Absolute zero cannot be reached

The third law of thermodynamics implies that no finite sequence of steps can cool a system to absolute zero.

Nernst’s heat theorem, now the third law, says the entropy of a perfect crystal goes to a minimum as temperature goes to zero, and that you cannot reach that zero by a finite number of operations. Each cooling stage — a demagnetisation, a dilution — takes out a fraction of what is left. The fraction of a vanishing remainder is a Zeno arrow.

Laboratories reach nanokelvin in dilute gases and microkelvin in solids. Those numbers are astonishing and they are not zero. Negative absolute temperatures exist in special spin systems and are hotter than infinity, not colder than zero. The floor is a limit, not a place.