What is Life?

This is the second generalist lecture and will address the problem of how to define life. It is approached through five of the great ideas of biology: the Cell, the Gene, Life as Chemistry, Life as Information, and Evolution by Natural Selection. These lead to principles defining life: living things are bounded physical entities, they are physical and informational machines, and they have to be able to evolve. It will be argued that life wherever it exists in the universe will be based on molecular systems which can be both chemically active and can store information, and that this will likely require polymer chemistry.