Do We Live in a Universe Without End, or do we Exist Inside a Cosmic Bubble?

Amongst the multitude of mysteries that the universe holds, the answers to what might be the most elusive ones are whether or not is finite or infinite, both in terms of its physical breadth, but also its age: is there a beginning and an end? And for that matter, if it is finite in its physical dimensions, are there other universes that are adjacent to our own? As Einstein famously put it, "Only two things are infinite, the universe and human stupidity, and I’m not sure about the former."

However, Einstein’s tongue-in-cheek quip about the universe have been addressed by two new studies that offer new insight into both the possible physical dimensions of the universe, and the possibility that it may indeed be ageless.

One team of researchers, from the University College London (UCL), Imperial College London and the Perimeter Institute for Theoretical Physics, have developed a new computer algorithm that can be used to search for patterns in the cosmic microwave background (CMB), the faint radiation left over from the Big Bang. The specific patterns they’re searching for are possible imprints that could be left at the edge of the universe from collisions with other, adjacent universes, that would leave an imprint in the CMB. The problem that’s been preventing such a search is that such patterns would be extremely subtle, and practically impossible for a human researcher to be able to tell a true pattern from random fluctuation in the CMB.

"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," explains UCL’s Dr Hiranya Peiris, one of the paper’s co-authors. The new algorithm is intended to remove the human tendency to look for patterns in apparent chaos, where none might exist to begin with.

The new program was written by fellow UCL member Stephen Feeney. He explains that the ultimate goal of this project would be to provide evidence of neighboring universes: "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."

Another multinational team, comprised of members from Canada and Egypt, think they’ve come up with an alternate model of the universe that would solve a great many problems faced by theoretical physicists, including eliminating the events of the Big Bang (and subsequent Big Crunch), and would explain the apparent absence of both dark matter and dark energy.

The classical model of the universe illustrates the current state of expansion that is being observed in the cosmos, an expansion that started with the Big Bang, and theorizes that, after that expansion looses enough momentum, it will contract back into a singularity similar to the one that the Big Bang originated from. The problem that the current model presents is that, while the mathematics applied to the universe as it exists now can only explain what happened immediately after the Big Bang — but not what happened either during, or before, the event.

Instead of the usual classical, geodesic trajectories (being the shortest distance between two points on a curved surface: think of how a geodesic dome is arranged) that are used by the generally-accepted model, this new model instead applies quantum trajectories to the model. Geodesic trajectories, where they meet, create singularities, but quantum ones, as one might expect, do not meet at all. The implication being made by this new model is that there was no singularity at the beginning of the universe — no Big Bang, and thus also no corresponding Big Crunch — meaning that the universe’s age might actually be infinite.

Dark matter and dark energy are, respectively, attempts to explain both why the universe’s larger structures (like galaxies) don’t fly apart, and at the same time what is driving the observed universal expansion. But this new model eliminates the need for both concepts, as it illustrates the universe as being filled with a "quantum fluid" comprised of gravitons — hypothetical massless particles that mediate the force of gravity. The team hopes to refine their quantum-corrected model even further, and are encouraged that such a simple concept can answer so many questions at once.

“It is satisfying to note that such straightforward corrections can potentially resolve so many issues at once,” says Saurya Das, a team member from the University of Lethbridge in Alberta, Canada.