by **Sideshow** » Tue Nov 17, 2009 2:42 am

Okay, so I know this is old, and I haven't posted in forever, but I've taken up an interest in string theory and have learned a few things (I highly recommend Brian Greene's The Elegant Universe). So, here goes:

The universe is, at its most basic level, composed of strings (later theorized to be branes), of different tension. Their vibrations, and variations thereof, result in every sub-atomic particle. What makes string theory a major candidate as the "theory of everything"is that there are mathematical equations for strings (or branes) that result in the graviton. In fact, all variations of string have a potential form that resulta in the properties of the graviton. Other, far more limited, options result in the other particles.

All of this makes perfect sense, except that these proper equations require the presence of tiny, coiled dimensions at every single point in the universe. However, unlike the three-plus-one dimensions we're used to, strings would have to resonate across six additional dimensions, coiled together, and at every point in our three-dimensional, uncoiled, universe. The specific arrangement of these dimensions that fulfill the equations properly are called Calabi-Yau shapes. That's how we get M-theory: We have our three-plus-one (time) dimensions, six coiled dimensions, and an even larger dimension to contain it all. That gives us eleven: 3 + 1 +6 +1.

Phew. I may have been a little long-winded and mangled the facts somewhat. The important piece is this, though: higher dimensions aren't expanded according to string theory. It is the properties of the way they are intertwined that result in gravitons, as well as every other particle. It might help to think of these six coiled dimensions as a uniquely shaped cave that branes echo around in; the shape of the cave (Calabi-Yau space) determines the echo (particle). Gravitons can't disappear into this space (we, or at least I, think), because they require them to simply exist.

There's a lot of work to be done in this field, and I may have missed something crucial. I've only started researching string theory, so I can't give specifics beyond what Wikipedia will tell you. If I'm blatantly wrong, somebody please correct me -- I'm rather curious now, too.