incorrect - but need a little more backup than that for such statements as
Quote
It's just as real and just as tangible as all other matter
Quote
it's a part of experimental fact
Quote
So yes, we can make this stuff in the lab

I would love to see the Nature/Science article (cos it would be in one of the real biggies)
 

Offline QuantumClue

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« Reply #20 on: 20/12/2010 16:53:51 »
You have a quibble with the statement that exotic matter is just as tangible as ordinary matter??
 

Offline QuantumClue

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« Reply #21 on: 20/12/2010 17:08:45 »
Just testing something c2 p2
 

Offline Bill S

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« Reply #22 on: 20/12/2010 17:10:10 »
Quote from: QC
I hate to state the obvious, but negative matter is a negative energy -Mc^2
It may be obvious to you, but some of us oldies take a while to catch up. I think I'm getting there,slowly.   :-\

Presumably you would have to do something to negative matter to convert it to negative energy; sort of "negative", nuclear reaction.    
 

Offline QuantumClue

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« Reply #23 on: 20/12/2010 17:35:44 »
An example of negative matter is imaginary mass. In a sense, there is nothing in the mathematics in general which tells us imaginary matter or even negative rest energy should not be tangible like ordinary matter. Imaginary matter has a mass M which also has an imaginary value at M2<0. The observable mass of these particles exists as E=gM, and is real and positive. The force enters the equation as Fg=-▼φMg.

The negative matter particles and even particles with a negative matter and an imaginary mass obey the equation E2=M2+p2. This means it has your usual rest mass M0. For tachyons, this means the energy has an usual property as E2=p2-|M2|. There is nothing in the equations which suggests that the mass is not real (not in the mathematical sense) or tangible, since we have regular rest masses.
 

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Offline Geezer

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« Reply #24 on: 20/12/2010 19:21:28 »
Shrunk
Don't they have some in Wimbledon?

Oh! I'm terribly sorry. I will have to get new specs. I thought this thread was about wombles.
 

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