Most of us are familiar with liquid nitrogen; either we’ve seen it at the doctor’s office when we’ve needed a pesky wart removed, or we’ve seen a cryogenics demonstration at a museum or at school or on YouTube where they do such fun things as dip a carnation into it to show how it freezes and becomes amazingly brittle.
But this one will probably be new to you. It certainly was to me. Liquid oxygen, placed into a vacuum chamber. It boils vigorously, of course, but then something surprising happens — followed by something amazing. The evaporation of N2 cools the remaining liquid enough that it freezes, and *then* it crystalizes, suddenly. It’s beautiful; check it out!