What Is Life? is a 1944 non-fiction science book written for the lay reader by physicist Erwin Schrödinger. The book was based on a course of public lectures delivered by Schrödinger in February 1943, under the auspices of the Dublin Institute for Advanced Studies at Trinity College, Dublin. The lectures attracted an audience of about 400, who were warned "that the subject-matter was a difficult one and that the lectures could not be termed popular, even though the physicist’s most dreaded weapon, mathematical deduction, would hardly be utilized." Schrödinger's lecture focused on one important question: "how can the events in space and time which take place within the spatial boundary of a ...view middle of the document...
One of the most successful branches of physics at this time was statistical physics, and quantum mechanics, a theory which is also very statistical in its nature. Schrödinger himself is one of the founding fathers of quantum mechanics.
Max Delbrück's thinking about the physical basis of life was an important influence on Schrödinger. Geneticist and 1946 Nobel-prize winner H.J. Muller had in his 1922 article "Variation due to Change in the Individual Gene" already laid out all the basic properties of the heredity molecule that Schrödinger derives from first principles in What is Life?, properties which Muller refined in his 1929 article "The Gene As The Basis of Life" and further clarified during the 1930s.
ContentIn chapter I, Schrödinger explains that most physical laws on a large scale are due to chaos on a small scale. He calls this principle "order-from-disorder." As an example he mentions diffusion, which can be modeled as a highly ordered process, but which is caused by random movement of atoms or molecules. If the number of atoms is reduced, the behaviour of a system becomes more and more random. He states that life greatly depends on order and that a naive physicist may assume that the master code of a living organism has to consist of a large number of atoms.
In chapter II and III, he summarizes what was known at this time about the hereditary mechanism. Most importantly, he elaborates the important role mutations play in evolution. He concludes that the carrier of hereditary information has to be both small in size and permanent in time, contradicting the naive 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 and crystals is due to the same principles and a molecule might be called "the germ of a solid." On the other hand an amorphous solid, without crystalline structure, should be regarded as a liquid with a very high viscosity. Schrödinger believes the heredity material to be a molecule, which unlike a crystal does not repeat itself. He calls this an aperiodic crystal. The aperiodic nature allows to encode an almost infinite number of possibilities with a small number of atoms. He finally compares this picture with the known facts and finds it in accordance with them.
In chapter VI...