Research concerning the relationship between the
thermodynamic quantity
entropy and the
evolution of
life began around the turn of the 20th century. In 1910, American historian
Henry Adams printed and distributed to university libraries and history professors the small volume
A Letter to American Teachers of History proposing a theory of
history based on the
second law of thermodynamics and on the principle of entropy. The 1944 book
What is Life? by
Nobel-laureate
physicist Erwin Schrödinger stimulated research in the field. In his book, Schrödinger originally stated that life feeds on negative entropy, or
negentropy as it is sometimes called, but in a later edition corrected himself in response to complaints and stated the true source is
free energy. More recent work has restricted the discussion to
Gibbs free energy because biological processes on Earth normally occur at a constant temperature and pressure, such as in the atmosphere or at the bottom of an ocean, but not across both over short periods of time for individual organisms.