How can antimatter exist at all? What amount of math had to be done until someone realized they can create it?
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Every particle in the universe came into existence as one half of a pair of particles: a particle, and its anti-particle.
One of the great mysteries astrophysics is trying to resolve is what happened to all the anti-particles for the matter in the universe we can observe now.
Artificial anti-particles are created in a vacuum in particle accelerators and are confined by magnetic fields to keep them separate from matter.
It’s really hard to do. Most anti-particles created this way exist for small fractions of a second before being annihilated.
Anti-matter isn’t special in any way except that for some unknown reason the universe is made of what we call normal matter.
Why is it that protons have a positive charge and electrons negative? I don’t mean why do we call one positive and the other negative. Rather, there’s no reason at all that their charges can’t be swapped. That’s what antimatter is – matter with its charges swapped. Other than that, it seems to be identical to everyday matter in every other way. An antiproton has the same mass as a proton and does all the same things as a proton, it just has an opposite electric charge.
There’s no reason it *can’t* exist. And any process that creates matter from energy will create both a particle and its antiparticle.
Antimatter is a poorly understood name. It’s really just “less common”. You’re used to a positive proton and a negative electron but there’s nothing inherent to physics that says those charges and masses have to go together. Antimatter basically just flips those charges so that you have a positive electron and negative proton. Anything you can do with a proton and electron you can do with their antiparticles, such as make atoms, molecules, even whole macroscopic objects and star systems.
As to how we realized it could exist and we could make it, Dirac was thinking about how electrons made sense with relativity. He came up with a useful equation (in that it explained some stuff that was this far observed but not explained and made sense starting from very basic principles) from his thoughts but there was a “problem” with his solution. It worked for negative energies. Working for electrons (the positive solution) could have been enough, but Dirac thought about these solutions and in collaboration with other scientists, concluded that there could be a particle that was like an electron but with positive charge. A few years later Carl David Anderson observed positrons in high energy cosmic rays using a bubble chamber and that was it, we knew they existed and how they were made.
There is actually a natural process that creates antimatter: Radioactive Beta Decay.
It comes in 2 types which involve a proton turning into a neutron or vice versa. To keep all of the energies balanced the nucleus will “throw out” this extra charge in the form of an electron or positron (antimatter electron).
If a positron is created, it is immediately annihilated with regular matter (electron) into 2 pure energy gamma rays. This amount of energy is based on the mass, which is always the same for electrons or positrons. So by measuring that specific gamma ray, we know an annihilation happened and what mass the antimatter particle was (which takes a surprisingly small amount of math IIRC, though at a pretty late stage in the development of physics).
Actually capturing antimatter is a whole different deal that I can’t even begin to confidently explain or even fathom, really. I do know that smashing atoms together with insane energy will release all sorts of weird particles, many being antimatter.
If we have the capability to measure particles that small in the first place, detecting their antimatter counterparts is actually very easy.
Bananas create antimatter all by themselves…..
A banana is a good source of fiber, vitamin C, manganese, and a host of other goodies. It’s also a good source of antimatter. That’s because a banana contains a tiny amount of a radioactive form of potassium. As the element decays, it produces positrons, the antimatter counterpart of electrons.
At first, they didn’t think it did exist. Paul Dirac came up with an elegant math formula 100 years ago, almost on a par with Einstein’s e= mc^2
But the formula seemed flawed because it indicated the existence of antimatter, which they thought was just science fiction.
But once again, the math came through and was proven correct all along.
Oh, and we use it every day when we get PET scans. (Positrons!)
Since no one is answering the second part of your question, I’ll mention the history of its mathematical discovery.
We were at a point in physics where special relativity was well-understood, but quantum mechanics was still being developed. One of the important “fathers” of QM, Paul Dirac, was attempting to create an equation to describe charged, relativistic particles with mass (so eg really fast moving electrons). We knew there had to be an equation, because the theory (Maxwell’s equations) that describes electric fields is relativistic (in fact Einstein used Maxwell’s equation to determine that the measured speed of light in a vacuum was the same in all inertial reference frames, which is the fundamental observation that leads to special relativity). Dirac was really hoping to describe some observations about the light emitted by Hydrogen when you excite its electron, because up until that time we had a really poor understanding of atomic spectra.
I won’t detail how he got his equation, but we already had the time-dependent Schrödinger equation. Dirac was only looking for a wave function to describe an electron, which would match with the Schrödinger equation, and which would match with some consequences of special relativity. The wave function can be thought of as something that describes the thing you’re interested in, eg, a spin-up electron. The equation reads something like:
(Energy) * (wave function) = i * h/(2 * pi) * (the change in the wave function with time).
(actually Dirac was probably using the Klein-Gordon equation, a known version of the Schrödinger equation that included relativistic momentum, but I can’t verify now if he specifically looked at this when deriving his equation).
Here, “i” is the imaginary unit, and “h” is Planck’s constant (an important unit of quantum mechanics). Dirac already had all of this, he just needed to write the correct relativistic energy for the electron, and find solutions (ie wave functions) using this equation.
Dirac was big on using matrices in QM. What he did was start by looking at “free” particles, and introduce new matrices to describe the free electron. He needed to incorporate spin (a fundamental property of particles, like charge), and he needed to incorporate charge. For a “free” particle, there’s no potential energy. So Dirac just focussed on the momentum of such a particle, because objects with momentum have a corresponding kinetic energy. You can see this if you’ve ever had to stop a moving object—it takes energy to do this! In special relativity we also have the concept of a “rest mass”, which is the energy you can extract from mass if you convert it completely into energy. This is the energy a nuclear bomb uses to go *boom*. It’s a LOT of energy
Since there was “rest mass” energy, and since there was energy from motion, Dirac figured he needed four matrices to describe his energy: one for the rest mass, three for the motion in three dimensions. He came up with these matrices, partly by knowing they had to satisfy certain observations, and partly through guesswork/creativity. When he solved the Schrödinger equation using this energy, he found that it matched the observations he was trying to explain extraordinarily well. However, he found *four* solutions, not two. We expect two (- charge, spin up, and – charge, spin down), but there were also + charge, spin up, and + charge, spin down. Dirac wrote this off at the time as a purely mathematical result, but some physicists were so sure that these “anti-electrons” were real that they wanted to find it. We soon found out the positrons (ie anti-electrons) indeed exist, and that Dirac’s equation could describe positrons just as they described electrons. So in fact, the Dirac equation predicted the existence of antimatter.
I’ve simplified and skipped over things because it gets very technical otherwise, but hope that answers your question.
Tl:dr: scientists stand on the shoulders of giants. Dirac was just trying to explain some properties of atomic spectra using the known maths of special relativity and QM, and accidentally discovered equations that also describe antimatter.
It’s a long story if you want to get the whole picture, so bear with me!
First, we found out that matter is made of little atoms. People had proposed this for a long time, at least since ancient Greece. Then in 1897, physicists discovered that atoms in matter can be split into two parts, one with positive charge and one with negative charge. They found this by trying to pass electricity through empty space in something called a vacuum tube and observing a stream of green substance coming out of the negative end (cathode) of the electric circuit. That’s how they knew that the stream is made of tiny negative charges, which we call electrons.
It turns out that electrical charges can be moved around by a magnet. If you hold a magnet near the green stream of electrons, the stream bends to one side. This fact will be important later.
In 1912, some physicists attached some instruments that can measure the amount of charged particles onto a balloon. They detected more and more charged particles as the balloons rose higher and higher into the atmosphere. These charged particles must’ve come from outside the Earth, and the physicists were sure they didn’t come from the Sun, as the experiment was done during a total solar eclipse, when the Moon blocked up the Sun completely. This was the discovery of cosmic rays.
By 1932, physicists had improved their instruments so cosmic rays could be detected from the ground instead of on balloons. They then tried to find out what these charged cosmic ray particles are. Using something called a cloud chamber, they could directly see the path of any charged particle passing through it, because it would leave a trail of bubbles through the cloud. They saw many trails coming from the sky—cosmic rays. But when they placed a magnet in the cloud chamber, they found that some cosmic ray particles left a curved trail that bent opposite to the expected direction for an electron, so it is positively rather than negatively charged! (Remember the magnet bending the green stream above?) This was the discovery of a new particle that is just as small as the electron but has the exact opposite charge as the electron. We call it the positron, the first discovery of antimatter!
From this point on, scientists gradually suspected that every “normal” particle that makes up regular matter (proton, neutron, etc.) has its own antiparticle (antiproton, antineutron, etc.), which has the same mass as the regular one but opposite charge. For example, the antiproton was discovered (produced) in 1955 by shooting lots of very fast protons towards a copper target and seeing what comes out.
When a regular particle touches its antimatter evil twin, the two would disappear into a burst of light (or other particles). This is why we don’t usually see antimatter around us and why it is so hard to make and keep around, because it would just destroy everything it touches.
To finish this part of the story, scientists believe that in the very early days in the history of the Universe, there were nearly equal amounts of matter and antimatter. However, since they’re all mixed together and touching each other, they kept destroying each other. At the end, only the tiny amount of remaining matter survived, making up all that we see in the Universe today. Why there were any remaining matter particles and how this whole process occurred is still a mystery that physicists are working on today.
As for what maths is needed to discover and learn about these things, here’s an incomplete list (and examples of their use):
* Algebra (to write down any formula or equation about the motion and behaviour of particles)
* Geometry (to figure out the shapes of trails made by particles and how to build measurement instruments)
* Differential equations (to describe and build electrical circuits)
* Multivariate calculus (to calculate the exact shapes of particle trails and how magnets affect them)
* Complex numbers (to describe electrical circuits; – to describe how electrons stay inside or get out of atoms using quantum mechanics)
* Linear algebra (also quantum mechanics)
* Quantum field theory (to describe how matter and antimatter particles disappear into light)
Most of the above are taught in a standard undergraduate physics curriculum. Quantum field theory is typically taught at the graduate level.
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