What is the relation between physics and biology?
I was musing, as one does, about the relation between physics and biology. Usually we think of biology as some domain that can (or, depending on your personal position, cannot) be reduced to physics. I, on the other hand think of biology, like chemistry, psychology and librarianship, as what physics does in some part of the the universe. This led me to Avoid Work (a technical manoeuvre I often engage in) by doing some simplistic math on the matter. The Anthropic Principle is basically the claim that the universe is fine tuned to produce life, and intelligent life at that. I wondered how fine tuned. How hospitable is the universe towards life? Basically, what’s the ratio of life-friendliness in the physical world to inhospitability? We know that the biosphere of earth is roughly a shell of 100km thickness on the earth, from about 20km below sea level to 80km above it. This is, generously, the part of the universe that we know is life-friendly. Taking the volume of the sphere of the eart
