This is, theoretically, the lowest temperature in the universe. Once in this temperature, the molecules of a body would stop moving and the entropy would reach its minimum value.

The notion of a “minimum temperature” in the universe was first considered by the scientist Robert Boyle in the 15th century. In the 16th century, the French physicist Guillaume Amontons, from tests on his air thermometer, defined that the lowest possible temperature was -240 °C.

Other scientists attempted to reach a lower temperature, and, in 1800, the British physicist William Thomson, also known as Lord Kelvin, conclude the absolute zero at -273.15 °C, or 0 Kelvin, thus creating an absolute temperature scale that is used until today.

How to achieve absolute zero?

The molecules that form the bodies are in constant movement, the smaller this movement, the less energy and heat they produce. Thus, when the kinetic energy of these molecules ceases, they have reached absolute zero, that is, they are immobile. However, this phenomenon has never been found in nature. For example, the coldest point in the universe known to man is the Boomerang Nebula, which reached -272°C.

Experiments with ultra-cold bodies (very close to 0 K) had three “side effects”: superconductivity, which creates a magnetic field; superfluidity, where a liquid appears to be free of viscosity and can raise walls; and the condensation of Bose-Einstein, where the various particles forming a body would act in a condensed form, as a single giant atom.

Is it impossible to reach absolute zero?

No. Scientists at Ludwig Maximilian University, in Germany, have achieved something incredible and considered impossible: they created a quantum gas, from potassium atoms, which surpassed in a few billionths the 0K. They were, for the first time, under the absolute zero! By then the closest that had reached this temperature was 0,000000000001 K.

In the produced gas, they could perceive a similar behavior to that of dark energy, a matter that intrigues scientists by maintaining the expansion of the universe, ignoring the action of gravity. This is an interesting point: Achim Rosch, a physicist at the University of Cologne, calculated that molecules in an absolute freeze-frame system can float and are not affected by gravity.

Absolute zero studies may allow scientists to better understand our universe and what is happening to it.