The objects of the Universe - galaxies, stars, quasars, planets, supernovae, animals and people - are composed of matter. It is formed by various elementary particles - quarks, leptons, bosons. But it turned out that there are particles in which one part of the characteristics completely coincides with the parameters of the "originals", and the other has the opposite values. This property prompted scientists to give the aggregate of such particles the general name "antimatter".
It also became clear that studying this mysterious substance is much more difficult than registering. Antiparticles in a stable state have not yet been encountered in nature. The problem is that matter and antimatter annihilate (mutually annihilate each other) upon "contact". It is quite possible to obtain antimatter in laboratories, although it is quite difficult to contain it. So far, scientists have been able to do this only for a few minutes.
According to the theory, the Big Bang should have produced the same number of particles and antiparticles. But if matter and antimatter annihilate with each other, then they should have ceased to exist at the same time. Why does the universe exist?
“More than 60 years ago, the theory said that all the properties of antiparticles coincide with the properties of ordinary particles in mirror-reflected space. However, in the first half of the 60s it was discovered that in some processes this symmetry is not satisfied. Since then, many theoretical models have been created, dozens of experiments have been carried out to explain this phenomenon. Now the most developed theories are that the difference in the amount of matter and antimatter is associated with the so-called violation of CP-symmetry (from the words charge - "charge" and parity - "parity"). But no one knows yet a reliable answer to the question why there is more matter than antimatter,”explains Alexey Zhemchugov, associate professor of the Department of Fundamental and Applied Problems of Physics of the Microworld of the Moscow Institute of Physics and Technology.
The history of antimatter began with the equation of motion for the electron, which had solutions in which it possessed negative energy. Since scientists could not imagine the physical meaning of negative energy, they "invented" an electron with a positive charge, calling it "positron".
He became the first experimentally discovered antiparticle. Installation, registering cosmic rays, showed that the trajectory of motion of some particles in a magnetic field is similar to the trajectory of an electron - only they deflected in the opposite direction. Then the meson-antimeson pair was discovered, the antiproton and antineutron were registered, and then scientists were able to synthesize antihydrogen and the antihelium nucleus.
Trajectories of motion of an electron and a positron in a magnetic field / Illustration by RIA Novosti. Alina Polyanina
What do all these "anti" mean? We usually use this prefix to denote the opposite phenomenon. As for antimatter - it can include analogs of elementary particles that have opposite charge, magnetic moment and some other characteristics. Of course, all the properties of a particle cannot be reversed. For example, mass and lifetime should always remain positive, focusing on them, particles can be attributed to one category (for example, protons or neutrons).
Promotional video:
If we compare a proton and an antiproton, then some of their characteristics are the same: the mass of both is 938.2719 (98) megaelectronvolt, spin ½ (spin is called the intrinsic angular momentum of a particle, which characterizes its rotation, while the particle itself is at rest). But the electric charge of the proton is 1, and the antiproton has minus 1, the baryon number (it determines the number of strongly interacting particles consisting of three quarks) is 1 and minus 1, respectively.
Proton and antiproton / Illustration by RIA Novosti. Alina Polyanina
Some particles, such as the Higgs boson and the photon, have no anti-analogs and are called true neutral.
Most antiparticles, along with particles, appear in a process called pairing. The formation of such a pair requires high energy, that is, tremendous speed. In nature, antiparticles arise when cosmic rays collide with the Earth's atmosphere, inside massive stars, next to pulsars and active galactic nuclei. Scientists use colliders-accelerators for this.
Accelerating section of the Large Hadron Collider, where particles are accelerated / Photo: CERN
The study of antimatter has practical applications. The point is that the annihilation of matter and antimatter generates high-energy photons. Let's say we take a bank of protons and antiprotons and start gradually releasing them towards each other through a special tube, literally one at a time. Annihilation of one kilogram of antimatter releases the same amount of energy as burning 30 million barrels of oil. One hundred and forty nanograms of antiprotons would be quite enough for a flight to Mars. The catch is that it takes even more energy to generate and hold antimatter.
However, antimatter is already being used in practice, in medicine. Positron emission tomography is used for diagnostics in oncology, cardiology and neurology. The method is based on the delivery of matter decaying with the emission of a positron to a specific organ. For example, a substance that binds well to cancer cells can act as a transport. In the desired area, an increased concentration of radioactive isotopes and, consequently, positrons from their decay is formed. The positrons immediately annihilate with electrons. And we can quite fix the point of annihilation by registering gamma quanta. Thus, with the help of positron emission tomography, it is possible to detect an increased concentration of the transport substance in a certain place.