Wormholes Unstable (BBC)

An anonymous reader writes that "The BBC reports on recent theoretical physics research showing that wormholes may not be very useful for space or time travel. Wormholes with smooth or classical spacetimes appear to be unstable and fall apart quickly. Too bad for budding time travelers and space explorers!"

Comments

Still might be useful having small ones

[Smiffa2001]

The real challenge was in explaining how to engineer wormholes big enough to be of practical use.

Well, surely a small wormhole would enable radio transmissions through? Or would interference be a problem? Wavelength? Maybe a light-based comms-medium...?

"Frankly no engineer is going to be able to do that," said the York researcher.

And that just seems so shortsighted...

Is computational power the only thing missing?

[Glowing Fish]

From the article:

But building a wormhole with a throat radius big enough to just fit a proton would require fine-tuning to within one part in 10 to the power of 30. A human-sized wormhole would require fine-tuning to within one part in 10 to the power of 60.

"Frankly no engineer is going to be able to do that," said the York researcher.

Well, I don't know if any engineer could do that with pencil and paper, but I am sure a computer could do it. Well, I am not sure a computer could do it, but growths in computational speed and power have certainly surprised us so far...

For real, or just in theory?

[pla]

Wormholes with smooth or classical spacetimes appear to be unstable and fall apart quickly.

Mathematically, physics says the same thing about a stable fixed-point in a static magnetic field.

And yet...

I have one of those cool little-magnet-levitating-over-a-big-magnet toys sitting on my desk at home, happily violating the (human-formalized) laws of physics.


Funny how, despite the numbers just not working well, little things like "friction" in the real world make sooooo many "impossible" things work just fine... All those nasty infinite series that would otherwise make the world very messy to calculate, eventually taper off to nothing, in a very real and practical way.

Human-compatible wormholes, not

[G4from128k]

I fear there are bigger reasons why people won't be traveling through wormholes. First, biologically tissues are far too fragile for the intense gravitational, electromagnetic and radiation fields that are likely to come with these phenomena. Second, biologically systems (and the attendant life support systems) are far too bulky. Creating a wormhole is uniform over the size of a person or ship will be extremely difficult. Even if the hole is big enough for a person, the center of the wormhole will likely stretch space in ways severely different from the edges of the hole. Macroscopic objects would be shredded.

WHAT!?!? Are there no Farscape fans on /. !?!?!?

[DeadMilkman]

Not a single John Crichton commment...Just a bunch of DS9/SG1 tripe -_- Where are the REAL nerds at!

All you need is PART of the wormhole

[Vitriol Angst]

The wormhole doesn't have to be stable to be useful. You could create a wormhole around a ship, and allow it to break apart behind. You could also say that rockets are unstable, because they only have a stable stream of plasma for a few feet--yet they still move the rocket.

Of course, putting limits on things that are still fiction is kind of ironic.

Re:Information Theory Hell

[dgatwood]

Actually, it isn't inconsistent at all. In Stargate, the gate disassembles matter that enters the event horizon and sends it through (presumably as a data stream, though this isn't clear) to the gate at the other end, which reassembles it. My assumption is that it isn't practical for solid matter to go through as a unit because of the size of the wormhole, but there could be other reasons. It's unclear.

It seems quite reasonable, then, for the gate systems to not attempt to handle disassembly and reassembly in opposite directions concurrently, presumably for safety reasons. One would not want to rematerialize in the middle of someone else who was in the process of dematerializing. Since there would be no reasonable mechanism for preventing someone from stepping into the event horizon at the wrong time with a bidirectional gate mechanism, the designers made it unidirectional. Seems perfectly reasonable.

That said, it should be possible to switch the direction of the gate connection while the connection is open. I can't see any valid reason for that not to be possible except while someone is in transit, as it should amount to a mode switch in software, coupled with a simple flow control mechanism.

Actually, it's likely much more

[jd]

I did a simple, back-of-the-envelope calculation on what it would take to keep a wormhole open.

You need to have a net negative mass, which means that your exotic matter (or energy equiv) must be equal to the mass of the object traversing the wormhole, PLUS the mass of the wormhole itself, PLUS the mass of any other particles within the wormhole, PLUS the mass equiv of the energy that the vaccuum created naturally has.

You also need to bear in mind that exotic matter is believed to have a very short half-life - about 10^-30 seconds - which means that it must be traversing the wormhole at high speed and must constantly be replaced at that rate.

But that isn't all! There is a problem with wormholes in close proximity to each other - they are unstable. And quantum-scale wormholes supposedly occur everywhere in the quantum vaccuum. So, you've got to do some fairly complex stuff to exclude other wormholes from the vicinity of the one you want.

Generating the exotic matter/energy is also a hard problem. Methods include the Casmir Effect, which requires generating fields of absolutely staggering strength to exclude all possible positive energy between two plates. The exclusion principle, combined with the requirement that a vaccuum must have a non-zero state in QM, is what forces the existance of a negative state.

So, what you need to do is basically have gigantic Casmir Effect-based exotic matter generators, which will require vastly more positive energy then the negative energy they create.

I think I figured out that you'd need to convert most of the galaxy into pure energy in order to move even a relatively small object via a wormhole over any kind of reasonable distance, once you take these additional requirements into account.

The problem is, if you are capable of collecting a galaxy together to convert it into enough energy to do this, you have sufficient technology to reach anywhere in the galaxy anyway, making the wormhole method of travel totally unnecessary. Besides which, you also get the benefit of having somewhere to go.

Re:Actually, it's likely much more

[jd]

There are no KNOWN ways of transmitting information through QE, that does NOT mean that it is impossible. (That would be like saying that space travel is impossible, because the ancient Chinese couldn't build a rocket that could work in a vaccuum.)

Another option would be to use quantum tunelling. You need to find a particle which can only exist under certain rarified conditions, such that space would "exclude" that particle, which would result in the particle "tunneling" through that space and appearing on the other side.

Re:Someone explain to me...

[lgw]

There's time travel, and then there's time travel.

If you travel more than a light year in less than a year, you've made a "time-like" journey. Theories about wormholes mostly permit this. That implies some strange causality, but not nearly as strange as what's ordinarily thought of as time travel. You still can't send yourself a signal "from the future", or affect your own past, even with multiple hops. From the point of view of your distant destination, you've traveled backwards in time, but not from your own point of view (well, you can watch your own past in real-time by "getting ahead of the light", but that doesn't lead to paradoxes by itself).

Even this kind of wormhole would present all sorts of difficulties, however. If the wormhole was "timelike" and the mouths were close to one another, it's quite possible for a photon to get caught in a loop, multiplying endlessly until the energy collapsed the wormhole. It's hard to see how this could be avoided for neutrinos.

Re:Duh

[eofpi]

Or at least the 38-minute limit.

Good or bad thing.. pseudo scifi theory

[mattr]

Like everyone else I've been wondering where the UFOs and encyclopediae galactae are to be found if SETI hasn't found them yet. Hoping it is a matter of discovering real soon now a quicker mode of communication, or just finding out that life is much less common (needing moon, few supernovae, etc.).

But I've had a sneaky ugly worry (founded by far too little knowledge of anything resembling necessary science) that it could conceivably be a quantum phenomenon, in other words no other species could exist within our light cone (or galaxy? farther?) due to some universal law that makes it impossible. Though anthropomorphic law aside, that would make it really, really unlikely that we exist, statistically speaking. Anyway, much as I would really like to see some FTL, and assuming the quantum worry I have is unfounded, there are two good things that could come out of this opinion that wormholes are unstable. For one thing, as much as I try to explain SETI etc. to my Dad, he says "I don't want to have any bug eyed monsters coming here" and of course, if they are like those in Starship Troopers then he's right. We're safely far away for a while maybe. Other thing is, no wormholes might mean that there is a chance of life existing outside our "light cone", i.e. the farthest we could ever go in the universe at light speed, I suppose. Those reasons both make me feel a little better. Any physicists out there?

"Negative Energy" a conceptual mistake?

[Pfhorrest]

This isn't exactly a response to your post, but more a question for this entire thread... but you seem like you may be a physicist or at least well versed enough in the mathematics thereof to be able to do "back-of-the-envelope calculations" about it, so maybe you can answer this question for me.

Why is it assumed that because something has negative mass - which I would define as "the quality of being repelled from, rather than attracted to, ordinary positive mass" - it has negative *energy*? Likewise, why is it assumed that any energy (such as vacuum energy) translates directly into positive mass?

I've always viewed it similarly to charge. Both mass and charge are a form of potential energy. An electron and a proton have the same amount of electrical potential energy as one another, only differing in the nature of that potential relative to other charges (whether it repels or attracts a positive or negative charge). But does a proton then have "positive" potential energy and an electron have "negative" potential energy? If the answer to that is no, then why does something with "negative" mass have to have "negative" energy? Is a space filled with a negative charge "less than empty vacuum"?

I'm well aware of e=mc^2 of course, and why that would lead to a negative value for e if you have a negative value for m. But given that physics traditionally deals with only positive values for m, wouldn't e=|m|c^2 (using the absolute value of m, instead of just m) return the same results for all physics thus far, dealing with positive mass, without the counterintuitive "less than nothing" idea of "negative energy" if ever we managed to produce something with negative mass?

Re:"Negative Energy" a conceptual mistake?

[Pfhorrest]

That was an intelligent answer, but I think you may have misunderstood the nature of my question, and as such have not entirely answered it.

I was not claiming that a negative charge was negative energy, or asking for clarification about that. I was analogizing the potential energy due to charge (electrostatic force) with the potential energy of a mass (gravity). An electron and proton, ignoring gravity, have a certain amount of potential energy relative to one another just because of their charges; that is to say, if released, they would move closer together and gain velocity, and kinetic energy. A hypothetical particle identical to an electron but with a greater charge would have *more* potential energy relative to that proton, as the attraction between them would be stronger, even though their masses are the same, so it's pretty clear that the attraction due to charge counts as "potential energy" the same as attraction due to mass.

But now, take the potential energy due to charge (again, ignoring gravity) of two electrons. As the charge of a proton and and an electron are equal but opposite, is the potential energy between them (ignoring gravity) not the same? Or would you say an electron has a negative potential energy (even considering gravity now) to another electron, since they would repel one another? In that case, the "positive" and "negative" differences of energy seem only to apply to potential, not kinetic, energy, and refer only to the direction of the force applied relative to another body.

Furthermore, in the case of electrical charges, that attraction or repulsion is relative to not only the strength but the sign of charge of another body, in which case, how do you know that this exotic matter with negative mass, while it may have negative (repulsive) potential energy to positive mass, does not have positive (attractive) potential energy to other exotic matter? After all, we know that likes attract with positive masses, so it stands to reason that likes would attract with negative masses as well.

Has anyone ever made or discovered particles of this "exotic matter" and measured the relative attraction of them to each other? I imagine for the extremely short lifespans you claim for it, it would be difficult to do such an experiment, especially here amongst all this positive mass, and especially to isolate the effects of gravity from electric and nuclear forces.

This is a common area that seems conceptually vague amongst every physicist I've personally spoken with and most of the ones I've read. Einstein seemed to clarify it best in his personal layman's version of relativity. People speak of the "size" of particles, and of "matter", as nebulous concepts separate from the force-fields which define the characteristics of those particles. For example, when pressed to define "volume" as an independent quality of a particle, as when people say "atoms are mostly empty space", most people, even physics professors, I speak to fail to give any definition.

Is it the size of an atom the radius of its outermost valence level? By that definition the entireity of space inside that valence shell IS the atom and is therefore not empty. So, scratch that idea, the space of the atom is only filled by the particles it's made out of and the rest is empty. Ok - what's the volume of an electron, or a proton? It's not clear how that should be defined - by it's mass? By its charge? How do you measure volume in units of mass or charge? Do you measure the volume by the extent that the strong nuclear force keeps other particles (of regular, non-antimatter at least) from overlapping that pointin space?

What is the extend or nature of something devoid of any of its force-fields? Can you run into an empty shell with no mass, charge, or nuclear forces? What exactly would you be running into? People say atoms are mostly empty space - I say everything is nothing but space, and none of it is empty.

From recollection, Einstein spoke in his laymen's book on relativity about an a c

Re:"Negative Energy" a conceptual mistake?

[Lobachevsky]

Would the existence of whiteholes and abundance of them suggest that large wormholes are ubiquitous? While there are a lot of measurements supporting blackholes - and rotating blackholes - at the epicenter of galaxies, there seem to be no sound measurements on whiteholes.

Correct me if I'm wrong, but isn't a whitehole a necessary endpoint for a unidirectional wormhole? Also, considering how most blackholes at the epicenter of galaxies lie dormant, their corresponding whiteholes, if any, would be dormant as well, observable only by how they influence ambient light. Since measurements suggesting blackholes are at the center of most all galaxies are relatively new, I need to ask, has there been much study or analysis of observable space to look for corroborating evidence of whiteholes?

negative energy?

[Driadan]

AFAIK (and that's not much) energy is something needed to "have potential", or ,in other words, to do work. Moving something is a kind of work. How do I move the entire fabric of space with some "exotic matter" that has energy in debt?

Also, if I am unable to measure the amount of energy or potential that I have (or that any other thing has), how do I recognize something that has negative energy?

This is old news

[5plicer]

All the points raised in the article were discussed in Robert L. Forward's Indistinguishable From Magic, which I read back in '95. And it's not like he came up with these ideas... his book is just a paperback.

One thing Dr. Forward talked about in his book was using micro-wormholes to send radio transmissions. Sure, it's not as cool as sending a ship through, and anyone who received the message couldn't send one back to us via the same wormhole, but maybe someone on the other end of the wormhole might have a few trick up their sleeves to let us know they received our transmission.

PS - this is my first post on Slashdot