Stephen Hawkings From here:
In The Grand Design we explain why, according to quantum theory, the cosmos does not have just a single existence, or history, but rather that every possible history of the universe exists simultaneously. We question the conventional concept of reality, posing instead a "model-dependent" theory of reality. We discuss how the laws of our particular universe are extraordinarily finely tuned so as to allow for our existence, and show why quantum theory predicts the multiverse--the idea that ours is just one of many universes that appeared spontaneously out of nothing, each with different laws of nature
There is not a shred of evidence, just speculation, I thought that scientists only believed in what they can see? How would it ever be proven?