The smallest particle in the soil. The lightest and most massive elementary particles

The neutrino, an incredibly tiny particle in the universe, has held the close attention of scientists for nearly a century. More Nobel Prizes have been awarded for research on the neutrino than for work on any other particles, and huge facilities are being built to study it with the budget of small states. Alexander Nozik, senior researcher at the Institute for Nuclear Research of the Russian Academy of Sciences, lecturer at the Moscow Institute of Physics and Technology and participant in the Troitsk nu-mass experiment to search for the neutrino mass, tells how to study it, but most importantly, how to catch it at all.

Mystery of the Stolen Energy

The history of the study of neutrinos can be read as a fascinating detective story. This particle tested the deductive abilities of scientists more than once: not every of the riddles could be solved immediately, and some have not been solved so far. Let's start with the history of discovery. Radioactive decays of various kinds began to be studied at the end of the 19th century, and it is not surprising that in the 1920s, scientists had instruments in their arsenal not only to register the decay itself, but also to measure the energy of emitted particles, albeit not very accurate by today's standards. . With the increase in the accuracy of the instruments, the joy of scientists grew, and the bewilderment associated, among other things, with beta decay, in which an electron flies out of a radioactive nucleus, and the nucleus itself changes its charge. Such a decay is called two-particle, since two particles are formed in it - a new nucleus and an electron. Any high school student will explain that it is possible to accurately determine the energy and momentum of fragments in such a decay, using conservation laws and knowing the masses of these fragments. In other words, the energy of, for example, an electron will always be the same in any decay of the nucleus of a certain element. In practice, a completely different picture was observed. The energy of electrons was not only not fixed, but also spread out into a continuous spectrum to zero, which baffled scientists. This can only happen if someone is stealing energy from beta decay. But there seems to be no one to steal it.

Over time, the instruments became more and more accurate, and soon the opportunity to attribute such an anomaly to the error of the equipment disappeared. Thus a mystery arose. In search of its solution, scientists expressed various, even completely absurd assumptions by today's standards. Niels Bohr himself, for example, made a serious statement that conservation laws do not apply in the world of elementary particles. Saved the day by Wolfgang Pauli in 1930. He was unable to attend the physics conference in Tübingen and, unable to participate remotely, sent a letter that he asked to be read. Here are excerpts from it:

“Dear radioactive ladies and gentlemen. I ask you to listen attentively at the most convenient moment to the messenger who delivered this letter. He will tell you that I have found an excellent tool for the law of conservation and correct statistics. It lies in the possibility of the existence of electrically neutral particles ... The continuity of the Β-spectrum will become clear if we assume that during Β-decay, such a “neutron” is emitted with each electron, and the sum of the energies of the “neutron” and the electron is constant ... "

At the end of the letter were the following lines:

“Don't take risks, don't win. The severity of the situation when considering the continuous Β-spectrum becomes especially striking after the words of prof. Debye, who told me with regret: "Oh, it's better not to think of all this ... as new taxes." Therefore, every path to salvation must be seriously discussed. So, dear radioactive people, put it to the test and judge."

Later, Pauli himself expressed fears that, although his idea saves the physics of the microcosm, a new particle will never be discovered experimentally. They say he even argued with his colleagues that if the particle exists, it will not be possible to detect it during their lifetime. In the next few years, Enrico Fermi created a theory of beta decay involving a particle he called the neutrino, which agreed brilliantly with experiment. After that, no one had any doubts that the hypothetical particle actually exists. In 1956, two years before Pauli's death, the neutrino was experimentally discovered in inverse beta decay by the group of Frederick Reines and Clyde Cowan (Reines received Nobel Prize).

The Case of the Missing Solar Neutrinos

As soon as it became clear that neutrinos, although difficult, can still be registered, scientists began to try to capture neutrinos of extraterrestrial origin. Their most obvious source is the Sun. Nuclear reactions are constantly taking place in it, and it can be calculated that about 90 billion solar neutrinos per second pass through every square centimeter of the earth's surface.

At that moment the most effective method catching solar neutrinos was a radiochemical method. Its essence is as follows: the solar neutrino arrives on Earth, interacts with the nucleus; it turns out, say, a 37Ar nucleus and an electron (this is the reaction that was used in the experiment of Raymond Davis, for which he was later awarded the Nobel Prize). After that, by counting the number of argon atoms, one can say how many neutrinos interacted in the detector volume during the exposure time. In practice, of course, things are not so simple. It must be understood that it is required to count single argon atoms in a target weighing hundreds of tons. The ratio of masses is approximately the same as between the mass of an ant and the mass of the Earth. It was then that it was discovered that ⅔ of solar neutrinos had been stolen (the measured flux turned out to be three times less than predicted).

Of course, in the first place, suspicion fell on the Sun itself. After all, we can judge his inner life only by indirect signs. It is not known how neutrinos are born on it, and it is even possible that all models of the Sun are wrong. Quite a lot of different hypotheses were discussed, but in the end, scientists began to lean towards the idea that it was not the Sun that mattered, but the cunning nature of the neutrinos themselves.

A small historical digression: in the period between the experimental discovery of neutrinos and experiments on the study of solar neutrinos, several more interesting discoveries occurred. First, antineutrinos were discovered and it was proved that neutrinos and antineutrinos participate in interactions in different ways. Moreover, all neutrinos in all interactions are always left-handed (the projection of the spin on the direction of motion is negative), and all antineutrinos are right-handed. Not only is this property observed among all elementary particles only for neutrinos, it also indirectly indicates that our Universe is not symmetrical in principle. Secondly, it was found that each charged lepton (electron, muon and tau lepton) has its own type, or flavor, of neutrino. Moreover, neutrinos of each type interact only with their lepton.

Let's return to our solar problem. Back in the 1950s, it was suggested that the lepton flavor (a type of neutrino) should not be conserved. That is, if an electron neutrino was born in one reaction, then on the way to another reaction, the neutrino can change clothes and run as a muon. This could explain the lack of solar neutrinos in radiochemical experiments sensitive only to electron neutrinos. This hypothesis was brilliantly confirmed by measurements of the solar neutrino flux in scintillation experiments with a large water target SNO and Kamiokande (for which another Nobel Prize was recently awarded). In these experiments, it is no longer the reverse beta decay that is being studied, but the neutrino scattering reaction, which can occur not only with electron, but also with muon neutrinos. When, instead of a flux of electron neutrinos, they began to measure the total flux of all types of neutrinos, the results perfectly confirmed the transition of neutrinos from one type to another, or neutrino oscillations.

Attack on the Standard Model

The discovery of neutrino oscillations, having solved one problem, created several new ones. The bottom line is that since the time of Pauli, neutrinos have been considered massless particles like photons, and this suited everyone. Attempts to measure the neutrino mass continued, but without much enthusiasm. Oscillations have changed everything, because for their existence the mass, however small, is indispensable. The discovery of mass in neutrinos, of course, delighted experimenters, but puzzled theorists. First, massive neutrinos do not fit into the Standard Model of particle physics, which scientists have been building since the beginning of the 20th century. Secondly, the same mysterious left-handedness of the neutrino and the right-handedness of the antineutrino is well explained only again for massless particles. In the presence of mass, left-handed neutrinos should with some probability turn into right-handed neutrinos, that is, into antiparticles, violating the seemingly unshakable law of conservation of the lepton number, or even turn into some kind of neutrinos that do not participate in the interaction. Today, such hypothetical particles are called sterile neutrinos.

Super-Kamiokande Neutrino Detector © Kamioka Observatory, ICRR (Institute for Cosmic Ray Research), The University of Tokyo

Of course, the experimental search for the neutrino mass immediately resumed abruptly. But the question immediately arose: how to measure the mass of something that cannot be caught in any way? There is only one answer: not to catch neutrinos at all. To date, two directions are being most actively developed - a direct search for the mass of neutrinos in beta decay and the observation of neutrinoless double beta decay. In the first case, the idea is very simple. The nucleus decays with the emission of an electron and a neutrino. It is not possible to catch a neutrino, but it is possible to catch and measure an electron with a very high accuracy. The electron spectrum also carries information about the neutrino mass. Such an experiment is one of the most complex in particle physics, but its undoubted advantage is that it is based on the basic principles of conservation of energy and momentum and its result depends on little. Now the best limit on the neutrino mass is about 2 eV. This is 250 thousand times less than that of an electron. That is, the mass itself was not found, but only limited by the upper frame.

With double beta decay, everything is more complicated. If we assume that a neutrino turns into an antineutrino during a spin flip (this model is named after the Italian physicist Ettore Majorana), then a process is possible when two beta decays occur simultaneously in the nucleus, but the neutrinos do not fly out, but contract. The probability of such a process is related to the neutrino mass. The upper limits in such experiments are better - 0.2 – 0.4 eV - but depend on the physical model.

The massive neutrino problem has not yet been solved. The Higgs theory cannot explain such small masses. It requires a significant complication or the involvement of some more cunning laws, according to which neutrinos interact with the rest of the world. Physicists involved in the study of neutrinos are often asked the question: “How can the study of neutrinos help the average layman? What financial or other benefit can be derived from this particle? Physicists shrug. And they really don't know it. Once the study of semiconductor diodes belonged to purely fundamental physics, without any practical application. The difference is that the technologies that are being developed to create modern experiments in neutrino physics are already widely used in industry, so every penny invested in this area pays off pretty quickly. Now several experiments are being carried out in the world, the scale of which is comparable to the scale of the Large Hadron Collider; these experiments are aimed exclusively at studying the properties of neutrinos. Which one can open new page in physics, it is unknown, but it will be discovered for sure.

What is the smallest known particle? They are today considered the smallest particles in the universe. The smallest particle in the universe is the Planck particle black hole(Planck Black Hole), which so far exists only in theory. Planck's black hole - the smallest of all black holes (due to the discreteness of the mass spectrum) - is a kind of boundary object. But, in the Universe, its smallest particle was also discovered, which is now being carefully studied.

The highest point in Russia is located in the Caucasus. Then mesons became the smallest particles, then bosons. This particle belongs to the category of black holes because its gravitational radius is greater than either equal to length waves. Of all the existing black holes, the Planckian is the smallest.

And they are formed, as is commonly believed, as a result of nuclear reactions. Despite such a hypothetical existence of this smallest particle in the Universe, its practical discovery in the future is quite possible. It was to detect it that an installation was created that only the laziest inhabitant on Earth had not heard of - the Large Hadron Collider. Higgs boson on this moment the smallest particle of those whose existence is practically proven.

And if particles didn't have mass, the universe couldn't exist. Not a single substance could be formed in it. Despite the practical proven existence of this particle, the Higgs boson, practical applications for it have not yet been invented. Our world is huge and something interesting, something unusual and fascinating happens in it every day. Stay with us and learn about the most interesting facts from all over the world, about unusual people or things, about the creations of nature or man.

An elementary particle is a particle without an internal structure, that is, not containing other particles [approx. one]. Elementary particles are fundamental objects of quantum field theory. They can be classified by spin: fermions have half-integer spin, while bosons have integer spin. The Standard Model of elementary particle physics is a theory that describes the properties and interactions of elementary particles.

They are classified according to their participation in the strong interaction. Hadrons are defined as strongly interacting compound particles. See also parton (particle). These include the pion, kaon, J/ψ meson, and many other types of mesons. Nuclear reactions and radioactive decay can transform one nuclide into another.

An atom consists of a small, heavy, positively charged nucleus surrounded by a relatively large, light cloud of electrons. There are also short-lived exotic atoms in which the role of the nucleus (positively charged particle) is played by a positron (positronium) or a positive muon (muonium).

Unfortunately, it has not yet been possible to somehow register them, and they exist only in theory. And although experiments have been proposed today to detect black holes, the possibility of their implementation runs into a significant problem. On the contrary, small things can go unnoticed, although this does not make them less important. The Haraguan sphero (Sphaerodactylus ariasae) is the smallest reptile in the world. Its length is only 16-18 mm, and its weight is 0.2 grams.

The smallest things in the world

The smallest single-stranded DNA virus is the porcine circovirus. Per last century science has taken a huge step towards understanding the vastness of the universe and its microscopic building materials.

At one time, the atom was considered the smallest particle. Then scientists discovered the proton, neutron and electron. Now we know that by pushing particles together (as in the Large Hadron Collider, for example), they can be broken down into even more particles, such as quarks, leptons, and even antimatter. The problem is only in determining what is less. So some particles have no mass, some have negative mass. The solution to this question is the same as dividing by zero, that is, impossible.

Do you think there is something in this?, namely: The smallest particle is the Higgs bason.

And although such strings have no physical parameters, the human tendency to justify everything leads us to the conclusion that these are the smallest objects in the Universe. Astronomy and telescopes → Question and answer of an astronomer and astrophysicist → Do you think there is something in this?, namely…

The smallest virus

The fact is that for the synthesis of such particles it is necessary to achieve an energy of 1026 electron volts in the accelerator, which is technically impossible. The mass of such particles is about 0.00001 grams, and the radius is 1/1034 meters. The wavelength of such a black hole is comparable to the size of its gravitational radius.

Where is the earth in the universe? What was in the universe before the big bang? What happened before the formation of the universe? How old is the universe? As it turned out, this was not the only ammunition in the collection of a 13-year-old boy.” The structure of such particles is critically minimal - they have almost no mass, and no atomic charge at all, since the nucleus is too small. There are numbers that are so incredibly, incredibly large that it would take the entire universe to even write them down.

The smallest objects visible to the naked eye

Google, born in 1920 as a way to keep kids interested big numbers. It's a number, according to Milton, that has a 1 first and then as many zeros as you can write before you get tired. If we talk about the largest significant number, there is a reasonable argument that this really means that you need to find the largest number with a value that actually exists in the world.

Thus, the mass of the Sun in tons will be less than in pounds. The largest number with any real world application - or, in this case, real world application - is probably one of the latest estimates of the number of universes in the multiverse. This number is so large that human brain will literally be unable to perceive all these different universes, since the brain is only capable of roughly configurations.

Here is a collection of the smallest things in the world, ranging from tiny toys, miniature animals and people to a hypothetical subatomic particle. Atoms are the smallest particles into which matter can be divided by chemical reactions. The world's smallest teapot was created by renowned ceramist Wu Ruishen and weighs only 1.4 grams. In 2004, Rumaisa Rahman became the smallest newborn child.

To the question What is the smallest particle in the universe? Quark, Neutrino, Higgs Boson or Planck Black Hole? given by the author Caucasian the best answer is Fundamental particles all have size zero (radius is zero). By weight. There are particles with zero mass (photon, gluon, graviton). Of the massive ones, neutrinos have the smallest mass (less than 0.28 eV / s ^ 2, more precisely, they have not yet been measured). Frequency, time - are not characteristics of particles. You can talk about the times of life, but this is a different conversation.

Answer from stitch[guru]
Mosk Zerobubus.

Answer from Mikhail Levin[guru]
in fact, there is practically no concept of "size" in the microworld. Well, for the nucleus one can still talk about some analogue of the size, for example, through the probability of electrons getting into it from the beam, but not for smaller ones.

Answer from to christen[guru]
"size" of an elementary particle - a characteristic of a particle, reflecting the spatial distribution of its mass or electric charge; usually they talk about the so-called. root-mean-square radius of the electric charge distribution (which simultaneously characterizes the mass distribution)
Gauge bosons and leptons, within the accuracy of the performed measurements, do not reveal finite "sizes". This means that their "sizes"< 10^-16 см
In contrast to true elementary particles, hadron "dimensions" are finite. Their characteristic root-mean-square radius is determined by the radius of confinement (or confinement of quarks) and is equal in order of magnitude to 10-13 cm. In this case, of course, it varies from hadron to hadron.

Answer from Kirill Odding[guru]
One of the great physicists said (not Niels Bohr for an hour?) "If you manage to explain quantum mechanics in visual terms, go and get your Nobel Prize."

Answer from SerШkod Sergey Polikanov[guru]
What is the smallest elementary particle in the universe?
Elementary particles creating a gravitational effect.
Even less?
Elementary particles that set in motion those that create a gravitational effect
but they also participate in it.
There are even smaller elementary particles.
Their parameters do not even fit into the calculations, because the structures and their physical parameters are unknown.

Answer from Misha Nikitin[active]
QUARK

Answer from Matipati kipirofinovich[active]
PLANKO'S BLACK HOLE

Answer from Bro qwerty[newbie]
Quarks are the smallest particles in the world. For the universe there is no concept of size, it is limitless. If you invent a machine to reduce a person, then it will be possible to decrease infinitely less, less, less ... Yes, Quark is the smallest "Particle" But there is something smaller than a particle. Space. Not. It has. size.

Answer from Anton Kurochka[active]
Proton Neutron 1*10^-15 1 femtometer
Quark-U Quark-D Electron 1*10^-18 1 attometer
Quark-S 4*10^-19 400 zeptometers
Quark-C 1*10^-19 100 zeptometers
Quark-B 3*10^-20 30 zeptometers
High energy neutrino 1.5*10^-20 15 zeptometers
Preon 1*10^-21 1 zeptometer
Quark-T 1*10^-22 100 yoctometers
MeV Neutrino 2*10^-23 20 yoctometers
Neutrino 1*10^-24 1 yoctometer -(very small size!!!) -
Plonk particle 1.6*10^-35 0.000 000 000 016 yoctometer
Quantum foam Quantum string 1*10^-35 0.000 000 000 01 yoctometer
This is a table of particle sizes. And here you can see that the smallest particle is the Planck particle, but since it is too small, the Neutrino is the smallest particle. But for the universe, only the Planck length is smaller

Doctor of Physical and Mathematical Sciences M. KAGANOV.

According to a long tradition, the journal "Science and Life" talks about the latest achievements modern science, about the latest discoveries in physics, biology and medicine. But in order to understand how important and interesting they are, it is necessary to at least in general terms have an understanding of the basics of science. Modern physics is developing rapidly, and people of the older generation, those who studied at school and at the institute 30-40 years ago, are unfamiliar with many of its provisions: they simply did not exist then. And our young readers have not yet had time to learn about them: popular science literature practically ceased to be published. That is why we asked M. I. Kaganov, a long-time author of the journal, to tell us about atoms and elementary particles and about the laws that govern them, about what matter is. Moisei Isaakovich Kaganov is a theoretical physicist, author and co-author of several hundred papers on the quantum theory of solids, the theory of metals, and magnetism. He was a leading member of the Institute for Physical Problems named after V.I. P. L. Kapitsa and professor at Moscow State University. M. V. Lomonosov, a member of the editorial boards of the journals "Nature" and "Quantum". Author of many popular science articles and books. Now lives in Boston (USA).

Science and life // Illustrations

The Greek philosopher Democritus was the first to use the word "atom". According to his teachings, atoms are indivisible, indestructible and in constant motion. They are infinitely diverse, they have depressions and bulges, with which they interlock, forming all material bodies.

Table 1. The most important characteristics of electrons, protons and neutrons.

deuterium atom.

The English physicist Ernst Rutherford is considered to be the founder of nuclear physics, the doctrine of radioactivity and the theory of the structure of the atom.

Pictured: the surface of a tungsten crystal magnified 10 million times; each bright dot is its individual atom.

Science and life // Illustrations

Science and life // Illustrations

Working on the creation of the theory of radiation, Max Planck in 1900 came to the conclusion that the atoms of a heated substance should emit light in portions, quanta, having the dimension of action (J.s) and energy proportional to the radiation frequency: E = hn.

In 1923, Louis de Broglie transferred Einstein's idea of ​​the dual nature of light - wave-particle duality - to matter: the motion of a particle corresponds to the propagation of an infinite wave.

Diffraction experiments convincingly confirmed de Broglie's theory, which stated that the movement of any particle is accompanied by a wave, the length and speed of which depend on the mass and energy of the particle.

Science and life // Illustrations

An experienced billiard player always knows how the balls will roll after a hit, and easily drives them into the pocket. With atomic particles it is much more difficult. It is impossible to indicate the trajectory of a flying electron: it is not only a particle, but also a wave, infinite in space.

At night, when there are no clouds in the sky, the moon is not visible and the lights do not interfere, the sky is filled with brightly shining stars. It is not necessary to look for familiar constellations or try to find planets close to Earth. Just watch! Try to imagine a huge space that is filled with worlds and stretches for billions of billions of light years. Only because of the distance the worlds seem to be points, and many of them are so far away that they are not distinguishable separately and merge into a nebula. It seems that we are at the center of the universe. Now we know that this is not the case. The rejection of geocentrism is a great merit of science. It took a lot of effort to realize that the little Earth is moving in a random, seemingly unallocated section of boundless (literally!) space.

But life originated on Earth. It developed so successfully that it managed to produce a person capable of comprehending the world around him, searching for and finding the laws that govern nature. The achievements of mankind in the knowledge of the laws of nature are so impressive that one involuntarily feels proud of belonging to this pinch of reason, lost on the periphery of an ordinary Galaxy.

Given the diversity of everything that surrounds us, the existence of general laws is amazing. No less striking is that everything is built from particles of only three types - electrons, protons and neutrons.

In order, using the basic laws of nature, to derive observable and predict new properties of various different substances and objects, complex mathematical theories, which are not easy to understand. But the contours scientific picture The world can be comprehended without resorting to a rigorous theory. Naturally, this requires desire. But not only: even a preliminary acquaintance will have to spend some work. One must try to comprehend new facts, unfamiliar phenomena, which at first glance do not agree with existing experience.

The achievements of science often lead to the idea that "nothing is sacred" for it: what was true yesterday is discarded today. With knowledge, an understanding arises of how reverently science treats every grain of accumulated experience, with what caution it moves forward, especially in those cases when it is necessary to abandon rooted ideas.

The purpose of this story is to introduce the fundamental features of the structure of inorganic substances. Despite their endless variety, their structure is relatively simple. Especially when compared with any, even the simplest living organism. But there is one thing in common: all living organisms, like inorganic substances are made up of electrons, protons and neutrons.

It is impossible to embrace the immensity: in order to, at least in general terms, acquaint with the structure of living organisms, a special story is needed.

The variety of things, objects - everything that we use, that surrounds us, is boundless. Not only in their purpose and structure, but also in the materials used to create them - substances, as they say, when there is no need to emphasize their function.

Substances, materials look solid, and touch confirms what the eyes see. It would seem that there are no exceptions. Flowing water and solid metal, so different from each other, are similar in one thing: both metal and water are solid. True, salt or sugar can be dissolved in water. They find their place in the water. Yes and in solid, for example, a nail can be driven into a wooden board. With considerable effort, it is possible to achieve that the place that was occupied by a tree will be occupied by an iron nail.

We know very well that a small piece can be broken off from a solid body, practically any material can be crushed. Sometimes it is difficult, sometimes it happens spontaneously, without our participation. Imagine yourself on the beach, on the sand. We understand that a grain of sand is far from the smallest particle of the substance that makes up sand. If you try, you can reduce the grains of sand, for example, by passing through the rollers - through two cylinders of very hard metal. Once between the rollers, the grain of sand is crushed into smaller pieces. In fact, this is how flour is made from grain in mills.

Now that the atom has firmly entered our worldview, it is very difficult to imagine that people did not know whether the crushing process is limited or whether a substance can be crushed to infinity.

It is not known when people first asked themselves this question. It was first recorded in the writings of ancient Greek philosophers. Some of them believed that, no matter how fractional a substance is, it allows division into even smaller parts - there is no limit. Others have suggested that there are tiny indivisible particles that make up everything. To emphasize that these particles are the limit of crushing, they called them atoms (in ancient Greek the word "atom" means indivisible).

It is necessary to name those who first put forward the idea of ​​the existence of atoms. These are Democritus (born around 460 or 470 BC, died at a ripe old age) and Epicurus (341-270 BC). So, atomic science is almost 2500 years old. The idea of ​​atoms was by no means immediately accepted by everyone. Even 150 years ago, there were few people confident in the existence of atoms, even among scientists.

This is because atoms are very small. They cannot be seen not only with the naked eye, but also, for example, with a microscope magnifying 1000 times. Let's think: what is the size of the smallest particles that can be seen? At different people different vision, but, probably, everyone will agree that it is impossible to see a particle smaller than 0.1 millimeter. Therefore, if you use a microscope, you can, albeit with difficulty, see particles about 0.0001 millimeters in size, or 10 -7 meters. Comparing the sizes of atoms and interatomic distances (10 -10 meters) with the length, accepted by us as the limit of the ability to see, we will understand why any substance seems to us to be solid.

2500 years is a long time. No matter what happens in the world, there have always been people who tried to answer the question of how the world around them works. At some times, the problems of the organization of the world worried more, at some times - less. The birth of science in its modern sense occurred relatively recently. Scientists have learned to experiment - to ask nature questions and understand its answers, to create theories that describe the results of experiments. The theories required rigorous mathematical methods to draw valid conclusions. science passed a long way. On this path, which for physics began about 400 years ago with the work of Galileo Galilei (1564-1642), an infinite amount of information was obtained about the structure of matter and the properties of bodies. different nature discovered and understood an infinite number of diverse phenomena.

Mankind has learned not only to passively understand nature, but also to use it for its own purposes.

We will not consider the history of the development of atomic concepts over 2500 years and the history of physics over the past 400 years. Our task is to tell as briefly and clearly as possible about what and how everything is built from - the objects around us, bodies and ourselves.

As already mentioned, all matter is made up of electrons, protons and neutrons. I know about it from school years, but it never ceases to amaze me that everything is built from particles of only three types! But the world is so diverse! In addition, the means that nature uses to carry out construction are also quite uniform.

A consistent description of how substances of different types are built is a complex science. She uses serious mathematics. It must be emphasized that there is no other, simple theory. But physical principles, underlying the understanding of the structure and properties of substances, although they are non-trivial and difficult to imagine, can still be comprehended. With our story, we will try to help everyone who is interested in the structure of the world in which we live.

It would seem that the most natural way to understand how a certain complex device(toy or mechanism) - disassemble, decompose into its component parts. You just have to be very careful, remembering that it will be much more difficult to fold. "To break - not to build" - says folk wisdom. And one more thing: what the device consists of, we, perhaps, will understand, but how it works is unlikely. It is sometimes necessary to unscrew one screw, and that's it - the device has stopped working. It is necessary not so much to disassemble, but to understand.

Since we are not talking about the actual decomposition of all the objects, things, organisms around us, but about the imaginary, that is, about mental, and not about real experience, then you don’t have to worry: you don’t have to collect. Also, let's not skimp on the effort. We will not think about whether it is difficult or easy to decompose the device into its component parts. Wait a second. And how do we know that we have reached the limit? Maybe with more effort we can go further? We admit to ourselves: we do not know if we have reached the limit. We have to use the generally accepted opinion, realizing that this is not a very reliable argument. But if you remember that this is only a generally accepted opinion, and not the ultimate truth, then the danger is small.

It is now generally accepted that elementary particles serve as the details from which everything is built. And while not all. Having looked in the appropriate reference book, we will be convinced: there are more than three hundred elementary particles. The abundance of elementary particles made us think about the possibility of the existence of subelementary particles - particles that make up the elementary particles themselves. This is how the idea of ​​quarks was born. They have that amazing property, which apparently do not exist in the free state. There are quite a lot of quarks - six, and each has its own antiparticle. Perhaps the journey into the depths of matter is not over.

For our story, the abundance of elementary particles and the existence of subelementary particles is not essential. Electrons, protons and neutrons are directly involved in the construction of substances - everything is built only from them.

Before discussing the properties of real particles, let's think about how we would like to see the details from which everything is built. When it comes to what we would like to see, of course, we must take into account the diversity of views. Let's pick out a few features that seem mandatory.

First, elementary particles must have the ability to unite into various structures.

Secondly, I would like to think that elementary particles are indestructible. Knowing what a long history the world has, it is difficult to imagine that the particles of which it is composed are mortal.

Thirdly, I would like the details themselves not to be too much. Looking at the building blocks, we see how different buildings can be created from the same elements.

Getting acquainted with electrons, protons and neutrons, we will see that their properties do not contradict our wishes, and the desire for simplicity undoubtedly corresponds to the fact that only three types of elementary particles take part in the structure of all substances.

Let us present the most important characteristics of electrons, protons and neutrons. They are collected in table 1.

The magnitude of the charge is given in coulombs, the mass is given in kilograms (SI units); the words "spin" and "statistics" will be explained below.

Let us pay attention to the difference in the mass of particles: protons and neutrons are almost 2000 times heavier than electrons. Consequently, the mass of any body is almost entirely determined by the mass of protons and neutrons.

The neutron, as its name implies, is neutral - its charge is zero. A proton and an electron have the same magnitude but opposite in sign charges. The electron is negatively charged and the proton is positively charged.

Among the characteristics of particles, there is no seemingly important characteristic - their size. Describing the structure of atoms and molecules, electrons, protons and neutrons can be considered material points. The size of the proton and neutron will have to be remembered only when describing atomic nuclei. Even compared to the size of atoms, protons and neutrons are monstrously small (on the order of 10 -16 meters).

Essentially, this short section is reduced to the presentation of electrons, protons, and neutrons as the building blocks of all bodies in nature. We could simply limit ourselves to Table 1, but we have to understand how from electrons, protons and neutrons construction is carried out, which causes the particles to combine into more complex structures and what are these structures.

There are many atoms. It turned out to be necessary and possible to arrange them in a special way. Ordering makes it possible to emphasize the difference and similarity of atoms. The reasonable arrangement of atoms is the merit of D. I. Mendeleev (1834-1907), who formulated the periodic law that bears his name. If we temporarily ignore the existence of periods, then the principle of the arrangement of elements is extremely simple: they are arranged sequentially according to the weight of atoms. The lightest is the hydrogen atom. The last natural (not artificially created) atom is the uranium atom, which is more than 200 times heavier than it.

Understanding the structure of atoms explained the presence of periodicity in the properties of elements.

At the very beginning of the 20th century, E. Rutherford (1871-1937) convincingly showed that almost the entire mass of an atom is concentrated in its nucleus - a small (even compared to an atom) region of space: the radius of the nucleus is approximately 100 thousand times smaller size atom. When Rutherford made his experiments, the neutron had not yet been discovered. With the discovery of the neutron, it was understood that nuclei consist of protons and neutrons, and it is natural to think of an atom as a nucleus surrounded by electrons, the number of which is equal to the number of protons in the nucleus - after all, in general, the atom is neutral. Like protons and neutrons construction material nuclei are collectively known as nucleons (from Latin nucleus- nucleus). This is the name we will use.

The number of nucleons in a nucleus is usually denoted by the letter BUT. It's clear that A = N + Z, where N is the number of neutrons in the nucleus, and Z- the number of protons, equal to the number of electrons in the atom. Number BUT is called atomic mass, and Z- atomic number. Atoms with the same atomic number are called isotopes: in the periodic table they are in the same cell (in Greek isos - equal , topos - place). The fact is that Chemical properties isotopes are almost identical. If you carefully consider the periodic table, you can see that, strictly speaking, the arrangement of the elements does not correspond to atomic mass, but the atomic number. If there are about 100 elements, then there are more than 2000 isotopes. True, many of them are unstable, that is, radioactive (from the Latin radio- radiate activus- active), they decay, emitting various radiations.

Rutherford's experiments not only led to the discovery of atomic nuclei, but also showed that the same electrostatic forces act in the atom, which repel like-charged bodies from each other and attract oppositely charged bodies (for example, electroscope balls) to each other.

The atom is stable. Therefore, the electrons in an atom move around the nucleus: the centrifugal force compensates for the force of attraction. Understanding this led to the creation of a planetary model of the atom, in which the nucleus is the Sun, and the electrons are the planets (from the point of view of classical physics, the planetary model is inconsistent, but more on that below).

There are a number of ways to estimate the size of an atom. Different estimates lead to similar results: the sizes of atoms, of course, are different, but approximately equal to several tenths of a nanometer (1 nm = 10 -9 m).

Consider first the system of electrons in an atom.

AT solar system planets are attracted to the sun by gravity. An electrostatic force acts in an atom. It is often called Coulomb after Charles Augustin Coulomb (1736-1806), who established that the force of interaction between two charges is inversely proportional to the square of the distance between them. The fact that two charges Q 1 and Q 2 are attracted or repelled with a force equal to F C = Q 1 Q 2 /r 2 , where r- the distance between the charges, is called "Coulomb's Law". Index " FROM" assigned to force F by the first letter of Coulomb's last name (in French Coulomb). Among the most diverse statements, there are few that are just as rightly called a law as Coulomb's law: after all, the scope of its applicability is practically unlimited. Charged bodies, whatever their size, as well as atomic and even subatomic charged particles - they all attract or repel in accordance with Coulomb's law.

Humans are introduced to gravity at an early age. As he falls, he learns to respect the force of gravity towards the Earth. Acquaintance with accelerated motion usually begins with the study of the free fall of bodies - the movement of a body under the influence of gravity.

Between two bodies of mass M 1 and M 2 force is acting F N=- GM 1 M 2 /r 2 . Here r- distance between bodies, G- gravitational constant equal to 6.67259.10 -11 m 3 kg -1 s -2 , the index "N" is given in honor of Newton (1643 - 1727). This expression is called the law gravity emphasizing its general character. Strength F N determines the movement of galaxies, celestial bodies and the fall of objects to the Earth. The law of universal gravitation is valid for any distance between bodies. Changes in the picture of gravity, which made general theory Einstein's relativity (1879-1955), we will not mention.

Both the Coulomb electrostatic force and the Newtonian force of universal gravitation are the same (as 1/ r 2) decrease with increasing distance between the bodies. This allows you to compare the action of both forces at any distance between the bodies. If the force of the Coulomb repulsion of two protons is compared in magnitude with the force of their gravitational attraction, then it turns out that F N / F C= 10 -36 (Q 1 =Q 2 = e p; M 1 = =M 2 =m p). Therefore, gravity does not play any significant role in the structure of the atom: it is too small compared to the electrostatic force.

It is not difficult to detect electric charges and measure the interaction between them. If the electrical force is so great, then why is it not important when, say, they fall, jump, throw a ball? Because in most cases we are dealing with neutral (uncharged) bodies. There are always a lot of charged particles (electrons, ions of different signs) in space. Under the influence of a huge (on an atomic scale) attractive electric force created by a charged body, charged particles rush to its source, stick to the body and neutralize its charge.

It is very difficult to talk about atomic and even smaller, subatomic, particles, mainly because their properties have no analogues in our daily life. One might think that the particles that make up such small atoms can be conveniently represented in the form material points. But everything turned out to be much more complicated.

A particle and a wave... It would seem that even comparing is meaningless, they are so different.

Probably, when you think about a wave, you first of all imagine a wave of the sea surface. Waves ashore come from high seas, wavelengths - the distances between two successive crests - can be different. It is easy to observe waves having a length of the order of several meters. During agitation, obviously, the mass of water fluctuates. The wave covers a considerable space.

The wave is periodic in time and space. Wavelength ( λ ) is a measure of spatial periodicity. The periodicity of wave motion in time is visible in the frequency of arrival of wave crests to the shore, and it can be detected, for example, by the up and down oscillation of the float. Let us denote the period of wave movement - the time during which one wave passes - by the letter T. The reciprocal of the period is called the frequency ν = 1/T. The simplest waves (harmonic) have a certain frequency that does not change with time. Any complex wave motion can be represented as a set of simple waves (see "Science and Life" No. 11, 2001). Strictly speaking, a simple wave occupies an infinite space and exists indefinitely. A particle, as we imagine it, and a wave are completely different.

Since the time of Newton, there has been a debate about the nature of light. What is light - a collection of particles (corpuscles, from the Latin corpusculum- body) or waves? Theories have long competed. The wave theory won: the corpuscular theory could not explain the experimental facts (interference and diffraction of light). The wave theory easily coped with the rectilinear propagation of a light beam. An important role was played by the fact that the wavelength of light waves, according to everyday concepts, is very small: the wavelength range visible light from 380 to 760 nanometers. Shorter electromagnetic waves- ultraviolet, x-ray and gamma rays, and longer ones - infrared, millimeter, centimeter and all other radio waves.

By the end of the 19th century, the victory of the wave theory of light over the corpuscular one seemed final and irrevocable. However, the 20th century made serious adjustments. It seemed to be light or waves or particles. It turned out - both waves and particles. For particles of light, for its quanta, as they say, a special word was invented - "photon". The word "quantum" comes from the Latin word quantum- how much, and "photon" - from Greek word photos- light. Words denoting the name of the particles, in most cases, have the ending he. Surprisingly, in some experiments light behaves like waves, while in others it behaves like a stream of particles. Gradually, it was possible to build a theory that predicts how, in what experiment, light will behave. At present, this theory is accepted by everyone, the different behavior of light is no longer surprising.

The first steps are always especially difficult. I had to go against the established opinion in science, to express statements that seemed to be heresy. Real scientists sincerely believe in the theory they use to describe the observed phenomena. It is very difficult to abandon the accepted theory. The first steps were taken by Max Planck (1858-1947) and Albert Einstein (1879-1955).

According to Planck-Einstein, it is in separate portions, quanta, that light is emitted and absorbed by matter. The energy carried by a photon is proportional to its frequency: E = h v. Proportionality factor h The Planck constant was named after the German physicist who introduced it to the theory of radiation in 1900. And already in the first third of the 20th century it became clear that Planck's constant is one of the most important world constants. Naturally, it was carefully measured: h= 6.6260755.10 -34 J.s.

A quantum of light - is it a lot or a little? The frequency of visible light is about 10 14 s -1 . Recall that the frequency and wavelength of light are related by the relation ν = c/λ, where With= 299792458.10 10 m/s (exactly) - the speed of light in vacuum. quantum energy hν, as it is easy to see, is about 10 -18 J. Due to this energy, a mass of 10 -13 grams can be raised to a height of 1 centimeter. On a human scale, monstrously small. But this is the mass of 10 14 electrons. In the microcosm, the scale is completely different! Of course, a person cannot feel a mass of 10 -13 grams, but the human eye is so sensitive that it can see individual light quanta - this was confirmed by a series of subtle experiments. AT normal conditions a person does not distinguish the "grain" of light, perceiving it as a continuous stream.

Knowing that light has both a corpuscular and a wave nature, it is easier to imagine that "real" particles also have wave properties. For the first time such a heretical thought was expressed by Louis de Broglie (1892-1987). He did not try to find out what the nature of the wave whose characteristics he predicted was. According to his theory, a particle of mass m, flying at a speed v, corresponds to a wave with wavelength l = hmv and frequency ν = E/h, where E = mv 2 /2 - particle energy.

Further development of atomic physics led to an understanding of the nature of waves that describe the motion of atomic and subatomic particles. A science arose that was called "quantum mechanics" (in the early years it was often called wave mechanics).

Quantum mechanics is applicable to the motion of microscopic particles. When considering the motion of ordinary bodies (for example, any details of mechanisms), there is no point in taking into account quantum corrections (corrections due to the wave properties of matter).

One of the manifestations of the wave motion of particles is their absence of a trajectory. For the existence of a trajectory, it is necessary that at each moment of time the particle has a certain coordinate and a certain speed. But this is precisely what is forbidden by quantum mechanics: a particle cannot have at the same time a certain value of the coordinate X, and a certain speed value v. Their uncertainties Dx and dv are related by the uncertainty relation discovered by Werner Heisenberg (1901-1974): D X D v ~ h/m, where m is the mass of the particle, and h- Planck's constant. Planck's constant is often referred to as the universal "action" quantum. Without specifying the term action, pay attention to the epithet universal. He emphasizes that the uncertainty relation is always true. Knowing the conditions of motion and the mass of the particle, it is possible to estimate when it is necessary to take into account the quantum laws of motion (in other words, when the wave properties of particles and their consequence, the uncertainty relations, cannot be neglected), and when it is quite possible to use classical laws movement. We emphasize that if it is possible, then it is necessary, since classical mechanics is much simpler than quantum mechanics.

Note that Planck's constant is divided by the mass (they are included in combinations h/m). The larger the mass, the smaller the role of quantum laws.

In order to feel when it is certainly possible to neglect quantum properties, we will try to estimate the magnitudes of the uncertainties D X and D v. If D X and D v are negligible compared to their average (classical) values, the formulas of classical mechanics perfectly describe the motion, if not small, it is necessary to use quantum mechanics. It makes no sense to take into account quantum uncertainty even when other causes (within the framework of classical mechanics) lead to greater uncertainty than the Heisenberg relation.

Let's consider one example. Keeping in mind that we want to show the possibility of using classical mechanics, consider a "particle" whose mass is 1 gram and the size is 0.1 millimeters. On a human scale, this is a grain, a light, small particle. But it is 10 24 times heavier than a proton and a million times larger than an atom!

Let "our" grain move in a vessel filled with hydrogen. If the grain flies fast enough, it seems to us that it is moving in a straight line with a certain speed. This impression is erroneous: due to the impacts of hydrogen molecules on a grain, its speed changes slightly with each impact. Let's estimate how much.

Let the temperature of hydrogen be 300 K (we always measure the temperature on an absolute scale, on the Kelvin scale; 300 K = 27 o C). Multiplying the temperature in kelvins by the Boltzmann constant k B , = 1,381.10 -16 J/K, we will express it in energy units. The change in grain speed can be calculated using the law of conservation of momentum. With each collision of a grain with a hydrogen molecule, its speed changes by approximately 10 -18 cm / s. The change is completely random and in a random direction. Therefore, it is natural to consider the value of 10 -18 cm/s as a measure of the classical uncertainty of the grain velocity (D v) cl for this case. So (D v) cl \u003d 10 -18 cm / s. It is apparently very difficult to determine the location of a grain with an accuracy greater than 0.1 of its size. Let's accept (D X) cl \u003d 10 -3 cm. Finally, (D X) cl (D v) cl \u003d 10 -3.10 -18 \u003d 10 -21. It seems to be a very small amount. In any case, the uncertainties of velocity and position are so small that one can consider the average motion of a grain. But compared to the quantum uncertainty dictated by the Heisenberg relation (D X D v= 10 -27), the classical inhomogeneity is enormous - in this case it exceeds it by a million times.

Conclusion: when considering the movement of a grain, it is not necessary to take into account its wave properties, that is, the existence of a quantum uncertainty of coordinates and speed. When it comes to the movement of atomic and subatomic particles, the situation changes dramatically.

The smallest particle of sugar is a sugar molecule. Their structure is such that sugar tastes sweet. And the structure of water molecules is such that pure water does not seem sweet.

4. Molecules are made up of atoms

And the hydrogen molecule is the smallest particle of hydrogen substance. The smallest particles of atoms are elementary particles: electrons, protons and neutrons.

All known matter on Earth and beyond is made up of chemical elements. Total naturally occurring elements - 94. When normal temperature 2 of them are in a liquid state, 11 are in a gaseous state, and 81 (including 72 metals) are in a solid state. The so-called "fourth state of matter" is plasma, a state in which negatively charged electrons and positively charged ions are in constant motion. The grinding limit is solid helium, which, as it was established back in 1964, should be a monoatomic powder. TCDD, or 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin, discovered in 1872, is lethal at a concentration of 3.1 10–9 mol/kg, which is 150 thousand times stronger than a similar dose of cyanide.

Matter is made up of individual particles. Molecules of different substances are different. 2 oxygen atoms. These are polymer molecules.

Just about the complex: the mystery of the smallest particle in the universe, or how to catch a neutrino

The Standard Model of elementary particle physics is a theory that describes the properties and interactions of elementary particles. All quarks also have an electric charge that is a multiple of 1/3 of the elementary charge. Their antiparticles are antileptons (the antiparticle of the electron is called the positron for historical reasons). Hyperons, such as Λ-, Σ-, Ξ- and Ω-particles, contain one or more s-quarks, decay rapidly and are heavier than nucleons. Molecules are the smallest particles of a substance that still retain its chemical properties.

What financial or other benefit can be derived from this particle? Physicists shrug. And they really don't know it. Once the study of semiconductor diodes belonged to purely fundamental physics, without any practical application.

The Higgs boson is a particle so important to science that it has been nicknamed the "God particle". It is she, as scientists believe, that gives mass to all other particles. These particles begin to break down as soon as they are born. Creating a particle requires huge amount energy, such as that produced by the Big Bang. As for the larger size and weight of the superpartners, the scientists believe the symmetry has been broken in a hidden sector of the universe that cannot be seen or found. For example, light is made up of zero-mass particles called photons that carry electromagnetic force. Similarly, gravitons are the theoretical particles that carry the force of gravity. Scientists are still trying to find gravitons, but it is very difficult to do this, since these particles interact very weakly with matter.