Carlo Rovelli's New Book Challenges Physics' Claim to Ultimate Reality

Rovelli begins with a simple point about human experience, according to the report. Because people live on the solid surface of a planet, they think there are solid objects. Because that surface offers fixed reference points such as mountain tops, they think solid objects can have fixed locations in space. And if those objects move, they think fixed reference points can give an absolute measure of that motion. Modern physics has shown each assumption to be an illusion. Albert Einstein's relativity revealed that measurements of time and space, including the sense of when two events are simultaneous, are relative. Quantum mechanics, the best theory of matter at the atomic level, showed that the properties ascribed to things cannot be disentangled from how they are measured. Rovelli argues that modern physics thus began to erode the idea that physics gives perfect access to a world seen from the outside, or a God's-eye view.

What remains, Rovelli argues, is the world as viewed from within. He dedicates considerable space to a view of quantum mechanics called the relational interpretation. When quantum physics appeared in the early 20th century, it shocked the physicists creating it. In the 250 years since Newton introduced his laws of motion, physicists had come to believe their equations described a reality entirely independent of human action or interpretation. The stuff described by Newton's laws, and the laws themselves, were thought to exist out there in an ultimate reality independent of observers. But in quantum mechanics it became difficult to speak of objects having properties before those properties were measured. This is the source of the famous Schrodinger's Cat parable, in which a cat in a box can be both dead and alive before the box is opened and a measurement is made.

For some physicists, it was so important to get that ultimate reality back that they invented interpretations of quantum physics claiming the universe splits into separate parallel versions of itself when the box is opened. Rovelli thinks these attempts are nonsense. For him, the lesson of quantum mechanics is relationality: everything exists only in relation to everything else. That means the properties of a system, any object, are always relational properties. There is no way to see them from an ultimate or absolute perspective because there are no ultimate or absolute perspectives. In the absence of an ultimate perspective, the power of physics to ultimately explain everything also falls apart. As Rovelli writes in the book, "Physics is often credited with a power it does not have: that of exhausting what can be known about the world. This is nonsense. Knowing the physical laws of the world does not amount to knowing the world."

NPR News describes this as a radical claim about physics, particularly coming from one of the world's most well-regarded physicists. It directly contradicts the scientific triumphalism found in many popular books about science and clashes with the perspectives of many contemporary philosophers of science. But as Rovelli writes, "we never leave the circle of perspectives." For him, this irreducibility of relationship is the central lesson of relativity and quantum mechanics.

One of the most original aspects of Rovelli's argument is that it draws on philosophical sources beyond the usual Greek or European tradition. He relies heavily on the classical philosophies of India and Asia. Thinkers such as Nagarjuna, from the 2nd century, and Zhuangzi, from 4th century BC China, appear many times in the book. Rovelli recognizes them as equals of Plato, Aristotle and others in their ability to penetrate difficult questions of reality, though from a different perspective.

The report says what is particularly compelling in the book is how lyrically Rovelli still vehemently defends the power and promise of physics, and science in general. Rather than making unworkable claims of absolute certainty about an absolute reality, he defends science while rejecting the idea that physics can exhaust what can be known about the world.