Not Even Absolute Zero Stops Your Atoms

An ice cube looks like the stillest thing there is. It isn't: every atom in it is moving, and no refrigerator anyone could ever build would change that.

Temperature measures how hard atoms jitter, so cooling can only slow them down. The bottom of that scale is absolute zero, -273.15 °C, and school teaches that the motion stops there. Two separate laws say otherwise. The third law of thermodynamics says no process reaches absolute zero in a finite number of steps. And quantum mechanics says that even at absolute zero, atoms would keep a minimum motion that is not heat and that no cooling can take away.

The nearest anyone has come was in 2021, when a team in Bremen slowed a cloud of about 100,000 atoms, for a moment, until their motion matched 38 trillionths of a degree above absolute zero. That figure measures how slowly an expanding Bose-Einstein condensate moved, not the temperature of anything at rest.

The proof you can see is helium. Cool it as far as you like and, at ordinary pressure, it never freezes: its atoms are so light that their leftover motion shakes any crystal apart. It takes about 25 atmospheres to force it solid. The same unremovable motion is in the ice cube, and in you.

Sources, in the order the video uses them:
Atoms in ice are never standing still, and at absolute zero a minimum motion remains; helium does not freeze at absolute zero without great pressure - The Feynman Lectures on Physics, Vol. I, ch. 1, section 1-2: https://www.feynmanlectures.caltech.edu/I_01.html
Absolute zero is -273.15 °C, the kelvin fixed by the Boltzmann constant; zero-point motion follows from the uncertainty principle and is not part of temperature - NIST, "Kelvin: Introduction": https://www.nist.gov/si-redefinition/kelvin-introduction
38 (+6/-7) trillionths of a degree, about 101,000 atoms in an expanding Bose-Einstein condensate - Deppner et al., Physical Review Letters 127, 100401 (2021): https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.100401
Why that figure is a motion and not an equilibrium temperature, and held only for a moment - University of Bremen, "Explain this, Professor": https://up2date.uni-bremen.de/en/article/explain-this-professor-the-coldest-place-in-the-universe
No process reaches absolute zero "by a finite number of steps and within a finite time" - Masanes & Oppenheim, Nature Communications 8, 14538 (2017), read as arXiv 1412.3828: https://arxiv.org/abs/1412.3828
Helium stays liquid down to absolute zero at ordinary pressure; helium-4 needs at least about 25 bar to solidify - Wikipedia, "Liquid helium", citing Wilks, The Properties of Liquid and Solid Helium (1967): https://en.wikipedia.org/wiki/Liquid_helium