The Human Clock

Burdick takes his time elegantly explaining its mysteries as a human phenomenon, blending philosophy, history, psychology, and candid introspection. The time he cares about is a “property of the mind,” a bodily function and a social agreement.

Even within our bodies, clocks must be synced. We have organs for each of our senses, but no one time-sensor. Our organs and cells contain clocks of their own, and our conscious sense of time, which arises from more than one area of the brain, must be coordinated by a “suprachiasmatic nucleus.”

As Burdick puts it, on a flight from Paris, “When my suprachiasmatic nucleus lands in New York, my liver may still be on Nova Scotia time and my pancreas may be somewhere over Iceland.” On long flights he advises timing your meals as if you’d already arrived at the destination city, to get your digestive organs ready. Your liver tends to set its clock to regular mealtimes. So if you need help getting up in the morning, you might be strict about eating breakfast, as your liver will help wake you. (On the other hand, nighttime binge-eating is the high, straight road to obesity.)

The origins of all those body time-sensors may lie in the scum on the surface of a pond. Every algal cell in that scum is a kind of clock responding to morning, noon, and night. Like algae, underneath the social clock, our bodies respond to the solar day.

One summer, Burdick joined a field station in the Arctic, at the edge of Toolik Lake on Alaska’s North Slope, where the sun doesn’t set from mid-May to mid-August. Under constant light, the biologists at Toolik slept and worked when they pleased, fanning “out across the landscape at all hours to gather, measure, synthesize, compare and converse.” A 6:30 a.m. breakfast became the social focal point, followed by bed for many. Others barely slept for weeks, putting themselves at risk of psychosis.

In darkness, we also drift away from the solar day. Burdick tells the touching and horrific tale of a scientist, Michel Siffre, who twice isolated himself underground for months (wired to a research team up above) to measure how his body responded to the absence of external time cues. Siffre kept his own calendar, based on when he woke up. On his 37th day underground, he thought he was on Day 30. Unglued from the solar day, his temperature and sleep cycle, normally in sync, separated. He began sleeping for 15-hour stretches while his temperature cycle maintained a 26-hour beat.

When he emerged, he reported that his entire stay underground felt like one continuous present, with no clear memories to establish sequence.

Here the reader will learn about everyday inaccuracy in our perceptions. Take duration: In lab tests, a larger or moving dot seems to last longer on a screen than one that is small or still. As Burdick notes, our brains bend time to enhance our sense of power. If you believe that pressing a button causes a beep, you’ll think the beep came sooner than it actually did. Our brains make up simultaneity so we can make sense of our world. Burdick gives the example of glancing at an American flag spread out on a lawn: Our neurons register red light before green and both before blue. But we don’t see a smear of red, green, then blue—because our brains “recalibrate the visual streams and intermittently set the time to zero,” Burdick explains, quoting a scientist who thinks that we do the reset when we’re blinking:

Time, at once a property of the mind and a tether to other people, regularly gets us in trouble. Burdick doesn’t delve into personality and its relationship to time, though he often confesses to anxiety. As I read his thoughtful account, I kept noticing how many of our issues might be understood as a gap or disorder of clocks. One person is chronically late; another always feels rushed or impatient.

Alone or together, we celebrate when we lose awareness of time, when the tether doesn’t pull. Time flies, or a peaceful afternoon feels rich and long. If we are with others, we say we are “in sync”—which is not, or not only, a metaphor. Matching your experience of time to another person’s is a hallmark of courtesy or intimacy, deliberate when we slow our pace to walk alongside our grandmothers and more instinctive when we match body language or the pace of emotional response and revelation.

Peace with time. Isn’t that a fair definition of happiness? We casually talk about hating time as a tether—yet that tether is also a source of our greatest satisfactions. We get a rush of competence meeting a deadline. Musicians coordinate with the conductor’s wand. We celebrate holidays. The trains are beautiful when they arrive and leave on time.

Time, as physicists debate it, runs at different speeds, is distorted by matter, and, according to Einstein, is not an arrow pointing in one direction. Burdick doesn’t give us any reason to believe in the fantasy of time machines. He also doesn’t explore mysticism, the extended experience of timelessness. But in showing how our sense of time is human (and culture-bound) he offers a kind of freedom. We learn that children can’t accurately distinguish “before” from “after” until the age of 4 or so. The Pirahã, in Brazil, rarely refer to time at all.

Aging doesn’t have to be regarded as a slipping-away. The answer to “why time flies” is that it probably doesn’t. We lament, “Where does the time go?” and believe that time feels faster as we age, yet we answer questionnaires in ways that suggest that, in fact, our sense of time doesn’t change much from decade to decade. If time is an ocean, we are the fish, complaining as we swim.

Temma Ehrenfeld is a writer in New York.