Firstly, the clock uses humanity as a means of program-time control.
Secondly, today the measurement of time is also the most accurate type of measurement of all conducted: the accuracy of time measurement is now determined by an incredibly error of the order of 1 10-11%, or 1 s in 300 thousand years.
And modern people achieved such accuracy when they began to use atoms, which, as a result of their oscillations, are the regulator of the atomic clock. Cesium atoms are in the two energy states we need (+) and (-). Electromagnetic radiation with a frequency of 9,192,631,770 hertz is produced when atoms move from the state (+) to (-), creating a precise constant periodic process - the controller of the atomic clock code.
In order for atomic clocks to work accurately, cesium must be evaporated in a furnace, as a result of which its atoms are ejected. Behind the oven is a sorting magnet, which has throughput atoms in the (+) state, and in it, due to irradiation in a microwave field, the atoms go into the (-) state. The second magnet directs atoms that have changed state (+) to (-) to the receiving device. Many atoms that have changed their state are obtained only if the frequency of the microwave emitter coincides exactly with the frequency of vibrations of cesium 9 192 631 770 hertz. Otherwise, the number of atoms (-) in the receiver decreases.
Instruments constantly monitor and adjust the constancy of the frequency 9 192 631 770 hertz. So, the dream of watch designers came true, an absolutely constant periodic process was found: the frequency of 9,192,631,770 hertz, which regulates the course of atomic clocks.
Today, as a result of international agreement, the second is defined as the period of radiation multiplied by 9,192,631,770, corresponding to the transition between two hyperfine structural levels of the ground state of the cesium atom (cesium-133 isotope).
To measure the exact time, you can also use vibrations of other atoms and molecules, such as atoms of calcium, rubidium, cesium, strontium, hydrogen molecules, iodine, methane, etc. However, the radiation of the cesium atom is recognized as the frequency standard. In order to compare the vibrations of different atoms with a standard (cesium), a titanium-sapphire laser was created that generates a wide frequency range in the range from 400 to 1000 nm.
The first creator of quartz and atomic clocks was an English experimental physicist Essen Lewis (1908-1997). In 1955, he created the first atomic frequency (time) standard on a beam of cesium atoms. As a result of this work, 3 years later (1958) a time service emerged based on the atomic frequency standard.
In the USSR, Academician Nikolai Gennadievich Basov put forward his ideas for creating atomic clocks.
So, atomic clock, one of the exact types of clocks is a device for measuring time, where the natural oscillations of atoms or molecules are used as a pendulum. The stability of atomic clocks is the best among all existing types hours, which is a pledge highest precision. The atomic clock generator produces more than 32,768 pulses per second, unlike conventional clocks. Oscillations of atoms do not depend on air temperature, vibrations, humidity and many other external factors.
AT modern world, when navigation is simply indispensable, atomic clocks have become indispensable assistants. They are able to locate spaceship, satellite, ballistic missile, aircraft, submarine, car automatically by satellite.
Thus, for the last 50 years, atomic clocks, or rather cesium clocks, have been considered the most accurate. They have long been used by timekeeping services, and time signals are also broadcast by some radio stations.
The atomic clock device includes 3 parts: 
quantum Discriminator,
quartz oscillator,
electronics complex.
A quartz oscillator generates a frequency (5 or 10 MHz). The oscillator is an RC radio generator, in which the piezoelectric modes of a quartz crystal are used as a resonant element, where the atoms that have changed the state (+) to (-) are compared. To increase stability, its frequency is constantly compared with the oscillations of a quantum discriminator (atoms or molecules) . When there is a difference in oscillations, the electronics adjusts the frequency of the quartz oscillator to zero, thereby increasing the stability and accuracy of the watch to the desired level.
In the modern world, atomic clocks can be made in any country of the world for use in Everyday life. They are very small in size and beautiful. The size of the latest novelty of atomic clocks is not more than matchbox and their low power consumption - less than 1 Watt. And this is not the limit, perhaps in the future technical progress reaches mobile phones. In the meantime, compact atomic clocks are installed only on strategic missiles to increase the accuracy of navigation many times over.
Today, men's and women's atomic watches for every taste and budget can be bought in online stores.
In 2011, the world's smallest atomic clock was created by Symmetricom and the Sandia National Laboratory. This watch, 100 times more compact than previous commercially available versions. The size of an atomic chronometer is no larger than a matchbox. It needs 100 mW of power to operate, which is 100 times less than its predecessors.
It was possible to reduce the size of the clock by installing instead of springs and gears a mechanism that operates on the principle of determining the frequency of electromagnetic waves emitted by cesium atoms under the influence of a laser beam of negligible power.
Such clocks are used in navigation, as well as in the work of miners, divers, where it is necessary to accurately synchronize time with colleagues on the surface, as well as accurate time services, because the error of atomic clocks is less than 0.000001 fractions of a second per day. The cost of the record-breaking small Symmetricom atomic clock was about $1,500.
A new impetus in the development of devices for measuring time was given by atomic physicists.
In 1949, the first atomic clock was built, where the source of oscillations was not a pendulum or a quartz oscillator, but signals associated with the quantum transition of an electron between two energy levels of an atom.
In practice, such clocks turned out to be not very accurate, moreover, they were bulky and expensive and were not widely used. Then it was decided to turn to the chemical element - cesium. And in 1955, the first atomic clock based on cesium atoms appeared.
In 1967, it was decided to switch to the atomic time standard, since the Earth's rotation is slowing down and the magnitude of this slowdown is not constant. This greatly hampered the work of astronomers and the keepers of Time.
The Earth is currently spinning at a rate of about 2 milliseconds per 100 years.
Fluctuations in the duration of the day also reach thousandths of a second. Therefore, the accuracy of Greenwich Mean Time (the world standard since 1884) has become insufficient. In 1967, the transition to the atomic time standard took place.
Today, a second is a period of time exactly equal to 9,192,631,770 periods of radiation, which corresponds to the transition between two hyperfine levels of the ground state of the Cesium 133 atom.
At the moment, Coordinated Universal Time is used as the time scale. It is formed by the International Bureau of Weights and Measures by combining data from the timekeeping laboratories of various countries, as well as data from the International Earth Rotation Service. Its accuracy is almost a million times better than the astronomical Greenwich Mean Time.
A technology has been developed that will make it possible to radically reduce the size and cost of ultra-precise atomic clocks, which will make it possible to widely use them in mobile devices for various purposes. Scientists were able to create an atomic time standard of ultra-small size. Such atomic clocks consume less than 0.075 W and have an error of no more than one second in 300 years.
A US research team has succeeded in creating an ultra-compact atomic standard. It became possible to power atomic clocks from conventional AA batteries. Ultra-precise atomic clocks, usually at least a meter high, were placed in a volume of 1.5x1.5x4 mm
An experimental atomic clock based on a single mercury ion has been developed in the United States. They are five times more accurate than cesium, which are accepted as international standard. Cesium clocks are so accurate that a difference of one second will be reached only after 70 million years, and for mercury clocks this period will be 400 million years.
In 1982, in a dispute between the astronomical definition of the standard of Time and those who defeated it atomic clock intervened a new astronomical object - a millisecond pulsar. These signals are as stable as the best atomic clocks
Did you know?
The first watch in Russia
In 1412, a clock was placed in Moscow in the courtyard of the Grand Duke behind the Church of the Annunciation, and Lazar, a Serb monk who came from the Serbian land, made them. Unfortunately, the description of these first clocks in Russia has not been preserved.
________How did the chimes appear on the Spasskaya Tower of the Moscow Kremlin?
In the 17th century, the Englishman Christopher Galovey made chimes for the Spasskaya Tower: the hour circle was divided into 17 sectors, the only clock hand was motionless, pointing down and pointing at any number on the dial, but the dial itself rotated.
Have you ever noticed that your clock in the house is showing different time? And how to understand which of all the options is correct? We will learn the answers to all these questions by thoroughly studying the principle of operation of atomic clocks.
Atomic clock: description and principle of operation
Let's first understand what the mechanism of an atomic clock is. An atomic clock is a device that measures time, but it uses its own vibrations as the periodicity of the process, and everything happens at the atomic and molecular level. Hence the accuracy.
It is safe to say that atomic clocks are the most accurate! It is thanks to them that the Internet and GPS navigation function in the world, we know the exact location of the planets in solar system. The error of this device is so minimal that we can confidently say that they are world-class! Thanks to atomic clocks, the entire world synchronization takes place, it is known where certain changes are located.
Who invented, who created, and also who came up with this miracle watch?
Back in the early forties of the twentieth century, it was known about the atomic beam of magnetic resonance. At first, its application did not concern watches in any way - it was only a theory. But already in 1945, Isidor Rabi proposed to create a device, the concept of which was that they work on the basis of the above technique. But they were arranged in such a way that they showed inaccurate results. And already in 1949, the National Bureau of Standards informed the whole world about the creation of the first atomic clock, which was based on molecular compounds of ammonia, and already in 1952, technologies were mastered to create a prototype based on cesium atoms.
Hearing about the atoms of ammonia and cesium, the question arises, but are these wonderful clocks radioactive? The answer is unequivocal - no! They do not have atomic decay.
Nowadays, there are many materials from which atomic clocks are made. For example, it is silicon, quartz, aluminum and even silver.
How does the device work?
Let's take a look at how nuclear-powered clocks look and work. To do this, we offer a description of their work:
For the correct functioning of this particular clock, not a pendulum is needed, nor a quartz oscillator. They use signals that arise due to the quantum transition of one electron between two energy levels of an atom. As a result, we are able to observe an electromagnetic wave. In other words, we get frequent fluctuations and an ultra-high level of system stability. Every year, due to new discoveries, processes are modernized. Not so long ago, the specialists of The National Institute fStandardsand Technology (NIST) became champions, setting an absolute world record. They were able to bring the accuracy of the atomic clock (based on strontium) to the very minimum deviation, namely: for 15 billion years, one second runs. Yes, yes, it didn’t seem to you that this is the age that is now being assigned to our Universe. This is a huge discovery! After all, it was strontium that played the most important role in this record. The moving atoms of strontium in its spatial lattice, which scientists created using a laser, acted as an analogue of the “ticking”. As always in science, in theory everything seems enchanting and already improved, but the instability of such a system may turn out to be less joyful in practice. It is because of its instability that the cesium-based device gained worldwide popularity.
Now consider what such a device consists of. The main details here are:
- quantum discriminator;
- quartz generator;
- electronics.
A quartz oscillator is a kind of self-oscillator, but to produce a resonant element, it uses piezoelectric modes of a quartz crystal.
Having a quantum discriminator and a quartz oscillator, under the influence of their frequency, they are compared and, if a difference is detected, the circuit feedback requires the crystal oscillator to adjust to the required value and improve stability and accuracy. As a result, at the output we see on the dial exact value, which means exact time.
Early models had quite big sizes, however, in October 2013, BathysHawaii made a splash by releasing miniature nuclear wrist watch. At first, everyone took this statement as a joke, but it soon became clear that it was really true, and they function on the basis of the atomic source Cesium 133. The safety of the device is ensured by the fact that the radioactive element is contained in the form of a gas in a special capsule. Photos of this device scattered around the world.
Many in the topic of atomic clocks are interested in the issue of a power source. The battery is a lithium-ion battery. But alas, it is not yet known how long such a battery will last.
The BathysHawaii watch was truly the first atomic wrist watch. Previously, cases of release of a relatively portable device were already known, but, unfortunately, it did not have an atomic power source, but only synchronized with real overall clocks via wireless radio. It is also worth mentioning the cost of such a gadget. The pleasure was estimated at 12 thousand US dollars. It was clear that with such a price, watches would not gain wide popularity, but the company did not strive for this, because they released them in a very limited batch.
We know of several types of atomic clocks. There are no significant differences in their design and principles, but there are still some differences. So, the main ones are in the means of finding changes and their elements. The following types of watches can be distinguished:
- Hydrogen. Their essence lies in the fact that hydrogen atoms are supported at the right level of energy, but the walls are made of special material. Based on this, we conclude that it is hydrogen atoms that very quickly lose their energy state.
- cesium. The basis for them are cesium beams. It is worth noting that these watches are the most accurate.
- Rubidium. They are the simplest and very compact.
As mentioned earlier, atomic clocks are a very expensive gadget. Thus, the pocket watch Hoptroff No. 10 is a bright representative of a new generation of toys. The price of such a stylish and very accurate accessory is 78 thousand dollars. Only 12 copies were released. The mechanism of this device uses a high-frequency oscillatory system, which is also equipped with a GPS signal.
The company did not stop there and it is in its tenth version of the watch that it wants to apply the method of placing the movement in a gold case, which will be printed on a popular 3D printer. It has not yet been calculated exactly how much gold will be used for this version of the case, but the estimated retail price of this masterpiece is already known - it amounted to about 50 thousand pounds sterling. And this is not the final price, although it takes into account all the volumes of research, as well as the novelty and uniqueness of the gadget itself.
Historical facts about the use of watches
How, when talking about atomic clocks, not to mention the most interesting facts, which are associated with them and time in general:
- Did you know that in ancient egypt the oldest sundial ever found?
- The error of atomic clocks is minimal - it is only 1 second for 6 million years.
- Everyone knows that there are 60 seconds in a minute. But few people delved into how many milliseconds are in one second? And they are not many and not few - a thousand!
- Every tourist who was able to visit London was sure to want to see Big Ben with their own eyes. But unfortunately, not many people know that Big Ben is not a tower at all, but the name of a huge bell that weighs 13 tons and rings inside the tower.
- Have you ever wondered why the hands of our clocks go exactly from left to right, or how we used to say “clockwise”? This fact is directly related to how the shadow moves on the sundial.
- The very first wristwatch was invented in the recent 1812. They were made by the founder of Breguet for the Queen of Naples.
- Before the First World War, wrist watches were considered only a women's accessory, but soon, due to their convenience, they were also chosen by the male part of the population.
Atomic clocks are the most accurate time-measuring instruments in existence today, and are becoming increasingly popular. greater value with development and complication modern technologies.
Principle of operation
Atomic clocks keep accurate time not due to radioactive decay, as it might seem from their name, but using vibrations of nuclei and the electrons surrounding them. Their frequency is determined by the mass of the nucleus, gravity and the electrostatic "balancer" between the positively charged nucleus and electrons. It doesn't quite match the usual clockwork. Atomic clocks are more reliable time keepers because their fluctuations do not change depending on such factors. environment like humidity, temperature or pressure.
The evolution of atomic clocks
Over the years, scientists have realized that atoms have resonant frequencies associated with the ability of each to absorb and emit electromagnetic radiation. In the 1930s and 1940s, high-frequency communications and radar equipment was developed that could interact with the resonance frequencies of atoms and molecules. This contributed to the idea of the watch.
The first copies were built in 1949 National Institute standards and technologies (NIST). Ammonia was used as a vibration source. However, they were not much more accurate than the existing time standard, and cesium was used in the next generation.
new standard
The change in time accuracy was so great that in 1967 the General Conference on Weights and Measures defined the SI second as 9,192,631,770 vibrations of a cesium atom at its resonant frequency. This meant that time was no longer related to the movement of the Earth. The most stable atomic clock in the world was created in 1968 and was used as part of the NIST time reference system until the 1990s.
Improvement car
One of the latest advances in this area is laser cooling. This improved the signal-to-noise ratio and reduced the uncertainty in the clock signal. This cooling system and other equipment used to improve the cesium clock would require space the size of a railroad car to house it, although commercial options can fit in a suitcase. One of these laboratory facilities counts time in Boulder, Colorado, and is the most precise clock on the ground. They are only wrong by 2 nanoseconds per day, or 1 s in 1.4 million years.
Sophisticated technology
This tremendous accuracy is the result of complex technological process. First of all, liquid cesium is placed in a furnace and heated until it turns into a gas. The metal atoms exit at high speed through a small hole in the furnace. Electromagnets cause them to separate into separate beams with different energies. The required beam passes through the U-shaped hole, and the atoms are exposed to microwave energy at a frequency of 9.192.631.770 Hz. Due to this, they are excited and move into a different energy state. The magnetic field then filters out the other energy states of the atoms.
The detector responds to cesium and shows a maximum at the correct frequency value. This is necessary to set up the crystal oscillator that controls the clocking mechanism. Dividing its frequency by 9.192.631.770 gives one pulse per second.
Not only cesium
Although the most common atomic clocks use the properties of cesium, there are other types as well. They differ in the applied element and means of determining the change in energy level. Other materials are hydrogen and rubidium. Hydrogen atomic clocks function like cesium clocks, but require a container with walls made of a special material that prevents the atoms from losing energy too quickly. Rubidium watches are the most simple and compact. In them, a glass cell filled with gaseous rubidium changes the absorption of light when exposed to microwave frequency.
Who needs accurate time?
Today, time can be counted with extreme precision, but why is this important? This is necessary in systems such as mobile phones, internet, GPS, aviation programs and digital television. At first glance, this is not obvious.
An example of how accurate time is used is packet synchronization. Through middle line communications go through thousands of phone calls. This is possible only because the conversation is not transmitted completely. The telecom company splits it into small packets and even skips some of the information. Then they pass through the line along with packets of other conversations and are restored at the other end without mixing. The telephone exchange clock system can determine which packets belong to a given conversation by the exact time the information was sent.
GPS
Another implementation of precise time is the global positioning system. It consists of 24 satellites that transmit their coordinates and time. Any GPS receiver can connect to them and compare broadcast times. The difference allows the user to determine their location. If these clocks were not very accurate, then the GPS system would be impractical and unreliable.
The limit of perfection
With the development of technology and atomic clocks, the inaccuracies of the universe became noticeable. The Earth moves unevenly, which leads to random fluctuations in the length of years and days. In the past, these changes would have gone unnoticed because timekeeping tools were too inaccurate. However, much to the dismay of researchers and scientists, the time of atomic clocks has to be adjusted to compensate for anomalies. real world. They are amazing tools for advancing modern technology, but their perfection is limited by the limits set by nature itself.
Often we hear the phrase that atomic clocks always show the exact time. But from their name it is difficult to understand why atomic clocks are the most accurate or how they work.
The fact that the name contains the word "atomic" does not mean at all that the watch is a danger to life, even if thoughts of an atomic bomb or a nuclear power plant immediately come to mind. In this case, we are just talking about the principle of the clock. If in ordinary mechanical watch vibrational movements are made by gears and their movements are counted, then in atomic clocks vibrations of electrons inside atoms are counted. To better understand the principle of operation, let's recall the physics of elementary particles.
All substances in our world are made up of atoms. Atoms are made up of protons, neutrons and electrons. Protons and neutrons combine with each other to form a nucleus, which is also called a nucleon. Electrons move around the nucleus, which can be at different energy levels. The most interesting thing is that when absorbing or giving off energy, an electron can move from its energy level to a higher or lower one. An electron can receive energy from electromagnetic radiation by absorbing or emitting electromagnetic radiation of a certain frequency at each transition.
Most often there are watches in which atoms of the element Cesium -133 are used to change. If in 1 second the pendulum conventional watches makes 1 oscillatory motion, then the electrons in atomic clocks based on Cesium-133, when moving from one energy level to another, they emit electromagnetic radiation with a frequency of 9192631770 Hz. It turns out that one second is divided into exactly this number of intervals, if it is calculated in atomic clocks. This value was officially adopted by the international community in 1967. Imagine a huge dial, where there are not 60, but 9192631770 divisions, which are only 1 second. It is not surprising that atomic clocks are so accurate and have a number of advantages: atoms do not age, do not wear out, and the oscillation frequency will always be the same for one chemical element, which makes it possible to simultaneously compare, for example, the readings of atomic clocks far in space and on Earth, not afraid of mistakes.
Thanks to atomic clocks, mankind in practice was able to test the correctness of the theory of relativity and make sure that, than on Earth. Atomic clocks are installed on many satellites and spacecraft, they are used for telecommunication needs, for mobile communications, they compare the exact time on the entire planet. Without exaggeration, it was thanks to the invention of the atomic clock that humanity was able to enter the era of high technology.
How do atomic clocks work?
Cesium-133 is heated by evaporating cesium atoms, which are passed through a magnetic field, where atoms with the desired energy states are selected.
Then the selected atoms pass through a magnetic field with a frequency close to 9192631770 Hz, which creates a quartz oscillator. Under the influence of the field, the cesium atoms change their energy states again, and fall on the detector, which fixes when the largest number falling atoms will have the "correct" energy state. Maximum amount atoms with a changed energy state indicates that the frequency of the microwave field is chosen correctly, and then its value is fed into electronic device- frequency divider, which, reducing the frequency by an integer number of times, gets the number 1, which is the reference second.
So cesium atoms are used to check if the frequency is correct magnetic field generated by the crystal oscillator, helping to keep it constant.
It is interesting: although the atomic clocks that exist today are unprecedentedly accurate and can run without errors for millions of years, physicists are not going to stop there. Using atoms of various chemical elements, they are constantly working to improve the accuracy of atomic clocks. From latest inventions- atomic clock strontium, which are three times more accurate than their cesium counterpart. It would take them 15 billion years to be just a second behind – a time longer than the age of our universe…
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