Atomic clock: operating principle.

An atomic clock is a device for very precise measurement of time. They got their name from the principle of their operation, since the natural vibrations of molecules or atoms are used as the period. Atomic clocks have found very wide application in navigation, in the space industry, for determining the location of satellites, in the military field, for the detection of aircraft, and also in telecommunications.

As you can see, there are a lot of areas of application, but why do they all need such accuracy, because today the error of conventional atomic clocks is only 1 second in 30 million years? But there is something even more precise. Everything is understandable, because time is used to calculate distances, and there a small error can lead to hundreds of meters, or even kilometers, if we take cosmic distances. For example, let’s take the American GPS navigation system; when using a conventional electronic clock in the receiver, the error in measuring coordinates will be quite significant, which can affect all other calculations, and this can lead to consequences if we're talking about about space technologies. Naturally for GPS receivers in mobile devices and other gadgets, greater accuracy is not at all important.

The most exact time in Moscow and the world, you can find out on the official website - “server of exact current time” www.timeserver.ru

What are atomic clocks made of?

An atomic clock consists of several main parts: a quartz oscillator, a quantum discriminator and electronics units. The main one that sets the reference is a quartz oscillator, which is built on quartz crystals and, as a rule, produces a standard frequency of 10, 5, 2.5 MHz. Because stable work quartz without error is quite small; it must be constantly adjusted.

The quantum discriminator records the frequency of the atomic line, and it is compared in the frequency-phase comparator with the frequency of the quartz oscillator. The comparator has feedback to the quartz oscillator to adjust it in case of frequency mismatch.
Atomic clocks cannot be built on all atoms. The most optimal is the cesium atom. It refers to the primary one by which all others are compared suitable materials, for example, such as: strontium, rubidium, calcium. The primary standard is absolutely suitable for measuring precise time, which is why it is called primary.

The most accurate atomic clock in the world

To date most accurate atomic clock are located in the UK (officially adopted). Their error is only 1 second in 138 million years. They are the standard for the national time standards of many countries, including the United States, and also determine international atomic time. But the kingdom contains not the most accurate clocks on Earth.

most accurate atomic clock photo

The United States announced that it had developed an experimental type of precise clock based on cesium atoms; its error was 1 second in almost 1.5 billion years. Science in this area does not stand still and is developing at a rapid pace.

Highly accurate atomic clocks that make an error of one second every 300 million years. This watch, which replaced old model, which allowed an error of one second in a hundred million years, now sets the standard for American civil time. Lenta.ru decided to recall the history of the creation of atomic clocks.

First atom

In order to create a clock, it is enough to use any periodic process. And the history of the appearance of time measuring instruments is partly the history of the emergence of either new energy sources or new oscillatory systems used in watches. The most simple watch are probably solar: for their operation, only the Sun and an object that casts a shadow are needed. The disadvantages of this method of determining time are obvious. Water and hourglass are also no better: they are suitable only for measuring relatively short periods of time.

The oldest mechanical clock was found in 1901 near the island of Antikythera on a sunken ship in the Aegean Sea. They contain about 30 bronze gears in a wooden case measuring 33 by 18 by 10 centimeters and date from about the hundredth year BC.

For almost two thousand years, mechanical watches were the most accurate and reliable. The appearance in 1657 of Christian Huygens's classic work “The Pendulum Clock” (“Horologium oscillatorium, sive de motu pendulorum an horologia aptato demonstrationes geometrica”), describing a time-keeping device with a pendulum as an oscillating system, was probably the apogee in the history of the development of mechanical instruments of such a type.

However, astronomers and sailors still used the starry sky and maps to determine their location and exact time. The first electric clock was invented in 1814 by Francis Ronalds. However, the first such device was inaccurate due to sensitivity to temperature changes.

The further history of watches is connected with the use of various oscillating systems in devices. Introduced in 1927 by Bell Laboratories, quartz clocks exploited the piezoelectric properties of a quartz crystal: when exposed to electric current the crystal begins to shrink. Modern quartz chronometers can be accurate to within 0.3 seconds per month. However, because quartz is susceptible to aging, watches become less accurate over time.

With the development of atomic physics, scientists proposed using particles of matter as oscillatory systems. This is how the first atomic clocks appeared. The idea of ​​​​the possibility of using atomic vibrations of hydrogen to measure time was proposed back in 1879 by the English physicist Lord Kelvin, but only by the middle of the 20th century did this become possible.

Reproduction of a painting by Hubert von Herkomer (1907)

In the 1930s, American physicist and nuclear pioneer magnetic resonance Isidor Rabi began working on atomic clock with cesium-133, but the outbreak of war prevented him. After the war, in 1949, the first molecular clock using ammonia molecules was created at the US National Standards Committee with the participation of Harold Lyonson. But the first such time measuring instruments were not as accurate as modern atomic clocks.

The relatively low accuracy was due to the fact that due to the interaction of ammonia molecules with each other and with the walls of the container in which this substance was located, the energy of the molecules changed and their spectral lines broadened. This effect is very similar to friction in a mechanical watch.

Later, in 1955, Louis Essen of the UK National Physical Laboratory introduced the first cesium-133 atomic clock. This clock accumulated an error of one second over a million years. The device was named NBS-1 and began to be considered a cesium frequency standard.

Schematic diagram atomic clock consists of a quartz oscillator controlled by a discriminator according to the circuit feedback. The oscillator uses the piezoelectric properties of quartz, while the discriminator uses the energetic vibrations of the atoms so that the vibrations of the quartz are tracked by signals from transitions from different energy levels in the atoms or molecules. Between the generator and the discriminator there is a compensator tuned to the frequency of atomic vibrations and comparing it with the vibration frequency of the crystal.

The atoms used in the clock must provide stable vibrations. For each frequency of electromagnetic radiation, there are atoms: calcium, strontium, rubidium, cesium, hydrogen. Or even molecules of ammonia and iodine.

Time standard

With the advent of atomic time measuring instruments, it became possible to use them as a universal standard for determining the second. Since 1884, Greenwich Time, considered the world standard, has given way to the standard of atomic clocks. In 1967, by decision of the 12th General Conference of Weights and Measures, one second was defined as the duration of 9192631770 periods of radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom. This definition of the second does not depend on astronomical parameters and can be reproduced anywhere on the planet. Cesium-133, used in the atomic clock standard, is the only stable isotope of cesium with 100% abundance on Earth.

Atomic clocks are also used in satellite navigation systems; they are necessary to determine the exact time and satellite coordinates. Thus, each GPS satellite has four sets of such clocks: two rubidium and two cesium, which ensure signal transmission accuracy of 50 nanoseconds. The Russian satellites of the GLONASS system are also equipped with cesium and rubidium atomic time measuring instruments, and the satellites of the deploying European Galileo geopositioning system are equipped with hydrogen and rubidium ones.

The accuracy of hydrogen clocks is the highest. It is 0.45 nanoseconds in 12 hours. Apparently, Galileo's use of such accurate clocks will make this navigation system a leader already in 2015, when there will be 18 of its satellites in orbit.

Compact atomic clock

Hewlett-Packard became the first company to develop a compact atomic clock. In 1964, she created the HP 5060A cesium device, the size of a large suitcase. The company continued to develop this direction, but in 2005 it sold its division developing atomic clocks to Symmetricom.

In 2011, specialists from Draper Laboratory and Sandia National Laboratories developed and Symmetricom released the first miniature atomic clock, Quantum. At the time of release, they cost about 15 thousand dollars, were enclosed in a sealed case measuring 40 by 35 by 11 millimeters and weighed 35 grams. The power consumption of the clock was less than 120 milliwatts. They were originally developed by order of the Pentagon and were intended to serve navigation systems operating independently of GPS systems, for example, deep under water or ground.

Already at the end of 2013 American company Bathys Hawaii introduced the first atomic wristwatch. They use the SA.45s chip manufactured by Symmetricom as the main component. Inside the chip there is a capsule with cesium-133. The design of the watch also includes photocells and a low-power laser. The latter ensures the heating of cesium gas, as a result of which its atoms begin to move from one energy level to another. The measurement of time is precisely carried out by recording such a transition. The cost of a new device is about 12 thousand dollars.

Trends towards miniaturization, autonomy and accuracy will lead to the fact that in the near future new devices using atomic clocks will appear in all spheres of human life, from space research on orbiting satellites and stations to household applications in room and wrist systems.

Isidor Rabi, a physics professor at Columbia University, has proposed a never-before-seen project: a clock operating on the principle of an atomic beam of magnetic resonance. This happened in 1945, and already in 1949 the National Bureau of Standards released the first working prototype. It read the vibrations of the ammonia molecule. Cesium came into use much later: the NBS-1 model appeared only in 1952.

The National Physical Laboratory in England created the first cesium beam clock in 1955. More than ten years later, during the General Conference on Weights and Measures, a more advanced clock was presented, also based on vibrations in the cesium atom. Model NBS-4 was used until 1990.

Types of watches

At the moment, there are three types of atomic clocks, which work on approximately the same principle. Cesium clocks, the most accurate, separate the cesium atom magnetic field. The simplest atomic clock, the rubidium clock, uses rubidium gas contained in glass flask. And finally, the hydrogen atomic clock takes as its reference point hydrogen atoms, closed in a shell of a special material - it prevents the atoms from quickly losing energy.

What time is it now

In 1999, the US National Institute of Standards and Technology (NIST) proposed an even more advanced version of the atomic clock. The NIST-F1 model allows for an error of only one second every twenty million years.

The most accurate

But NIST physicists didn't stop there. Scientists decided to develop a new chronometer, this time based on strontium atoms. The new watch operates at 60% of the previous model, which means that it loses one second not in twenty million years, but in as many as five billion.

Measuring time

International agreement has determined the only precise frequency for the resonance of a cesium particle. This is 9,192,631,770 hertz - dividing the output signal by this number equals exactly one cycle per second.

Which “watchmakers” invented and perfected this extremely precise mechanism? Is there a replacement for him? Let's try to figure it out.

In 2012, atomic timekeeping will celebrate its forty-fifth anniversary. In 1967, the category of time in International system units began to be determined not by astronomical scales, but by the cesium frequency standard. This is what the common people call the atomic clock.

What is the operating principle of atomic oscillators? These “devices” use quantum energy levels of atoms or molecules as a source of resonant frequency. Quantum mechanics relates to the system " atomic nucleus- electrons" several discrete energy levels. An electromagnetic field of a certain frequency can provoke a transition of this system from a low level to a higher one. The opposite phenomenon is also possible: an atom can move from a high energy level to a lower one by emitting energy. Both phenomena can be controlled and record these energy interlevel jumps, thereby creating a semblance of an oscillatory circuit. The resonant frequency of this circuit will be equal to the difference in the energies of the two transition levels divided by Planck’s constant.

The resulting atomic oscillator has undoubted advantages over its astronomical and mechanical predecessors. The resonant frequency of all atoms of the substance chosen for the oscillator will be, unlike pendulums and piezocrystals, the same. In addition, atoms do not wear out or change their properties over time. Perfect option for a virtually eternal and extremely precise chronometer.

For the first time, the possibility of using interlevel energy transitions in atoms as a frequency standard was considered back in 1879. British physicist William Thomson, better known as Lord Kelvin. He proposed using hydrogen as a source of resonator atoms. However, his research was rather theoretical in nature. Science at that time was not yet ready to develop an atomic chronometer.

It took almost a hundred years for Lord Kelvin's idea to come to fruition. It was a long time, but the task was not easy. Transforming atoms into ideal pendulums turned out to be more difficult in practice than in theory. The difficulty lay in the battle with the so-called resonant width - a small fluctuation in the frequency of absorption and emission of energy as atoms move from level to level. The ratio of the resonant frequency to the resonant width determines the quality of the atomic oscillator. Obviously, the larger the value of the resonant width, the lower the quality of the atomic pendulum. Unfortunately, it is not possible to increase the resonant frequency to improve quality. It is constant for the atoms of each specific substance. But the resonant width can be reduced by increasing the time of observation of atoms.

Technically, this can be achieved as follows: let an external, for example quartz, oscillator periodically generate electromagnetic radiation, causing the atoms of the donor substance to jump across energy levels. In this case, the task of the atomic chronograph tuner is to bring the frequency of this quartz oscillator as close as possible to the resonant frequency of the interlevel transition of atoms. This becomes possible in the case of a sufficiently long period of observation of atomic vibrations and the creation of feedback that regulates the frequency of quartz.

True, in addition to the problem of reducing the resonant width in an atomic chronograph, there are a lot of other problems. This is the Doppler effect - a shift in the resonant frequency due to the movement of atoms, and mutual collisions of atoms, causing unplanned energy transitions, and even the influence of the pervasive energy of dark matter.

The first attempt at the practical implementation of atomic clocks was made in the thirties of the last century by scientists at Columbia University under the leadership of the future Nobel laureate Dr. Isidor Rabi. Rabi proposed using the cesium isotope 133 Cs as a source of pendulum atoms. Unfortunately, Rabi's work, which greatly interested NBS, was interrupted by World War II.

After its completion, the lead in the implementation of the atomic chronograph passed to NBS employee Harold Lyons. His atomic oscillator ran on ammonia and gave an error comparable to the best examples of quartz resonators. In 1949, the ammonia atomic clock was demonstrated to the general public. Despite the rather mediocre accuracy, they implemented the basic principles of future generations of atomic chronographs.

The prototype of a cesium atomic clock obtained by Louis Essen provided an accuracy of 1 * 10 -9, while having a resonance width of only 340 Hertz

A little later, Harvard University professor Norman Ramsey improved Isidor Rabi's ideas, reducing the impact of the Doppler effect on the accuracy of measurements. He proposed, instead of one long high-frequency pulse exciting atoms, to use two short ones sent to the arms of the waveguide at some distance from each other. This made it possible to sharply reduce the resonant width and actually made it possible to create atomic oscillators that are an order of magnitude superior in accuracy to their quartz ancestors.

In the fifties of the last century, based on the scheme proposed by Norman Ramsey, at the National Physical Laboratory (UK), its employee Louis Essen worked on an atomic oscillator based on the cesium isotope 133 Cs previously proposed by Rabi. Cesium was not chosen by chance.

Scheme of hyperfine transition levels of atoms of the cesium-133 isotope

Belonging to the group of alkali metals, cesium atoms are extremely easily excited to jump between energy levels. For example, a beam of light can easily knock out a flow of electrons from the cesium atomic structure. It is due to this property that cesium is widely used in photodetectors.

Design of a classical cesium oscillator based on a Ramsey waveguide

First official cesium frequency standard NBS-1

Descendant of NBS-1 - the NIST-7 oscillator used laser pumping of a beam of cesium atoms

It took more than four years for the Essen prototype to become a true standard. After all, precise adjustment of atomic clocks was possible only by comparison with existing ephemeris units of time. Over the course of four years, the atomic oscillator was calibrated by observing the Moon's rotation around the Earth using a precision lunar camera invented by the US Naval Observatory's William Markowitz.

The "adjustment" of atomic clocks to lunar ephemeris was carried out from 1955 to 1958, after which the device was officially recognized by the NBS as a frequency standard. Moreover, the unprecedented accuracy of cesium atomic clocks prompted NBS to change the unit of time in the SI standard. Since 1958, the second has been officially adopted as “the duration of 9,192,631,770 periods of radiation corresponding to the transition between two hyperfine levels of the standard state of an atom of the cesium-133 isotope.”

Louis Essen's device was named NBS-1 and was considered the first cesium frequency standard.

Over the next thirty years, six modifications of NBS-1 were developed, the latest of which, NIST-7, created in 1993 by replacing magnets with laser traps, provides an accuracy of 5 * 10 -15 with a resonant width of only sixty-two Hertz.

Comparison table of characteristics of cesium frequency standards used by NBS

NBS devices are stationary stands, which allows them to be classified as standards rather than practically used oscillators. But for purely practical purposes, Hewlett-Packard worked for the benefit of the cesium frequency standard. In 1964, the future computer giant created a compact version of the cesium frequency standard - the HP 5060A device.

Calibrated using NBS standards, the HP 5060 frequency standards fit into a typical radio equipment rack and were a commercial success. It was thanks to the cesium frequency standard set by Hewlett-Packard that the unprecedented accuracy of atomic clocks became widespread.

Hewlett-Packard 5060A.

As a result, such things as satellite television and communications, global navigation systems and time synchronization services became possible. information networks. Applications brought to industrial design There was a lot of atomic chronograph technology available. At the same time, Hewlett-Packard did not stop there and is constantly improving the quality of cesium standards and their weight and dimensions.

Hewlett-Packard family of atomic clocks

In 2005, Hewlett-Packard's atomic clock division was sold to Simmetricom.

Along with cesium, the reserves of which in nature are very limited, and the demand for it in a variety of technological fields is extremely high, rubidium, whose properties are very close to cesium, was used as a donor substance.

It would seem that the existing atomic clock scheme has been brought to perfection. Meanwhile, it had an annoying drawback, the elimination of which became possible in the second generation of cesium frequency standards, called cesium fountains.

Fountains of time and optical molasses

Despite the highest accuracy of the NIST-7 atomic chronometer, which uses laser detection of the state of cesium atoms, its design is not fundamentally different from the designs of the first versions of cesium frequency standards.

A design disadvantage of all these schemes is that it is fundamentally impossible to control the speed of propagation of a beam of cesium atoms moving in a waveguide. And this despite the fact that the speed of movement of cesium atoms at room temperature is one hundred meters per second. Very quickly.

That is why all modifications of cesium standards are a search for a balance between the size of the waveguide, which has time to influence fast cesium atoms at two points, and the accuracy of detecting the results of this influence. The smaller the waveguide, the more difficult it is to make successive electromagnetic pulses affecting the same atoms.

What if we find a way to reduce the speed of cesium atoms? It was this idea that preoccupied MIT student Jerold Zacharius, who studied the influence of gravity on the behavior of atoms in the late forties of the last century. Later, involved in the development of a variant of the cesium frequency standard Atomichron, Zacharius proposed the idea of ​​a cesium fountain - a method to reduce the speed of cesium atoms to one centimeter per second and get rid of the double-armed waveguide of traditional atomic oscillators.

Zacharius' idea was simple. What if you fired cesium atoms vertically inside an oscillator? Then the same atoms will pass through the detector twice: once while traveling up, and again down, where they will rush under the influence of gravity. In this case, the downward movement of atoms will be significantly slower than their takeoff, because during their journey in the fountain they will lose energy. Unfortunately, in the fifties of the last century, Zacharius was unable to realize his ideas. In his experimental setup, atoms moving upward interacted with those falling downward, which confused the accuracy of detection.

The idea of ​​Zacharius was returned only in the eighties. Scientists at Stanford University, led by Steven Chu, have found a way to realize the Zacharius Fountain using a method they call "optical molasses."

In the Chu cesium fountain, a cloud of cesium atoms fired upward is pre-cooled by a system of three pairs of counter-directed lasers that have a resonant frequency just below the optical resonance of the cesium atoms.

Scheme of a cesium fountain with optical molasses.

The laser-cooled cesium atoms begin to move slowly, as if through molasses. Their speed drops to three meters per second. Reducing the speed of atoms gives researchers the opportunity to more accurately detect states (you must admit that it is much easier to see the license plates of a car moving at a speed of one kilometer per hour than a car moving at a speed of one hundred kilometers per hour).

A ball of cooled cesium atoms is launched upward about a meter, passing a waveguide along the way, through which the atoms are exposed to an electromagnetic field of a resonant frequency. And the detector of the system records the change in the state of atoms for the first time. Having reached the “ceiling”, the cooled atoms begin to fall due to gravity and pass through the waveguide a second time. On the way back, the detector again records their condition. Since the atoms move extremely slowly, their flight in the form of a fairly dense cloud is easy to control, which means that in the fountain there will not be atoms flying up and down at the same time.

Chu's cesium fountain facility was adopted by NBS as a frequency standard in 1998 and named NIST-F1. Its error was 4 * 10 -16, which means that NIST-F1 was more accurate than its predecessor NIST-7.

In fact, NIST-F1 reached the limit of accuracy in measuring the state of cesium atoms. But scientists did not stop at this victory. They decided to eliminate the error that black body radiation introduces into the operation of atomic clocks - the result of the interaction of cesium atoms with the thermal radiation of the body of the installation in which they move. The new NIST-F2 atomic chronograph placed a cesium fountain in a cryogenic chamber, reducing black body radiation to almost zero. The NIST-F2 error is an incredible 3*10 -17.

Graph of error reduction of cesium frequency standard options

Currently, atomic clocks based on cesium fountains provide humanity with the most accurate standard of time, relative to which the pulse of our technogenic civilization beats. Thanks to engineering tricks, the pulsed hydrogen masers that cool cesium atoms in the stationary versions of NIST-F1 and NIST-F2 were replaced by a conventional laser beam working in tandem with a magneto-optical system. This made it possible to create compact and highly resilient versions of the NIST-Fx standards that can work in spacecraft. Quite imaginatively called "Aerospace Cold Atom Clock", these frequency standards are installed in the satellites of navigation systems such as GPS, which ensures their amazing synchronization to solve the problem of very accurate calculation of the coordinates of the GPS receivers used in our gadgets.

A compact version of the cesium fountain atomic clock, called the "Aerospace Cold Atom Clock", is used in GPS satellites

The time reference calculation is performed by an "ensemble" of ten NIST-F2s located at various research centers collaborating with the NBS. Exact value atomic second is obtained collectively, and thereby eliminates various errors and the influence of the human factor.

However, it is possible that one day the cesium frequency standard will be perceived by our descendants as a very crude mechanism for measuring time, just as we now look condescendingly at the movements of the pendulum in the mechanical grandfather clocks of our ancestors.

Time, despite the fact that scientists still cannot finally unravel its true essence, still has its own units of measurement established by humanity. And a calculation device called a clock. What are their varieties, what are the most accurate watches in the world? About it we'll talk in our material today.

What is the most accurate watch in the world?

They are considered to be atomic - they have minute errors that can reach only seconds per billion years. The 2nd, no less honorable, podium is won. They lag behind for a month or rush forward by only 10-15 seconds. But mechanical watches are not the most accurate in the world. They need to be started and started up all the time, and here the errors are of a completely different order.

The most accurate atomic clock in the world

As has already been said, atomic instruments for qualitative measurement of time are so meticulous that the errors they give can be compared with measurements of the diameter of our planet down to every microparticle. Undoubtedly, the average person in everyday life does not need such precise mechanisms at all. These are used by scientific researchers to conduct various experiments where extreme calculations are required. They provide opportunities for people to check "time progress" in various areas globe or conduct experiments to confirm general theory relativity, as well as other physical theories and hypotheses.

Paris standard

What is the most accurate watch in the world? It is generally accepted that they are Parisian, belonging to the Institute of Time. This device is the so-called time standard; people all over the world check it against it. By the way, in fact, it is not quite similar to “walkers” in the traditional sense of the word, but resembles a very precise device of the most complex design, which is based on the quantum principle, and the main idea is the calculation of space-time using particle oscillations with errors equal to only 1 second for 1000 years.

Even more precise

What is the most accurate watch in the world today? In current realities, scientists have invented a device that is 100 thousand times more accurate than the Paris standard. Its error is one second in 3.7 billion years! A group of physicists from the USA is responsible for the development of this technology. It is already the second version of time devices built on quantum logic, where information processing is carried out using a method similar to, for example,

Research assistance

The latest quantum devices not only set new standards in the measurement of such a quantity as time, but also help researchers in many countries resolve some questions that are associated with such physical constants as the speed of a light beam in a vacuum or Planck’s constant. The increasing precision of measurements is beneficial for scientists, who hope to track the time dilation caused by gravity. And one technology company in the United States plans to launch even mass-produced quantum watches for everyday use. True, how high will their primary cost be?

Operating principle

Atomic clocks are also commonly called quantum clocks, because they operate on the basis of processes that occur at the molecular level. To create high-precision devices, not just any atoms are taken: usually the use of calcium and iodine, cesium and rubidium, and also hydrogen molecules is typical. At the moment, the most accurate mechanisms for calculating time based on ittiberium were produced by the Americans. Over 10 thousand atoms are involved in the operation of the equipment, which ensures excellent accuracy. By the way, the previous record holders had an error per second of “only” 100 million, which, you see, is also a considerable period.

Precision quartz...

When choosing household “walkers” for everyday use, of course, nuclear devices should not be taken into account. Among household watches today, the most accurate watches in the world are quartz ones, which also have a number of advantages over mechanical ones: they do not require winding and work using crystals. Their running errors average 15 seconds per month (mechanical ones can usually lag by this amount of time per day). And the most accurate wrist watch Of all the quartz watches in the world, according to many experts, the Citizen company is Chronomaster. They can have an error of only 5 seconds per year. In terms of cost, they are quite expensive - around 4 thousand euros. On the second step of the imaginary Longines podium (10 seconds per year). They are already much cheaper - about 1000 euros.

...and mechanical

Most mechanical instruments, as a rule, are not particularly accurate. However, one of the devices can still boast. The watch, made in the 20th century, has a huge mechanism of 14 thousand elements. Thanks to complex design, as well as the rather slow functionality of their measurement errors - a second for every 600 years.