Antimatter: what is it, applications and discovery

Kennedy Space Center. May 16, 2011, 08:56 am NASA’s space shuttle Endeavour, after nearly twenty years of operation and 25 missions later, embarks on its last mission , STS-134. This program, one of the most important in the history of the US space agency, had the objective of transferring precious cargo to the International Space Station.

We are talking about the AMS, the Alpha Magnetic Spectrometer, an experimental module developed by CERN and under the direction of Samuel Ting, an American particle physicist and Nobel Prize winner. This researcher, with his team, had developed a team that would change our understanding of the Universe and solve one of the greatest enigmas in the history of Physics.

But in 2008, when this module was ready, then President George W. Bush denied the funds that would allow CERN to send this spectrometer into space. But in the spring of 2009, the Barack Obama administration released those funds and NASA launched the mission. Two years later, Endeavor was carrying the experimental module to the International Space Station , assembling this device to begin operating.

And on May 19, the spectrometer started taking data. But not in the usual way. The AMS was not looking for planets, galaxies, supernovae or any known object in the Universe. I was looking for something strange. Something we had never ventured to look for. Something that represents one of the greatest enigmas of the Cosmos and whose nature can help us understand the very origin of the Universe.

The AMS installed on the International Space Station was searching for traces of antimatter in the vacuum of space. The module was an antiparticle detector; and the mission, a project to reveal the nature of said antimatter. An entity that, as much as it seems something typical of science fiction and that is potentially the most dangerous substance in the Universe due to its unimaginable destructive power and, at the same time, an entity that, as soon as we are able to control it, can mark a new era in the history of humanity for its technological applications, it hides the keys to understanding where we come from and that makes us see how close everything was, in the first moments of creation, to total annihilation. And in today’s article, hand in hand with the most prestigious scientific publications, we will analyze everything we know (and what we don’t know) about antimatter.

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A dark truth emerges from mathematics: how was antimatter discovered?

The year was 1898. Arthur Schuster, a German-British physicist known mainly for his studies in spectroscopy, published an article in the journal Nature that, at the time, was branded as sensationalist, with many other physicists attacking said publication for lacking scientific foundations . And, at the time, they were right. Schuster had just theorized the existence of what he named antimatter .

This physicist, when the Big Bang theory had not even been developed yet, believed that, at the origins of the Universe, for each particle of matter created, its opposite must have been created. Some particles that he called antiparticles and that, despite being exactly the same as the particles of ordinary matter, had the peculiarity of being of opposite charge.

These, when added to each other, would form antiatoms and these, in turn, would form an antimatter that, in contact with baryonic matter, would cause the instantaneous annihilation of both, releasing huge amounts of energy. Schuster hypothesized that antimatter, in this fight, would have been relegated to remote corners of the Universe. Islands of antimatter in the void separated from ordinary matter where it would constitute antiplanets, antistars, antigalaxies and even antiliving beings.

It is not surprising that no one defended this theory of Schuster. And it is that he had no mathematical foundation beyond pure speculation. But a few decades later, an 80-year-old Arthur Schuster would see how his apparently crazy hypothesis hid a terrifying truth. The physicist had not been wrong. And he was more right than he probably expected and wanted to be.

The year was 1928. Paul Dirac, a British electrical engineer, mathematician and theoretical physicist considered one of the fathers of quantum mechanics, came up with a relativistic wave equation with which he intended to describe how particles behave when they travel at speeds close to that of light He wanted a relativistic version of the Schrödinger equation, as Dirac was concerned that quantum mechanics would not fit Einstein’s General Relativity.

With this equation, Dirac had achieved the first mathematical unification of quantum physics with relativistic physics, something that would earn him the Nobel Prize in Physics in 1933. The entire scientific community praised Dirac’s work, but he could only think of one thing. In the strange prediction that he hid the equation from him.

Dirac was the only one to realize that the equation led to two solutions in a similar way to how the square root of a positive number always has two results. Dirac saw how one of the solutions did describe the electron, but the other solution appealed to something strange, a particle not covered by the standard model. Something was emerging from the math, but Dirac forced himself to think that something was wrong with his equation . From him. But as much as he tried to disprove himself, the evidence was still there.

He hadn’t been wrong. Mathematics had just shown that there was a whole world beyond the standard model. The equation was fine. And this predicted the existence of an inverse for each known particle. And although it took him three years to work up the courage to announce his discovery to the world, in the end he did. Dirac had just given the first mathematical evidence for the existence of, at that time, fanciful antimatter. His equation had just revealed the antiworld that had been hidden from our eyes.

Dirac showed how the first solution of his equation described the electron; but the other, to a particle of the same mass and spin as this one but of opposite electrical charge. We were dealing with an antielectron, which was also known as a positron . But it did not apply only to electrons, but to the rest of the particles in the model, including quarks. There would also be antiquarks, and since these constitute the protons of the nucleus, there would be antiprotons. And, in turn, there would be antiatoms.

Schuster, perhaps he was right. Antimatter probably existed. And Dirac’s theory, if considered true, could revolutionize everything. Not only would we double the number of known particles, but we would open the door to a new era of physics. But, for the moment, its existence was only inferred from mathematics. We had to find signs of them experimentally. And this fact, luckily, would not be long in coming.

The year was 1932. Carl David Anderson, an American physicist who won the Nobel Prize in Physics in 1936, was studying, at the California Institute of Technology, the photoelectrons produced by cosmic radiation in a bubble chamber, a detector of charged particles electrically formed by a vat with liquid hydrogen at a temperature slightly lower than its boiling point. In it, when a charged particle passes close to an atom, it is enough to cause bubbles of vaporized liquid. And this trace can be photographed.

And in one of the many studies carried out, in one of the photographs he saw something strange. A trace whose measurements and curvature showed that they had photographed an electron, but was tilted in the opposite direction. The particle they had captured behaved exactly like an electron but curved as if it had a positive charge. An electron had to have a negative charge. It did not make sense. Unless what he had photographed was not an electron…

Anderson had just detected an antielectron. And this discovery of the positron, which earned the scientist his Nobel Prize, showed that what the mathematics of the Dirac equation hid was true. Antimatter existed. But the journey has just begun. Now we had to solve his puzzle.

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What is antimatter?

With his mathematical theorizing and subsequent discovery, we learned that antimatter is the extension of the antiparticle concept to matter . An entity composed, then, of antiatoms that, in turn, are composed of antiparticles, which have the same properties of mass, size, spin and fundamental interactions as the particles of baryonic matter, only with an opposite electrical charge. And at the level of quantum field theory, which sees particles as excitations in these quantum fields, the antiparticles would be opposite excitations in them.

Thus, it has nothing to do with dark matter, much less with dark energy. Antimatter is like ordinary matter, that which is made up of baryons (protons and neutrons) and leptons (electrons) and that makes up everything that we can see, perceive, measure and interact with in the Universe, only that the antiparticles that they make up have an electrical charge opposite to that of ordinary particles in the standard model.

The positron discovered in 1932 by Carl Anderson was the first evidence of its existence , thus seeing how antielectrons, exactly the same as electrons in their properties with the “simple” difference of having a positive instead of negative electric charge, were a reality. And since then, knowing that there must be an antiparticle for each particle, we went in search of the others. But we ran into a problem.

Detecting antielectrons is easy. They are constantly bombing us. And not just from cosmic rays. A banana releases an antielectron approximately every hour. Even you emit 180 antielectrons per hour. But with more massive antiparticles, things change. For antiprotons, we need to accelerate a boson to higher and higher energies that you have enough for this particle to go through a pair creation process. The process through which a subatomic particle and its corresponding antiparticle are created.

And although we knew the scientific foundation, given the technological limitations, we spent a couple of decades without discovering other antiparticles. But in 1955, Emlio Segre and Owen Chamberlain, American physicists from the University of Berkeley, thanks to the Bevatron particle accelerator, managed to discover the antiproton .

But, at the same time, we realized how complicated its study was going to be and, above all, a future production for technological purposes. Because being in contact, matter and antimatter annihilate each other in less than a nanosecond. This fact is what leads antimatter to be one of the great mysteries of the Universe and, at the same time, both the curse and the dream of future prospects that we have with said antimatter. But let’s go step by step.

When a positron meets an electron, two photons are simply released. But when an antiproton meets a proton, the atomic nucleus rips apart. And this instantaneous annihilation of matter-antimatter is what opened the doors to one of the greatest unknowns that Physics has faced and continues to face . A mystery that we have spent more than sixty years trying to solve.

Because if physical laws have no preference for a positive or negative sign, we expect that the same amounts of matter and antimatter will be created in the Big Bang and we know that antimatter and matter have the same properties and instantly annihilate when they enter in touch… What are we doing here? Why, in the first instant of life of the Universe, was not absolutely everything annihilated? Why was matter left behind and not just an eternal void? Why weren’t they completely annihilated? Why did matter win the war? Where is all the antimatter? These questions are what make up what is known as the anomaly of baryogenesis.

The anomaly of baryogenesis: why is there an asymmetry between matter and antimatter?

The year was 1967. Andrei Sakharov, Soviet nuclear physicist and human rights activist who won the Nobel Peace Prize in 1975, focused his studies on this anomaly of baryogenesis, a problem that appealed to the unobserved asymmetry that must have occurred between baryons and antibaryons during the first moments of existence of the Universe.

The anomaly appealed to the apparent impossibility that the formation of the Cosmos would result in high amounts of baryonic matter and in such minute amounts of antimatter . Observations and theories about matter-antimatter behavior told us that the Universe simply could not exist. Everything should have been annihilated. But, nevertheless, here we were. Something must have happened at the birth of the Cosmos.

Sakharov said that, if the symmetry between matter and antimatter existed and if they had been created under equal conditions, they would have had to be annihilated and leave only radiation in the vacuum. After a trillionth of a second after the Big Bang, the Universe cooled enough for fundamental particles to emerge in oppositely charged matter-antimatter pairs. First the quarks and antiquarks and then the leptons.

Assuming perfect symmetry, matter and antimatter would have instantly annihilated and, less than a second after the creation of the Cosmos, there would be nothing left. Everything would have been annihilated. Our very existence was a paradox. We shouldn’t be here. Every last particle of our being should have disappeared 13.8 billion years ago, when the Cosmos was born.

The Soviet physicist proposed that something must have happened that broke the symmetry. Something had to happen so that for every trillion antiparticles that were created, a trillion plus one particle was created. This tiny, tiny imbalance was what saved us from annihilation. In the most devastating fight in the history of the Universe, in just one second, for every trillion particles of matter and antimatter annihilated, one of matter survived. And these survivors are the ones that gave rise to the Universe as we know it.

But with that came the big question. What is the origin of this imbalance? Unfortunately, neither Andrey Sakharov nor any other scientist has been able to answer this question. And since then, the matter-antimatter asymmetry problem has remained one of the great unknowns in the world of modern physics and cosmology. An enigma that, as soon as we solve it, we will be able to understand the origin of the Universe as we have never done before.

In 1964, James Cronin, an American nuclear physicist, together with Val Logsdon Fitch, an American physicist, studying the decay of kaons, a type of particle of the meson group, discovered that, in its antiparticle, the transformation to a particle did not return to occur with the same probability. It was the first time that we saw slight differences in the physical laws that govern matter and antimatter, but it was not enough to transfer it to the rest of the particles.

So we still don’t understand why there was no symmetry in the Big Bang and what happened to preferentially create matter or destroy antimatter. Because, at the moment, the observations do not indicate that there was any imbalance. Gravitational waves can give us clues about what happened , but we are not yet able to detect them well. So in the face of this conflict, different hypotheses have emerged.

Richard Feynman, an American theoretical physicist, provided a solution to this anomaly in asymmetry. He postulated that it was possible for antimatter to be the same as matter but moving backwards in time. Thus, he proposed the hypothesis that in the Big Bang, antimatter began to go backwards in time, never to meet matter. If you were to wind the cosmic clock back to the Big Bang and walk past it, then you would see how the Universe branched off in two opposite time directions. In ours, the arrow of time favored matter. And in the opposite, to antimatter.

At the same time, it has been theorized that something had to happen at the origin of the Universe to prevent the annihilation of matter and antimatter. The Cosmos protected itself from annihilation by separating matter and antimatter so quickly that they never had time to annihilate. And to the question of why antimatter is so strange in the Universe, an answer is offered that is very much in line with the ideas that were considered the fantasy of Arthur Schuster, who coined the concept of antimatter.

As he predicted, it is possible that antimatter would be relegated to remote corners of the Universe, forming islands of antimatter where we would have antiplanets, antistars and antigalaxies. Even so, we would have to see gamma rays coming from the borders between the ordinary Universe and the islands of antimatter produced by the annihilation of antiparticles; something that, at least for now, we have not detected…

Along the same lines, it has also been theorized that antimatter would remain condensed in antistars within this our Universe . They would not be cosmic islands of antimatter. But simply stars composed of antiparticles that could survive in the Universe, because in the vacuum there is so little matter that they would annihilate very slowly.

And this hypothesis is so strong that, last year 2021, a group of astronomers from Toulouse, France, analyzed data from the Fermi telescope, a gamma-ray telescope that already discovered how antimatter was formed by acceleration around the Sagittarius A black hole. in the center of our galaxy, looking for strange brightnesses in stars in our galaxy that would fit with what would be expected in the event of matter-antimatter annihilations.

And this study, to the surprise of the entire international astronomical community, concluded with the discovery of 14 antistar candidates in the nearby regions of our galactic neighborhood. And right now, they’re investigating them. But the team believes that 2 out of a million stars would be antistars.

At the same time, the AMS module we were talking about at the beginning is collecting data in the hope of finding atoms of antihelium, anticarbon and other heavier elements. Because, for now, we are only detecting antiparticles. If anti-atoms were found, this finding would show that there are anti-stars in whose hearts they were formed and that the symmetry was not broken after all. Quite simply, antimatter found its place in the Universe.

And it is that although we have only discovered antiparticles that are created and annihilated in nanoseconds, as in the nuclear fusion reactions of the Sun, in the upper areas of the Earth’s upper atmosphere due to the impact of high-energy particles and even in the rays of storms, everything seems to indicate that, if it were not for the fact that matter overwhelmingly dominates and these antiparticles annihilate very quickly, this antimatter could be perfectly stable if it managed to isolate itself from matter and that, in fact, it would look like ordinary matter , being even impossible to differentiate it from her.

We will see what these and other studies lead us to. But for now, one thing is clear. We know almost everything about antimatter, except why it’s so rare. But, well, basically, nothing happens. Because we are able to build it here on Earth. Yes, prepare your wallet. Let’s talk about antimatter factories.

The Antimatter factory: how much does it cost and what is it for?

CERN ( Conseil Européen pour la Recherche Nucléaire ) has a facility that, however typical of science fiction it may seem, is a real antimatter factory. The only one in the whole world. A facility where research teams have been producing antimatter for more than 30 years , the potentially most dangerous substance in the Universe, as we shall see.

To create something that could have annihilated the Universe you just need some hydrogen and accelerate the protons after breaking these atoms. When you speed them up enough, almost to the speed of light, and they hit a block of iridium, the kinetic energy is converted into pairs of particles and antiparticles.

Later, another machine comes into play, the ELENA decelerator of antiprotons, which reduces its speed to 1/10 the speed of light . So, you can already catch some. This facility is producing 10 million antiprotons per minute. And over the course of a year, it’s generating 10 to the 14th antiproton. How can this be allowed? Well, because 10 to the 14th antiproton is roughly a tenth of a nanogram. In one year.

If you were to put together all the antimatter produced in the last 30 years, you would have about 10 nanograms, which is one billionth of a gram. But then again, you couldn’t even get it together. Because the maximum time we have managed to retain antiatoms is 16 minutes. A record that was achieved in 2010 with a few hundred antihydrogen atoms. You have to trap the antiatoms in an electromagnetic field because the moment they come into contact with matter, bye-bye.

But in a hypothetical case that we could retain antimatter indefinitely, if you wanted to have 1 gram of it, you would need this machine at CERN to be in continuous operation for 600 million years . After this time, you would have your gram of antimatter. Hence, it is said, more as a curiosity than proportionally, antimatter is the most expensive substance in the world.

Because obviously, keeping this CERN facility running for 600 million years would cost you a bit. Specifically and according to estimates, about 60 trillion dollars. That is, 60 million million dollars. Or what is the same, 68% of world GDP. It would not be cheap.

But as we say, this is all hypothetical. Until today, we have barely manufactured 10 nanograms in total and we are losing all of it. We cannot retain the antimatter because the moment it comes into contact with the walls of the container, it is annihilated. In 2022, they hope to build an electromagnetic container that can hold and transport antimatter . Although, well, given what we have seen, it may not be a good idea to get into these troubles.

Because although we have joked about it, antimatter is really one of the most potentially dangerous substances in the Universe. For the simple fact that matter-antimatter annihilation is a reaction that releases 100% of the energy contained in it. A nuclear bomb converts only 7% of its mass into energy. A matter-antimatter annihilation, 100%.

Two marbles, one antimatter and one antimatter, colliding would cause destruction comparable to a nuclear bomb. A single gram of antimatter would be enough to create a bomb 40% more powerful than the one on Hiroshima. And if two tablespoons of matter and antimatter annihilated, there would be an explosion that would destroy the entire city of Manhattan, since the energy released would be equivalent to 10 nuclear bombs or 200,000 metric tons of TNT. And 2.5 kilotonnes of antimatter would be as devastating as the meteorite that caused the extinction of the dinosaurs .

But don’t worry, if all the antimatter we’ve produced over the last 30 years exploded at your fingertips, it would be just like watching a matchstick strike. All quiet. Furthermore, not everything related to antimatter is dangerous and can lead to the destruction of humanity.

Because if that one gram of antimatter would be enough to drive around the Earth about 1,000 times, it would clearly be the perfect fuel for spacecraft . We are still a long way from having the technology to produce enough quantities and hold it in a stable way to use its annihilations with matter, but in the distant future, a piece of antimatter the size of a coin will be enough to put us in orbit. And larger amounts would even allow travel at speeds close to 50% that of light, thus making interstellar travel possible.

But without going to assumptions so movie, the closest future of antimatter is, without a doubt, in the world of Medicine. In fact, we are already using antimatter in PET scanners, a positron emission tomography where antiparticles emitted by radioactive materials are incised to obtain detailed images of the interior of the body to, generally, diagnose and analyze the status of a malignant tumor.

And it is possible that, in time, we will be able, with greater energy and greater precision, to use matter-antimatter annihilations by impinging antiparticles very precisely on a cancer to destroy it without damaging healthy tissue. The possibilities offered by antimatter can, when technology joins us, completely change the world in which we live.

Because antimatter hides not only the key to take the next step in our technological evolution and cross the borders that nature had established for us, but also the ingredient to understand the origin of the Universe. Because the secret of creation is hidden in the fight between antimatter and matter . And with time, we will be able to unveil this great mystery.