
String Theory Demensions
I have several questions about the string theory.
First, it predicts 10 (or is it 11) demensions. I can understand 4, but what would the other 6/7 be? I read that they were tightly curled up, so we did not notice them, but isn't a demension supposed to be infinate?
Second, how does String Theory help scientists create a "Theory of Everything"? It is because all particles and forces would just be strings?
Thanks,
Rosie

I think the extra dimensions in the theory are resultant variation's of including 5 dimensional geometry, kaluza Klien's 5D vacuum space time geometry, its exiting because it theoretically ties all the forces together using just the 5 dimension's the others really have no relevance to our 3 dimension's.
I think its gotten a bit wild, but i really think the theory has a great basis for understanding the connection of all the forces, as different manifestations of the same energy field.
The relevant idea for understanding is to imagine a human hand above a plane/sheet , that sheet represent's our 3D universe, the hand represents the 5D gravitational field (vacuum space time), the forefinger is extended onto the plane/sheet representing EM intersection, and the thumb is extended representing Gravitational intersection, both displaying different interacting properties but proponent's of the same field.
How it helps towards a theory of everything is simple it shows the strong possibility that a higher symmetry methodolgy (better theoretical models including more possible phenomenon) is needed to evidentially find the connecting component's of EM and gravity, It shows we will have to look for clues in our visible studies that indicate a more fundemental control mechanisim.
A few mechanisims have actually already been found and recorded, The Arahonov Bohm Effect, is one, where under certain condition's a virtual element creates a directly influenced physically observable change...
and the casimir effect where virtual flux under certain condition's is creating/manifesting a physically observalbe reflex, you need energy to do that, and that energy is coming directly from the 5D gravity field (vacuum space time).
This evidence of a substructure can be understood within the 5D geometry, it also can postulate that under certain condition's you may beable to manipulate vacuum density and flux..
ie. non linear vaccum interaction intersect's the 3D universe as observable phenomenon, linear vaccum is unobservable but still creative and dynamic.
Which beautifully ties into einstein's relativity. ie increasing the non linear state in vacuum creates positive space time curvature giving you more manifested 3D energy. Or decreasing it, taking 3 dimensional observable energy away from the environment back into a more linear vaccum state.
For example the earth.. visible EM energy, and the mass, visibly different because of the duality in it being a result of different interactions within non linear vacuum state, gravity.. attributed to non linear vaccum also modelled as positive space time curvature. Gravity is weaker because its a more uniform wide spread fundemental interaction.. EM is concentrated but the two are in balance within the theory.
From that you can theorise that if EM bleed off is blocked (cancelling the intersection) it would diminish in 3D, gravity would theoretically entropy and become stronger because that natural feeding of energy from the 5D field has to go somewhere else to keep a balance.. like having a smaller (gravity) and larger hole (EM) in a pressure cooker you would block energy bleed off in EM form out of the larger hole, now forcing that energy out the smaller hole as gravity, and vice versa.
Simply put, blocking EM energy from becoming 3D may naturally increase gravitational field. Within the theory you now have a working understanding/methodology for increasing/decreasing a masses gravity or EM field.
The string and the membranes are just a piece of mathmatical geometry to fit it all into, nothing more nothing less.. it does not mean vaccum contains strings or membranes.. it is a 3 dimensional model, a correlation between the physical and non physical, in our reality it is impossible to know what it looks like.
So who are we as 3 dimensional being's to say the 5D gravity field isnt infinite, just because it doesnt totally compliment conservation within quantum theory? that is where people always seem to get confused. 3D conservation goes out the window with the 5D gravity field, all our models consider at present and dogmatically adhere to is 3D conservation (it keeps the status quo within the energy economy going great by the way).
Nothing goes outside of 3D conservation at the moment because with present theory the virtual elements arnt real, oh .. hah yeh apart from the 'special case' Arahonov Bohm effect and Casimir effect, which gives evidence to the contrary.

This is a long story, but I think it begins with two swedish scientists named Kaluza and Klein. Kaluza found that if General Relativity was rewritten in 5 dimensions, you get Maxwell's equations for electric and magnetic forces creating a unified theory for gravity, electric and magnetic forces. It is a classical theory rather than a quantum theory. The discovery was not taken seriously because there was no 5th dimension. Klein suggested, however, that the 5th dimension could be very small and tightly curled up, in which case we would never see it. But the KaluzaKlein theory was still considered just a curiousity.
Then Steven Weinberg found that he could use symmetries to create a unified field theory of the weak nuclear force with electricity and magnetism. An unified theory based on this and including the strong nuclear force soon followed and is now called the Standard Model. This revived the interest in the theory of Kaluza an Klein in an effort to see whether symmetries and a quantization of General Relativity in a higher number of dimensions could bring about a unification of all of the forces. The best attempt was called SuperGravity using supersymmetry and 11 dimensions. But the theory was plagued with some fatal problems when we calculation were made using the usual techniques of quantum field theory (using Feynman diagrams). Adding up the forces they appeared to infinite. Supersymmetry solved some of these problems by making some infinities cancel out but others still remained.
Well string theory solved a lot more of these problems with infinities simply by the fact that it used extended strings instead of point particles. Another valuable insight was that the many different types of particles could be explained as simply the different vibrational modes of these strings that was possible in a tendimensional spacetime (the eleventh dimension in Supergravity was discovered to be a mistake and impossible). It soon developed that one of the biggest problems with string theory was that there was too many of them, and we had no way to determine which if any were correct. Finally, someone showed that all the different string theories were related as derivatives from a theory which included higher dimensional object than strings which were called branes (and the theory is known as Mtheory).
Well that is a quick history off the top of my head. I am sure you can do better by reading a book on the topic.

An good example for visualizing curled up dimensions from Brian Greene's "The Elegant Universe" (which, if you want to read something about string theory, is a good place to start).
Picture the universe is a long string of rope stretched across a canyon, and picture an ant on the string as an inhabitant of that universe. He can go lengthwise, back and forth, and that's a normal, extended dimension for him. Now turn right or left, and travel around the circumference of the rope. You end up back where you started in a hurry  this dimension is closed, curled up. You can make the rope fatter, or thinner and thinner to the point where you can't even see that other dimension anymore and to the ant, the universe seems linear.
It's just an analogy to help visualize the concept, though.

Completion Dimensions
"Completion Dimensions"
Consider that 4, 6, 8, 12, 20 are completion dimensions  http://en.wikipedia.org/wiki/Platonic_solids
A consideration is whether the 10 dimension speculation is half of 20.
Or perhaps 10 is incomplete and 12 moreover 20 are required for entirety.
http://en.wikipedia.org/wiki/Pappus%27s_hexagon_theorem