Exactly how many universes are out there in the vast expanse of space? Are we the only one? The idea of multiple universes, possibly with their own set of natural laws, coalesced into a giant multiverse has been gaining ground recently-- only it's not something that at this time is more than just speculation. Cosmologists Andrei Linde and Vitaly Vanchurin at Stanford University in California calculate that the number of universes dwarfs the 10⁵⁰⁰ universes postulated in string theory, and raise the provocative notion that the answer may depend on the human brain.