Last year, 2012, it was forty-five years since humanity decided to use atomic timekeeping to measure time as accurately as possible. In 1967, in the International SI system, the 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 they allow you to determine has a negligible 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 measurement of time 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 clockappeared 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 the accuracy of measurements increased many times over and the error per second can only accumulate in 2-3 hundreds of millions of years.
Atomic clocks: how they work
How does this ingenious "device" work? As a resonant frequency generator, atomic clocks use the energy levels of molecules or atoms at the quantum level. Quantum mechanics establishes a connection between the system "atomic nucleus - electrons" with several discrete energy levels. If such a system is affected by an electromagnetic field with a strictly specified frequency, then this system will go 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 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 onesuch an 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, the atomic clock is an extremely accurate and almost perpetual chronometer.
Precise 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, synchronized 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.
