The Re-Enchantment
On the robin’s compass, the photosynthesizing leaf, the new physics of consciousness, and why mainstream science is quietly walking back the disenchantment of the world
Friend,
I want to tell you about a bird.
The bird is the European robin, Erithacus rubecula, and at this very moment, somewhere in northern Europe, several million of them are preparing for their autumn migration to the western Mediterranean. They will fly, mostly at night, mostly alone, for distances of several hundred to a few thousand kilometers, and they will do so with extraordinary directional precision. Most of them will arrive within a few dozen kilometers of where they have arrived in previous years. This is the kind of fact that people who study migration get used to, and which the rest of us tend to file under the wonders of nature and stop thinking about.
I want to ask a question that bird researchers have been asking, in various forms, for almost two centuries: how does the robin know where it is going?
There are several candidate answers, all of them important, and the field has spent a long time sorting out their relative contributions. Robins use stellar cues. They use polarized light at twilight. They use landmarks. They use, on shorter trajectories, scent. But the master orientation system — the one that allows them to navigate at night, in cloud, in featureless terrain, over open ocean — is something else. Robins, like many other migratory species, have a magnetic compass. They can detect the direction of the Earth’s magnetic field, and they can do so with enough accuracy to maintain a precise heading across thousands of kilometers.
This was, by itself, a remarkable finding when it was first established in laboratory experiments by Wolfgang and Roswitha Wiltschko in the 1960s. But the Wiltschkos discovered something else, something that, when its full implications became clear, eventually rewrote large portions of biology. The robin’s magnetic compass is not, as everyone had assumed it would be, based on small magnetic particles in the bird’s tissue, like a compass needle. The compass operates only in light. If you put a robin in complete darkness, it cannot navigate by the magnetic field. If you put a robin in monochromatic red light, it cannot navigate. If you put it in blue or green light, the compass works.
A magnetic sense that requires light. A directional system that depends on the wavelength of incident photons. The Wiltschkos and a generation of subsequent researchers spent decades trying to figure out what, mechanistically, was going on. The answer, when it finally arrived, was almost too strange to be believed.
The robin is using quantum mechanics.
Specifically, the robin’s compass appears to work via a class of light-sensitive molecules called cryptochromes, located in specialized cells of the retina. When a photon of blue or green light strikes a cryptochrome molecule, it excites a pair of electrons into what is called a radical pair state — a configuration in which two electrons remain quantum mechanically entangled across a small molecular distance. The Earth’s magnetic field, weak as it is, is sufficient to influence the relative orientation of the entangled electrons’ spins. The molecular outcome of the chemistry that follows depends on the spin orientation, which depends on the magnetic field, which depends on the bird’s heading.
The robin, in other words, is detecting magnetic direction by reading the chemical output of a quantum process happening in its own eye. Quantum entanglement, which most physicists in the early twentieth century considered to be a mathematical artifact relevant only to laboratory situations involving frigid temperatures and shielded apparatus, is being used routinely, at body temperature, in the daily life of a small wild bird, to make decisions about which way to fly to Africa.
This letter is about what that means, and about a body of research that has been quietly accumulating, across the past two decades, that suggests the robin is far from alone. It suggests that the universe of living organisms is not, as the Cartesian and Newtonian and Darwinian inheritances have taught us, a clockwork of mechanism overlaid with an emergent illusion of mind. It suggests, instead, that something the philosophers used to call anima mundi — a world infused with sensitivity, with response, with pattern, with something that increasingly looks like elementary forms of awareness — was right all along. And that science, which spent four hundred years arguing the contrary, is now in the curious position of having to take it back.
