h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

OK, to clarify a couple of things about wormhole time machines.

The dimension that the wormhole pokes into is *not* the same dimension that is time. In fact, although you could view it as an extra dimension on top of normal space, it's actually just a convenience for imagining a non-Euclidean geometry; our brains have become accustomed to a near-perfect Euclidean universe, at least as far as our everyday experience goes, so we need to translate these 'strange' geometries into something that we can grasp.

Also, oscillating the wormhole mouth is easy (provided you can build the thing in the first place!). Just dump some electrical charge into the wormhole, stick 2 metal plates around the mouth that you want to move, and apply an alternating electrical signal. The wormhole mouth will jiggle away!

For more details, see the classic paper (from memory, so forgive me if some of this is slightly wrong) "Wormholes, Time-Machines and the Averaged Weak Energy Condition", in Phys. Rev. Lett. D, 26 September 1988.

jd

I agree with your first note. When I say that the wormhole uses the forth dimention, I do not mean time. It is my opinion that time is not a real dimention, but is somthing entirly different. Therfore, the forth dimention would be another dimention of space.
About the way to move the wormhole's mouth, this could work. The only question is whether you could stick electrical material in the mouth without it going through the wormhole.

I think it's safe to say that time *is* a dimension in the technical sense; i.e. it's one of the parameters required to uniquely define the location of an event.

That doesn't imply that it's a dimension in the same sense as space; that one is still up for grabs. It bears some similarities to space, but also great differences, e.g. non-reversibility.

As to charging the woemhole mouth, this is the standard scheme that has been suggested. The charge probably would go through the wormhole; I don't know if this is a problem. If the hole couldn't cope with a bit of charge going through it, then it'd probably make a pretty poor time machine!

But there are currently many interesting questions on ways that you might be able to 'hold' the wormhole open without having it collapse on itself the moment you switch it on.

And I ain't got a clue what the answers are!

Alright, I think I will need to clarify my idea of time again. When it comes to defining a specific event, you need four numbers: 3 for each dimention of space, and 1 for the "dimention" of time. If there are any other dimentions, it is safe to assume that the value for this dimention would be the same for all events in the known universe, and can therefore be ignored. However, even though describing the "dimention" of time is necessary to define an event, I do not think it is a dimention, in the same sense that the other three are. Right now, I can move either north or south, east or west, and up or down (gravity and the earth interfere with this one, but I think we can ignore this), at my will. I have no say in my movenment thorugh time, except by manipulating the General and Special Laws of Relitivity. Therefore, time is not a real dimention.

Well, I'm not very sure about time not being a dimension in the real sense, but it has to be treated as such in relativity. My idea is essentially this: "The laws of physics unify in higher dimensions". For example, take Maxwell's equations. These eight equations are not "beautiful" to a physicist - they're ugly and don't possess much symmetry. However, when Einstein wrote these down using time as the fourth dimension, they collapsed into a single tensor equation. This is one of the main reasons I like physics - the simple complexity is complexly simple! This, by the way, is also why most physicists think quantum mechanic's Standard Model is incomplete - its neither beautiful nor symmetric.
For more information on higher dimensions and superstring theory, read "Hyperspace" by Michio Kaku.

Actually, allong the lines of "The laws of physics unify under higher dimentions," I just read a Scientific American article saying that, with a few extra dimentions, the force of gravity could unite with the other three forces (electromagnetic, strong, and weak) at areas as large as 10^ -19 meters. With only four dimentions (or three - see my last entry in this forum), gravity wouldn't unite until 10^ -35 meters. The only question is: Why are the extra dimentions rolled up into tiny cylinders?

Actually, all this comes under the framework of Kaluza-Klein theory and modern day superstring theory. I'm not sure of the reason as to why the extra dimensions are all rolled up into a ball, but I think you end up with a scenario in which the four dimensional universe was expanding at the expense of the other six dimensional universe(if you assume ten dimensions in all) - its like the six dimensional universe collapsed, while the four dimensional universe expanded. If we end up with a Big Crunch, then any civilisation intelligent enough to calculate the expansion of the other universe should be able to escape destruction by shifting to the six dimensional universe - since they would presumably uncoil at this time.