Could the Universe be a Bubble?

Scientists from the Perimeter Institute are working to prove the multiverse hypothesis, a long-debated and controversial theory that the Universe is actually a giant bubble.

The Big Bang aside, when the Universe started it was a vacuum simmering with energy (also called dark energy, or the Higgs field - the Higgs boson particle that makes up all matter, discovered in 2012, some say should have supposedly made the Universe collapse, in fact).

This high energy, according to the hypothesis, began to evaporate and form bubbles, and within each one was another vacuum. Even though each bubble formed contained less energy than the last, they still had enough to cause the bubbles to expand. Inevitably, some bubbles bumped into one another, producing secondary bubbles.

The gist of the multiverse hypothesis is that within all of these bubbles was a Universe.

Scientists who support the bubble theory believe that it arose from the idea of cosmic inflation - a concept that also is not universally accepted.

Inflation holds that in the instant after the Big Bang, the Universe expanded rapidly - so rapidly that an area of space once a nanometer square ended up more than a quarter-billion light years across in just a trillionth of a trillionth of a trillionth of a second.

Proponents of the multiverse theory argue that it's the next logical step in the inflation story, while deniers believe that it is not physically possible - though neither could ever actually test the theory.

"That's what this research program is all about," lead researcher Matthew Johnson said in a statement. "We're trying to find out what the testable predictions of this picture would be, and then going out and looking for them."

Johnson's aim is to use computers to simulate the multiverse hypothesis, something which he says is actually easier to do than it sounds.

"All I need is gravity and the stuff that makes these bubbles up. We're now at the point where if you have a favorite model of the multiverse, I can stick it on a computer and tell you what you should see," he explained.

Johnson hopes that such advanced computer models can help cross the line between an appealing story and finding the actual science to back it up.

The study is described in four separate journals, Physical Review D, Journal of Cosmology and Astroparticle Physics, arXiv and another in Physical Review D.