Penny: So, so, did we do it? Did we just solve string theory?
Sheldon: Oh. (laughs) I appreciate your enthusiasm, but this is not the sort of thing we can figure out in a night. People have been stuck on this for decades.
Penny: What, decades? Really? It's-it's a string. How hard can it be? It's straight, it's in a loop, it gets knotted up with other strings.
Sheldon: Well, actually there are no knots in anything greater than four dimensions. Ooh, unless we get around that by considering them as sheets. You know, topologically speaking, that has a lot of interesting possibilities.
Penny: See? How long did that take me, like a minute?