"When one studies the properties of atoms one found that the reality is far stranger than anybody would have invented in the form of fiction. Particles really do have the possibility of, in some sense, being in more than one place at one time. Thus, and essentially, anything that can happen does happen in one of the alternatives which means that superimposed on top of the Universe that we know of, is an alternative universe where Elvis Presley is still alive. This idea was so uncomfortable that for decades scientists dismissed it, but in time parallel universes would make a spectacular comeback. This time they'd be different, they'd be even stranger than Elvis being alive. There's an old proverb that says: be careful what you wish for in case your wish comes true. The most fervent wish of physics has long been that it could find a single elegant theory which would sum up everything in our Universe. It was this dream which would lead unwittingly to the rediscovery of parallel universes. It's a dream which has driven the work of almost every physicist."