Last year, 2012, it was forty-five years since humanity decided to use atomic timekeeping to measure time as accurately as possible. In 1967, the International category of time ceased to be determined by astronomical scales - they were replaced by the cesium frequency standard. It was he who received the now popular name - atomic clocks. The exact time that they allow you to determine has an insignificant error of one second in three million years, which allows them to be used as a time standard in any corner of the world.
A bit of history
The very idea of using atomic vibrations for ultra-precise time measurement was first expressed in 1879 by the British physicist William Thomson. In the role of the emitter of resonator atoms, this scientist proposed the use of hydrogen. The first attempts to put the idea into practice were made only in the 1940s. twentieth century. And the world's first working atomic clock appeared in 1955 in the UK. Their creator was the British experimental physicist Dr. Louis Essen. This clock worked on the basis of vibrations of cesium-133 atoms, and thanks to them, scientists were finally able to measure time with much greater accuracy than before. Essen's first device allowed an error of no more than a second for every hundred years, but subsequently it increased many times over and the error per second can only accumulate in 2-3 hundreds of millions of years.
Atomic clock: how it works
How does this ingenious "device" work? As a resonant frequency generator, atomic clocks use molecules or atoms at the quantum level. establishes a connection between the system "atomic nucleus - electrons" with several discrete energy levels. If such a system is affected with a strictly specified frequency, then the transition of this system from a low level to a high one will occur. The reverse process is also possible: the transition of an atom from a higher level to a lower one, accompanied by the emission of energy. These phenomena can be controlled and recorded all energy jumps by creating something like an oscillatory circuit (it is also called an atomic oscillator). Its resonant frequency will correspond to the energy difference between neighboring atomic transition levels, divided by Planck's constant.
Such an oscillatory circuit has undeniable advantages over its mechanical and astronomical predecessors. For one such atomic oscillator, the resonant frequency of the atoms of any substance will be the same, which cannot be said about pendulums and piezocrystals. In addition, atoms do not change their properties over time and do not wear out. Therefore, atomic clocks are extremely accurate and almost eternal chronometer.
Accurate time and modern technologies
Telecommunication networks, satellite communications, GPS, NTP servers, electronic transactions on the stock exchange, online auctions, the procedure for buying tickets via the Internet - all these and many other phenomena have long been firmly established in our lives. But if humanity had not invented the atomic clock, all this simply would not have happened. Accurate time, synchronization with which allows you to minimize any errors, delays and delays, enables a person to make the most of this invaluable irreplaceable resource, which is never too much.
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 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 radiation periods, 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 is accepted as an 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, a new astronomical object, a millisecond pulsar, intervened in the dispute between the astronomical definition of the Time standard and the atomic clock that won it. These signals are as stable as the best atomic clocks
Did you know?
The first watch in Rus'
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 Rus' 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 the 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.
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 clocks gears perform vibrational movements and their movements are counted, then in atomic clocks oscillations 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, thanks to which it is 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 telecommunications 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 again change their energy states, and fall on the detector, which fixes when the largest number of incoming atoms will have the “correct” energy state. The maximum number of atoms with a changed energy state indicates that the frequency of the microwave field is chosen correctly, and then its value is fed into an electronic device - a frequency divider, which, reducing the frequency by an integer number of times, gets the number 1, which is the reference second.
Thus, the cesium atoms are used to check the correct frequency of the magnetic field produced by the crystal oscillator, helping to keep it constant.
This 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. Of the latest inventions - atomic clocks on 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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Atomic clock January 27th, 2016
Switzerland, or even Japan, will not be the birthplace of the world's first pocket watch with a built-in atomic time standard. The idea of their creation originated in the heart of the UK from the London-based brand Hoptroff
Atomic, or as they are also called "quantum clocks", is a device that measures time using natural vibrations associated with processes occurring at the level of atoms or molecules. Richard Hoptroff decided that it was time for modern gentlemen who are interested in high-tech devices to change their pocket mechanical watches for something more extravagant and extraordinary, and also in line with modern urban trends.
So, the public was shown an elegant pocket atomic watch Hoptroff No. 10, which can surprise the modern generation, tempted by an abundance of gadgets, not only with its retro style and fantastic accuracy, but also with its service life. According to the developers, having this watch with you, you will be able to remain the most punctual person for at least 5 billion years.
What else can you find out about them interesting ...
Photo 2. 
For all those who have never been interested in such watches, it is worth briefly describing the principle of their operation. Inside the "atomic device" there is nothing that resembles a classic mechanical watch. In Hoptroff no. 10 there are no mechanical parts as such. Instead, atomic pocket watches are equipped with a sealed chamber filled with a radioactive gaseous substance, the temperature of which is controlled by a special furnace. The exact timing is as follows: lasers excite the atoms of a chemical element, which is a kind of "filler" of the clock, and the resonator captures and measures each atomic transition. Today, the basic element of such devices is cesium. If we recall the SI system of units, then in it the value of a second is connected with the number of periods of electromagnetic radiation during the transition of cesium-133 atoms from one energy level to another.
Photo 3. 
If in smartphones the processor chip is considered the heart of the device, then in Hoptroff No. 10 this role is taken by the module-generator of the reference time. It is supplied by Symmetricom, and the chip itself was originally focused on use in the military industry - in unmanned aerial vehicles.
The CSAC atomic clock is equipped with a temperature-controlled thermostat containing a cesium vapor chamber. Under the influence of a laser on cesium-133 atoms, their transition from one energy state to another begins, for which a microwave resonator is used to measure it. Since 1967, the International System of Units (SI) has defined one second as 9,192,631,770 periods of electromagnetic radiation arising from the transition between two hyperfine levels of the ground state of the cesium-133 atom. Based on this, it is difficult to imagine a more technically accurate watch based on cesium. In time, with recent advances in timekeeping, new optical clocks based on an aluminum ion pulsing at ultraviolet frequency (100,000 times the microwave frequencies of cesium clocks) will be hundreds of times more accurate than atomic chronometers. To put it simply, Hoptroff's new No.10 pocket watch has an accuracy of 0.0015 seconds per year, 2.4 million times better than COSC standards.
Photo 4. 
The functional side of the device is also on the verge of fantasy. With it, you can find out: time, date, day of the week, year, latitude and longitude in different values, pressure, humidity, sidereal hours and minutes, tide forecast and many other indicators. The watch comes in gold, and it is planned to use 3D printing to create its precious metal case.
Richard Hoptrof sincerely believes that this particular production option for his offspring is the most preferable. To slightly change the design component of the design, it will not be necessary to rebuild the production line at all, but to use the functional flexibility of the 3D printing device for this. True, it is worth noting that the shown prototype watch was made in the classical way.
Photo 5. 
Time is very precious these days, and the pocket watch Hoptroff No. 10 is a direct confirmation of this. According to preliminary information, the first batch of nuclear devices will be 12 units, and as for the cost, the price for 1 copy will be $78,000.
Photo 6. 
According to Richard Hoptroff, Managing Director of the brand, Hoptroff's London residence played a key role in the idea. “In our quartz movements, we use a high-precision oscillatory system with a GPS signal. But in the center of London it is not so easy to catch this very signal. Once, during a trip to the Greenwich Observatory, I saw a Hewlett Packard atomic clock there and decided to purchase something similar for myself via the Internet. And I couldn't. Instead, I came across information about a Symmetricon chip, and after three days of thinking, I realized that it would be perfect for a pocket watch.”
The chip in question is the SA.45s cesium atomic clock (CSAC), a first generation of miniature atomic clocks for GPS receivers, backpack radios and drones. Despite its modest dimensions (40 mm x 34.75 mm), it is unlikely to fit in a wrist watch. Therefore, Hoptroff decided to equip a rather solid pocket model (82 mm in diameter) with them.
In addition to being the most accurate watch in the world, Hoptroff No 10 (the brand's tenth movement) also claims to be the first gold case made using 3D printing technology. Hoptroff is not yet sure how much gold will be needed to make the case (work on the first prototype was completed when the issue went to press), but he suggests that its cost will be “a minimum of several thousand pounds”. And with all the R&D required to develop the product (think of the tide function for harmonic constants for 3,000 different ports), you'd expect the final retail price to be around £50,000.
Gold case of model No. 10 at the exit from the 3D printer and in finished form
Buyers automatically become members of an exclusive club and will be required to sign a written commitment not to use the atomic clock chip as a weapon. “This is one of the terms of our contract with the supplier,” explains Mr. Hoptroff, “because the atomic chip was originally used in missile guidance systems.” Not much for being able to get a watch with impeccable accuracy.
The lucky owners of the No.10 by Hoptroff will have much more than just a high-precision watch at their disposal. The model also doubles as a pocket navigation device, allowing longitude to be determined to within one nautical mile, even after many years at sea, using a simple sextant. The model will receive two dials, but the design of one of them is still kept secret. The other is a whirlwind of counters displaying as many as 28 complications: from all possible chronometric functions and calendar indicators to a compass, thermometer, hygrometer (a device for measuring humidity levels), barometer, latitude and longitude counters, and an indicator of high / low tide. And this is not to mention the vital indicators of the state of the atomic thermostat.
Hoptroff plans to launch a number of new products, including an electronic version of George Daniels' legendary complicated Space Traveler watch. They are currently being worked on to integrate Bluetooth technology into the watch to store the wearer's personal information and allow automatic adjustment of complications such as the moon phase display.
When the light suddenly goes out and comes back on a little later, how do you know what time the clock needs to be set? Yes, I'm talking about electronic watches, which many of us probably have. Have you ever thought about how time is regulated? In this article, we will learn all about atomic clocks and how they make the whole world tick.
Atomic clocks tell time better than any other clock. They tell the time better than the rotation of the Earth and the movement of the stars. Without atomic clocks, GPS navigation would be impossible, would not be synchronized, and the position of the planets would not be known with sufficient accuracy for space probes and vehicles.
Atomic clocks are not radioactive. They don't rely on atomic decay. Moreover, they have a spring, just like regular watches. The biggest difference between standard clocks and atomic clocks is that oscillations in atomic clocks occur in the nucleus of an atom between the surrounding electrons. These oscillations can hardly be called parallel to the balance wheel in a winding watch, but both types of oscillation can be used to keep track of the passing time. The oscillation frequency within an atom is determined by the mass of the nucleus, gravity, and the electrostatic "spring" between the positive charge of the nucleus and the cloud of electrons around it.
What types of atomic clocks do we know?
Today there are different types of atomic clocks, but they are built on the same principles. The main difference is related to the element and means of detecting changes in the energy level. Among the different types of atomic clocks, there are the following:
- Cesium atomic clocks using beams of cesium atoms. The clock separates cesium atoms with different energy levels by a magnetic field.
- A hydrogen atomic clock keeps the hydrogen atoms at the right energy level in a container whose walls are made of a special material, so the atoms don't lose their high-energy state too quickly.
- Rubidium atomic clocks, the simplest and most compact of all, use a glass cell filled with rubidium gas.
The most accurate atomic clocks today use a cesium atom and a conventional magnetic field with detectors. In addition, cesium atoms are held back by laser beams, which reduces small frequency changes due to the Doppler effect.
How do cesium-based atomic clocks work?
Atoms have a characteristic vibrational frequency. A familiar example of frequency is the orange glow of sodium in table salt when thrown into a fire. The atom has many different frequencies, some in the radio range, some in the visible spectrum, and some in between. Cesium-133 is most often chosen for atomic clocks.
In order to cause the resonance of cesium atoms in an atomic clock, one of the transitions, or the resonant frequency, must be accurately measured. This is usually done by blocking the crystal oscillator in the fundamental microwave resonance of the cesium atom. This signal is in the microwave range of the radio frequency spectrum and has the same frequency as the signals from direct broadcast satellites. Engineers know how to create equipment for this region of the spectrum, down to the smallest detail.
To create a clock, cesium is first heated so that the atoms vaporize and pass through a high vacuum tube. First, they pass through a magnetic field, which selects atoms with the desired energy state; then they pass through an intense microwave field. The frequency of microwave energy jumps back and forth in a narrow band of frequencies, so that at some point it reaches a frequency of 9,192,631,770 hertz (Hz, or cycles per second). The range of the microwave oscillator is already close to this frequency, since it is produced by a precise crystal oscillator. When a cesium atom receives microwave energy of the desired frequency, it changes its energy state.
At the end of the tube, another magnetic field separates the atoms, which have changed their energy state if the microwave field was at the right frequency. The detector at the end of the tube gives an output proportional to the number of cesium atoms that hit it, and peaks when the microwave frequency is sufficiently true. This peak signal is needed for correction in order to bring the crystal oscillator, and hence the microwave field, to the desired frequency. This locked frequency is then divided by 9,192,631,770 to give the familiar one pulse per second that the real world needs.
When was the atomic clock invented?
In 1945, Columbia University physics professor Isidore Rabi proposed a clock that could be made using techniques developed in the 1930s. It was called the magnetic resonance atomic beam. By 1949, the National Bureau of Standards announced the creation of the world's first atomic clock based on the ammonia molecule, the vibrations of which were read, and by 1952 it had created the world's first atomic clock based on cesium atoms, NBS-1.
In 1955, the National Physical Laboratory in England built the first clock using a cesium beam as a calibration source. Over the next decade, more advanced watches were created. In 1967, during the 13th General Conference on Weights and Measures, the SI second was determined based on vibrations in the cesium atom. There was no better definition in the world timekeeping system than this. NBS-4, the world's most stable cesium clock, was completed in 1968 and was in use until 1990.
In 1999, NBS, renamed NIST, began working with the NIST-F1 clock, which was accurate to within one second every 20 million years. 
How is atomic time measured?
The correct frequency for a cesium particle to resonate today is internationally agreed to be 9,192,631,770 hertz, so dividing the output by this number should give 1 Hz, or 1 cycle per second.
The accuracy of measuring time is a million times compared to astronomical methods. Today it loses one second in five billion years.
