Rachel's Blog: How long is a piece of string?
Just finished reading A Brief History of Time by Stephen Hawking. And although everyone I've spoken to about it so far (OK Richard and Xander) has said they didn't get the last bit, I am happy to report that I think this is a fault of the writing and not my family's brains. I know I've seen better explanations of string theory in tv documentaries. Perhaps it's the age of the book (it was first published in 1988), but it seems to me to lack a couple of paragraphs on the actual why of strings, as opposed to the how and what.
So I went searching for more and have discovered the Official String Theory Web Site (of course!). In particular this made a lot of sense to me:
But it wasn't enough that there be a graviton predicted by string theory. One can add a graviton to quantum field theory by hand, but the calculations that are supposed to describe Nature become useless. This is because, as illustrated in the diagram above, particle interactions occur at a single point of spacetime, at zero distance between the interacting particles. For gravitons, the mathematics behaves so badly at zero distance that the answers just don't make sense. In string theory, the strings collide over a small but finite distance, and the answers do make sense.