User blog comment:Xilinoc/Ch. 567 (Rukia be like "I ain't even scared though")/@comment-24099400-20140208051313/@comment-34677470-20140210054121

Absolute Zero is merely the temperatures at which atoms stop vibrating away from each other. It is possible to go below absolute zero, it has been done before.

(when you go below absolute zero, the atoms start to move towards each other instead of away)