My attempt to learn quantum mechanics, which has consumed me for more than a year now, has dredged up a creepy, long-buried memory. It dates back to the late 1970s, when I was living in Denver, Colorado. One day I found myself in a grungy saloon on Denver’s dusty eastern outskirts. Behind the bar was an aquarium with a single, nasty-looking fish hovering in it. A silver, saucer-sized, snaggle-toothed, milky-eyed, blind piranha.
Now and then, the bartender netted a few minnows from a fishbowl and dropped them into the piranha’s cubicle. The piranha froze for an instant, then darted this way and that, jaws snapping, as the minnows fled. The piranha kept bumping, with audible thuds, into the glass walls of its prison. That explained the protuberance on its snout, which resembled a tiny battering ram. Sooner or later the piranha gobbled all the hapless minnows, whereupon it returned to its listless, suspended state.
What does this poor creature have to do with quantum mechanics? Here’s what. Our modern scientific worldview and much of our technology—including the laptop on which I’m writing these words–is based on quantum principles. And yet a century after its invention, physicists and philosophers cannot agree on what quantum mechanics means. The theory raises deep and, I’m guessing, unanswerable questions about matter, mind and “reality,” whatever that is.
The more I dwell on puzzles such as superposition, entanglement and the measurement problem, the more I identify with the piranha. I’m blindly thrashing about for insights, epiphanies, revelations. Every now and then I think I’ve grasped some slippery truth, but my satisfaction is always fleeting. Sooner or later, I end up crashing into an invisible barrier. I don’t really know where I am or what’s going on. I’m in the dark.
The main difference between me and piranha is that it is inside the aquarium, and I’m on the outside, looking in. I can take solace from the fact that my world is much bigger than the piranha’s, and that I know many things that the fish cannot. But it’s all too easy to imagine some enlightened, super-intelligent being standing outside our world, looking at us with the same pity and smug superiority that we feel toward the piranha.
Plato presents himself as this enlightened being in his famous parable of the cave, which I make my freshman humanities classes read every semester. The parable describes people confined to a cave for their entire lives. They are prisoners, but they don’t know they are prisoners. An evil trickster behind them has built a fire, by means of which he projects shadows of everything from aardvarks to zebras onto the cave-wall in front of the prisoners. The cave-dwellers mistake these shadows for reality. Only by escaping the cave can the prisoners discover the brilliant, sunlit reality beyond it.
We are the benighted prisoners in the cave, and Plato, the enlightened philosopher, is trying to drag us into the light. But isn’t it possible, even probable, that Plato and other self-appointed saviors, who say they’ve seen the light and want us to see it too, are charlatans? Or loons? Given our profound capacity for self-deception, isn’t it likely that when you think you’ve left the cave, you’ve actually just swapped one set of illusions for another?
These are the questions with which I torment my students. To make them feel a little better, I bring up another possibility: If we realize we’re in the cave, isn’t that the same, sort of, as escaping from it? Actually, if “ultimate reality” is inaccessible to us, isn’t that the same, sort of, as saying that it doesn’t exist? And hence that the cave, the world in which we live each and every day, is the one and only reality? And hence that we should just chill out and enjoy ourselves?
Maybe. On good days, I look out the window of my apartment at the shining Hudson River, crisscrossed by boats, and at the Manhattan skyline, a symbol of humanity’s ever-growing knowledge of and power over nature, and I think, Yes, this is reality, there is nothing else. But then I remember the quantum mist at the core of reality, which not even the smartest sages can penetrate, and to which most of us are oblivious. And I remember the piranha, bumping over and over again into the walls of its world, blind to its own blindness.
Scientific Curmudgeon is an Opinion column written by CAL Professor and Director of the Stevens Center for Science Writings, John Horgan. Columns are adapted from ones originally published on ScientificAmerican.com.
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