The Theory of Nothing

What is so important about absolute zero?

What is so important about absolute zero?
Absolute zero is the lowest possible temperature, and it is, by definition, -273.16 C or -459.67 F. Man, that's cold! But, what's so important about this temperature? Absolute zero is important in thermodynamics because it's theoretically where molecular motion stops. What the heck does that mean?
Molecular motion has to do with kinetics, or the motion of atoms and molecules. These little devils never sit still. They are continuously in motion because any temperature above absolute zero imparts energy to keep them moving. Molecules of gas rapidly move around, bouncing off other gas molecules and the sides of the container they're in, and the crazy part is that they never slow down. The higher the temperature the faster gas molecules move. This is why the pressure of a gas increases with temperature. Faster moving gas molecules impact harder and more often against things to create a higher pressure. This action is part of the ideal (Boyle's) gas law: Pressure times volume equals the number of moles of the gas times a gas constant times temperature. A mole is a molecular weight of a substance expressed in grams. A mole also consists of an Avogadro's number (6.022 times ten to the twenty third power) of molecules of a gas. Carbon has a molecular weight of 12 grams. This is the amount of carbon one would have with an Avogadro's number of carbon atoms.
Wasn't that thrilling? What's important is that when a gas is cooled to absolute zero its molecules stop moving. This is a theoretical concept because science has not achieved this temperature. This is because any method would involve something (a machine or substance) above absolute zero, thus keeping the gas also above it. Scientists have been able to get down to a billionth of degree K. K stands for Kelvin, which has its zero at absolute zero. A Kelvin degree is the same as a Celsius degree. The only difference is that zero on the Celsius scale is 273.16 degrees K.
The reason why the Kelvin scale is used in science is that it fits into thermodynamic equations, which rely on the fact that absolute zero is 0 degrees K. It's easier to express very low and very high temperatures using the Kelvin scale.
One of the interesting things about absolute zero is that entropy (the measure of disorder in a system) at that point is zero because all molecular motion ceases. This is a theoretical idea because it's not possible to reach zero entropy. This is because the gas liquefies and then freezes to a solid, both processes release energy in the form of heat. What this means is the gas is at its ground state, or point of lowest energy and that's not zero entropy.
The other interesting thing is that at near absolute zero a dilute gas becomes a Bose-Einstein condensate in which the bosons (quantum paricles) that make up the gas atoms occupy the lowest quantum state possible. At this point one observes macroscopic quantum phenomena, such as superfluidity, and more important, superconductivity. Superfulidity is where a liquid behaves as if it has zero viscosity and does crazy things like flow up hill and find its own level despite the presence of a wall. Superconductivity is where a substance has zero resistance to current flow. This is the Holy Grail of electric phenomena where conductivity can be increased to unlimited levels. Magnets can be made to float above a superconductor, even though the superconductor surface is not a magnet. This is all the rage in physics as a means of making electrical transmission very efficient.
Absolute zero is important to all branches of science. Now you know.
Thanks for reading.