Whatever happened to the theory of everything?

A theory of everything was all the rage in the 1980s. So where did it go? It is only the optimists who achieve anything in this world--theorist John Ellis once read this adage on a candy wrapper. It stuck with him, so much so that in 1986 he referenced this candy-wrapper wisdom in his Nature article "The superstring: theory of everything, or of nothing?" "I was pretty upbeat," Ellis says. "I was pretty positive about it." According to Ellis, 'theory of everything' is a rather tongue-in-cheek ter...