Our future survival might depend on finding a way into one of these new universes. The fate of the Earth we already know is to be consumed by the extraordinary death of the sun. But if the predictions about the expansion of our universe are correct, it’ll die someday too, whether by a Big Crunch or expansion on such a wide scale that we’ll just be particles floating in empty space. Eventually — very, very far into the future — even this whole universe won’t be hospitable to us anymore.