Something Faster Than Light? What Is It?

The Irish physicist John Stewart Bell, who in 1964 proposed a way to observe ‘spooky action’ of particles experimentally, at the Large Electron-Positron Collider at CERN, near Geneva, Switzerland, 1989
Corbin O’Grady Studio/Science Source
The Irish physicist John Stewart Bell, who in 1964 proposed a way to observe ‘spooky action’ of particles experimentally, at the Large Electron-Positron Collider at CERN, near Geneva, Switzerland, 1989

In physics, as in politics, there is a time-honored notion that all action is ultimately local. Aptly enough, physicists call this the “principle of locality.” What the principle of locality says, in essence, is that the world consists of separately existing physical objects, and that these objects can directly affect one another only if they come into contact.

It follows from the principle of locality that remote things can affect each other only indirectly, through causal intermediaries that bridge the distance between them. I can affect you, for instance, by extending my arm and giving you a pat on the cheek, or by calling you on your cell phone (electromagnetic radiation), or even—very, very slightly—by wiggling my little finger (gravitational waves). But I can’t affect you in a way that jumps instantly across the expanse of space that separates us, without anything traveling from me to you—by sticking a pin in a voodoo doll, say. That would be a “nonlocal” influence.

The idea of locality emerged early in the history of science. For the Greek atomists, it was what distinguished naturalistic explanations from magical ones. Whereas the gods were believed to be capable of acting nonlocally, by simply willing remote events to occur, genuine causality for the atomists was always local, a matter of hard little atoms bumping into one another. Aristotle adhered to the principle of locality; so did Descartes. Newton (to his own distress) seemed to depart from it, since gravity in his theory was an attractive force that somehow reached across empty space, perhaps instantaneously. But in the nineteenth century Michael Faraday restored locality by introducing the concept of a “field” as an all-pervading, energy-carrying medium through which forces like gravity and electromagnetism are transmitted from one object to another—not instantaneously, as would be the case with nonlocal action, but at a fixed and finite speed: the speed of light.

The principle of locality promises to render the workings of nature rational and transparent, allowing complex phenomena to be “reduced” to local interactions. Nonlocality, by contrast, has always been the refuge of the occult and the hermetic, of believers in “sympathies” and “synchronicity” and “holism.”

Albert Einstein had a deep philosophical faith in the principle of locality. He couldn’t imagine how science could proceed without it. “Unless one makes this kind of assumption,” Einstein said, “physical thinking in the familiar sense would not be possible.” He dismissed the possibility of voodoo-like, space-defying, nonlocal influences as “spooky action at a distance” (spukhafte Fernwirkung).



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