Devices for registering charged particles are called detectors. There are two main types of detectors:

1) discrete(counting and determining the energy of particles): Geiger counter, ionization chamber, etc.;

2) track(making it possible to observe and photograph traces (tracks) of particles in the working volume of the detector): Wilson chamber, bubble chamber, thick-layer photographic emulsions, etc.

1. Gas-discharge Geiger counter. To register electrons and \(~\gamma\)-quanta (photons) of high energy, a Geiger-Muller counter is used. It consists of a glass tube (Fig. 22.4), to the inner walls of which the cathode K is adjacent - a thin metal cylinder; anode A is a thin metal wire stretched along the axis of the counter. The tube is filled with a gas, usually argon. The counter is included in the registering circuit. A negative potential is applied to the body, a positive potential is applied to the thread. A resistor R is connected in series with the counter, from which the signal is fed to the recording device.

The operation of the counter is based on impact ionization. Let a particle enter the counter that has created at least one pair on its way: "ion + electron". The electrons, moving towards the anode (filament), fall into the field with increasing intensity (voltage between A and K ~ 1600 V), their speed rapidly increases, and on their way they create an ion avalanche (impact ionization occurs). Once on the thread, the electrons reduce its potential, as a result of which a current will flow through the resistor R. A voltage pulse arises at its ends, which enters the registration device.

A voltage drop occurs across the resistor, the anode potential decreases, and the field strength inside the counter decreases, as a result of which the kinetic energy of the electrons decreases. The discharge stops. Thus, the resistor plays the role of resistance, automatically extinguishing the avalanche discharge. Positive ions flow down to the cathode within \(~t \approx 10^(-4)\) s after the start of the discharge.

The Geiger counter allows you to register 10 4 particles per second. It is used mainly for registration of electrons and \(~\gamma\)-quanta. However, \(~\gamma\)-quanta are not directly registered due to their low ionizing ability. To detect them, the inner wall of the tube is covered with a material from which \(~\gamma\)-quanta knock out electrons. When registering electrons, the efficiency of the counter is 100%, and when registering \(~\gamma\)-quanta, it is only about 1%.

Registration of heavy \(~\alpha\)-particles is difficult, since it is difficult to make a sufficiently thin "window" transparent for these particles in the counter.

2. Wilson chamber.

The chamber uses the ability of high-energy particles to ionize gas atoms. A cloud chamber (Fig. 22.5) is a cylindrical vessel with piston 1. The upper part of the cylinder is made of transparent material, a small amount of water or alcohol is introduced into the chamber, for which the vessel is covered with a layer from below wet velvet or cloth 2. A mixture is formed inside the chamber rich vapor and air. With the rapid lowering of the piston 1 the mixture expands adiabatically, which is accompanied by a decrease in its temperature. By cooling the steam becomes supersaturated.

If the air is free of dust particles, then the condensation of vapor into a liquid is difficult due to the absence of condensation centers. However condensation centers ions can also serve. Therefore, if a charged particle flies through the chamber (let in through window 3), ionizing molecules on its way, then vapor condensation occurs on the ion chain and the trajectory of the particle inside the chamber becomes visible due to the settled small droplets of liquid. The chain of formed liquid droplets forms a particle track. The thermal motion of molecules quickly smears the particle track, and the particle trajectories are clearly visible only for about 0.1 s, which, however, is sufficient for photographing.

The appearance of a track in a photograph often allows one to judge nature particles and size her energy. So, \(~\alpha\)-particles leave a relatively thick solid trace, protons - thinner, and electrons - dotted (Fig. 22.6). The emerging splitting of the track - "forks" indicates an ongoing reaction.

To prepare the chamber for action and clean it of the remaining ions, an electric field is created inside it, which attracts the ions to the electrodes, where they are neutralized.

Soviet physicists P. L. Kapitsa and D. V. Skobeltsyn proposed to place the camera in a magnetic field, under the influence of which the trajectories of particles are bent in one direction or another, depending on the sign of the charge. The radius of curvature of the trajectory and the intensity of the tracks determine the energy and mass of the particle (specific charge).

3. bubble chamber. The bubble chamber is currently used in scientific research. The working volume in the bubble chamber is filled with liquid under high pressure, which prevents it from boiling, despite the fact that the temperature of the liquid is higher than the boiling point at atmospheric pressure. With a sharp decrease in pressure, the liquid turns out to be overheated and is in an unstable state for a short time. If a charged particle flies through such a liquid, then the liquid will boil along its trajectory, since the ions formed in the liquid serve as centers of vaporization. In this case, the particle trajectory is marked by a chain of vapor bubbles, i.e. is made visible. Liquid hydrogen and C 3 H 3 propane are mainly used as liquids. The duration of the working cycle is about 0.1 s.

Advantage bubble chamber in front of the cloud chamber is due to the greater density of the working substance, as a result of which the particle loses more energy than in a gas. The particle paths turn out to be shorter, and particles of even higher energies get stuck in the chamber. This makes it possible to determine much more accurately the direction of the particle's motion and its energy, and to observe a series of successive transformations of the particle and the reactions it causes.

4. Method of thick-layer photographic emulsions developed by L. V. Mysovsky and A. P. Zhdanov.

It is based on the use of blackening of the photographic layer under the action of fast charged particles passing through the photographic emulsion. Such a particle causes the disintegration of silver bromide molecules into Ag + and Br - ions and blackening of the photographic emulsion along the motion trajectory, forming a latent image. When developing in these crystals, metallic silver is reduced and a particle track is formed. The energy and mass of the particle are judged by the length and thickness of the track.

To study traces of particles that have very high energy and give long traces, a large number of plates are stacked.

A significant advantage of the photographic emulsion method, in addition to ease of use, is that it gives non-disappearing trace particles, which can then be carefully examined. This led to the wide application of this method in the study of new elementary particles. This method, with the addition of boron or lithium compounds to the emulsion, can be used to study traces of neutrons, which, as a result of reactions with boron and lithium nuclei, create \(~\alpha\)-particles that cause blackening in the nuclear emulsion layer. Based on the traces of \(~\alpha\)-particles, conclusions are drawn about the speed and energies of the neutrons that caused the appearance of \(~\alpha\)-particles.

Literature

Aksenovich L. A. Physics in high school: Theory. Tasks. Tests: Proc. allowance for institutions providing general. environments, education / L. A. Aksenovich, N. N. Rakina, K. S. Farino; Ed. K. S. Farino. - Mn.: Adukatsy i vykhavanne, 2004. - S. 618-621.

Elementary particles can be observed due to the traces they leave when passing through matter. The nature of the traces makes it possible to judge the sign of the charge of the particle, its energy, momentum, etc. Charged particles cause ionization of molecules on their way. Neutral particles do not leave traces, but they can reveal themselves at the moment of decay into charged particles or at the moment of collision with any nucleus. Therefore, eventually neutral particles are also detected by the ionization caused by the charged particles generated by them.

Instruments used to register ionizing particles are divided into two groups. The first group includes devices that register the fact of the passage of a particle and, in addition, make it possible in some cases to judge its energy. The second group is formed by the so-called track devices, i.e., devices that make it possible to observe traces (tracks) of particles in matter.

Recording devices include a scintillation counter, a Cherenkov counter, an ionization chamber, a gas-discharge counter, and a semiconductor counter.

1. Scintillation counter. A charged particle flying through a substance causes not only ionization, but also excitation of atoms. Returning to their normal state, the atoms emit visible light. Substances in which charged particles cause a noticeable light flash (scintillation) are called phosphorus. The most commonly used phosphors are (zinc sulfide activated with silver) and (sodium iodide activated with thallium).

The scintillation counter consists of phosphorus, from which light is fed through a special light guide to the photomultiplier. The pulses produced at the output of the photomultiplier are counted. The amplitude of the pulses, which is proportional to the flash intensity, is also determined. This gives additional information about the registered particles. For this type of counters, the detection efficiency for charged particles is 100%.

2. Cherenkov counter. The principle of operation of this counter is considered in paragraph 3.3.3. (p. 84). The purpose of counters is to measure the energy of particles moving in matter at a speed exceeding the phase speed of light in a given medium. In addition, counters make it possible to separate particles by mass. Knowing the angle of emission of radiation, it is possible to determine the velocity of a particle, which, with a known mass, is equivalent to determining its energy. If the mass of the particle is unknown, then it can be determined from an independent measurement of the energy of the particle.

Cherenkov counters are installed on spacecraft to study cosmic radiation.

3. Ionization chamber is an electrical capacitor filled with gas, to the electrodes of which a constant voltage is applied. The registered particle, getting into the space between the electrodes, ionizes the gas. The voltage on the capacitor plates is selected so that all the formed ions, on the one hand, reach the electrodes without having time to recombine, and on the other hand, do not accelerate so much as to produce secondary ionization. Consequently, ions that have arisen directly under the action of charged particles are collected on the plates: the total ionization current is measured or the passage of single particles is recorded. In the latter case, the camera works like a counter.

4. Gas discharge counter usually performed in the form of a gas-filled metal cylinder with a thin wire stretched along its axis. The cylinder serves as the cathode, the wire as the anode. In contrast to the ionization chamber, secondary ionization plays the main role in a gas-discharge counter. There are two types of gas discharge counters: proportional counters and Geiger-Muller counters. In the first, the gas discharge is non-self-sustaining, and in the second, it is independent.

In proportional counters, the output pulse is proportional to the primary ionization, i.e., the energy of the particle that has flown into the counter. Therefore, these counters not only register the particle, but also measure its energy.

The Geiger-Muller counter does not differ significantly from a proportional counter in design and principle of operation, but it operates in the region of the current-voltage characteristic corresponding to a self-sustained discharge, i.e., in the region of high voltages, when the output pulse does not depend on primary ionization. This counter registers a particle without measuring its energy. To register individual pulses, the self-sustained discharge that has arisen must be extinguished. For this, such a resistance is switched on in series with the filament (anode) so that the discharge current that has arisen in the counter causes a voltage drop across the resistance sufficient to interrupt the discharge.

5. semiconductor counter. The main element of this counter is a semiconductor diode, which has a very small thickness of the working area (tenths of a millimeter). As a result, the counter cannot register high-energy particles. But it is highly reliable and can operate in magnetic fields, because for semiconductors the magnetoresistive effect (dependence of resistance on magnetic field strength) is very small.

To the number track devices include cloud chamber, diffusion chamber, bubble chamber and nuclear emulsions.

1. cloud chamber. This is the name of the device created by the English physicist Wilson in 1912. A path of ions, laid by a flying charged particle, becomes visible in a cloud chamber, because supersaturated vapors of a liquid condense on the ions. The chamber is usually made in the form of a glass cylinder with a tight-fitting piston. The cylinder is filled with neutral gas saturated with water vapor or alcohol. With a sharp expansion of the gas, the vapor becomes supersaturated, and on the trajectories of particles flying through the chamber, fog tracks are formed, which are photographed at different angles. By the appearance of the tracks, one can judge the type of flying particles, their number and their energy. By placing the camera in a magnetic field, it is possible to judge the sign of their charge by the curvature of the particle trajectories.

The cloud chamber was for a long time the only instrument of the track type. However, it is not without drawbacks, the main of which is the short working time, which is approximately 1% of the time spent on preparing the camera for the next launch.

2. Diffusion chamber is a type of cloud chamber. Supersaturation is achieved by diffusion of alcohol vapor from the heated lid to the cooled bottom. A layer of supersaturated vapor appears near the bottom, in which flying charged particles create tracks. Unlike the cloud chamber, the diffusion chamber operates continuously.

3. Bubble camera. This device is also a modification of the cloud chamber. The working medium is a superheated liquid under high pressure. By a sharp release of pressure, the liquid is transferred to an unstable overheated state. The flying particle causes a sharp boiling up of the liquid, and the trajectory turns out to be indicated by a chain of vapor bubbles. The track, as in the cloud chamber, is photographed.

The bubble chamber works in cycles. Its dimensions are the same as those of the cloud chamber. The liquid is much denser than vapor, which makes it possible to use the chamber to study long chains of creations and decays of high-energy particles.

4. Nuclear photographic emulsions. When using this method of registration, a charged particle passes through the emulsion, causing the ionization of atoms. After the development of the emulsion, traces of charged particles are found in the form of a chain of silver grains. Emulsion is a denser medium than vapor in a cloud chamber or liquid in a bubble chamber, so the length of the track in the emulsion is shorter. (The track length in an emulsion corresponds to the track length in a cloud chamber.) The photographic emulsion method is used to study ultrahigh-energy particles that are in cosmic rays or are produced in accelerators.

The advantages of counters and track detectors are combined in spark chambers, which combine the speed of registration inherent in counters with the more complete information about particles obtained in the chambers. We can say that the spark chamber is a set of counters. Information in spark chambers is issued immediately, without further processing. At the same time, particle tracks can be determined from the action of many counters.

Instruments used to detect nuclear radiation are called nuclear radiation detectors. The most widely used are detectors that detect nuclear radiation by their ionization and excitation of the atoms of matter. The gas-discharge counter was invented by the German physicist G. Geiger, then improved jointly with W. Müller. Therefore, gas-discharge counters are often called Geiger-Muller counters. The cylindrical tube serves as the body of the counter; a thin metal thread is stretched along its axis. The thread and the body of the tube are separated by an insulator. The working volume of the counter is filled with a mixture of gases, such as argon with an admixture of methyl alcohol vapor, at a pressure of about 0.1 atm.

To register ionizing particles, a high constant voltage is applied between the counter case and the filament, the filament is the anode. Fast charged particle flying through the working volume of the counter

produces on its way the ionization of atoms of the filling gas. Under the action of an electric field, free electrons move towards the anode, positive ions move towards the cathode. The electric field strength near the counter anode is so high that free electrons, when approaching it on the way between two collisions with neutral atoms, acquire energy sufficient for their ionization. A corona discharge occurs in the counter, which stops after a short period of time.

A voltage pulse is supplied to the input of the recording device from a resistor connected in series with the counter. A schematic diagram of switching on a gas-discharge counter for registering nuclear radiation is shown in Figure 314. According to the readings of an electronic counting device, the number of fast charged particles registered by the counter is determined.

scintillation counters.

The device of the simplest device designed to detect alpha particles, the spinthariscope, is shown in Figure 302. The main parts of the spinthariscope are screen 3, covered with a layer of zinc sulfide, and a short-focus magnifier 4. An alpha radioactive preparation is placed at the end of rod 1 approximately against the middle of the screen. When an alpha particle hits zinc sulfide crystals, a flash of light occurs, which can be registered when viewed through a magnifying glass.

The process of converting the kinetic energy of a fast charged particle into the energy of a light flash is called scintillation. Scintillation is one of the varieties of the phenomenon of luminescence. In modern scintillation counters, light flashes are registered using photocells, which convert the energy of a light flash in a crystal into the energy of an electric current pulse. The current pulses at the output of the photocell are amplified and then recorded.

Wilson chamber.

One of the most remarkable instruments of experimental nuclear physics is the cloud chamber. The appearance of the demonstration school cloud chamber is shown in Figure 315. In a cylindrical

a vessel with a flat glass lid contains air with saturated vapors of alcohol. The working volume of the chamber is connected to a rubber bulb through a tube. Inside the chamber, a radioactive preparation is fixed on a thin rod. To actuate the camera, the pear is first gently squeezed, then abruptly released. With rapid adiabatic expansion, the air and vapors in the chamber are cooled, the vapor passes into a state of supersaturation. If at this moment an alpha particle flies out of the preparation, a column of ions is formed along the path of its movement in the gas. Supersaturated vapor condenses into liquid droplets, and droplets are formed primarily on ions, which serve as centers of vapor condensation. A column of droplets condensed on ions along the trajectory of a particle is called a particle track.

To perform accurate measurements of the physical characteristics of the detected particles, the cloud chamber is placed in a constant magnetic field. Tracks of particles moving in a magnetic field turn out to be curved. The radius of curvature of the track depends on the speed of the particle, its mass and charge. With a known magnetic field induction, these characteristics of the particles can be determined from the measured radii of curvature of the particle tracks.

The first photographs of alpha particle tracks in a magnetic field were taken by the Soviet physicist P. L. Kapitsa in 1923.

The method of using a cloud chamber in a constant magnetic field to study the spectra of beta and gamma radiation and study elementary particles was first developed by Soviet physicist Academician Dmitry Vladimirovich Skobeltsin.

bubble chamber.

The principle of operation of the bubble chamber is as follows. The chamber contains liquid at a temperature close to the boiling point. Fast charged particles penetrate through a thin window in the chamber wall into its working volume and produce ionization and excitation of liquid atoms on their way. At the moment when the particles penetrate the working volume of the chamber, the pressure inside it is sharply reduced and the liquid passes into an overheated state. Ions that appear along the path of the particle have an excess of kinetic energy. This energy leads to an increase in the temperature of the liquid in a microscopic volume near each ion, its boiling and the formation of vapor bubbles. A chain of vapor bubbles that arise along the path of a fast charged particle through a liquid forms a trail of this particle.

In a bubble chamber, the density of any liquid is much higher than the density of a gas in a cloud chamber; therefore, it is possible to more effectively study the interactions of fast charged particles with atomic nuclei in it. Liquid hydrogen, propane, xenon and some other liquids are used to fill bubble chambers.

photographic emulsion method.

The photographic method is historically the first experimental method for detecting nuclear radiation, since the phenomenon of radioactivity was discovered by Becquerel using this method.

The ability of fast charged particles to create a latent image in a photographic emulsion is widely used in nuclear physics at the present time. Nuclear photographic emulsions are especially successfully used in research in the field of elementary particle and cosmic ray physics. A fast charged particle moving in a photoemulsion layer creates latent image centers along the path of motion. After development, an image appears of traces of the primary particle and all charged particles that appear in the emulsion as a result of nuclear interactions of the primary particle.

Questions.

1. According to Figure 170, tell about the device and the principle of operation of the Geiger counter.

The Geiger counter consists of a glass tube filled with a rarefied gas (argon) and sealed at both ends, inside of which there is a metal cylinder (cathode) and a wire stretched inside the cylinder (anode). The cathode and anode are connected through a resistance to a high voltage source (200-1000 V). Therefore, a strong electric field arises between the anode and cathode. When an ionizing particle enters the tube, an electron-ion avalanche is formed and an electric current appears in the circuit, which is recorded by a counting device.

2. Which particles are registered by a Geiger counter?

The Geiger counter is used to register electrons and ϒ-quanta.

3. According to Figure 171, tell us about the device and the principle of operation of the cloud chamber.

The cloud chamber is a low glass cylinder with a lid, a piston at the bottom and a mixture of alcohol and water saturated with steam. When the piston moves down, the vapors become supersaturated, i.e. capable of rapid condensation. When any particle enters the chamber through a special window, they create ions that become condensation nuclei and a trace (track) of condensed droplets appears along the trajectory of the particle, which can be photographed. If you place the camera in a magnetic field, then the trajectories of charged particles will be curved.

4. What characteristics of particles can be determined using a cloud chamber placed in a magnetic field?

By the direction of the bend, the charge of the particle is judged, and by the radius of curvature, one can find out the magnitude of the charge, mass and energy of the particle.

5. What is the advantage of a bubble chamber over a cloud chamber? How are these devices different?

In the bubble chamber, instead of supersaturated steam, a liquid superheated above the boiling point is used, which makes it faster.

In this article, we will help prepare for a lesson in physics (grade 9). particle research is not an ordinary topic, but a very interesting and exciting excursion into the world of molecular nuclear science. Civilization was able to achieve such a level of progress quite recently, and scientists are still arguing whether humanity needs such knowledge? After all, if people can repeat the process of an atomic explosion that led to the emergence of the Universe, then maybe not only our planet, but the entire Cosmos will be destroyed.

What particles are we talking about and why to study them

Partial answers to these questions are given by the course of physics. Experimental particle research is a way to see what is inaccessible to humans even with the most powerful microscopes. But first things first.

An elementary particle is a collective term that refers to particles that can no longer be split into smaller pieces. In total, more than 350 elementary particles have been discovered by physicists. We are most used to hearing about protons, neurons, electrons, photons, quarks. These are the so-called fundamental particles.

Characteristics of elementary particles

All the smallest particles have the same property: they can mutually transform under the influence of their own influence. Some have strong electromagnetic properties, others have weak gravitational properties. But all elementary particles are characterized by the following parameters:

• Weight.
• Spin is the intrinsic moment of momentum.
• Electric charge.
• Lifetime.
• Parity.
• magnetic moment.
• baryon charge.
• lepton charge.

A brief excursion into the theory of the structure of matter

Any substance consists of atoms, which in turn have a nucleus and electrons. Electrons, like the planets in the solar system, move around the nucleus, each on its own axis. The distance between them is very large, on an atomic scale. The nucleus consists of protons and neurons, the connection between them is so strong that it is impossible to separate them in any way known to science. This is the essence of experimental methods for studying particles (briefly).

It is hard for us to imagine this, but nuclear communication surpasses all forces known on earth by millions of times. We know chemical, nuclear explosion. But what holds the protons and neurons together is something else. Perhaps this is the key to unraveling the mystery of the origin of the universe. That is why it is so important to study experimental methods for studying particles.

Numerous experiments led scientists to the idea that neurons are made up of even smaller units and called them quarks. What is inside them is not yet known. But quarks are inseparable units. That is, there is no way to single out one. If scientists use particle experimentation to isolate one quark, no matter how many attempts they make, at least two quarks are always released. This once again confirms the indestructible strength of the nuclear potential.

What are the methods of studying particles

Let us proceed directly to the experimental methods for studying particles (Table 1).

Method name		Operating principle
	Glow (luminescence)	The radioactive drug emits waves, due to which the particles collide and individual glows can be observed.
	Ionization of gas molecules by fast charged particles	It lowers the piston at high speed, which leads to strong cooling of the steam, which becomes supersaturated. Droplets of condensate indicate the trajectories of the chain of ions.
bubble chamber	Liquid ionization	The volume of the working space is filled with hot liquid hydrogen or propane, which is acted upon under pressure. Bring the state to overheated and sharply reduce the pressure. Charged particles, acting with even more energy, cause hydrogen or propane to boil. On the trajectory along which the particle moved, vapor droplets are formed.
Scintillation method (Spinthariscope)	Glow (luminescence)	When gas molecules are ionized, a large number of electron-ion pairs are produced. The greater the tension, the more free pairs arise until it reaches a peak and there is not a single free ion left. At this moment, the counter registers the particle. This is one of the first experimental methods for studying charged particles, and was invented five years later than the Geiger counter - in 1912. The structure is simple: a glass cylinder, inside - a piston. Below is a black cloth soaked in water and alcohol, so that the air in the chamber is saturated with their vapors. The piston begins to lower and raise, creating pressure, causing the gas to cool. Condensation should form, but it does not exist, since there is no condensation center (ion or dust grain) in the chamber. After that, the flask is raised to get particles - ions or dust. The particle begins to move and condensate forms along its trajectory, which can be seen. The path that a particle travels is called a track. The disadvantage of this method is that the range of particles is too small. This led to a more progressive theory based on a device with a denser medium. bubble chamber The following experimental method for studying particles has a similar principle of operation of a cloud chamber - Only instead of a saturated gas, there is a liquid in a glass flask. The basis of the theory is that under high pressure, a liquid cannot begin to boil above the boiling point. But as soon as a charged particle appears, the liquid begins to boil along the track of its movement, turning into a vapor state. The droplets of this process are captured by a camera. Method of thick-layer photographic emulsions Let's return to the table in physics "Experimental Methods for Investigating Particles". In it, along with the cloud chamber and the bubble method, a method for detecting particles using a thick-layer photographic emulsion was considered. The experiment was first staged by Soviet physicists L.V. Mysovsky and A.P. Zhdanov in 1928. The idea is very simple. For experiments, a plate covered with a thick layer of photographic emulsions is used. This photographic emulsion consists of silver bromide crystals. When a charged particle penetrates a crystal, it separates electrons from the atom, which form a hidden chain. It can be seen by developing the film. The resulting image allows you to calculate the energy and mass of the particle. In fact, the track is very short and microscopically small. But the method is good because the developed picture can be enlarged an infinite number of times, thereby studying it better. Scintillation Method It was first held by Rutherford in 1911, although the idea arose a little earlier from another scientist, W. Krupe. Despite the fact that the difference was 8 years, the device had to be improved during this time. The basic principle is that a screen coated with a luminescent substance will display flashes of light as a charged particle passes through. Atoms of a substance are excited when exposed to a particle with a powerful energy. At the moment of collision, a flash occurs, which is observed under a microscope. This method is very unpopular among physicists. It has several drawbacks. First, the accuracy of the results obtained depends very much on the visual acuity of the person. If you blink, you can miss a very important moment. The second is that with prolonged observation, the eyes get tired very quickly, and therefore, the study of atoms becomes impossible. conclusions There are several experimental methods for studying charged particles. Since the atoms of matter are so small that they are difficult to see even with the most powerful microscope, scientists have to experiment to understand what is in the middle of the center. At this stage in the development of civilization, a long way has been made and the most inaccessible elements have been studied. Perhaps it is in them that the secrets of the universe lie.