Negative temperatures are not at all unheard of in physics, as lasers are based on this very principle: At positive temperatures, states with higher energy will

Negative temperatures are not at all unheard of in physics, as lasers are based on this very principle: At positive temperatures, states with higher energy will always be (statistically) less occupied than states with lower energy. In a laser one inverts this for some states of the system by pumping energy to meta-stable high-energy states, thus creating a "population inversion". http://en.wikipedia.org/wiki/Negative_temperature http://en.wikipedia.org/wiki/Negative_temperature