It seems an obvious question: What is life? But science writer Carl Zimmer says the answer to it is far more complicated than it appears at first glance.
In his new book Life’s Edge, Zimmer explores the work of scientists and philosophers who have made it their aim to define life’s boundaries. But the more he dug into this world, the more definitions of life he encountered — and the more he realized just how important this question is. Does life start when an egg is fertilized? Do we get it right when we declare someone legally dead? And as we search the universe for other lifeforms, what — and who — are we looking for? Zimmer joins us Friday at noon to talk about life and why it’s so difficult to pin down. (Rebroadcast)