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View Full Version : Why can't Wormholes exist?



cjackson
2014-May-31, 11:58 PM
I've read works by Kip Thorne, Brian Greene, Sean Carroll, Leonard Susskind and I get the impression that wormholes are highly problematic and are based on relativistic equations, but not reality. I want to know why wormholes are impossible.

Jens
2014-Jun-01, 12:24 AM
I'm not sure if anybody is saying they are impossible. Just that it's speculative, and there is no evidence to indicate they do exist, just like tachyons and negative mass. They can be put into equations, but that doesn't mean there's any reason to believe they actually exist.

Shaula
2014-Jun-01, 06:04 AM
It is not that they are impossible it is more than they are hard to create and even harder to keep open. The main argument, as I understand it, against them is essentially the 'chronology protection mechanism' one. That is to say that in order to prevent time travel there must be some reason why you cannot keep them open for a long time and travel through them safely.

Cheap Astronomy
2014-Jun-01, 09:15 AM
I am more of the view that they probably are impossible. The extreme space-time torsion required to create a wormhole should be the result of something - which by Einsteinian math should be an extreme energy/mass density.

An extremely compact post-supernovae stellar core is able to contort space-time in such a manner and thereby form a black hole. However, a black hole isn't a worm hole since it has a compact post-supernovae stellar core inside it, which would prevent any possibility of movement 'through' what might initially seem like the entrance to a hole.

I can see no grounds for assuming you could have anything like a black hole without having an object of extreme energy/mass density embedded within it.

Unless it is something of the nature of a quantum fluctuation, which is inherently ephemeral/unstable and is at this time just a hypothetical concept anyway (i.e. no evidence).

antoniseb
2014-Jun-01, 11:18 AM
Adding to what Cheap Astronomy has said, we don't have a model yet for how General Relativity and Quantum Theory will work themselves out, but they will. Evidence for that expanded theory will come from extreme gravity environments, which we have not yet observed, and we'll need those models and theories to say anything you should believe about wormholes. So the answer to the OP is that we can't know yet.

Jeff Root
2014-Jun-01, 12:19 PM
I haven't studied the subject, but Cheap Astronomy captured
exactly my impression of the problem with wormholes.

-- Jeff, in Minneapolis

Ara Pacis
2014-Jun-01, 03:07 PM
Recently, some astrophysicists recently announced that they think the SuperMassive BlackHole at the center of galaxies might actually be wormholes. This is supported by the observation that even young galaxies seem to have them but have not had enough time to grow an SMBH.

Extrasolar
2014-Jun-01, 06:19 PM
Recently, some astrophysicists recently announced that they think the SuperMassive BlackHole at the center of galaxies might actually be wormholes. This is supported by the observation that even young galaxies seem to have them but have not had enough time to grow an SMBH.

http://arxiv.org/abs/1405.1883

WayneFrancis
2014-Jun-02, 12:49 AM
A lot has already been touched upon but I'll put my, very basic, understanding of the topic in. Worm holes are mathematically possible given GR. They require very special conditions to be created and they seem to need even more special conditions to stay open. Forgetting about dark matter and energy atm everything else we know would cause these worm holes to collapse if they went through it. The reason is that everything else, and this probably goes for dark matter too, warps space time in a way that would collapse the hole as it got near. You'd need a some thing with negative mass to curve spacetime enough that the opening wouldn't collapse. We don't know anything that has negative mass, even though the equations allow it, so in practice we seem to be out of luck.

So while not impossible it is, given our current knowledge, not very likely but then again there is a lot we don't know.

Glom
2014-Jun-04, 07:26 AM
This whole business with negative mass. Is it simply a case of "well if made this quantity less than 0, then this would happen with my maths" or is possibility of negative mass derived from some work?

Jeff Root
2014-Jun-04, 11:36 AM
I have hypothesized that antimatter could have negative
gravitational mass (though not negative inertial mass) for
reasons of symmetry. Others hypothesized that before me,
and an experiment to test it is currently underway at CERN
as part of the ALPHA experiment. This has been promised
for years and years, and it is finally getting to the point
where there should be definitive results within the next
year or so.

I don't know whether this kind of negative mass is what
wormholes would need or not. It seems unlikely, since the
negative mass I hypothesize is only negative relative to
ordinary mass, not negative in any absolute sense. Similar
to how negative electric charges are negative relative to
positive charges, but not in any absolute sense. That is,
which one you call "positive" and which you call "negative"
is completely arbitrary.

-- Jeff, in Minneapolis

Ara Pacis
2014-Jun-04, 05:08 PM
Light has been manipulated in such a way to give it negative effective mass (http://www.iflscience.com/physics/scientists-have-made-light-appear-break-newton%E2%80%99s-third-law), though I don't know if that will help here.

JustAFriend
2014-Jun-04, 07:18 PM
Everything is impossible or speculative until we actually see one in the wild.

swampyankee
2014-Jun-05, 07:33 PM
I have hypothesized that antimatter could have negative
gravitational mass (though not negative inertial mass) for
reasons of symmetry. Others hypothesized that before me,
and an experiment to test it is currently underway at CERN
as part of the ALPHA experiment. This has been promised
for years and years, and it is finally getting to the point
where there should be definitive results within the next
year or so.

I don't know whether this kind of negative mass is what
wormholes would need or not. It seems unlikely, since the
negative mass I hypothesize is only negative relative to
ordinary mass, not negative in any absolute sense. Similar
to how negative electric charges are negative relative to
positive charges, but not in any absolute sense. That is,
which one you call "positive" and which you call "negative"
is completely arbitrary.

-- Jeff, in Minneapolis

I believe that anti-matter has been shown, in experiments, to have the same gravitational mass as normal matter. It's certainly been shown to have the same sign, so anti-matter does not have negative gravitational mass.

On to wormholes!

I think that GR permits them to exist, but the requirements to stabilize them are probably (almost certainly) not physically realizable, and certainly impossible with current technology. I'm kind of sad about this, as a Alcubierre drive or Krasnikov tube would open up the galaxy. As for causality if FTL is discovered? That runs into the area of "tough": if FTL exists, causality will just have to deal.

Noclevername
2014-Jun-05, 08:02 PM
I'm kind of sad about this, as a Alcubierre drive or Krasnikov tube would open up the galaxy.

They could hypothetically exist and be limited to lightspeed or less. They'd still allow for interstellar travel to nearby stars, and return within a lifetime.

Extrasolar
2014-Jun-05, 08:42 PM
I believe that anti-matter has been shown, in experiments, to have the same gravitational mass as normal matter. It's certainly been shown to have the same sign, so anti-matter does not have negative gravitational mass.

On to wormholes!

I think that GR permits them to exist, but the requirements to stabilize them are probably (almost certainly) not physically realizable, and certainly impossible with current technology. I'm kind of sad about this, as a Alcubierre drive or Krasnikov tube would open up the galaxy. As for causality if FTL is discovered? That runs into the area of "tough": if FTL exists, causality will just have to deal.

I know that both a wormhole and a Alcubierre drive warp space, but they don't exactly have the same effect. I mean, we know that space can be warped for sure and that indeed there must be FTL warpage due to light not being able to escape an event horizon. Partially warping space and warping space into a black hole seem like completely different tasks.

Swift
2014-Jun-06, 05:10 AM
... As for causality if FTL is discovered? That runs into the area of "tough": if FTL exists, causality will just have to deal.
:lol:

Yeah you tell causality, never liked it much anyway:D

Ara Pacis
2014-Jun-06, 05:33 PM
:lol:

Yeah you tell causality, never liked it much anyway:D

It'd be really funny if you could edit the thread to post your response ahead of his comment. ;)

mkline55
2014-Jun-06, 05:42 PM
That's not likely to happen.
Or is it?

mkline55
2014-Jun-06, 05:44 PM
That's not likely to happen.