Absolute zero is the temperature at which the particles of matter (molecules and atoms) are at their lowest energy points. Some might think that at absolute zero particles lose all energy and stop moving. This is not correct. In quantum physics there is something called zero point energy, which means that even after all the energy from particles has been removed, the particles still have some energy. This is due to Heisenberg's uncertainty principle, which states that the more that is known about a particle's position, the less that can be known about its momentum, and vice versa. Therefore, a particle cannot be completely stopped because then its exact position and momentum would be known. 