You Are Not an Ape-Brained Meat Sack

On November 6, 2024, the day after Donald Trump’s election victory, “the term ‘darkest timeline’ trended in Google searches, and several physicists posted musings on social media about whether we were actually in it.” So wrote George Musser in Scientific American a few days later. Maybe the multiverse is real, and we all just drew the short straw. “Somewhere out there in the great beyond,” he asks, “might there be a parallel world in which Kamala Harris electorally triumphed instead?”

Alas, Musser responds, these “escapist sociopolitical fantasies” are not what quantum theory is about. Physics just doesn’t flatter human beings with this kind of special regard.

Or so we are used to hearing, anyway. For a long time now, physics has been saddled with the conviction that the world is just a mindless jumble of objects in motion, indifferent to humanity and its concerns. “The human race is just a chemical scum on a moderate-size planet,” said Stephen Hawking in 1995 on the TV show Reality on the Rocks. This same idea motivates the widespread anxiety that we are but “ape-brained meat sacks,” as Oxford’s Elise Bohan puts it in her book Future Superhuman, primitive accidents destined to be replaced by AI, or upgraded by merging with machines into something unrecognizable.

This picture, of a physics ruthlessly indifferent to us, is hardly any less a nightmare than the idea that the multiverse is out to get us. But there is good reason to think that it’s a fantasy too. The reality of quantum physics is much stranger than any of this — and less radically set apart from human concerns than Hawking and the popularizers have led us to believe.

The quantum revolution a hundred years ago was one of those epochal shifts in human thought that will take centuries to make its full implications felt. A revolution had been brewing for some time: In 1905, Albert Einstein’s discovery of special relativity led to the famous “mass–energy equivalence” described by the equation e=mc², implying that solid objects can be converted into pure energy and vice versa. But it was Louis de Broglie, youngest son of a storied French dynasty, who put Einstein’s equations to their most devilishly mystifying use.

De Broglie’s 1924 doctoral thesis proposed that subatomic particles — little bits of matter such as electrons — should be described not only as solid chunks of stuff, but also as shifting waves of energy. This conclusion alarmed everyone, most of all Einstein himself. It also won de Broglie a Nobel Prize once the idea of “wave–particle duality” was experimentally confirmed as fact. A century later, we are still coming to grips with what it means.

Wave–particle duality scrambled a picture of the world established in the seventeenth century, when Isaac Newton published his Principia Mathematica. Newton’s universe is appealingly easy to imagine: think of a big empty box called “space,” then fill it with things like apples and planets. The Principia singled out a few relatively simple equations that can predict every object’s trajectory through that box, from the humble arc of a football down the field, to the careening sweep of a comet across the sky.

Like every mathematical model, Newton’s had its limitations. His rival Gottfried Wilhelm Leibniz was particularly dissatisfied with the idea of “absolute space,” that empty box in which all things are contained. “I hold space to be something purely relative, as time is,” Leibniz wrote, anticipating Einstein by nearly two centuries. We might find it convenient to picture a big empty box full of comets and footballs, but really there’s no such thing. There are just the comets, and the footballs, and the planets — and us, charting relationships between them all.

There is also no such thing as “gravity,” at least not in the sense of the invisible tether we usually imagine latching us to the ground. In fact, all “forces” and “energy” are just abstractions — mathematical ideas that predict what we’ll observe under certain conditions. Drop your cell phone in a moment of distraction and it will plummet heartbreakingly toward the pavement. We may say gravity “pulled” it, but that’s just convenient shorthand for describing how its motion relates to its mass and the Earth’s. As Einstein showed, there is nothing there doing the pulling. It’s just a feature of the way the world is shaped.

A wave is like gravity: it is a pattern of motion in things, not a thing in itself. The surge of water through the ocean in a tsunami isn’t itself an object but an arrangement of objects in time, the water particles whipping up and down in a repeated pattern. And that is why de Broglie’s thesis changed everything: it suggested that subatomic particles themselves, the smallest building blocks of matter, are not only objects; they are also waves.

Most astonishingly, the particles cease to occupy one specific location when not under human observation. As Erwin Schrödinger and Werner Heisenberg later showed with dizzying mathematical precision, a particle like an electron is not exactly in any one place until we measure its position: it is in a range of possible places, and the likelihood of finding it in any given place is described by a wave. The world described by the new “quantum physics” is not just a collection of solid objects jostling each other in space. It is a dynamic relationship between matter and the human mind.

Impossible as this scheme is to picture, it has any number of tangible effects. To give just one example: in quantum cryptography, you can tell whether a secret message has been intercepted by checking whether the quantum state of the light waves accompanying it has been altered. If they have, you know someone has examined them. Light photons, like electrons, have key physical properties that only become defined once they meet with an observer.

Einstein’s friendly adversary Niels Bohr made peace with all this. After all, he argued, concepts like space and time are not things in the world; they refer to the ways we organize our experience of the world. But “if all this is true,” countered Einstein, “then it means the end of physics.”

Certainly it means the end of the mechanical picture of the world, in which the universe goes clanking along without human involvement. But that was only ever a convenient image, anyway — a useful picture, not the whole truth. The quantum revolution has raised the possibility that reality is brought into focus, is resolved into the world that mathematics can describe, by us.

If this seems like a threat to the world of physics, perhaps that’s because the conviction that humanity is an afterthought to it was needless. Chemical scum on a moderate-size planet? Ape-brained meat sacks? Maybe we are not so expendable after all. As George Musser explains in his book Putting Ourselves Back in the Equation, “there is only one place” where the jumble of quantum potential is known to become reality, and that is in the subjective experience of a human mind: “The waves that ripple through the quantum ocean break on the shores of our conscious selves.”

Physics is and will remain an incalculable gift and a source of wondrous knowledge. But it is a gift to humanity, and the wonder we feel is human wonder. The universe is made to contain us.