I’ve talked earlier about both quantum mechanics and the theory of relativity which both come together to provide an almost all-encompassing explanation for everything in the physical universe, but there are in fact other theories out there that build off of these. These other theories are “theories of everything” because they mean to unify and provide a complete consistent description of our universe. One of the most pressing issues in physics today is formulating a quantum theory of gravity. The issue is that gravity, unlike the other fundamental forces, is solely explained by classical physics through Einstein’s general theory of relativity. The other fundamental forces, the strong, weak, and electromagnetic force, can all be explained within the bounds of quantum mechanics. For looking at all of the forces at once, it simply does not make sense to have to approach gravity differently than the others. This is where string theory among other somewhat new theories come into play.

String theory is pretty much exactly what you might expect it to be. Often times in physics, things don’t quite turn out like how you would expect them, but string theory I find to be rather straight forward. The whole concept is that all of the fundamental particles that I had talked about in my first post are actually just incredibly tiny strings.

So maybe that doesn’t seem to make everything fall into place, but it does give us options. Thinking again about the fundamental particles, we can assume that these are just little points in space. Sure they may take up some volume, but they are just points with no more structure to them than that. However, if we were to zoom into these points enough, we might find that they really are pieces of string. If you’ve ever partaken in the game of Cat’s cradle, you know that playing with string can get complicated. In the same sense, these strings can move and oscillate and just act in so many more ways than a simple dot can. Now, imagine that each fundamental particle correlates to the same kind of string, but just one that does a particular movement. The electron for instance might have a string that tends to zig zag and the up quark might have a sin wave. This creates a baseline for all of the fundamental particles, including the fundamental particle for gravity, the graviton. This string theory then takes the place of ordinary quantum field theory which involved point particles and allows all of the fundamental forces and the individual particles play nicely.

There are, of course, some issues with string theory. One of the larger issues with string theory is that because of the incredibly small size of the strings, they are currently near impossible to see with the technology we have. The proposed size of the string is called a Planck length which is about 10^(-35) m. The other issue with string theory is that sure the strings would serve to explain the fundamental particles, the bosons, but would it also explain regular matter, the fermions? The answer to this is supersymmetry which is just a complicated way of saying that for every boson, there’s a fermion. Proof of supersymmetry would be extremely convincing evidence to support string theory. As particle accelerators improve, they may soon be stumbling upon high-energy supersymmetry which would then finally give us a unified theory.