Absolute zero is the lowest possible temperature. Theoretically, the subatomic particles would lose all their energy, so the electrons and protons would join in a "quantum soup". This temperature is -273.15 ° C or 0 ° Kelvin.
Lord Kelvin was the one who calculated the absolute zero, and for this was based on the fact that when a gas cools, its volume decreases in proportion to its temperature. That is to say that each degree of temperature that lowers the gas, also decreases its volume in a specific percentage, from this fact it deduced that at a temperature of -273.15 ° C the volume would become zero, something that possibly does not happen in practice, without However, many curious things happen when approaching this temperature.
"We call absolute zero of temperature at the value for which the internal movement of atoms or molecules constituting matter ceases.Temperature is a measure of the motion energy of the microscopic constituents of a physical system. You may think that since it is possible to lower the temperature of a system then it should be possible to reach a temperature (zero) for which there is no internal movement of its constituents, it would be a kind of ultra-frozen state of any material or system ".
The above means that no matter what substance, material or system is spoken, such a system cooled down to absolute zero of temperature will have all its constituent particles immobile, there will be no internal energy of movement. It is worth clarifying that quantum mechanics, the branch of physics that describes phenomena at the atomic and molecular scales, predicts that even at absolute zero of temperature there will be some energy of movement of the components of a system that can not be eliminated, so this energy is called the zero point energy of a system.


One of the first scientists to discuss the possibility of an absolute minimum temperature was Robert Boyle. His text of 1665 New Experiments and Observations touching Cold (New experiments and observations about the cold), articulates the dispute known as the primum frigidum. The concept was well known among naturalists of the time. Some argued that this absolute minimum temperature occurred within the Earth (since it was one of the so-called four "elements"), others that within the water and others that in the air, and some more recently in the nitro. Although all of them seemed to agree that: "There is a body or another that by its very nature is extremely cold and that by their participation all other bodies get that warm"
In 1906 the German chemist Walther Nernst formulated the heat theorem, which says that when a perfect crystal approaches absolute zero (-273.15 degrees Celsius), the entropy of the system goes to zero as well. This work received neither more nor less than the Nobel Prize of 1920 in chemistry. In 1912 Nernst defended his version by adding a new clause, which he called the "principle of unavailability", where it is indicated that absolute zero can not be obtained physically. Taking these two rules (or laws), make them become the third law of thermodynamics.
However, the physicists had no proof of this, but many accepted it as a law that had no contradictions and that worked. There were always physicists who rejected the idea of ​​not being able to reach absolute zero.

What happens at absolute zero

But what happens at such low temperatures? Well, at temperatures close to absolute zero subatomic particles are losing their energy, and leave "combining" or superimposing forming a "super-atom", known as Bose-Einstein condensate. In this state, matter acquires amazing peculiarities such as superconductivity (considerably greater than that of gold and copper) and superfluidity (helium at low temperatures becomes a liquid with virtually no viscosity).
Until now, it is still a theoretical temperature since it has been impossible to reach such a low temperature, however, if temperatures as low as 0.45 ° nanoKelvin (0.00000000045 Kelvin) have been reached in an experiment conducted at the Massachusetts Institute of Technology with sodium atoms in 2003.
In Earth laboratories, physicists can get very close to this temperature, but scientists say that it is impossible to reach absolute zero. In fact, the minimum temperature ever achieved was obtained by cooling a gas in a magnetic field to half a nanokelvin (ie, 5 · 10-10 K) above the theoretical minimum, absolute zero.
The decrease of the temperature to unsuspected limits is of enormous utility for the scientists, because certain materials completely change their behavior. This is the case of superconductors, which are currently used in magnetic levitation systems.
In our solar system it has been possible to detect temperatures as low as -240 ° C in areas that are in permanent shadow such as the craters located at the south pole of the Moon. In the universe the lowest recorded temperature is in the Boomerang Nebula 5,000 light years from us, in the constellation Centaurus, some gases emitted by a dying star have expanded and cooled rapidly up to 1 ° Kelvin. In general, gas clouds tend to have a temperature around 2.7 ° Kelvin due to cosmic microwave radiation.

What is the use of reaching such a low temperature?

We could verify the existing theories and deepen our understanding of the behavior of the matter that surrounds us in our universe. In the long scientific-technological race to achieve increasingly lower temperatures, amazing phenomena have been discovered, such as superconductivity, superfluidity, the entrapment of atoms by laser light, and invented many devices of technological importance, such as example something as common to us as refrigerating machines.



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