A dinner plate spinning in the vacuum is not in a ground state -- it has substantial kinetic energy that is being converted into heat and electromagnetic radiat

A dinner plate spinning in the vacuum is not in a ground state -- it has substantial kinetic energy that is being converted into heat and electromagnetic radiation as it spins, and it will gradually slow down and stop. (Veeery gradually.) The theory here is that you can have a system that is already in a ground state, where it can't decay further, and is still spinning (and will spin forever without gaining or losing energy.) I don't have the expertise to properly understand the details, but it seems like it's along similar lines as something like an electron 'orbiting' a nucleus in ground state -- unlike the plate, the electron will never stop 'orbiting' because it has no energy to lose. The electron, though, is delocalized -- it's in every place around the nucleus at once. So there's no periodic motion involved. By contrast, this experiment will tag one of the atoms in the ring so we can watch it move periodically.