Negative Absolute Temperatures (!)

A "negative absolute temperature" is a temperature below 0° Kelvin. Zero degrees Kelvin is known as "absolute zero" for a reason. We have laws, people.

Well, anyway, now some highfalutin German physicists have gone and published a paper titled Negative Absolute Temperature for Motional Degrees of Freedom reporting that they have "created an atomic gas with a sub-absolute-zero temperature for the first time," according to Nature.

Schneider and his colleagues reached such sub-absolute-zero temperatures with an ultracold quantum gas made up of potassium atoms. Using lasers and magnetic fields, they kept the individual atoms in a lattice arrangement. At positive temperatures, the atoms repel, making the configuration stable. The team then quickly adjusted the magnetic fields, causing the atoms to attract rather than repel each other. “This suddenly shifts the atoms from their most stable, lowest-energy state to the highest possible energy state, before they can react,” says Schneider.

Well, I never.

What's next? Travel back in time?

I did use to have a math teacher who moved so slowly that I theorized that any substantial increase in slowness would require time to become negative. Yet, if one views temperature as the extent of vibration of a particle, then "negative absolute temperature" could be viewed as reversing time ... yes? Well, let's think that through ...

I have to admit I am a skeptic about the time thing, but then there is this thing with flipable interactions in Feynman diagrams where time is supposedly reversed -- supposedly for antimatter, though Richard Feynman, with his mentor at Princeton, John Wheeler, thought of that as one way of approaching quantum dynamics.