What Was It Like When The Universe First Created More Matter Than Antimatter?
“This is only one of three known, viable scenarios that could lead to the matter-rich Universe we inhabit today, with the other two involving new neutrino physics or new physics at the electroweak scale, respectively. Yet in all cases, it’s the out-of-equilibrium nature of the early Universe, which creates everything allowable at high energies and then cools to an unstable state, which enables the creation of more matter than antimatter. We can start with a completely symmetric Universe in an extremely hot state, and just by cooling and expanding, wind up with one that becomes matter-dominated. The Universe didn’t need to be born with an excess of matter over antimatter; the Big Bang can spontaneously make one from nothing. The only open question, exactly, is how.”
One of the biggest unsolved questions in physics today is how the Universe came to be filled with matter and not antimatter. After all, the laws of physics are completely matter-antimatter symmetric, and yet when we look at what we have today, every planet, star, and galaxy is made of matter and not antimatter. How did it come to be this way? The young, hot, but rapidly expanding-and-cooling Universe gives us all the ingredients we need for this to occur. We are certain of the exact mechanism, but theoretically, there are some enticing possibilities. Here’s a walk through one of those scenarios in great detail, but expressed so simply that even someone with no physics knowledge can follow it.
Here’s what the Universe was like when it was matter-antimatter symmetric, along with how it could have become matter-rich without breaking the laws of physics.
How Did The Matter In Our Universe Arise From Nothing?
“[Y]ou can start with a completely symmetric Universe, one that obeys all the known laws of physics and that spontaneously creates matter-and-antimatter only in equal-and-opposite pairs, and wind up with an excess of matter over antimatter in the end. We have multiple possible pathways to success, but it’s very likely that nature only needed one of them to give us our Universe.
The fact that we exist and are made of matter is indisputable; the question of why our Universe contains something (matter) instead of nothing (from an equal mix of matter and antimatter) is one that must have an answer. This century, advances in precision electroweak testing, collider technology, and experiments probing particle physics beyond the Standard Model may reveal exactly how it happened. And when it does, one of the greatest mysteries in all of existence will finally have a solution.”
On one hand, we have all the stars, galaxies, gas, plasma, and the great cosmic web, all made out of matter and not antimatter. On the other hand, we have the laws of physics, which are almost completely symmetric between matter and antimatter, so much so that we’ve never created or observed more matter than antimatter in any reaction throughout human history. Yet somehow, such a reaction must have occurred, since the Universe exists as we see it: made of matter. So how did it get to be this way? How did a completely symmetric, early Universe give rise to a matter-dominated existence, complete with two trillion galaxies, each containing billions of stars? Believe it or not, we’re closer than ever before to answering this question, and the 21st century is poised to be the one where the answer to this existential question goes from speculative to solid.
Come learn the science behind why we live in a matter-rich Universe instead of a matter/antimatter symmetric one!