In the past, 2012, forty-five years have passed since the moment when mankind decided to use atomic timekeeping to measure time as accurately as possible. In 1967, in the International SI system, the time category was no longer determined by astronomical scales - it was replaced by the cesium frequency standard. It was he who received the now popular name - atomic clocks. The exact time that they can be determined has a negligible error of one second in three million years, which allows them to be used as the standard of time in any corner of the world.
A bit of history
The very idea of using atomic vibrations for ultra-precise measurement of time was first expressed in 1879 by the British physicist William Thomson. In the role of a radiator of atomic resonators, this scientist proposed the use of hydrogen. The first attempts to put the idea into practice were made only in the 40s. twentieth century. And the world's first working atomic clocks appeared in 1955 in the UK. Their creator was the British experimental physicist Dr. Louis Essen. This watch 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 the
measurement accuracy increased many times and the error per second can only run for 2-3 hundred million years.
Atomic clock: principle of operation
How does this ingenious “device” work? Atomic clocks use the
energy levels of molecules or atoms at the quantum level as a generator of resonant frequency.
Quantum mechanics establishes a connection between the "atomic nucleus - electrons" system and several discrete energy levels. If an
electromagnetic field with a strictly specified frequency will act on such a system, then this system will transition from a low level to a high one. The reverse process is also possible: the transition of an atom from a higher level to a low one, accompanied by radiation of energy. These phenomena can be controlled and recorded all energy jumps, creating something like an oscillatory circuit (it is also called an atomic oscillator). Its resonant frequency will correspond to the difference in energy of neighboring atomic transition levels, divided by Planck's constant.
Such an oscillatory circuit has undeniable advantages in comparison with its mechanical and astronomical predecessors. For one such atomic oscillator, the resonant frequency of 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, an atomic clock is an extremely accurate and almost timeless chronometer.
Exact time and modern technology
Telecommunication networks, satellite communications, GPS, NTP servers, electronic transactions on the exchange, online auctions, the procedure for buying tickets through the Internet - all these and many other phenomena have long been firmly entrenched in our lives. But if humanity had not invented the atomic clock, all this would simply not have happened. The exact time, synchronization with which allows to minimize any errors, delays and delays, enables a person to make the most of this invaluable irreplaceable resource, which is never too much.