Life, not particles, may be physics' next great frontier
Sara Walker says new physics lies in the problems of life and intelligence rather than high-energy physics, Sean Carroll has shifted from guessing new laws to studying how complexity emerges, and Adam Frank calls the question of what life is the biggest question in physics. Three researchers independently pointing to the same frontier suggests where the next big breakthroughs may come from.
The next great frontier of physics may be life, not smaller particles or higher energies. Three physicists, in separate conversations, conclude that the most important unanswered questions sit where matter starts to organize itself, carry information and innovate. They disagree on a great deal, and this is not a formal consensus. But the convergence is a real signal of where breakthroughs may come from.
Sara Walker, an astrobiologist and theoretical physicist, says it most strongly. The frontier, she argues, is not high-energy physics or quantum gravity but life and intelligence. What we call fundamental particles mark the limits of our instruments, and she doubts a theory of everything exists. She thinks standard definitions of life all fail and offers her own: life is the process of how information structures matter over time and space. Living things, in her view, are enormous structures in time, carrying billions of years of history. Her assembly theory, developed with chemist Lee Cronin, gives this something to measure: how many steps it takes to build an object and how many copies exist. In organic chemistry, molecules needing more than about 15 steps are found in abundance only when life makes them.
Sean Carroll, a theoretical physicist, shows the shift through his own career. He describes his earlier papers on dark energy and gravity as guesses about how the laws might differ, several of which the data could not settle. He now asks how complexity arises from a simple early universe, a field he says has no governing framework yet. His picture is thermodynamic. Disorder always rises, but complexity starts low, peaks and then falls, and we live in the middle. Life does not break that law: "We are surfers riding the wave of increasing entropy." He believes the key is information, with parts of the universe learning to use it to survive.
Adam Frank, an astrophysicist, says the biggest question in physics is what life is, and specifically how an agent that acts for itself arises. Physics can predict a star's whole life from its mass and makeup. Nobody could predict from a single cell what its descendants would become billions of years later. He puts the unit of life at the scale of the whole biosphere: "Life doesn't happen on a planet. It happens to a planet."
They share a focus on information, on scales larger than the single organism, and on rigor. They part ways on much else. Carroll explains life through rising disorder, while Walker calls that the wrong approach. They hold three different views of quantum theory and differ on whether everything is physical. The article also notes that they are colleagues in overlapping circles, not three isolated discoveries.
The limits are plain. This does not mean particle physics and cosmology are finished. There is no settled theory here, and Walker's own work has drawn heavy criticism. The bar for evidence has not moved.
What to do with it: watch where the claims are being tested, including searches for life on other worlds. Separate complex from disordered. Think of living things as structures in time. Look at whole systems. Be wary of elegant simplifications, and keep the disagreements open.