But you all have left out on very important principal in the impossibility of absolute zero. The Pauli exclusion principal. It states that the mare accuratly you know the position of a particle, the less accurately you can know its velocity and vice versa. At absolute zero, you know with 100% certainty, a particle's location because it's velocity is zero. And this of course is impossible because of the principal. And yes, a particles temperature is a measurement of its velocity because even in a sealed container, the particle is constantly moving in some arbitrary direction (i.e. Brownian motion)