““As we showed in figure 5, water molecules oscillate about their rest positions in ice. Quantum mechanics says that this remains true at absolute zero and will not admit a molecule at full rest. Similarly, we saw that what we call empty space is replete with the appearance and disappearance of virtual particles. Add energy, and these particles can become real. Add energy to ice, and it will melt. Moving in the opposite direction, remove energy from water and it will freeze because the water molecules attract each other; ice lets them approach as close as possible. The resulting crystalline structure is destroyed by thermal motion of the molecules when energy is added. Moving at random, the molecules emerge as individual particles, much as an electron-positron pair emerges from the vacuum when we add energy.””
