Absolute zero sounds like an unbreachable limit beyond which it is impossible to explore. In fact there is a weird realm of negative temperatures that not only exists in theory, but has also proved accessible in practice. An improved way of getting there, outlined last week, could reveal new states of matter.
To read the rest of the article, click here."A laser emitting coherent light has a negative temperature because more emitter are in the higher energy excited state than in the lower energy state in the chain reaction by stimulated emission. A Carnot engine with hot negative temperature coupled to cold positive temperature has more than 100% efficiency since the waste heat goes into the work rather than dissipates into the environment. That is
W/Q = 1 + Tnegative/Tpositive > 1 " - Jack Sarfatti