As temperatures decrease, atoms and molecules lose kinetic energy, implying that they should grind to a halt when they approach absolute zero. But this is where a weird quantum mechanics quirk comes into play. The ‘uncertainty principle’ dictates that a particle’s exact momentum and position cannot both be known, allowing atoms a minute amount of energy. A CO2 molecule, for example, would still rotate at a speed equivalent to several tens of centimetres per second at absolute zero. In any case, the uncertainty principle makes it impossible to measure such ‘motion’, or ‘rotation’. The slowest speeds on Earth might instead be those of our planet’s tectonic plates, which shift by just a few centimetres per year.
Answered by Alex Cheung.