The idea of a multiverse (an ensemble of universes like our own visible one) has been criticized as unscientific because it would be unobservable, even in principle.  Now, however, some theoretical physicists are claiming that bubble universes beyond ours could be detected in the cosmic microwave background radiation – provided they collide with our universe.  Does this bring multiverse theory back into the realm of science?

National Geographic News, posting an article on this idea, said, “The multiverse, if it exists, may have sprung out of a chaotic fluctuation of empty space.”  Chaotic motions from other bubble universes might “bruise” our universe and leave telltale patterns in the cosmic microwave background (CMB).  Matthew Johnson, a theoretical physicist at the Perimeter Institute, with colleagues, is working on an algorithm to find the patterns.

But what to look for?  Sean Carroll, physicist at Caltech, warned that “People tend to recognize patterns whether or not they are there.”  Trouble is, nobody knows what the needle in the haystack would look like.  “Even with better data from Planck” (a new space telescope measuring the CMB in finer detail), “finding evidence of a universe-to-universe smashup is a game of chance, thanks to the nearly infinite possible outcomes.”….

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