When we think of aliens, we might conjure images of humanoid creatures emerging from massive spaceships. At least, that's how movies would have us picture extraterrestrial beings. But do we really understand what an alien might be — and what it would mean to have first contact with one? SFI External Professor Sara Walker (Arizona State University) tackles these baffling questions in Life as No One Knows It: The Physics of Life’s Emergence, a new book that probes fundamental questions about life in the universe — and proposes some provocative answers.
Walker, a theoretical physicist, argues in the book that our current life-model concepts are too focused on Earth. We can’t discover alien life unless we define what life means within the context of the universe. Explaining life may also help shed more light on its origins. While scientists have successfully demonstrated how life evolved on Earth, they have yet to solve the mystery of how it originated. For example, little is known about how our last universal common ancestor came into existence. In fact, the lack of an overarching theory explaining how non-living matter changed to living beings prompted Walker to embrace the origin-of-life conundrum as her research focus.
Walker hopes the book reaches curious people outside of academia who enjoy pondering the nature of life and may appreciate the significance of addressing these knowledge gaps. “I wanted to inspire people to think differently about these problems and realize how deep they are and that there's some transformative knowledge if we can understand what life is,” says Walker. She also aims to change the cultural dialogue around the topic. The book challenges us to reimagine first encounters with extraterrestrial beings. One of its key arguments is that our first true interaction with aliens will be in the form of an all-encompassing definition of life and, by extension, alien life. Walker also speculates in the book that rethinking the origin-of-life problem can potentially spur an innovation revolution leading to novel technologies and tools that can help test theories and aid experiments in this research area.
The book introduces readers to assembly theory, which Walker calls the “new physics.” Initially developed by University of Glasgow chemist Leroy Cronin and later expanded by Walker, the theoretical framework can potentially demystify life’s origins and help us determine whether it exists elsewhere in the vast universe.
The book deep dives into how that might be achieved. To begin with, assembly theorists have tried to explain how the universe generates complexity. They are specifically interested in complex objects that lifeforms (such as humans) would typically build. On our planet, such a thing could be a hatchet, a phone, or a Lego Castle — on another planet, lifeforms may create wholly different things. But, according to assembly theory, all of these objects have a common trait — they are unlikely to come into existence because of natural environmental processes and require many steps to complete. “Our conjecture is that things that are very hard to build, like Lego castles, require evolution and learning to be produced in the universe,” says Walker. In the book, she describes how scientists could use the principles of assembly theory to observe a sample of molecules on another planet and determine whether it’s a product of evolution.
Walker and her colleagues hope to establish assembly theory as an explanatory framework of life. The book details their ambition to conduct a large-scale experiment that can demonstrate the origin of life using the theory’s principles. However, such studies are expensive. "I hope the book will enable people to understand the problem as we're thinking about it and really get excited about the new frontier in physics and potentially inspire them to invest in doing those kinds of experiments," says Walker.