Prologue. knowledge of existence or what is the smallest particle in the universe? Just about the complex: the mystery of the smallest particle in the Universe, or how to catch a neutrino

The answer to the ongoing question: which one evolved with humanity.

People once thought that grains of sand were the building blocks of what we see around us. The atom was then discovered and thought to be indivisible until it was split to reveal the protons, neutrons and electrons within. They also did not turn out to be the smallest particles in the Universe, since scientists discovered that protons and neutrons consist of three quarks each.

So far, scientists have not been able to see any evidence that there is anything inside the quarks and that the most fundamental layer of matter or the smallest particle in the Universe has been reached.

And even if quarks and electrons are indivisible, scientists don't know if they are the smallest bits of matter in existence or if the Universe contains objects that are even smaller.

The smallest particles in the Universe

They come in different flavors and sizes, some have amazing connection, others essentially evaporate each other, many of them have fantastic names: quarks consisting of baryons and mesons, neutrons and protons, nucleons, hyperons, mesons, baryons, nucleons, photons, etc.

The Higgs boson is a particle so important to science that it is called the “God particle.” It is believed that it determines the mass of all others. The element was first theorized in 1964, when scientists wondered why some particles were more massive than others.

The Higgs boson is associated with the so-called Higgs field, which is believed to fill the Universe. Two elements (the Higgs field quantum and the Higgs boson) are responsible for giving the others mass. Named after the Scottish scientist Peter Higgs. With the help of March 14, 2013, the confirmation of the existence of the Higgs Boson was officially announced.

Many scientists argue that the Higgs mechanism has solved the missing piece of the puzzle to complete the existing "standard model" of physics, which describes known particles.

The Higgs boson fundamentally determined the mass of everything that exists in the Universe.

Quarks (meaning quarks) are the building blocks of protons and neutrons. They are never alone, existing only in groups. Apparently, the force that binds quarks together increases with distance, so the further you go, the more difficult it will be to separate them. Therefore, free quarks never exist in nature.

Quarks are fundamental particles are structureless, pointy approximately 10−16 cm in size .

For example, protons and neutrons are made up of three quarks, with protons containing two identical quarks, while neutrons have two different ones.

Supersymmetry

It is known that the fundamental “building blocks” of matter, fermions, are quarks and leptons, and the guardians of the force, bosons, are photons and gluons. The theory of supersymmetry says that fermions and bosons can transform into each other.

The predicted theory states that for every particle we know, there is a related one that we have not yet discovered. For example, for an electron it is a selectron, a quark is a squark, a photon is a photino, and a higgs is a higgsino.

Why don't we observe this supersymmetry in the Universe now? Scientists believe they are much heavier than their regular cousins and the heavier they are, the shorter their lifespan. In fact, they begin to collapse as soon as they arise. Creating supersymmetry requires very large quantity energy that only existed shortly after big bang and could possibly be created in large accelerators like the Large Hadron Collider.

As for why the symmetry arose, physicists theorize that the symmetry may have been broken in some hidden sector of the Universe that we cannot see or touch, but can only feel gravitationally.

Neutrino

Neutrinos are light subatomic particles that whistle everywhere at close to the speed of light. In fact, trillions of neutrinos are flowing through your body at any moment, although they rarely interact with normal matter.

Some come from the sun, while others from cosmic rays interacting with Earth's atmosphere and astronomical sources such as exploding stars in the Milky Way and other distant galaxies.

Antimatter

All normal particles are thought to have antimatter with the same mass but opposite charge. When matter meets, they destroy each other. For example, the antimatter particle of a proton is an antiproton, while the antimatter partner of an electron is called a positron. Antimatter refers to those that people have been able to identify.

Gravitons

In the field of quantum mechanics, all fundamental forces are transmitted by particles. For example, light is made up of massless particles called photons, which carry an electromagnetic force. Likewise, the graviton is a theoretical particle that carries the force of gravity. Scientists have yet to detect gravitons, which are difficult to find because they interact so weakly with matter.

Threads of Energy

In experiments, tiny particles such as quarks and electrons act as single points of matter with no spatial distribution. But point objects complicate the laws of physics. Since it is impossible to get infinitely close to a point, since active forces, can become infinitely large.

An idea called superstring theory could solve this problem. The theory states that all particles, instead of being pointlike, are actually small threads of energy. That is, all objects in our world consist of vibrating threads and membranes of energy.
Nothing can be infinitely close to the thread, because one part will always be a little closer than the other. This loophole appears to solve some of the problems with infinity, making the idea attractive to physicists. However, scientists still have no experimental evidence that string theory is correct.

Another way of solving the point problem is to say that space itself is not continuous and smooth, but is actually made up of discrete pixels or grains, sometimes called space-time structure. In this case, the two particles will not be able to approach each other indefinitely, because they must always be separated by a minimum grain size of space.

Black hole point

Another contender for the title of smallest particle in the Universe is the singularity (a single point) at the center of a black hole. Black holes form when matter condenses into a space small enough that gravity grabs, causing matter to be pulled inward, eventually condensing into a single point of infinite density. At least according to the current laws of physics.

But most experts don't think black holes are truly infinitely dense. They believe that this infinity is the result of an internal conflict between two current theories - general relativity and quantum mechanics. They suggest that when the theory of quantum gravity can be formulated, the true nature of black holes will be revealed.

Planck length

Threads of energy and even the smallest particle in the Universe can be the size of a “planck length.”

The length of the bar is 1.6 x 10 -35 meters (the number 16 is preceded by 34 zeros and a decimal point) - an incomprehensibly small scale that is associated with various aspects of physics.

The Planck length is a “natural unit” of length measurement that was proposed by the German physicist Max Planck.

Planck's length is too short for any instrument to measure, but beyond that, it is believed to represent the theoretical limit of the shortest measurable length. According to the uncertainty principle, no instrument should ever be able to measure anything less, because in this range the universe is probabilistic and uncertain.

This scale is also considered the dividing line between general relativity and quantum mechanics.

The Planck length corresponds to the distance where the gravitational field is so strong that it can begin to make black holes from the energy of the field.

Obviously now, the smallest particle in the Universe is approximately the size of a plank: 1.6 x 10 −35 meters

From school it was known that the smallest particle in the Universe, the electron, has a negative charge and a very small mass, equal to 9.109 x 10 - 31 kg, and the classical radius of the electron is 2.82 x 10 -15 m.

However, physicists are already operating with the smallest particles in the Universe, the Planck size which is approximately 1.6 x 10 −35 meters.

Neutrinos, an incredibly tiny particle in the universe, have fascinated scientists for nearly a century. More Nobel Prizes have been awarded for research on neutrinos than for work on any other particle, and huge facilities are being built to study it with the budget of small states. Alexander Nozik, a senior researcher at the Institute of Nuclear Research of the Russian Academy of Sciences, a teacher at MIPT and a 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 in the first place.

The Mystery of Stolen Energy

The history of neutrino research can be read like a fascinating detective story. This particle has tested the deductive abilities of scientists more than once: not every riddle could be solved immediately, and some have not yet been solved. Let's start with the history of the discovery. Radioactive decays various kinds began to be studied at the end of the 19th century, and it is not surprising that in the 1920s scientists had in their arsenal not only instruments for recording the decay itself, but also for measuring the energy of escaping particles, albeit not particularly accurate by today’s standards. As the accuracy of the instruments increased, so did the joy of scientists 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. This decay is called two-particle, since it produces two particles - 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 electron energy not only was not fixed, but was also spread out into a continuous spectrum down to zero, which baffled scientists. This can only happen if someone steals 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 possibility of attributing such an anomaly to an equipment error disappeared. Thus a mystery arose. In search of its solution, scientists have expressed various, even completely absurd by today's standards, assumptions. Niels Bohr himself, for example, made a serious statement that conservation laws do not apply in the world of elementary particles. Wolfgang Pauli saved the day in 1930. He was unable to attend the physics conference in Tübingen and, unable to participate remotely, sent a letter which he asked to be read. Here are excerpts from it:

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

At the end of the letter there were the following lines:

“If you don't take risks, you won't win. The gravity of the situation when considering the continuous B-spectrum becomes especially clear after the words of Prof. Debye, who said to me with regret: “Oh, it’s better not to think of all this ... as new taxes.” Therefore, it is necessary to seriously discuss each path to salvation. So, dear radioactive people, put this to the test and judge.”

Later, Pauli himself expressed fears that, although his idea saved the physics of the microworld, the new particle would never be discovered experimentally. They say that he even argued with his colleagues that if the particle existed, it would not be possible to detect it during their lifetime. Over the next few years, Enrico Fermi developed a theory of beta decay involving a particle he called the neutrino, which agreed brilliantly with experiment. After this, no one had any doubt that the hypothetical particle actually existed. In 1956, two years before Pauli's death, neutrinos were experimentally discovered in reverse beta decay by the team of Frederick Reines and Clyde Cowan (Reines received a Nobel Prize).

The Case of the Missing Solar Neutrinos

As soon as it became clear that neutrinos, although complex, could still be detected, scientists began trying to catch neutrinos extraterrestrial origin. Their most obvious source is the Sun. Nuclear reactions constantly occur in it, and it can be calculated that every square centimeter earth's surface About 90 billion solar neutrinos pass through every second.

At that moment the most effective method catching solar neutrinos was a radiochemical method. Its essence is this: a solar neutrino arrives on Earth, interacts with the nucleus; the result is, say, a 37Ar nucleus and an electron (this is exactly the reaction that was used in the experiment of Raymond Davis, for which he was later given the Nobel Prize). After this, by counting the number of argon atoms, we can say how many neutrinos interacted in the detector volume during the exposure. In practice, of course, everything is not so simple. You must understand that you need to count single argon atoms in a target weighing hundreds of tons. The mass ratio 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 was three times less than predicted).

Of course, suspicion first fell on the Sun itself. After all, we can judge his inner life only by indirect signs. It is not known how neutrinos are created 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 toward the idea that it was not the Sun, but the cunning nature of the neutrinos themselves.

A small historical digression: in the period between the experimental discovery of neutrinos and experiments on studying solar neutrinos, several more interesting discoveries occurred. First, antineutrinos were discovered and it was proven that neutrinos and antineutrinos participate in interactions differently. 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 in neutrinos, it also indirectly indicates that our Universe is, in principle, not symmetrical. Secondly, it was discovered 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 50s of the 20th century, it was suggested that the leptonic flavor (a type of neutrino) does not have to 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 that are sensitive only to electron neutrinos. This hypothesis was brilliantly confirmed by measurements of the solar neutrino flux in the SNO and Kamiokande large water target scintillation experiments (for which another Nobel Prize was recently awarded). In these experiments, it is no longer 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 the 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.

Assault on the Standard Model

The discovery of neutrino oscillations, having solved one problem, created several new ones. The point is that since the time of Pauli, neutrinos have been considered massless particles like photons, and this suited everyone. Attempts to measure the mass of neutrinos continued, but without much enthusiasm. Oscillations changed everything, since mass, however small, is required for their existence. 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 neutrinos and right-handedness of antineutrinos is well explained only, again, for massless particles. If there is mass, left-handed neutrinos should, with some probability, transform into right-handed ones, that is, into antiparticles, violating the seemingly immutable 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 commonly called sterile neutrinos.

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

Of course, the experimental search for the neutrino mass immediately resumed sharply. But the question immediately arose: how to measure the mass of something that cannot be caught? There is only one answer: do not catch neutrinos at all. Today, two directions are most actively being developed - the 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 electron and neutrino radiation. It is not possible to catch a neutrino, but it is possible to catch and measure an electron with very high accuracy. The electron spectrum also carries information about the neutrino mass. Such an experiment is one of the most difficult in particle physics, but its undoubted advantage is that it is based on basic principles conservation of energy and momentum and its result depends on little. Currently, the best limit on 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 was only limited by the upper frame.

With double beta decay, things are more complicated. If we assume that a neutrino turns into an antineutrino during a spin flip (this model is called 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 are reduced. 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 problem of massive neutrinos has not yet been solved. The Higgs theory cannot explain such small masses. It requires significant complication or the use of some more cunning laws according to which neutrinos interact with the rest of the world. Physicists involved in neutrino research are often asked the question: “How can neutrino research help the average person? What financial or other benefit can be derived from this particle? Physicists shrug their shoulders. And they really don't know it. Once upon a time, the study of semiconductor diodes was 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 widely used in industry now, so every penny invested in this area pays off fairly quickly. Currently, several experiments are being carried out around 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. It is unknown in which of them it will be possible to open a new page in physics, but it will definitely be opened.

The world and science never stand still. Just recently, physics textbooks confidently wrote that the electron is the smallest particle. Then mesons became the smallest particles, then bosons. And now science has discovered a new the most smallest particle in the Universe- Planck black hole. True, it is still open only in theory. This particle is classified as a black hole because its gravitational radius is greater than or equal to the wavelength. Of all the existing black holes, Planck's is the smallest.

The lifetime of these particles is too short to make their practical detection possible. At least on at the moment. And they are formed, as is commonly believed, as a result nuclear reactions. But it is not only the lifetime of Planck black holes that prevents their detection. Now, unfortunately, this is impossible from a technical point of view. In order to synthesize Planck black holes, an energy accelerator of more than a thousand electron volts is needed.

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Despite this hypothetical existence of this smallest particle in the Universe, its practical discovery in the future is quite possible. After all, not so long ago the legendary Higgs boson could not be detected either. It was for its discovery that an installation was created that only the laziest inhabitant on Earth has not heard of - the Large Hadron Collider. The scientists' confidence in the success of these studies helped achieve a sensational result. The Higgs boson is currently the smallest particle whose existence has been practically proven. Its discovery is very important for science; it allowed all particles to acquire mass. And if particles had no mass, the universe could not exist. Not a single substance could be formed in it.

Despite the practically proven existence of this particle, the Higgs boson, practical applications for it have not yet been invented. For now this is just theoretical knowledge. But in the future everything is possible. Not all discoveries in the field of physics immediately had practical application. Nobody knows what will happen in a hundred years. After all, as mentioned earlier, the world and science never stand still.

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 the field of physics, biology and medicine. But to understand how important and interesting they are, it is necessary to at least general outline 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 college 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 has practically ceased to be published. Therefore, we asked the long-time author of the magazine M.I. Kaganov to talk about atoms and elementary particles and the laws that govern them, about what matter is. Moses Isaakovich Kaganov is a theoretical physicist, author and co-author of several hundred works on the quantum theory of solids, the theory of metals and magnetism. He was a leading employee of the Institute of Physical Problems named after. P. L. Kapitsa and professor at Moscow State University. M. V. Lomonosov, 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 teaching, atoms are indivisible, indestructible and are in constant movement. They are infinitely varied, have depressions and convexities 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 rightfully considered the founder nuclear physics, the doctrine of radioactivity and the theory of atomic structure.

In the photo: the surface of a tungsten crystal, magnified 10 million times; each bright point is its individual atom.

Science and life // Illustrations

Working on the creation of the theory of radiation, Max Planck in 1900 came to the conclusion that atoms of heated matter should emit light in portions, quanta, having an action dimension (J.s) and energy proportional to the frequency of radiation: 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 being 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 no lights are in the way, 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. It is only because of the distance that the worlds appear to be points, and many of them are so far away that they are not distinguishable individually and merge into nebulae. It seems that we are at the center of the universe. Now we know that this is not true. The rejection of geocentrism is a great merit of science. It took a lot of effort to realize that little Earth is moving in a random, seemingly unmarked area of vast (literally!) space.

But life originated on Earth. It developed so successfully that it was able to produce a person capable of comprehending the world around him, searching for and finding the laws governing nature. The achievements of mankind in understanding the laws of nature are so impressive that you involuntarily feel proud of belonging to this pinch of intelligence, lost on the periphery of an ordinary Galaxy.

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

In order, using the basic laws of nature, to derive observables and predict new properties of various substances and objects, complex mathematical theories, which are not at all easy to understand. But the contours of the scientific picture of the World can be comprehended without resorting to strict theory. Naturally, this requires desire. But not only that: even preliminary acquaintance will require some work. We must try to comprehend new facts, unfamiliar phenomena that 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 comes an understanding 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 ingrained ideas.

The purpose of this story is to introduce the fundamental features of the structure of inorganic substances. Despite the endless variety, their structure is relatively simple. Especially if you compare them with any, even the simplest living organism. But there is also something in common: all living organisms, like inorganic substances, built from electrons, protons and neutrons.

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

INTRODUCTION

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

Substances and materials look solid, and the sense of 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, you can dissolve salt or sugar in water. They find a place for themselves in the water. Yes and in solid, for example, you can drive a nail into a wooden board. With considerable effort, you can achieve that the place that was occupied by the tree will be occupied by an iron nail.

We know well: you can break off a small piece from a solid body, you can grind almost any material. Sometimes it is difficult, sometimes it happens spontaneously, without our participation. Let's imagine ourselves on the beach, on the sand. We understand: a grain of sand is far from the smallest particle of the substance that sand consists of. If you try, you can reduce the grains of sand, for example, by passing them through rollers - through two cylinders made of very hard metal. Once between the rollers, the grain of sand is crushed into smaller pieces. Essentially, this is how flour is made from grain in mills.

Now that the atom has firmly entered into our perception of the world, it is very difficult to imagine that people did not know whether the crushing process is limited or the substance can be crushed indefinitely.

It is unknown 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 small a substance is, it can be divided into even smaller parts - there is no limit. Others expressed the idea that there are tiny indivisible particles from which everything consists. To emphasize that these particles are the limit of fragmentation, 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 very old age) and Epicurus (341-270 BC). So, atomic science is almost 2500 years old. The concept of atoms was not immediately accepted by everyone. Even about 150 years ago, there were few people who were confident in the existence of atoms, even among scientists.

The fact is that atoms are very small. They cannot be seen not only with the naked eye, but also, for example, with a microscope that magnifies 1000 times. Let's think about it: what is the size of the smallest particles that can be seen? U different people different eyesight, 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, although with difficulty, see particles measuring about 0.0001 millimeters, or 10 -7 meters. By comparing the sizes of atoms and interatomic distances (10 -10 meters) with the length we accepted as the limit of the ability to see, we will understand why any substance seems solid to us.

2500 years is a huge time. No matter what happened in the world, there were always people who tried to answer the question of how the world around them works. At some times, the problems of the structure of the world were more of a concern, at others - less. The birth of science in its modern sense occurred relatively recently. Scientists have learned to conduct experiments - to ask nature questions and understand its answers, to create theories that describe the results of experiments. The theories required rigorous mathematical methods to reach reliable conclusions. Science has come 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 has been obtained about the structure of matter and the properties of bodies of different natures, an infinite number of various phenomena have been discovered and understood.

Humanity 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 - the objects around us, bodies and ourselves.

As already mentioned, all matter consists of electrons, protons and neutrons. I’ve known about this since school, 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 monotonous.

A coherent description of how substances are built different types, is a complex science. She uses some serious math. It must be emphasized that there is no other, simple theory. But the 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.

METHOD OF FRAGMENTS, OR DIVIDE AND UNDERSTAND

It would seem that the most natural way to understand how a certain complex device (toy or mechanism) works is to disassemble it and decompose it into its component parts. You just need to be very careful, remembering that folding will be much more difficult. “To break is not to build,” says folk wisdom. And one more thing: we may understand what the device consists of, but we are unlikely to understand how it works. Sometimes you need to unscrew one screw, and that’s it - the device stops working. It is necessary not so much to disassemble as to understand.

Because we're talking about not about the actual decomposition of all 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. Moreover, let's not skimp on our efforts. Let's not think about whether it is difficult or easy to decompose the device into its component parts. Just a second. How do we know that we have reached the limit? Maybe with more effort we can go further? Let us admit to ourselves: we do not know whether 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 the parts from which everything is built are elementary particles. And this is not all. Having looked at the corresponding 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 came about. They have that amazing property, which apparently do not exist in 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 ones is unimportant. 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 what we would like to see the parts 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 select a few features that seem mandatory.

Firstly, elementary particles must have the ability to combine into various structures.

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

Thirdly, I would like there not to be too many details. Looking at building blocks, we see how many 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.

ELECTRONS, PROTONS, NEUTRONS

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 in kilograms (SI units); The words "spin" and "statistics" will be explained below.

Let's 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 suggests, is neutral - its charge is zero. And a proton and an electron have charges of the same magnitude, but opposite in sign. An electron is negatively charged and a 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 sizes 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 comes down to introducing 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 electrons, protons and neutrons construction is carried out, what causes particles to combine into more complex structures and what these structures are.

ATOM IS THE SIMPLEEST OF COMPLEX 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 differences and similarities 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, the principle of the arrangement of elements is extremely simple: they are arranged sequentially according to the weight of the 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.

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 than the size of the atom. When Rutherford carried out his experiments, the neutron had not yet been discovered. With the discovery of the neutron, it was realized 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, the atom as a whole is neutral. Protons and neutrons are like building material kernels, received common name- nucleons (from Latin nucleus - core). This is the name we will use.

The number of nucleons in a nucleus is usually denoted by the letter A. 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 an atom. Number A is called atomic mass, and Z- atomic number. Atoms with the same atomic numbers are called isotopes: in the periodic table they are located in the same cell (in Greek isos - equal , topos - place). The point is that chemical properties isotopes are almost identical. If you examine the periodic table carefully, you can be convinced that, strictly speaking, the arrangement of elements does not correspond atomic mass, and 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- I 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 similarly charged bodies from each other and attract differently charged ones to each other (for example, electroscope balls).

The atom is stable. Consequently, 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).

Let us first consider the system of electrons of an atom.

IN solar system planets are attracted to the Sun by gravity. An electrostatic force acts in an atom. It is often called Coulomb in honor of 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 attract or repel with a force equal to F C =Q 1 Q 2 /r 2 , Where r- the distance between charges is called "Coulomb's Law". Index " WITH" assigned to force F by the first letter of Coulomb's surname (in French Coulomb). Among the most diverse statements, there are few that are 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.

A DISCOVERY ABOUT GRAVITY

A person becomes familiar with gravity in early childhood. By falling, he learns to respect the force of gravity towards the Earth. Acquaintance with accelerated motion usually begins with the study of 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 acts 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 universal gravity, emphasizing its universal character. Strength F N determines the movement of galaxies, celestial bodies and objects falling to the ground. The law of universal gravitation is valid at any distance between bodies. We will not mention the changes in the picture of gravity that Einstein's general theory of relativity (1879-1955) introduced.

Both the Coulomb electrostatic force and the Newtonian force of universal gravitation are the same (as 1/ r 2) decrease with increasing distance between 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, 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.

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

WAVE OR PARTICLE? BOTH WAVE AND PARTICLE!

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

A particle and a wave... It would seem that it is even pointless to compare, they are so different.

Probably, when you think about a wave, you first of all imagine a rippling sea surface. Waves come ashore from open sea, 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 waves, the mass of water obviously vibrates. The wave covers a significant area.

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 oscillation of a float up and down. Let us denote the period of wave motion - the time during which one wave passes - by the letter T. The reciprocal of the period is called frequency ν = 1/T. The simplest waves (harmonic) have a certain frequency that does not change over 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 infinite space and exists for an infinitely long time. 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 light is is a collection of particles (corpuscles, from the Latin corpusculum- little body) or waves? Theories competed for a long time. 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 length of light waves, according to everyday concepts, is very small: the range of wavelengths visible light from 380 to 760 nanometers. Shorter electromagnetic waves- ultraviolet, x-rays and gamma rays, and longer ones - infrared, millimeter, centimeter and all other radio waves.

TO end of the 19th century century, the victory of the wave theory of light over the corpuscular theory seemed final and irrevocable. However, the twentieth century made serious adjustments. It seemed like 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 coined - “photon”. The word "quantum" comes from Latin word quantum- how many, and "photon" - from the Greek word photos - light. Words denoting the names of 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 predicted how light would behave in which experiment. This theory is now generally accepted. different behavior light is no longer surprising.

The first steps are always especially difficult. I had to go against the established opinion in science and make statements that seemed like heresy. Real scientists truly believe in the theory they use to describe the phenomena they observe. It is very difficult to abandon an 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 = hν. Proportionality factor h called Planck's constant in honor of the German physicist who introduced it into 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.

Is a quantum of light a lot or a little? The frequency of visible light is about 10 14 s -1 . Recall: 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 a vacuum. Quantum energy hν, as 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, it is monstrously small. But this is a 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 quanta of light - this was confirmed by a series of subtle experiments. Under 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. This heretical thought was first expressed by Louis de Broglie (1892-1987). He did not try to find out what the nature of the wave was, the characteristics of which he predicted. According to his theory, a particle with mass m, flying at 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 the waves that describe the movement of atomic and subatomic particles. A science arose called “quantum mechanics” (in the early years it was more often called wave mechanics).

Quantum mechanics applies to the movement of microscopic particles. When considering the motion of ordinary bodies (for example, any parts 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 lack of trajectory. For a trajectory to exist, 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 prohibited by quantum mechanics: a particle cannot simultaneously have a certain coordinate value X, and a certain speed value v. Their uncertainties Dx And Dv 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 called the universal quantum of "action". Without specifying the term action, pay attention to the epithet universal. He emphasizes that the uncertainty relation is always valid. Knowing the conditions of motion and the mass of the particle, one can 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 the classical laws of motion. Let us emphasize: if it is possible, then it is necessary, since classical mechanics is significantly simpler than quantum mechanics.

Please note that Planck's constant is divided by mass (they are included in combinations h/m). The greater the mass, the less the role of quantum laws.

To feel when to neglect quantum properties certainly possible, we will try to estimate the magnitude 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 they are not small, it is necessary to use quantum mechanics. It makes no sense to take into account quantum uncertainty even when other reasons (within the framework of classical mechanics) lead to greater uncertainty than the Heisenberg relation.

Let's look at one example. Remembering that we want to show the possibility of using classical mechanics, consider a “particle” whose mass is 1 gram and whose 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 a grain flies fast enough, it seems to us that it is moving in a straight line at a certain speed. This impression is erroneous: due to the impacts of hydrogen molecules on the grain, its speed changes slightly with each impact. Let's estimate exactly how much.

Let the temperature of hydrogen be 300 K (we always measure temperature by absolute scale, on the Kelvin scale; 300 K = 27 o C). Multiplying the temperature in Kelvin by Boltzmann's constant k B = 1.381.10 -16 J/K, we will express it in energy units. The change in the speed of a grain 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 occurs completely randomly 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) class = 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 us accept (D X) cl = 10 -3 cm. Finally, (D X) class (D v) cl = 10 -3 .10 -18 = 10 -21 . It would seem a very small value. In any case, the uncertainties in speed and position are so small that the average motion of the grain can be considered. But compared to the quantum uncertainty dictated by Heisenberg's relation (D X D v= 10 -27), the classical heterogeneity is enormous - in this case it exceeds it a million times.

Conclusion: when considering the movement of a grain, there is no need to take into account its wave properties, that is, the existence of quantum uncertainty of coordinates and speed. When it comes to the movement of atomic and subatomic particles, the situation changes dramatically.

They appear in different forms and sizes, some come in destructive duos, meaning they end up destroying each other, and some have incredible names like "neutralino". Here is a list of tiny particles that amaze even physicists themselves.

God Particle

The Higgs boson is a particle that is so important to science that it has been nicknamed the "God particle." It is this that, as scientists believe, gives mass to all other particles. It was first discussed in 1964, when physicists wondered why some particles had more mass than others. The Higgs boson is associated with the Higgs field, a kind of lattice that fills the universe. The field and boson are considered responsible for other particles gaining mass. Many scientists believe that the Higgs mechanism contains the missing pieces of the puzzle to fully understand the standard model, which describes all known particles, but the connection between them has not yet been proven.

Quarks

Quarks are delightfully named blocks of protons and neutrons that are never alone and only ever exist in groups. Apparently, the force that binds quarks together increases with distance, that is, the more someone tries to move one of the quarks away from the group, the more it will be attracted back. Thus, free quarks simply do not exist in nature. There are six types of quarks in total, and protons and neutrons, for example, are made up of several quarks. In a proton there are three of them - two of the same type, and one of the other, but in a neutron - only two, both of different types.

Super partners

These particles belong to the theory of supersymmetry, which states that for every particle known to man, there is another similar particle that has not yet been discovered. For example, the superpartner of an electron is a selectron, the superpartner of a quark is a squark, and the superpartner of a photon is a photino. Why are these superparticles not observed in the universe now? Scientists believe that they are much heavier than their partners, and greater weight shortens their service life. These particles begin to break down as soon as they are born. Creating a particle requires enormous amounts of energy, such as the one produced Big Bang. Perhaps scientists will find a way to reproduce superparticles, for example, in the Large Hadron Collider. Regarding larger size and the weights of the superpartners, scientists believe that the symmetry has been broken in a hidden sector of the universe that cannot be seen or found.

Neutrino

These are light subatomic particles that move at speeds close to the speed of light. In fact, trillions of neutrinos are moving through your body at any given moment, but they almost never interact with ordinary matter. Some neutrinos come from the Sun, others from cosmic rays interacting with the atmosphere.

Antimatter

All ordinary particles have a partner in antimatter, identical particles with opposite charges. When matter and antimatter meet each other, they destroy each other. For a proton such a particle is an antiproton, but for an electron it is a positron.

Gravitons

In quantum mechanics, all fundamental forces are carried out by particles. For example, light is made up of particles with zero mass called photons, which carry an electromagnetic force. Likewise, gravitons are theoretical particles that carry the force of gravity. Scientists are still trying to find gravitons, but this is very difficult, since these particles interact very weakly with matter. However, scientists do not give up trying, because they hope that they will still be able to catch gravitons in order to study them in more detail - this could be a real breakthrough in quantum mechanics, since many similar particles have already been studied, but the graviton remains exclusively theoretical. As you can see, physics can be much more interesting and exciting than you might imagine. The whole world is filled with various particles, each of which is a huge field for research and study, as well as a huge knowledge base about everything that surrounds a person. And you just have to think about how many particles have already been discovered - and how many people still have to discover.