What is absolute zero in thermodynamics?

The temperature of the environment is and has been throughout history a very determining element for the survival of the different living beings, and something that has marked the future of evolution and in the case of human beings, the way of understanding the world that surrounds us. surrounds.

In fact, much of known life can only live within thermal limits, and even the motion and energy of particles is altered at the molecular level. The existence of extreme temperatures has even been stipulated that can cause the movement of subatomic particles to cease completely, as they remain in a total absence of energy. This is the case of absolute zero, a concept developed by Kelvin and whose research has great scientific relevance.

But... what is absolute zero exactly? Throughout this article we are going to check it.

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Absolute zero: what does this concept refer to?

We call absolute zero the lowest temperature unit considered possible, -273.15ºC

, a situation in which the subatomic particles themselves would find themselves without any type of energy and would not be able to carry out any type of movement.

This occurs due to the fact that the fact of decreasing the temperature of an object implies subtracting energy from it, with which absolute zero would imply the total absence of this.

This is a temperature that is not found in nature and which is assumed for the moment hypothetical (in fact, according to the Nernst unattainability principle to achieve this temperature is impossible), although scientific experimentation has managed to reach very similar temperatures.

However, the previous description is linked to a perception of this concept from the perspective of classical mechanics. Subsequent investigations that would leave classical mechanics aside to enter quantum mechanics propose that in reality in this temperature, there would still exist a minimum amount of energy that would keep the particles in motion, the so-called energy of zero point.

Although before the first classical visions in this hypothetical state, matter should appear in a solid state since there is no movement or disappear when equating mass to energy and the latter being totally absent, quantum mechanics proposes that when there is energy, other states of the subject.

Kelvin's investigations

The name and concept of absolute zero comes from the research and theory of William Thomson, better known as Lord Kelvin, who set out to develop this concept of the observation of the behavior of gases and how they vary their volume proportionally to the drop in temperature.

Based on this, this researcher began to calculate at what temperature the volume of a gas would be zero, reaching the conclusion that it would correspond to the aforementioned temperature.

Based on the laws of thermodynamics, the author created his own temperature scale, the Kelvin scale, placing the point of origin at this lowest possible temperature, absolute zero. Thus, a temperature of 0ºK corresponds to absolute zero, -273.15ºC. part of the creation by said author of a temperature scale generated from the laws of thermodynamics of the time (in 1836).

Is there something beyond?

Bearing in mind that absolute zero is a temperature at which there would be no movement of particles or only there would be a residual energy of absolute zero, one wonders if something could exist beyond this temperature.

Although logic may make us think not, research carried out by different researchers at the Max Planck Institute they seem to indicate that in fact there could be an even lower temperature, and that it would correspond to negative temperatures on the Kelvin scale (ie below absolute zero). It is a phenomenon that could only occur at the quantum level.

This would occur in the case of some gases, which through the use of lasers and experimentation managed to go from being somewhat above absolute zero to negative temperatures below zero. These temperatures would ensure that the gas in question, prepared in such a way that it should contract at high speed, remains stabilized. In this sense it is similar to dark energy, which according to some experts prevents the universe from collapsing in on itself.

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What can it be used for?

Knowing the existence of absolute zero has repercussions not only at a theoretical level but also at a practical level. And it is that when exposed to temperatures close to absolute zero, many materials greatly change their properties.

An example of this is found in the fact that at these temperatures subatomic particles condense into a single large atom called the Bose-Einstein condensate. Likewise, some especially interesting properties due to their practical application can be found in the superfluidity or the superconductivity that certain elements can reach under these conditions thermal.

Bibliographic references:

• Braun, S. et al. (2013). Atoms at negative absolute temperature- the hottest systems in the world. Science, 4. Max Planck Society.
• Merali, Z. (2013). "Quantum gas goes below absolute zero". Nature. doi: 10.1038/nature.2013.12146.