What theoretically happens when at atom hits absolute zero?

A black hole would only destroy the earth. It's vacuum decay that would destroy the entire universe within a bubble expanding at the speed of light in all directions. A black hole has been proven to be impossible via an argument by a blue ribbon panel of experts. Their authority is so great, that they skipped the whole peer review process for their report due to it being a waste of their time. The panel also concluded that the odds of vacuum decay destroying space was acceptably small by using a statistical argument that ignores Bayes' Theorem of conditional probability (If the odds were significant, we probably wouldn't be here). However, the argument did quell the voices of worry-warts (which was the whole point), so experiments will proceed as planned.