CARLO ROVELLI is a professor of physics at the Centre de Physique Théorique de Luminy, Université de la Mediterranée, Marseille. He is the author of Quantum Gravity.
There is a major dangerous scientific idea in contemporary physics, with a potential impact comparable to that made by Copernicus or Darwin. It is the idea that what the physics of the twentieth century says about the world might in fact be true.
Quantum mechanics must dramatically change our understanding of reality. If we take it seriously, we cannot, for instance, think that objects have a definite position. They have a position only when they interact with something else, and even then they have that position only with respect to that something else—they are still without position with respect to the rest of the world.
This is a change in our image of the world far more radical than that given by Copernicus, and a change in our way of thinking about ourselves far more consequential than that given by Darwin.
Still, few people take the quantum revolution seriously. The danger is exorcised by various strategies, for instance by saying something on the order of “Well, quantum mechanics is relevant only for atoms and very small objects.” We still haven’t fully recognized that the world is quantum mechanical, or accepted the immense conceptual revolution needed to make sense of this basic factual discovery about nature.
Another example is Einstein’s relativity theory. Relativity makes clear that asking, “What is happening right now on Andromeda?” is complete nonsense. There is no “right now” elsewhere in the universe; nevertheless, we keep thinking of the universe as if there were an immense clock ticking away the instants, and we have a lot of difficulty adapting to the idea that a phrase like “the present state of the universe right now” is physical nonsense.
In these cases, what we do is use concepts we have developed in our very special environment—which is characterized by low velocities and low energy—and we think of the world as if it were all just like that. We are like ants in a little garden with green grass and pebbles, who cannot apprehend any reality different from one of green grass and pebbles.
Many of today’s audacious scientific speculations—about extra dimensions, the multiverse, and the like—are not only unsupported experimentally but also quite often formulated within a worldview that has not even fully digested quantum mechanics and relativity!