When we ask questions about the universe as a whole, we usually focus on how it began, what was before? But there is just as much value in asking the opposite. How will the universe end? One may think we should have a clearer idea of what will come next based on our understanding of the current laws of physics, but the distant past and distant future are as nebulous as each other.
A group of theoretical physicists aimed to shine a light on this far future and approached the problem in an unconventional way. They looked at all the different scenarios for when the laws of particles physics – what we call the standard model – might break down to work out the model's complete lifetime, essentially when the universe will end. They estimated that this will happen after 10139 years and they are 95 percent confident that the universe will last more than 1058 years. These results are published in Physical Review D.
“We wanted to fix all the previous approximations and get the exact date as pinned down as we could,” Anders Andreassen, from Harvard University, told New Scientist.
The rules of particle physics encoded in the standard model includes fundamental particles (quarks, electrons, neutrinos), three of the four fundamental forces (electromagnetic, weak, and strong interactions but not gravity), and the Higgs boson. While it is one of the most successful theories we have, with a great record of predictions, it has uncertainties, and in those uncertainties, there’s the possibility for some really weird physics.
According to the paper, the uncertainty of the mass of the Top quark (the very heavy cousin of the Up quark one of the components of protons and neutrons), considered together with the (smaller) uncertainty on the Higgs boson mass, shows that the universe is right on the boundary between being a stable universe or a meta-stable one. And there are some strange consequences to this.
It is possible that the Higgs boson is not in its lowest possible configuration (its lowest mass) that the standard model accounts for. It is in an energy state (mass value) that is stable but not completely and it might be possible that some quantum mechanism could push it to its lowest possible energy state, so there could exist a lighter Higgs boson. If this was the case and it was to happen, devastation would ensue. The Higgs boson gives other particles mass so a variation of its properties would wreak havoc on the universe. Its collapse would generate a bubble of negative energy moving at the speed of light, destroying everything it encounters.
How likely is this scenario? Well, not even the researchers know for sure. The standard model doesn’t include gravity or dark matter and dark energy, which could either make the universe more stable or more unstable. And it also depends if the universe is finite or infinite. As always there’s a lot we don’t know, but at least we might have an idea of how long we have left to learn as much as we can.
[H/T: New Scientist]