Atomism, that is, the doctrine of the existence of the smallest indivisible particles that make up matter, arose long before scientists were able to verify its provisions by experiment. However, when they did so, it turned out that the microcosm is filled not only with atoms, but also with even smaller particles that demonstrate amazing properties.
Mr. Lubin microcosm
The concept of "atom" was brought back to scientific use by John Dalton, a schoolteacher from Manchester, who created a convincing theory of chemical interaction in the early 19th century. He came to the conclusion that there are simple substances in nature, which he called "elements", and each is made up of atoms that are characteristic only of him. Dalton also introduced the concept of atomic weight, which allowed the elements to be ordered within the famous Periodic Table, proposed by Dmitry Mendeleev in March 1869.
The fact that in addition to atoms there are some other particles, scientists began to guess when studying electrical phenomena. In 1891, the Irish physicist George Stoney suggested calling a hypothetical charged particle an electron. After 6 years, the Englishman Joseph Thomson found that the electron is much lighter than the atom of the lightest element (hydrogen), in fact, having discovered the first of the fundamental particles.
In 1911, Ernest Rutherford, on the basis of experimental data, proposed a planetary model of the atom, according to which there is a dense and positively charged nucleus in its center, around which negatively charged electrons revolve. The subatomic particle with a positive charge, from which nuclei are composed, was called a proton.
Soon another surprising discovery awaited physicists: the number of protons in an atom is equal to the number of an element in the periodic table. Then a hypothesis arose that there are some other particles in the composition of atomic nuclei. In 1921, the American chemist William Harkins proposed to call them neutrons, but it took another 10 years to record and describe neutron radiation, the discovery of which, as we know, was of key importance for the development of nuclear power.
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Phantoms of the Antiworld
In the early 1930s, physicists knew four fundamental particles: photon, electron, proton, and neutron. It seemed that they were enough to describe the microcosm.
The situation changed dramatically when Paul Dirac proved the theoretical possibility of the existence of antielectrons. If an electron and an anti-electron collide, then annihilation will occur with the release of a high-energy photon. At first, Dirac believed that the proton is the anti-electron, but his colleagues ridiculed his idea, because then all the atoms in the world would instantly annihilate. In September 1931, the scientist suggested that there must be a special particle (later called a positron), which is born from a vacuum when hard gamma rays collide. It soon became clear that scientists had registered such a particle earlier, but could not give its manifestations a reasonable basis. The discovery of the positron suggested that the proton and neutron must have the same analogs.
Russian physicist Vladimir Rozhansky went even further, publishing in 1940 an article in which he argued that some bodies in the solar system (for example, meteorites, comets and asteroids) are composed of antimatter. The educated public, first of all science fiction writers, took up the idea, believing in the physical reality of the anti-world that exists somewhere nearby.
The process of artificially obtaining antiparticles turned out to be quite laborious: for this it was necessary to build a special accelerator "Bevatron". Antiprotons and antineutrons were detected on it in the mid-1950s. Since then, despite the growing labor costs, it has been possible to obtain only negligible amounts of antimatter, so the search for its natural "deposits" continues.
The hope of the supporters of the Rozhansky hypothesis is fueled by the registered discrepancy (by a factor of 100!) Between the theoretically predicted and real intensity of antiproton fluxes in cosmic rays. This discrepancy can be explained, among other things, with the help of the assumption that somewhere outside our Galaxy (or even the Metagalaxy), there really is a vast region consisting of antimatter.
Elusive particle
In 1900, physicists established that the beta rays produced by radioactive decay are actually electrons.
In the course of further observations, it turned out that the energy of the emitted electrons turns out to be different, which clearly violated the law of conservation of energy. No theoretical and practical tricks helped explain what was happening, and in 1930 Niels Bohr, the patriarch of quantum physics, called for the abandonment of this law in relation to the microworld.
The Swiss Wolfgang Pauli found a way out: he suggested that during the decay of atomic nuclei, another subatomic particle is released, which he called a neutron and which cannot be detected by the available instruments. Since it was at that time that the previously predicted neutron was finally discovered, it was decided to call the hypothetical Pauli particle a neutrino (later it turned out that during beta decay, not a neutrino, but an antineutrino is born).
Although the idea of neutrinos was initially received with skepticism, over time it took over the minds. At the same time, a new problem arose: the particle is so small and has such an insignificant mass that it is practically impossible to fix it even when passing through the densest substances. Yet the researchers did not give up: when nuclear reactors appeared, they managed to be used as generators of a powerful neutrino flux, which led to its discovery in 1956.
"Ghost" particles learned to register and even built a huge neutrino observatory "Ice Cube" in Antarctica, but they themselves largely remain a mystery. For example, there is a hypothesis that antineutrinos interact with matter like an ordinary neutrino. If the hypothesis is confirmed by experiment, it will become clear why, during the formation of the Universe, a global asymmetry arose and matter today is much larger than antimatter.
Scientists associate with the further study of neutrinos getting answers about the possibility of motion with superluminal speed, about the nature of "dark matter", about the conditions of the early Universe. But, perhaps most importantly, the recently proven presence of mass in neutrinos destroys the Standard Model, encroaching on the foundations of modern physics.
Outside the Standard Model
The study of cosmic rays and the construction of powerful accelerators contributed to the discovery of dozens of previously unknown particles, for which an additional classification had to be introduced. For example, all subatomic particles that cannot be split into their constituent parts are called elementary today, and only those of them that are considered to have no internal structure (electrons, neutrinos, etc.) are called fundamental.
In the early 1960s, the Standard Model began to take shape - a theory that takes into account all known particles and force interactions, except for gravity. The current version describes 61 elementary particles, including the legendary Higgs boson. The success of the Standard Model is that it predicts the properties of particles that have not yet been discovered, thereby making it easier to find them. And yet there are reasons to talk, if not about revising, then about expanding the model. This is precisely what the supporters of New Physics are doing, which is called upon to solve the accumulated theoretical problems.
Going beyond the Standard Model will be accompanied by the discovery of new elementary particles, which are still hypothetical. Perhaps scientists will discover tachyons (moving at superluminal speed), gravitons (carrying gravitational interaction) and vimps (making up "dark" matter). But it is just as likely that they will stumble upon something even more fantastic. However, even then there will be no guarantee that we have cognized the microcosm as a whole.
Anton Pervushin