EVERY LIFE IS ON FIRE

A largely successful effort to explain biology through the principles of physics.

Physics depends heavily on reductionism: breaking complex actions down to the simplest mechanism. This holds little appeal to biologists who deal with the messy phenomenon of life. England, a former associate professor of physics at MIT who is now senior director in artificial intelligence at GlaxoSmithKline, begins with a problem: Every living thing has sprung from another living thing, but that “implies that the first life that ever was grew from stuff that was not alive,” so the laws of chemistry and physics had to be involved. Life is clearly an emergent property, which England illustrates by the example of a frog put through a blender. Every atom remains, but it is no longer a frog. The author introduces two physical concepts that explain how a complex frog emerges from a few trillion elemental atoms. The first is “macroscopic coarse-graining,” which maintains that any system can be described by numbers specifying what every individual particle is doing. This works for simple systems such as crystals; while impossible for even the most primitive organism, it enables scientists to create useful models. The second concept, entropy, measures the probability that a collection of atoms will assemble into something interesting such as a frog. Overwhelmingly, it won’t, but the odds are not zero, and they can be calculated. Seen as a measure of disorder, entropy is extremely low in a living organism. Living things keep their entropy low by extracting energy from the environment through eating and respiration. Since total energy in the universe remains constant, this is a complex process that England explains using many simple drawings of curves that go up and down because that’s how energy flows. The process is simple, but the details are not.

Those who put in the effort to read closely will discover illuminating insights into the physics of life.