What Is Life? information has to be both small in size and permanent in time, contradicting the naïve physicist's expectation. This contradiction cannot be resolved by classical physics. In chapter IV, Schrödinger presents molecules, which are indeed stable even if they consist of only a few atoms, as the solution. Even though molecules were known before, their stability could not be explained by classical physics, but is due to the discrete nature of quantum mechanics. Furthermore, mutations are directly linked to quantum leaps. He continues to explain, in chapter V, that true solids, which are also permanent, are crystals. The stability of molecules
Atomic, molecular, and optical physics by photons or collisions with atomic particles. While modelling atoms in isolation may not seem realistic, if one considers molecules in a gas or plasma then the time-scales for molecule-molecule interactions are huge in comparison to the atomic and molecular processes that we are concerned with. This means that the individual molecules can be treated as if each were in isolation for the vast majority of the time. By this consideration atomic and molecular physics provides the underlying theory in plasma physics and atmospheric physics even though both deal with huge numbers of molecules. Electrons form notional shells around the