Theory of everything and unifications

[ShayanJ]

Do we have a theory of everything now?
I read somewhere that now there are just two fundamental forces.electronuclear and gravity.is it correct?
From what theories,unification theories are concluded?
Is the most acceptable theory of gravity NOW is general relativity?
thanks

 

[zhermes]

That's basically the right idea.
Electromagnetism, and the nuclear forces (weak and strong) are described by quantum field theory (QFT) and gravity is still only adequately described by general relativity.

 

[ShayanJ]

I'm confused.I hear the name of a lot of theories.could someone tell me what is the relationship of all of them.QFT,QG,M-theory and so on.
thanks again

 

[zhermes]

Quantum field theory takes the basic methodology of electricity and magnetism (i.e. the use of fields as propagators of interactions) and formulates it in a way which produces the correct quantization of charge, angular momentum, mass, etc etc. It fully incorporates special relativity (which traditional 'quantum mechanics' doesn't).

QFT still does not include gravity. QFT and general relativity (which explains gravity) do not mesh-well; i.e. they contradict each other, and don't reproduce the other's results. Many people think that gravity will have to be quantized before these theories can be combined; this is the concept between Quantum Gravity---which does not exist yet.

M-Theory (which is an extension of, and very similar to, string theory) is a candidate theory of everything. I.e. it might include the three quantum forces, and gravity, with special relativity, and all of the bells and whistles are crazy other things. We don't know yet, because the mathematics is only vaguely understood by a handful of people in the world; and no one has really been able to pull everything together (if it can be done). The big problem with m/string-theory is that none of its current predictions are testable. The only way we (or at least that I'm familiar with) know to test string-theories, would be to use energies that may never be accessible (one of the classic examples: if you were to build a particle accelerator with high enough energy to test ST, it would have to be the size of the galaxy---or something like that).

 

[ShayanJ]

I suppose all four forces are unified in M-theory.But I want to ask Is M-theory a set of theories?if yes,what are they?
I also heard a lot of names of gravity theories(all boil down to GR)supergravity,KK-theory,quantum gravity and so on.which is the most acceptable?
and could you give me a time line of theories leading to M-theory?
thanks