Tearing The Universe A New Wormhole

[SkepticJ]

I watched an interesting Nova program about String Hypothesis, M Hypothesis and Branes recently. It talked about some really far out sounding stuff, like maybe just maybe being able to create wormholes to travel through. In an Einsteinian Universe this is impossible but under String Hypothesis it maybe could be done someday. What do you make of this and the various String Hypotheses?

[01101001]

I watched an interesting Nova program about String Hypothesis, M Hypothesis and Branes recently. It talked about some really far out sounding stuff, like maybe just maybe being able to create wormholes to travel through. In an Einsteinian Universe this is impossible but under String Hypothesis it maybe could be done someday. What do you make of this and the various String Hypotheses?

I'd have to first be convinced that wormholes can even exist, before I believed there was a method to create them.

[Plat]

String theory very interesting

[eburacum45]

To make a wormhole you don't just need strings, you need negative strings; strings with negative energy density.

Nice props for science fiction, but demmed difficult to acheive in practice.

[Gullible Jones]

Well, you can have an Einstein-Rosen bridge... The thing is, it would almost certainly collapse if anything went through it.

Or, supposedly, you could go through a spinning black hole's singularity by traveling down vertically along the axis of rotation... But you'd have to survive the tidal forces, and even with an absolutely humongous black hole you'd have to contend with the sheer crushing gravity. Then there's the problem of aiming exactly right... And of course, the problem of probably landing in some other universe, which may or may not be compatible with your laws of physics, and almost certainly never being able to find your way back... :P

[Spacewriter]

Love your title...

[Amadeus]

Well, you can have an Einstein-Rosen bridge... The thing is, it would almost certainly collapse if anything went through it.

Don't they use this as an explaination in Star Gate?

[SkepticJ]

To make a wormhole you don't just need strings, you need negative strings; strings with negative energy density.

Nice props for science fiction, but demmed difficult to acheive in practice.

Well for this lets just say it can be done now. What would they be like? Would you just walk up to one and step inside it and be carried to the other end? How fast would transit be? What would it look like on the inside? Would they be a one time thing or once made could be used forever, like a highway that never wears out? I guess all these questions will have to be answered with not much beyond good guesses.

[eburacum45]

Well I can tell you what it would be like to travel through an Orion's Arm wormhole; the early ones, based on the theories of Morris, Thorne and Krasnikov, occupy quite large volumes of space, and are located far out on the empty edges of stellar systems to preserve asymptotic flatness (that means they cannot exist in a strong gravity field).

The Krasnikov wormhole is usually spherical, and needs only a relatively small amount of exotic or negative energy to support it; this exotic energy will be distributed evently around the spherical mouth of the hole, in a mathematically intricate distribution; but apart from the warning lights you won't see much. There may be distortion similar to Einstein's rings around the hole itself.

The large mouth encloses a much smaller spherical throat, which (no matter which direction you approach it from) leads to a long blue tunnel which you have to accelerate into until the half way point (which may be several million kilometers away- don't touch the sides). The blue light is blue shifted starlight from the other end. Once through you have to accelerate again till you are well clear of the mouth, as the presence of your mass disturbs the delicate balance of the hole.

Later in our timeline more advanced wormholes are used, with larger concentrations of negative exotic energy, in the form of negative cosmic strings, as described by Matt Visser. These are less exotic to look at, the strings define a box-like shape which enclose a wormhole mouth and a throat of practically the same diameter. You can actually see through the throat to the other side; the hole is so short (although there is still some blueshifting, apparently)...
This is a Visser hole, with some habitats in the background (because of the greater amount of negative energy used, these holes do not require such extreme flatness in the local spacetime)...

[eburacum45]

Here is an Einstein Ring;


and John Cramer on various wacky ideas
http://www.npl.washington.edu/AV/altvw69.html

[SkepticJ]

So Orion's Arm holes are a lot more like Deep Space Nine than Stargate.

I know it's hard if not impossible to predict off of String/Brane hypothesises since they only have some fancy math so far. They'll need to actually fit and explain aspects of how the universe works to become theories. But could small sizes maybe be made? By small I mean two meters in diameter. Why is it that it takes an energy input to keep Orion's Arm holes stable? If I'm understanding the concept of wormholes correctly they would be tubes made of space-time fabric that connect one place to another distant place and thus allow travel much faster than going the long way; a short cut as it were. Why couldn't a space-time tube remain stable once created without energy input?

[Evan]

It isn't possible to give answers to those sorts of questions. This is all hand waving and pure speculation with no evidence to support it. It just happens to fit some of the extreme extrapolations allowed by some of the math.

[eburacum45]

Evan is right; a lot of handwaving is involved; traversible wormholes are unlikely, and there is no evidence of their use by imagined alien civilisations, for instance.
Negative energy is the big problem; see here for limitations on its use.
http://www.physics.hku.hk/~tboyce/sf.../wormhole.html

Actually dark energy is negative energy, so is a major constituent of our universe; but it is incredibly thinly spread, and useless for our purposes.

Without negative energy support, any wormhole would collapse whenever positive mass or energy passed through it, so would not be traversible. Einstein -Rosen bridges are also supposedly non-traversible, as Hawking has recently suggested. Once the wormhole has closed, there is no connection between the two volumes of space, so the hole cannot be re-opens as far as I can see, (not sure what is happening to that open and shut hole in DS9)...