The theory that our universe isn’t limitless, but is actually contained within a celestial bubble that bounces off of other universal bubbles in a multiverse, has gained traction with physicists in recent years. The only problem has been proving a multiverse actually exists. Imagine the situation: everything encompassed by our entire universe may really just be one little orb mixed in with a bunch of other orbs like Skittles in a vending machine.
But those other universes likely have completely different physical properties than our own, and may exist in a state that’s simply incomprehensible to us beings who barely understand the laws of our own universe. On top of all those mind-melting possibilities, the other universes may not even be touching our own little bubble, so light or radio (or anything we’d normally search for as evidence of the existence of a celestial body) might not even be able to pass through. So how in the holy expanses of space are we to test if other universes even exist?
Physicists have previously sought evidence by looking at cosmic microwave background radiation, which is a leftover of the heat radiation produced in the Big Bang. Physicists think, if multiverses exist, the spots where they collide will created disc-like patterns in the CMB radiation. The only problem is, because the discs could exist literally anywhere in the universe, no one’s been able to mount an efficient search for them, especially considering there hasn’t been a way to prove that any CMB radiation patterns they find aren’t random anomalies in the unfathomably-noisy data source that is interstellar radiation.
But now, a team of cosmologists at University College London, Imperial College London and the Perimeter Institute for Theoretical physics think they’ve found the answer.
"It's a very hard statistical and computational problem to search for all possible radii of the collision imprints at any possible place in the sky," Dr. Hiranya Peiris, co-author of the research, said in a release. "But that's what pricked my curiosity."
To help prove the existence of CMB radiation discs, the team was able to simulate what the sky would look like with and without universe-on-universe contact. Using the simulations, they created an algorithm that tests the viability of either model against the overwhelming ocean of CMB radiation data captured by NASA’s Wilkinson Microwave Anisotropy Probe. Not only did their work show that there is definitely evidence that the CMB discs exist, but it put an "observational upper limit" on how many CMB discs there are. In essence, while the discs don’t definitively prove the existence of a multiverse, these scientists now have evidence of how many collisions between our universe and others there might have been.
An example of CMB disc imaging. Top left shows a universe collision, which creates an anomaly in the CMB temperature map (what can actually be measured) at top right. The bottom left shows another collision representation, while the hot spot on the bottom right indicates the presence of a universe’s edge colliding with ours. Via.
"The work represents an opportunity to test a theory that is truly mind-blowing: that we exist within a vast multiverse, where other universes are constantly popping into existence," Stephen Feeney, a PhD candidate who wrote the search algorithm, said.
The issue with the search for CMB discs is one that’s often a problem with any statistical search: humans are naturally predisposed to finding patterns, and in the past it was tough to tell if what physicists found were actually discs or simply wishful interpretations of random data. What lends credence to the findings of the UCL team’s algorithm is that, because data must fit very rigid parameters to be considered the proper pattern, the algorithm is much harder to trick.
"It’s all too easy to over-interpret interesting patterns in random data (like the ‘face on Mars’ that, when viewed more closely, turned out to just a normal mountain), so we took great care to assess how likely it was that the possible bubble collision signatures we found could have arisen by chance," Dr. Daniel Mortlock, another co-author of the study, said.
The study is only a first step, albeit a big one, and there still isn’t enough evidence to prove that either our universal bubble is the only one around or that universes collide on the regular. But by unlocking an avenue in which evidence of the multiverse can realistically be searched for, the team has opened up the debate to whole lot more research. And the ramifications are astounding.
On the one hand, we’ve found evidence that, at the very least, our universe has limits. If it turns out we don’t live in a multiverse, then it’s possible we’re stuck in a limited bubble with absolutely nothing on the outside. Sure, the universe is expanding, but proof that it has limits means our future may be one marred by celestial cabin fever.
On the other, if a multiverse does indeed exist, and new universes are popping up like a shaken lava lamp, we still have no damned clue what those other universes could be like. It’s possible that they’re all a total hodgepodge of different physical laws that we can’t even comprehend. Or they could be continually-sprouting alternate dimensions that are based on ours yet drastically different. Hell, they could all just be exact copies of our own. We just don’t know. But the evidence that they exist is mounting.
Lead photo via