Transcription
Why is there matter in the universe at all? That's one of the longest standing questions in modern astrophysics. And the largest particle accelerator in the world may have cracked the egg of that question.
Let's go back in time to when the universe was this seething soup of matter and energy. The energy manifest as photons, the matter manifesting as particles. In fact, they were matter antimatter particle pairs. Anytime the photon has sufficient energy, it will spontaneously convert itself into pairs of particles. According to E= MC², E for energy, M for matter. This is the famous Einstein equation from 1905, not the reason why he was given the Nobel Prize 16 years later by the way.
So the way it works is you start out with energy. If you're going to make matter, the matter has to be such that if you recombine it, you get the energy again. So when a photon becomes matter, it becomes a matter antimatter particle pair. Then that particle pair finds each other and becomes the photon again. And this is that soup that was sustained in the early universe back and forth. Anytime there was matter, there was an equal amount of antimatter ready to reanihilate and become photons again.
The universe was happy in that state while it was expanding and cooling until for some mysterious reason one in a billion conversions of a photon into matter antimatter particle pairs made only a matter particle and no antimatter for every 999,999,999 photons. And the dance card of one of those particles, a matter particle, went unmatched. So as the universe expanded and cooled, the matter antimatter particles that could find mates did became photons, leaving stranding one matter particle. And that is the universe we live in today.
There was some symmetry broken in the early universe. Symmetry laws are very powerful tools in physics that give us insights into phenomenon, experiments, time, place, pressure that you wouldn't otherwise know were not for these symmetry rules. And if at any time symmetry breaks, oh my gosh, we better find out why. This has been a long-standing problem in modern astrophysics.
As the universe cools, the energy of the photon systematically drops. When it drops below the energy of any two particles that it could possibly make. These are particles with a mass. Convert that through E= MC² to find out how much energy it takes to make these two particles. If the energy of all the photons drops below that, then the conversion of energy into matter stops. Yeah, it can still happen in the centers of stars, but overall in the universe, it stops.
We've not understood this symmetry breaking. We've not been able to duplicate it in our laboratories, in our particle accelerators, which are nothing more than the physicist petri dish of the early universe. We set up the conditions in our particle accelerators that resemble what was going on in the early universe. And that's how we know anything that was happening near the big bang itself. All right?
So, the Greeks imagined that if you broke down matter to smaller and smaller bits, you'd get to something that was indivisible. And the Greek word for indivisible is atom. In late 19th century science, we would learn that atoms are in fact divisible. They're composed of particles themselves. Electrons, that gives us our electrical current. The nucleus of atoms are protons and neutrons. Then people figured, well, now we have the fundamental particles, electrons, protons, and neutrons. But then we found out you can bust open protons and neutrons into smaller particles still. And that's when physicist theorist Murray Galman realized that maybe there are three particles contained within each the neutron and the proton. And remembering a quote from James Joyce's Finnegan's Wake, three quarks for muster mark. He said, "Oh, there's three." And that that sentence has the word quark in it. Let's call them quarks. Uh we would later learn that there are more kinds of quarks than those three, but it the name has stuck and we're fine with it. Won't be the last time physicists use fanciful terms to describe newly discovered particles.
These quarks have fractional charges. Think about it. If a proton is composed of three quarks and a proton has plus one, then the charges on these three quarks have to add up to plus one. So the proton has two quarks that have plus 2/3 charge. At 2/3 + 2/3, what do you get? You get 1 and a3. And it has a quark that has a minus 1/3 charge. So 2/3 + 2/3 minus 1/3 that gives you plus one. And if you take these and combine them in all kinds of ways, or you get the antimatter versions of those quirks that have the opposite charge, you can add them up to get a minus1 charge, or you can add them up to get no charge at all. So if you want to make an antimatter neutron, you say, "Well, what's the opposite charge of no charge?" You got to go inside, find out which quarks it's made of, then get the anti-quarks of that, put them together to still get you no charge. So you get a matter, no charge neutron, and an antimatter, no charge, neutron. This is fun with particle physics.
And we would learn in my lifetime, by the way, because that's how old I am, that there are three energy levels of particles, three families. The low energy one, which we live in, the electrons, protons, neutrons, this sort of thing. The next level has heavier versions of those particles and those quarks. Heavier versions. And there's a third level as well at even higher energies that we discovered in our most powerful particle accelerators. So you combine all three of these regimes together into one description and that is the standard model of particle physics.
Recently at the European organization for nuclear research acronymed CERN ce in their large hadron collider hadrons are nuclear particles. So it's really busting up atomic nuclei. They found an asymmetry in the formation of matter and antimatter particle pairs, but it was for a special configuration of particles.
So, how did they do it? It turns out the neutron is unstable. Within about 15 minutes, a neutron will decay into a proton, an electron, and an anti-utrino. Well, why those three particles? Well, a neutron is what we call a baron. We need another baron on the other side of that equation. It's the proton. Check. But neutron has no charge. Proton has a plus charge. Got to get rid of that somehow. You know what's created? An electron with a negative charge. Cancels out the charges. We're good there. The electron is what's called a leptton. I didn't start with lepttons. By the time I'm done, I better not have any either in the particle arithmetic. So, you know what comes out? An anti-nutrino. Nutrinos are lepttons just like electrons. So an anti-utrino cancels the electron. And so now there's nothing that we started with that we didn't also end with. That's how the particle physics works. It works magnificently.
But what CERN did was they made a special kind of neutron. They took out one of the quarks of the neutron and swapped in a quark from the higher energy level regime. This would not normally happen. You don't normally see this. So, they made a heavy neutron and then they waited and watched and out of 80,000 decays of that neutron, 2.5% of them did not make an antimatter particle violating the symmetry laws of physics.
Now, who thought this up? Who said, "Hey, let's take a quark from here where it doesn't belong and put it over here and see what happens." That's part of the creativity of the scientists to figure out how to test what nature is up to, what nature's capable of, what might have been happening in the early universe. It's not clear whether this kind of particle prevailed in the early universe, but it wouldn't take much of an asymmetry to set things into motion and end up with a universe made of just matter and no antimatter.
What do I mean by no antimatter? create antimatter in the lab. The sun makes antimatter in its core, but it's always paired with a matter particle. We're talking about loner matter particles. Okay, it's a crack in the egg of this matter antimatter asymmetry. And maybe there's more to be revealed, but right now it's a measurement for which there is no understanding. There is no theory of physics that accounts for it because in fact it's a violation of very strongly held physical principles. So watch that space. It's the famous matter antimatter asymmetry in the universe.
So let's have fun with that briefly. Maybe the antimatter particles were created in the early universe but they slipped out of this universe and made another universe. Maybe there's another universe that's made of all antimatter. So if there were planets and stars and life, they'd be made of antimatter. Maybe they're aliens in that other universe. And if they can tunnel, take a wormhole and come into our universe. The first thing I do if you greet an alien is flip it a coin. If the alien spontaneously explodes upon catching the coin, it was made of antimatter and it came from another universe. So, I always carry a coin just in case there's an alien that I have to greet. Right now, that's the frontier of science fiction. Uh, maybe one day becoming science fact. And that's what's up with that. I'm watching that space and I invite you to do so as well. As always, keep looking up.