Scientists say it is the closest they’ve come to real magic. In October, a team of physicists in the Netherlands reported in the journal Nature the most definitive evidence yet for what Einstein called “spooky action at a distance”—subtle and seemingly inexplicable connections between objects in the quantum realm. This month, teams in Vienna and in Boulder, Colorado, weighed in with equally dramatic results. Two or more particles can act in a coordinated way, no matter how far apart they may be, and they do so without sending out a sound wave, beaming a radio signal, or otherwise communicating across the gap that separates them. Their spooky synchronicity has many of the qualities of the Force: You can’t use it to misdirect stormtroopers or feel the pain of a distant planetary holocaust, but it does bind together the fates of things that could lie on opposite sides of the galaxy. And it violates our deepest intuitions about nature.
Physicists have tried for decades to explain away the phenomenon, which is known as quantum entanglement. With these latest experiments, they’ve pretty much run out of prosaic explanations. You might think, for example, that the particles are no more mysterious than socks, which are coordinated for the simple reason that you paired them when folding the laundry. But experiments have ruled out the possibility that particles remain matched due to any kind of advance preparation. The particles are behaving like bewitched socks: They’re not white, pink, or any other color. They don’t actually have a color when you put them on. They take on a color only when observed. You look at the left sock and—boom!—it turns pink. You look at the right, and it, too, is pink. The socks are choosing a color on the fly, and they are choosing the same color. (You can see why this strikes physicists as magical.)
Nor could some exotic force be passing between the particles, because the particles are being measured at exactly the same moment; it is only at that moment that they settle into a given state (or color, in the socks metaphor), according to the standard interpretation of quantum theory. Any force that transmitted the information to the other particle would need to propagate instantaneously. That would violate Einstein’s theory of relativity, and in any case, instantaneous propagation isn’t propagation in any meaningful sense of the term.
Whatever is going on has got to be weird. For decades, that’s where the discussion got stuck: with exclamations that something weird is going on, followed by inconclusive debate in which scientists weighed different degrees of weirdness. But in recent years theoretical physicists have been inching toward a possible explanation. As I write in my new book, Spooky Action at a Distance, the phenomenon may not be inexplicable magic but a glimpse of a deeper reality, one that underlies the space and time we inhabit.
This radical idea makes contact with a separate branch of fundamental physics: the effort to understand the force of gravity. According to Einstein’s general theory of relativity, which he first presented to the world 100 years ago, gravity reflects the curvature of the spacetime continuum. When you throw a baseball, it follows an arc and returns to the ground, because Earth’s mass distorts the spacetime around our planet, and this distortion brings the baseball’s path back to intersect with the ground’s.
But as Einstein himself recognized, his theory conflicts with quantum theory. Physicists have been working nearly a century to unify these two conceptual frameworks, trying to create a quantum theory of gravity that would supersede Einstein’s theory. Candidates include string theory, loop quantum gravity, and many others, about which many books have been written, by Brian Greene, Lee Smolin, and others; my first book, The Complete Idiot’s Guide to String Theory, surveys the options. You might not know it from the vocal disputes among protagonists of these various theories, but they agree on one essential lesson: The space (and, possibly, time) that we inhabit is a construction. In some way or other, space consists of primitive building blocks and takes on its familiar properties from how those building blocks are assembled. In fact, that’s precisely why it is taking so long for physicists to develop a quantum theory of gravity. Every past theory has taken space to be a fundamental ingredient of the natural world, the venue in which everything happens. If space is itself a product of an even more fundamental level, it demands a completely different framework.
Physicists have built up considerable intuition for how ordinary substances are made of building blocks, and they can apply that intuition to space. Water, for example, consists of H2O molecules. It can undergo a change of state—freezing or boiling—as those molecules rearrange themselves into new structures. The same might be true of space. Cosmic mysteries such as black holes and the big bang might be situations where space undergoes a change of state: It melts. The result is a new state that is no longer spatial. (I have an animation of this process on my website.) And indeed black holes do behave in some ways as though their interior volume has ceased to exist.
Space might be analogous to an ice crystal, and any crystal has its defects—irregularities in the regular arrangement of molecules. Such irregularities would appear to us as small failures of space, such as when two distant particles retain a connection despite the distance that appears to separate them. The very concept of “distance” might not be fundamental, in which case it stands to reason that particles might sometimes behave as though they were right next to each other.
This is still speculative, but it shows how scientists are wrestling with spooky action. Just as every form of magic that people used to believe in proved to have a rational explanation, so, too, might physicists demystify the phenomenon that Einstein puzzled over. Space might be like a Turkish carpet. It is a beautiful textile that you can set a coffee table on. But looking closely, you might notice imperfections—little breakages in the pattern that show you, for example, the carpet is hand-woven rather than machine-made. Spooky action is not an insoluble puzzle. It may be our view of how the fabric of space is woven.