to date, is likely to involve “other laws of physics” hitherto unknown,
which, however, once they have been revealed, will form just as integral
a part of this science as the former.What is Life?—its author one of the best-known scientists of the
time—attracted a wide readership, especially among physicists.
Additionally, after World War II many physicists, having spent the
war years doing weapons-related work, were receptive to tackling
problems in a completely new and refreshing domain of inquiry. A
significant number of physicists, after being inspired by What is Life?,
became interested in researching the physical basis of life. Some of
them became key figures in the early years of the discipline that would
come to be called molecular biology.
Meanwhile, in 1937, Delbriick had left Germany for the United
States on a fellowship to study genetics. There he had encountered the
idea of using a species of bacteria, Escherichia coli, and viruses (called
bacteriophages) that infect the bacteria, as a way to investigate the
physical properties of hereditary. Just as there are viruses that infect
people—like the flu, common cold, hepatitis, and HIV—there are
viruses that specifically infect certain bacteria. Indeed, a substantial
percentage of the biomass on Earth consists of bacteria and bacterio-
phage viruses. They are everywhere.
Viruses lie at the definitional boundary of life. They contain the
genetic information (genes) needed to build copies of themselves but
not the machinery, so they must commandeer (infect) an appropriate
host organism to carry out the process. Being small and presumably
relatively simple particles that contain genes, Delbriick felt they
would be ideal subjects for the study of the physical basis of heredity.
He described his first encounter with bacteriophages like this:
I was absolutely overwhelmed that there were such very simple