The smallest particle known to science. What is spin? The smallest mobile phone in the world

To the question What is the smallest particle in the universe? Quark, Neutrino, Higgs Boson or Planck Black Hole? given by the author Caucasoid the best answer is Fundamental particles are all zero size (radius is zero). By mass. There are particles with zero mass (photon, gluon, graviton). Of the massive ones, the neutrino has the smallest mass (less than 0.28 eV / s ^ 2, more precisely, it has 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 it is still possible to speak of some kind of analog of the size, for example, through the probability of electrons hitting it from the beam, but for smaller ones, not.

Answer from christen[guru]
"size" of an elementary particle - a characteristic of a particle, reflecting the spatial distribution of its mass, or electric charge; usually talk about the so-called. the root-mean-square radius of the electric charge distribution (which also characterizes the mass distribution)
Gauge bosons and leptons do not exhibit finite "sizes" within the accuracy of the measurements performed. This means that their "sizes"< 10^-16 см
In contrast to truly elementary particles, the "sizes" of hadrons 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. Moreover, it, of course, varies from hadron to hadron.

Answer from Kirill odding[guru]
Some of the great physicists said (for an hour not Niels Bohr?) "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 that create a gravitational effect.
Even less?
Elementary particles that set in motion those that create a gravitational effect
but they themselves participate in this.
There is 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]
PLANKOV'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 a machine is invented 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 less 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 neutrinos 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 !!!) -
Plonkovskaya 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 particle size table. And here you can see that the smallest particle is a 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 latest achievements modern science, O recent discoveries in the field of physics, biology and medicine. But in order to understand how important and interesting they are, it is necessary at least in 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 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 find out about them: popular science literature has practically ceased to be published. Therefore, we asked the longtime author of the journal M.I.Kaganov to talk about atoms and elementary particles and about the laws governing them, about what matter is. Moisei Isaakovich Kaganov is a theoretical physicist, author and co-author of several hundred works on quantum theory solid state, metal theory and magnetism. He was a leading researcher at the Institute for Physical Problems. P. L. Kapitsa and professor at Moscow State University. MV Lomonosov, a member of the editorial boards of the journals "Priroda" and "Kvant". Author of many popular science articles and books. Now he lives in Boston (USA).

Science and Life // Illustrations

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

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

Deuterium atom.

English physicist Ernst Rutherford is rightfully considered the founder of nuclear physics, the doctrine of radioactivity and the theory of atomic structure.

In the picture: the surface of a tungsten crystal, magnified 10 million times; each bright point is its separate 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. c) 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.

Experiments on diffraction convincingly confirmed the theory of de Broglie, which asserted 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 pockets them. Atomic particles are much more complicated. 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 lanterns do not interfere, the sky is filled with brightly shining stars. You don't have to look for familiar constellations or try to find planets close to Earth. Just watch! Try to imagine a huge space filled with worlds and stretching for billions of billions of light years. Only because of the distance, the worlds seem to be points, and many of them are so distant that they are indistinguishable separately and merge into a nebula. It seems that we are at the center of the universe. We now 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 baby-Earth is moving in a random, seemingly unselected area of ​​boundless (literally!) Space.

But life began on Earth. It developed so successfully that it was able to produce a person capable of comprehending the world around him, to seek and find the laws governing nature. The achievements of mankind in the knowledge of the laws of nature are so impressive that one involuntarily feels pride from 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. Equally 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 the observed and predict new properties of various substances and objects, complex mathematical theories, which is not at all easy to understand. But the contours of the scientific picture of 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. It is necessary to try to comprehend new facts, unfamiliar phenomena, which at first glance do not agree with the existing experience.

Achievements of science often lead to the idea that for it "there is nothing sacred": what was true yesterday is discarded today. With knowledge, an understanding arises of how anxiously science relates to 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 acquaint with the fundamental features of the structure of inorganic substances. Despite the endless variety, their structure is relatively simple. Especially when you compare them with any, even the simplest living organism. But there is one thing in common: all living organisms, like inorganic substances, are built of electrons, protons and neutrons.

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

The variety of things, objects - everything we use, what surrounds us, is immense. 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 appear 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 unlike each other, are similar in one thing: both metal and water are solid. True, salt or sugar can be dissolved in water. They find a place for themselves in the water. And in a solid, for example, in wooden board, you can drive in a nail. With a noticeable effort, you can ensure that the place that was occupied by the tree will be occupied by an iron nail.

We know very 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. Imagine ourselves on the beach, on the sand. We understand: a grain of sand is far from the most small particle the substance of which the sand is composed. If you try, you can reduce the grains of sand, for example, by passing through the rollers - through two cylinders from very hard metal... Once between the rollers, the grain of sand will be crushed into smaller pieces. In fact, this is how flour is made from grain in mills.

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

It is not known when people first asked themselves this question. It was first recorded in the writings ancient greek philosophers... Some of them believed that, no matter how much the fraction of the substance, it allows division into even smaller parts - there is no limit. Others expressed the idea that there are the smallest indivisible particles, of 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 were the first to put forward the idea of ​​the existence of atoms. This is Democritus (born about 460 or 470 BC) new era, died at a ripe old age) and Epicurus (341-270 BC). So, atomic science is almost 2500 years old. The concept of atoms was by no means immediately accepted by everyone. Even 150 years ago, there were few confident in the existence of atoms, even among scientists.

The point is that atoms are very small. They cannot be seen not only with a simple 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 you can see? Have different people different vision, but, probably, everyone will agree that it is impossible to see a particle less than 0.1 millimeter in size. Therefore, using a microscope, it is possible, albeit with difficulty, to see particles of about 0.0001 millimeters, or 10 -7 meters. Comparing the sizes of atoms and interatomic distances (10 -10 meters) with the length, which we accepted as the limit of the possibility of seeing, we will understand why any substance seems to us to be continuous.

2500 years is a long time. No matter what was happening in the world, there were always people who tried to answer to themselves the question of how the world around them works. In some times, the problems of the structure of the world worried more, in some - less. The birth of science in its modern sense happened relatively recently. Scientists have learned to set up experiments - to ask nature questions and understand its answers, to create theories that describe the results of experiments. Theories required rigorous mathematical methods to arrive at reliable conclusions. Science has come a long way. On this path, which for physics began about 400 years ago with the works of Galileo Galilei (1564-1642), an infinite amount of information about the structure of matter and the properties of bodies of different natures was obtained, an infinite number of various phenomena were 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 substances are composed of electrons, protons and neutrons. I have known this since my school years, but it never ceases to amaze me that everything is built of only three kinds of particles! But the world is so diverse! In addition, the means used by nature to carry out construction are also rather monotonous.

A consistent description of how substances are built different types, is a complex science. She uses serious mathematics. 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 nontrivial 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 the most natural way to understand how a certain complex device (toy or mechanism) works - to disassemble, decompose into its component parts. You just need to be very careful, remembering that it will be much more difficult to fold. "To break is not to build" - says folk wisdom... And one more thing: what the device consists of, we may understand, but how it works is unlikely. Sometimes it is worth unscrewing one screw, and that's it - the device 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 the mental, and not about the real experience, then you do not have to worry: you will not have to collect. Also, 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. Wait a second. And how do we know that we have reached the limit? Maybe by adding more effort, we can go further? We 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 elementary particles serve as the details from which everything is built. And yet not all of them. Looking at 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 sub-elementary particles - the particles that make up the elementary particles themselves. This is how the idea of ​​quarks appeared. They have the amazing property that, apparently, they do not exist in a free state. There are 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 sub-elementary ones is insignificant. Electrons, protons and neutrons are directly involved in the construction of substances - everything is built only of them.

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

First, elementary particles must have the ability to combine into a variety of structures.

Secondly, I would like to think that elementary particles are indestructible. Knowing how long the history of 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 to be not too many. Looking at the building blocks, we can 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.

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

The magnitude of the charge is given in pendants, the mass is 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 implies, is neutral - its charge is zero. And the proton and the electron have the same charge, but opposite in sign. The electron is negatively charged and the proton is positively.

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 in comparison with the size of atoms, protons and neutrons are monstrously small (about 10 -16 meters).

In fact, this short section boils down to presenting 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 forces the particles to combine into more complex structures and what these structures are.

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. 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 abstract ourselves from the existence of periods, then the principle of the arrangement of the elements is extremely simple: they are arranged sequentially according to the weight of the atoms. The lightest is a hydrogen atom. The last natural (not artificially created) atom is uranium, 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 all the mass of an atom is concentrated in its nucleus - a small (even in comparison with an atom) region of space: the radius of the nucleus is approximately 100 thousand times smaller atom. When Rutherford carried out 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 imagine 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, as the building material of the nucleus, received common name- nucleons (from Latin nucleus - core). We will use this name.

The number of nucleons in the 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 the 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 in the same cell (in Greek isos - equal , topos - place). The fact is that Chemical properties isotopes are almost identical. If you examine the periodic table carefully, you can make sure that, strictly speaking, the arrangement of the elements corresponds not to the atomic mass, but to 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 radiation.

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

The atom is stable. Consequently, electrons in an atom move around the nucleus: centrifugal force compensates for the force of gravity. Understanding this led to the creation of a planetary model of the atom, in which the core 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 a few tenths of a nanometer (1 nm = 10 -9 m).

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

V Solar system planets are attracted to the Sun by gravity. An electrostatic force acts in the 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 just as rightly called a law as Coulomb's law: after all, the area 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 person gets acquainted with gravity in early childhood. As he falls, he learns to respect the force of gravity to 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 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 of universal gravitation, emphasizing its universal nature. Power F N determines the movement of galaxies, celestial bodies and falling objects to Earth. The law of universal gravitation is valid for any distance between bodies. We will not mention the changes in the picture of gravity introduced by Einstein's general theory of relativity (1879-1955).

Both the Coulomb electrostatic force and the Newtonian gravitational force 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, 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 in comparison with 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 (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 Everyday life no. You might think that the particles that make up such small atoms are conveniently thought of as material points. But everything turned out to be much more complicated.

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

Probably, when you think about a wave, you first of all imagine a wavy sea surface. Waves ashore come from open sea, wavelengths - the distance between two successive crests - can be different. It is easy to observe waves having a length of the order of several meters. With waves, obviously, the mass of water fluctuates. The wave covers a significant area.

The wave is periodic in time and space. Wavelength ( λ ) is a measure of spatial periodicity. Periodicity wave motion in time it is visible in the frequency of arrival of wave crests to the coast, and it can be detected, for example, by the oscillation of the float up and down. Let us denote the period of the 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 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 infinitely long. The particle, as we imagine it, and the wave are absolutely different.

Since the time of Newton, there has been a debate about the nature of light. What is light is a collection of particles (corpuscles, from Latin corpusculum- body) or waves? Theories have long competed. The wave theory won out: 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 late XIX century the victory of the wave theory of light over the corpuscular one seemed final and irrevocable. However, the twentieth century has 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 invented - "photon". The word "quantum" comes from the Latin word quantum- how much, and "photon" - from the Greek word photos - light. Particle names usually end with 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, the light will behave. At present, this theory is accepted by all, 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 make statements that seemed heresy. Real scientists truly believe in the theory they use to describe the observed phenomena. It is very difficult to reject 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 = hν. Aspect ratio h named the Planck constant after the German physicist who introduced it to the theory of radiation in 1900. And already in the first third of the XX 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 of the order of 10 14 s -1. Recall that the frequency and wavelength of light are related by the relationship ν = c/ λ, where With= 299792458.10 10 m / s (exactly) - the speed of light in a vacuum. Quantum energy hν, as it is easy to see, is of the order of 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 microworld, completely different scales! 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 - we were convinced of this by performing a series of subtle experiments. Under normal conditions, a person does not distinguish the "graininess" of light, perceiving it as a continuous stream.

Knowing that light has both corpuscular and 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 figure out what is the nature of the wave, the characteristics of which he predicted. According to his theory, a particle of mass m flying at a speed v, corresponds to a wave with a wavelength l = hmv and frequency ν = E/h, where E = mv 2/2 is the energy of the particle.

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

Quantum mechanics is applicable to the movement of microscopic particles. When considering the motion of ordinary bodies (for example, any details of mechanisms), it makes no sense to take 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 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 exactly what is prohibited. quantum mechanics: a particle cannot have a specific coordinate value at the same time 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 "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 the classical laws of motion. We emphasize: if possible, then it is necessary, since classical mechanics is much simpler than quantum mechanics.

Pay attention to the fact that Planck's constant is divided by mass (they are included in the combination h / m). The greater the mass, the less the role of quantum laws.

To feel when to neglect quantum properties is certainly possible, we will try to estimate the values ​​of the uncertainties D X and D v... If D X and D v are negligible in comparison with 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 reasons (within the framework of classical mechanics) lead to greater uncertainty than the Heisenberg relation.

Let's take a look at 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, it is a grain, 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: because of the impacts of hydrogen molecules on a grain, its velocity slightly changes with each impact. Let's estimate how much.

Let the temperature of hydrogen be 300 K (we always measure the temperature by absolute scale, on the Kelvin scale; 300 K = 27 o C). By multiplying the temperature in kelvin by the Boltzmann 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 velocity 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 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 = 10 -18 cm / s. The location of the grain is apparently very difficult to determine with an accuracy greater than 0.1 of its size. We take (D X) cl = 10 -3 cm. Finally, (D X) cl (D v) cl = 10 -3 .10 -18 = 10 -21. It would seem a very small value. In any case, the uncertainties in the velocity and coordinates are so small that the average motion of the grain can be considered. But compared with the quantum uncertainty dictated by the Heisenberg relation (D X D v= 10 -27), the classical heterogeneity is huge - in this case it exceeds it by a factor of a million.

Conclusion: considering the motion 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 velocity. When it comes to the movement of atomic and subatomic particles, the situation changes dramatically.

The world and science never stand still. More recently, in physics textbooks, they confidently wrote that the electron is the smallest particle. Then the smallest particles were mesons, then bosons. And now science has discovered a new the smallest particle in the universe Is a Planck black hole. True, it is still open only in theory. This particle belongs to the category of black holes because its gravitational radius is greater than or equal to the wavelength. Of all the existing black holes, the Planck one is the smallest.

Too short a lifetime of these particles cannot make their practical detection possible. At least for now. And they are formed, as is commonly believed, as a result of nuclear reactions. But it is not only the lifetime of Planck black holes that prevents them from being detected. Now, unfortunately, this is not possible 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.

Video:

Despite such a 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 detection that the installation was created, which only the laziest inhabitant on Earth has not heard of - the Large Hadron Collider. Scientists' confidence in the success of these studies helped to achieve a sensational result. The Higgs boson is currently the smallest particle of those whose existence has been practically proven. Its discovery is very important for science; it allowed all particles to acquire mass. And if the particles had no mass, the universe could not exist. Not a single substance could form in it.

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

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 Black Hole, which so far exists only in theory. The Planck 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, they also discovered its smallest particle, which is now being carefully investigated.

The highest point in Russia is located in the Caucasus. Then the smallest particles were mesons, then bosons. This particle belongs to the category of black holes because its gravitational radius is greater than or equal to the wavelength. Of all the existing black holes, the Planck one 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 for its detection that the installation was created, which only the laziest inhabitant on Earth has not heard of - the Large Hadron Collider. The Higgs boson is currently the smallest particle of those whose existence has been practically proven.

And if the particles had no mass, the universe could not exist. Not a single substance could form 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 every day something interesting happens in it, something unusual and fascinating. 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, it does not contain other particles [approx. one]. Elementary particles are fundamental objects of quantum field theory. They can be classified by spin: fermions have half-integer spin, and bosons have whole spin. The Standard Model of Particle Physics is a theory that describes the properties and interactions of elementary particles.

They are classified according to their participation in strong interactions. 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 convert one nuclide to 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 register them somehow, and they exist only in theory. And although today experiments have been proposed to detect black holes, but 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. It is only 16-18 mm long and weighs 0.2 grams.

The smallest things in the world

The smallest single-stranded DNA virus is 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 colliding particles together (as, for example, in the Large Hadron Collider), they can be broken into even more particles, such as quarks, leptons and even antimatter. The problem is just determining which is less. So some particles have no mass, some have negative mass. The solution to this question is like dividing by zero, that is, impossible.

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

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?

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 on the order of 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 there is no atomic charge at all, since the nucleus is too small. There are numbers that are so incredibly, incredibly large that even to write them down would require the entire universe.

Smallest objects visible to the naked eye

Google was born in 1920 as a way to get kids interested in big numbers. This is a number, according to Milton, in which there is 1 in the first place, followed by as many zeros as you could write before you get tired. If we talk about the biggest significant number, there is a reasonable argument that this really means that you need to find the largest number with a real value in the world.

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

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

In physics, elementary particles are called physical objects on the scale of the atomic nucleus, which cannot be divided into their component parts. However, for today, scientists still managed to split some of them. The structure and properties of these smallest objects are studied by the physics of elementary particles.

O smallest particles that make up all matter was known in antiquity. However, the founders of the so-called "atomism" are considered to be the philosopher Ancient Greece Leucippus and his more famous student, Democritus. It is assumed that the second introduced the term "atom". From the ancient Greek "atomos" is translated as "indivisible", which determines the views of the ancient philosophers.

Later it became known that the atom can still be divided into two physical objects - the nucleus and the electron. The latter later became the first elementary particle, when in 1897 the Englishman Joseph Thomson conducted an experiment with cathode rays and revealed that they are a stream of identical particles with the same mass and charge.

In parallel with the work of Thomson, an X-ray researcher, Henri Becquerel, conducts experiments with uranium and discovers the new kind radiation. In 1898, a French couple of physicists, Marie and Pierre Curie, study various radioactive substances, detecting the same radioactive radiation. Later it will be found that it consists of alpha (2 protons and 2 neutrons) and beta particles (electrons), and Becquerel and Curie will receive the Nobel Prize. Carrying out her research with elements such as uranium, radium and polonium, Maria Sklodowska-Curie did not take any safety measures, including not even wearing gloves. As a consequence, leukemia overtook her in 1934. In memory of the achievements of the great scientist, the element, polonium, discovered by a pair of Curies, was named after the motherland of Mary - Polonia, from Latin - Poland.

Photo from the V Solvay Congress 1927. Try to find all the scientists from this article in this photo.

Beginning in 1905, Albert Einstein devoted his publications to the imperfection of the wave theory of light, the postulates of which were at variance with the results of experiments. Which subsequently led the outstanding physicist to the idea of ​​a "light quantum" - a portion of light. Later, in 1926, it was named as "photon", translated from the Greek "phos" ("light"), by the American physiochemist - Gilbert N. Lewis.

In 1913, Ernest Rutherford, a British physicist, based on the results of experiments already carried out at that time, noted that the masses of the nuclei of many chemical elements multiples of the mass of the hydrogen nucleus. Therefore, he suggested that the hydrogen nucleus is a constituent of the nuclei of other elements. In his experiment, Rutherford irradiated a nitrogen atom with alpha particles, which as a result emitted a certain particle, named by Ernest as a "proton", from another Greek "protos" (the first, the main one). Later it was experimentally confirmed that the proton is the nucleus of hydrogen.

Obviously the proton is not the only one component nuclei of chemical elements. This is due to the fact that two protons in the nucleus would repel, and the atom would instantly decay. Therefore, Rutherford put forward a hypothesis about the presence of another particle, which has a mass equal to that of a proton, but is uncharged. Some experiments of scientists on the interaction of radioactive and lighter elements, led them to the discovery of another new radiation. In 1932, James Chadwick determined that it was composed of the very neutral particles that he called neutrons.

Thus, the most famous particles were discovered: photon, electron, proton and neutron.

Further, the discovery of new subnuclear objects became more and more frequent event, and at the moment there are known about 350 particles, which are usually considered "elementary". Those of them that have not yet been split are considered structureless and are called “fundamental”.

What is spin?

Before proceeding to further innovations in the field of physics, it is necessary to determine the characteristics of all particles. The most famous, apart from mass and electric charge, also includes spin. This value is called otherwise as "proper angular momentum" and is in no way associated with the movement of the subnuclear object as a whole. Scientists managed to find particles with spins 0, ½, 1, 3/2 and 2. To visualize, albeit simplified, spin as a property of an object, consider the following example.

Let the object have a spin equal to 1. Then such an object, when rotated 360 degrees, will return to its original position. On a plane, this object can be a pencil, which, after being turned 360 degrees, will be in its original position. In the case of zero spin, any rotation of the object will always look the same, for example, a one-color ball.

For a ½ back, you need an object that retains its appearance when turned 180 degrees. It can be the same pencil, only sharpened symmetrically on both sides. A spin of 2 will require a spin of 720 degrees, and a 3/2 spin will require 540.

This characteristic has a very great importance for the physics of elementary particles.

Standard Model of Particles and Interactions

Having an impressive set of micro-objects that make up the world, scientists decided to structure them, so a well-known theoretical construction called the "Standard Model" was formed. She describes three interactions and 61 particles using 17 fundamental ones, some of which were predicted by her long before the discovery.

The three interactions are:

• Electromagnetic. It occurs between electrically charged particles. In a simple case, known from school, oppositely charged objects are attracted, and objects of the same name are repelled. This happens through the so-called carrier of electromagnetic interaction - a photon.
• Strong, otherwise - nuclear interaction. As the name implies, its action extends to objects of the order of the atomic nucleus, it is responsible for the attraction of protons, neutrons and other particles, also consisting of quarks. Strong interactions are carried over with gluons.
• Weak. Acts at distances one thousand less than the size of the nucleus. This interaction involves leptons and quarks, as well as their antiparticles. Moreover, in the case of weak interaction, they can reincarnate into each other. The carriers are the bosons W +, W− and Z0.

So the Standard Model was formed in the following way. It includes six quarks that make up all hadrons (particles subject to strong interactions):

• Top (u);
• Enchanted (c);
• True (t);
• Lower (d);
• Strange (s);
• Adorable (b).

It can be seen that physicists are not occupied with epithets. The other 6 particles are leptons. These are fundamental spin ½ particles that do not participate in strong interactions.

• Electron;
• Electronic neutrino;
• Muon;
• Muon neutrino;
• Tau lepton;
• Tau neutrino.

And the third group of the Standard Model is gauge bosons, which have spin equal to 1 and are represented as carriers of interactions:

• Gluon is strong;
• Photon - electromagnetic;
• Z-boson - weak;
• W-boson - weak.

They also include the recently discovered spin 0 particle, which, to put it simply, endows all other subnuclear objects with inert mass.

As a result, according to the Standard Model, our world looks like this: all matter consists of 6 quarks that form hadrons and 6 leptons; all these particles can participate in three interactions, which are carried by gauge bosons.

Disadvantages of the Standard Model

However, even before the discovery of the Higgs boson, the last particle predicted by the Standard Model, scientists had gone beyond it. A striking example of this is the so-called. "Gravitational interaction", which today is on a par with others. Presumably, its carrier is a particle with spin 2, which has no mass, and which physicists have not yet been able to detect - "graviton".

Moreover, the Standard Model describes 61 particles, and today mankind already knows more than 350 particles. This means that the work of theoretical physicists is not over yet.

Particle classification

To make life easier for themselves, physicists have grouped all the particles depending on the features of their structure and other characteristics. Classification is based on the following criteria:

• Lifetime.
  1. Stable. These include a proton and an antiproton, an electron and a positron, a photon, and also a graviton. The existence of stable particles is not limited by time, as long as they are in a free state, i.e. do not interact with anything.
  2. Unstable. All other particles after some time decay into their constituent parts, therefore they are called unstable. For example, a muon lives only 2.2 microseconds, and a proton - 2.9 10 * 29 years, after which it can decay into a positron and a neutral pion.
• Weight.
  1. Massless elementary particles, of which there are only three: photon, gluon and graviton.
  2. Massive particles are all others.
• The value of the spin.
  1. Whole spin, incl. zero, have particles called bosons.
  2. Particles with half-integer spin are fermions.
• Participation in interactions.
  1. Hadrons (structural particles) are subnuclear objects that take part in all four types of interactions. It was mentioned earlier that they are made up of quarks. Hadrons are divided into two subtypes: mesons (whole spin, are bosons) and baryons (half-integer spin are fermions).
  2. Fundamental (structureless particles). These include leptons, quarks and gauge bosons (read earlier - "Standard Model ..").

Having familiarized yourself with the classification of all particles, you can, for example, pinpoint some of them. So the neutron is a fermion, hadron, or rather a baryon, and a nucleon, that is, it has a half-integer spin, consists of quarks and participates in 4 interactions. Nucleon is the general name for protons and neutrons.

• Interestingly, opponents of the atomism of Democritus, which predicted the existence of atoms, claimed that any substance in the world is infinitely divisible. To some extent, they may turn out to be right, since scientists have already managed to divide an atom into a nucleus and an electron, a nucleus into a proton and a neutron, and they, in turn, into quarks.
• Democritus assumed that the atoms have a clear geometric shape, and therefore the "sharp" atoms of fire - burn, rough atoms solids are firmly held together by their protrusions, and smooth water atoms slip during interaction, otherwise they flow.
• Joseph Thomson compiled his own model of the atom, which seemed to him as a positively charged body, into which electrons were, as it were, "stuck". His model is called the Plum pudding model.
• Quarks got their name from the American physicist Murray Gell-Mann. The scientist wanted to use a word similar to the sound of quacking a duck (kwork). But in James Joyce's novel Finnegans Wake, I came across the word "quark", in the line "Three quarks for Mr. Mark!" Murray decided to name the particles by this word, since at that time only three quarks were known.
• Although photons, particles of light, are massless, near a black hole, they seem to change their trajectory, being attracted to it by gravitational interaction. In fact, a supermassive body bends space-time, due to which any particles, including those without mass, change their trajectory towards a black hole (see).
• The Large Hadron Collider is precisely "hadronic" because it collides two directed beams of hadrons, particles with dimensions of the order of an atomic nucleus, which participate in all interactions.