Originally posted by -K-M-
Yep
Below absolute zero? /facepalm
If we have a system at a given non-zero temperature, the energies of its individual particles are not all equal: some have higher energy, some lower. Particle collisions redistribute the energy until a certain thermal equilibrium distribution of energies has been reached: this is called the Boltzmann distribution (of particle energies).
According to the Boltzmann distribution, the number of particles possessing energy E is
This distribution is characterized by a parameter T, which in statistical thermodynamics is the DEFINITION of absolute temperature (k is a physical constant, Boltzmann constant). For example, the distribution tells us that if the amount of particles having the energy E1 = kT is F(E1) = 100, then the amount of particles having twice that energy (i.e. E2 = 2E1 = 2kT) is only F(E2) = 37.
(Proof: according to the eq above, F(E2)/F(E1) = e^(-E2/kT) / e^(-E1/kT) = e^(-2)/e^(-1) = e^(-1) = 0.368.)
This makes only sense when the temperature T is positive: then the number of particles at higher energies is smaller than the number of particles at lower energies. But if the absolute temperature of the system was negative we would end up in a paradox: the number of particles with a given energy would be an exponentially increasing function of energy! Thus, if a (non-empty) system had negative absolute temperature, it would have an infinite amount of infinitely energetic particles. Such a system would be, not extremely cold, but extremely hot. It would release infinite amounts of heat to its surroundings. In fact, creating a negative absolute temperature anywhere within the universe would collapse the entire universe into a giant black hole ("big crunch"😉.
I highly doubt captain Cold's weapon is a universe-buster.