Everyone knows this koan-like query: If a tree falls in the forest and there's no one there to hear it, does it make a sound? When I was introduced to this puzzle as a young child, it confounded me. My first thought was: Why do people care about unobserved trees toppling over? What was the point of thinking about it at all? The idea of such a thorny query existing struck me as both profound and absurd. Why not ask instead: If a ham sandwich sits on a kitchen counter in Hoboken, New Jersey, will it make me hungry? But when I tried to picture a tree falling, I realized that I was just replaying television footage of giant pines crashing to the ground with a great whoosh and thump (from some PBS special on clear-cutting undoubtedly). The woods I knew were populated by people wielding cameras, observing. That wasn't going to work.
So then I squeezed my eyes shut tight and imagined myself walking through the woods, just walking around aimlessly, kicking through the pine needles, not expecting a tree to fall but waiting for a tree to fall. Maybe it would fall way off in the distance so I could pretend I wasn't actually listening. This scenario wasn't going to work either, as I was still going to be there to hear the sound, and the point of the exercise was to address whether or not the poor tree could be heard keeling over. I needed a depopulated, silent forest, a dying tree, and a way to record it.
This was the profound bit: How to imagine a tree and whether or not it made a sound. Trying to envision this was one of the first mind-bending moments I remember. It was a Schrodinger's cat type of thing: How could you find out what happened if you weren't allowed to be there? Was silence just the lack of human perception? If so, did the universe go dormant when people weren't around? And then further down the solipsistic rabbit hole: Did things stop when I was napping, like everyone just sort of slumped over like they ran low on batteries and then perked up when I awoke?
Typical greasy kid's stuff. And then I had a breakthrough: Just leave a tape recorder in the forest and come back later. You'd need a long-playing tape, of course. You'd have to hope the tree wouldn't fall on the tape recorder as well; or that you wouldn't be eaten by bears. But then we would know—all you'd have to do was playback the tape. If only there had been woods near my house I'd have done it myself. I'd have solved this dilemma once and for all! I pictured playing the tape at the UN (which is where I thought the Nobel Prize was awarded) and receiving the grateful, thunderous applause of the assembled nations, just reward for a boy genius.
I was too young to know that this was a theoretical question about how we define sound—whether it's a vibration independent of its reception by the brain or whether it relies on being perceived to make it sound. The fact that this theoretical question persists tell us an amazing thing about ourselves: We're quite self-centered to think that the universe needs our perception to validate its existence. Was the universe silent before the arrival of homo sapiens? Did disturbances of air become sound only 200,000 years ago, when we made the scene? Two hundred thousand years is an awfully short period in geological time—it must have been awfully quiet out there. Is it still a sound if a pterodactyl makes it and a stegosaurus hears it?
All this reminiscing about my early philosophizing was brought to mind by Wendy Kagan's exploration of silence as a spiritual practice ("Daring to Be Silent"). Nearly all religions have meditative quietude as part of their tradition, as a road to the interior, a way to get closer to the divine.
Contemporary silent practice is different from that practiced by monks in the 16th century. Those monks didn't have to contend with their iPhones beeping at them every minute with updates from Facebook, Instagram, and Twitter. Our world is noisier than ever. But as cacophonous as our environment is, it's noisier inside. Silent meditation brings the interior chatter to light. "Silence acts as an intensifier," says meditation teacher Sharon Salzberg. "We can see more clearly the lack of silence that's going on in our minds." And that's a scary thought—I can see myself on the third day of a silent retreat repeating to myself the suspense film cliché: "It's quiet in here. Too quiet."
What we consider silence, however, is not the genuine article. The composer John Cage went in search of it, visiting the anechoic chamber at Harvard University. An anechoic chamber is a room designed to completely absorb sound—a silent room. When Cage emerged, he told the technician he had heard two sounds: one high and one low. The technician told Cage that the high sound was his nervous system operating, and the low sound was his blood circulating. Cage concluded that there was no such thing as silence in an auditory sense. "Silence is not acoustic," Cage later wrote. "It is a change of mind, a turning around."
Cage's best-known work, 4'33", debuted on August 29, 1952 at Maverick, an open-air concert hall in the woods outside the village of Woodstock. The piece consists of any instrument or combination of instruments not being played for roughly four-and-a-half minutes. I imagine the baffled crowd at the premiere watching the lone pianist on the stage, not playing. Cage's point was to get people to listen to the accidental sounds around them, like the wind through the pines, or the late summer crickets, or the sound of their own blood circulating. Maybe they heard a tree falling somewhere in the distance. Maybe not.