What's the Latest Development?

As NASA works to build a machine that can detect extraterrestrial life in space, cosmologist Charley Lineweaver argues that our traditional definition of life is too strict and therefore ill-suited to allow for the diversity of what life may look like on other planets. While defining life has always been tricky--scientists still disagree on whether viruses are alive--Lineweaver disagrees with the very idea that life is something that undergoes Darwinian evolution. Why? "What is the unit of Darwinian evolution?" he asks. "Is it the gene? Is it the cell? Is it a multicellular organism? Is a city evolving? How about Gaia? Is that a life form?"

What's the Big Idea?

Lineweaver offers his own definition of life: "A far-from-equilibrium dissipative system." In other words, a system which feeds on energy associated with different gradients in the environment. Here, Lineweavers moves from a biological definition to a physical definition of life. By his standard, fire or a hurricane would be considered living. While that sounds like a step backwards in the search for a suitable definition of life, Lineweaver concludes: "It makes more sense to me to increase the size of what we call 'life' than to continually search for a meaningful boundary where there is none."

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