Absolute zero and beyond

[Dult]

So if movement virtually stops at absolute zero, when does it really stop?

[Irishman]

By definition, when molecules actually stop moving is absolute zero. However, it is difficult to get to absolute zero because quantum effects keep things destabilized.

[ftg]

Originally Posted by Dult

So if movement virtually stops at absolute zero, when does it really stop?

It can't. Quantum mechanics and the uncertainty principle. If something wasn't moving at all it's uncertainty of momentum is zero which means it's uncertainty of position is infinite. It's like everywhere, man!

Throw in the effects of particles popping into and out of existence due to the unavoidable quantum vacuum state, etc., and nothing can ever really be stopped.

Zero-point energy can be such a bother. It even prevents Helium from freezing (at normal pressure).

So absolute zero is best defined based on Thermodynamic principles such as minimum entropy. Thermo only applies to the statistical properties of lots of particles. It doesn't describe the behavior of a single particle.

[Old Red]

It's when it is so cold, your nuts fall off.