Frost: how to get the temperature close to absolute zero

© Depositphotos / ShotsstudioУченые conduct experiments in the laboratoryFrost: how to get the temperature close to absolute zero© Depositphotos / Shotsstudio

The lowest natural temperature recorded in the Guinness Book of records (minus 89,2 °C) was recorded in Antarctica. In the studied space colder just in the nebula, the boomerang — it expands and ejects the cooled gas with a temperature of minus 271 ° C. But scientists have long surpassed nature, creating a system where the temperature is close to absolute zero.

Temperature in physics is analogous to the internal energy, so the hotter the material the faster moving particles in it. The lowest temperature physically possible of matches minus 273,15 ° C (or 0 Kelvin), and at this point the thermal motion stops completely.

To study phenomena at the micro level, scientists need to know exactly what caused a particular effect. For example, an electron is suddenly accelerated, for which he needed the energy. But how to understand where it came from: from the trapped electron photon or heat from the environment? Scientists have found the answer to this question is to examine these particles is necessary when cooling, the most close to absolute zero.

The easiest method of obtaining low temperatures using liquid helium. In the «free» state is a gas that is part of the atmosphere and many of the funny property of making a funny voice. The fact that the frequency of vibration of the vocal cords depends on the density of the air environment. The density of helium is seven times lower than that of air, and the speed of sound is three times higher. Therefore, in the cavity of the larynx resonance enhanced higher harmonics of vibrations of the vocal cords, through which the voice becomes squeaky.

«For science is an important property of helium is its natural low temperature when it is in liquid form, for which the gas is literally compressed in a special compressor. Then he acquires a temperature of 4.2 Kelvin. But it can be improved if the use of two isotopes (the so-called varieties of atoms with the same charge, but different numbers of neutrons) of helium — 3 and 4. Upon cooling of the mixture, including the isotope data, it is divided into two phases rich in helium-3 and helium-4. At the transition of the first of them in the phase rich in helium-4, a decrease in temperature. So it is possible to cool the system to 10 to 20 millikelvin in refrigerators dissolution», — says Vladimir Gurtovoy, senior researcher of the laboratory of artificial quantum systems, Moscow physical-technical Institute.

Therefore, those wishing to continue freezing the scientists have to use the so-called Sisyphus cooling. Meet the atom directed two laser beam with polarization perpendicular to each other. Received light wave «dropping» an atom in a lower energy state, imposing the natural frequency is already available.

The disadvantage of the latter two methods is the inability to cool large systems, because with lasers you can freeze, only individual atoms. For larger objects of study used scheme based on helium.

 

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