O zeroabsolute and the lowest theoretical temperature which a body can reach. It is the lower limit of thermal agitation and corresponding to a physical state in which the whole kinetic energy and potential of a system is equal to zero. According to the third law of Thermodynamics, if some system reaches absolute zero temperature, its entropy becomes null.
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Definition
At thermodynamic scale of temperature, graduated in kelvins, absolute zero is equivalent to 0 K, -273.15 ºC, or even -459.67 ºF. Theoretically, if any thermodynamic system is at this temperature, all of its molecules, atoms and electrons they are in a perfect state of rest, without any kinetic energy or any type of interaction between their constituents.
However, when matter is at temperatures close to absolute zero, the Physics laws change behavior. At such low levels of energy, quantum effects start to influence the dynamics of atoms and molecules.
The consequence of the emergence of quantum effects is that all determinism and the possibility of measurements accurate (which are common in classical physics) no longer make sense, thanks to a quantum property call of Heisenberg's Uncertainty Principle.
Quite simply, the Heisenberg's principle it is an imposition of nature that prevents us from knowing, with total precision, any greatness physics related to quantum systems.
In other words, thanks to this principle, it is not possible to determine with maximum precision the position of a atom, because for that, it should be perfectly static, and this is not allowed by the properties gives quantum physics.
Why is it not possible to reach absolute zero?
THE impossibilityfrom absolute zero is explained by the third law of thermodynamics. This law, also known as Nernst's theorem or postulate, states that it is impossible, by a finite number of transformations, for the entropy of a system to become nil.
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What would happen at absolute zero?
in spite of not being able to reach absolute zero, when we get to just a few degrees beyond that temperature, some interesting effects emerge: the atoms are very close each other, even the gases, like hydrogen and helium, become solid. At this temperature, some substances present superconducting properties, like the leagues of niobium and titanium.
Some theoretical physicists also believe that if a body were to reach a temperature of absolute zero, its mass would cease to exist. The reason for this behavior is in the resting energy, a concept created by the German physicist Albert Einstein. According to Einstein's relationship between pasta and resting energy, a body without any energy cannot have mass.
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How to reach absolute zero?
There are several techniques used by scientists to artificially create temperatures close to absolute zero. One of the most used ways by scientists to reach 0 K is the laser cooling.
The process works like this: a photon is emitted towards an atom, this photon is absorbed and, in sequence, re-emitted in the opposite direction. However, the re-emitted photons have energies a little higher than the incident photons, the difference of energy is extracted from the motion of the atom itself, which has its oscillation reduced until it is almost completely stopped.
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The impossibility of absolute zero
absolute zero is unattainable, that is, we will never measure anything at that temperature. This impossibility has its origins in the laws of Thermodynamics and also in the properties of quantum physics. The uncertainty principle, for example, guarantees that the energy of a quantum system is never zero.
Another way of understanding the impossibility of absolute zero concerns the measurement process of temperature. When we need to measure the temperature of a body or system, we use a thermometer. However, if we put a thermometer to measure the temperature of some body, supposedly at a temperature of 0 K, that instrument will exchange heat with the body, which will have its temperature increased, even at microscopic levels.
By Me. Rafael Helerbrock