LIFE AS NO ONE KNOWS IT

An astrobiologist takes a hard look at life.

Walker, director of Arizona State’s Beyond Center for Fundamental Concepts in Science, writes that until well into the 19th century, the vitalism movement “was driven by the idea that what makes matter come alive cannot be described mechanically and is therefore not material.” But if life is not a property of matter, and matter is all there is, then what is life? Biologists approach the problem in terms of life on Earth, which hasn’t proven to be an effective strategy and is even less helpful today with the discovery of innumerable planets and the possibility of sentient life throughout the universe. In addition to her work in the field of astrobiology, Walker is a theoretical physicist with a special interest in the possibilities of alien life, and she emphasizes that physics deals with “the heart of reality.” She continues, “It’s not that the idiosyncratic details of biology as it evolved on Earth don’t matter. They just don’t matter if you want to understand life as a universal phenomenon.” Eschewing the anthropomorphic viewpoint, she and colleagues have developed “assembly theory,” which proposes that things never form spontaneously, but must be constructed via selection and evolution. Life is an example of “high-dimensional combinatorial space of what is possible,” she writes. The author’s startling conclusion is that, while an alien life form may be detected first on a distant planet, it’s more likely to turn up in a laboratory here on Earth, “but there is an even larger universe of chemical possibilities we may need to explore to find them.” This is an honorable addition to a small genre that began with Noble Prize–winning physicist Erwin Schrodinger’s What Is Life? in 1944. It’s never easy, but diligent readers will be rewarded.

Ingenious, but not for the faint of heart.