Unlike most scientists, Demetrios Matsakis happily admits he has a “crackpot theory.” In fact, he’s eager to test it on me. I’m standing in a hallway near his office, facing a large window and looking into a room filled with multiple towers of electronics. Each device helps keep precise time, but out of all the dials, displays, and wires snaking about, I’m concentrating on a tiny screen that flashes once a second. Blip . . . blip. Meanwhile, I’m pressing a telephone to my ear, waiting for a beep. On the phone, an actor—Fred Covington, whose photograph hangs nearby—reads off the time. “At the tone . . . 16 hours, 12 minutes, five seconds”—beep. Matsakis smiles and asks me to judge which comes first, the blip or the beep.
Matsakis has a sly sense of humor: Jokes bubble up unexpectedly, and I can’t always tell when he’s making one—including now. He runs the Time Service Department at the US Naval Observatory, which keeps official time for the country. Without his department’s ultra-precise clocks, the Global Positioning System (GPS), cell phones, and the Internet would flounder, but few people even know the department exists.
Most visitors here are either fellow time geeks or officers interested in military applications. And after years of informally testing visitors, Matsakis theorizes that each camp has its brains wired differently. Military people generally see the blip first, he suggests, because they need to scan quickly for danger. Scientists, working in less perilous situations, hear the beep first. Now Matsakis wants to classify me.
I concentrate, but the beeps and blips seem to alternate, one arriving first, then another. Because that sort of averages out, I tell Matsakis they seem simultaneous. He appears satisfied with this, but I feel I’ve proved myself unfit for both science and soldiering. Or maybe Matsakis is messing with me. (Months later he informs me that, having gathered additional data, he’s rejected his theory about military people and scientists.)
Regardless, there’s a serious lesson behind the exercise. The beep and the blip are both wired into the US Master Clock, so they really are simultaneous. But many people have trouble sensing that. In fact, humans stink at keeping time on their own. We’ve all had days when the hours flit along like thoughts and others when time drags like an anchor. That’s why we’ve always used celestial bodies or mechanical clocks to track time.
But the clocks Matsakis works with vastly exceed the precision that any human could detect. Official US time usually drifts less than 0.0000000001 second (one-tenth of a nanosecond) per day. Satellites and computers need to track time on that scale, and they’re constantly bugging the Time Service Department for updates. Indeed, the department probably intersects with more people’s lives each day than any other government agency. Yet the only time the public notices is when something goes wrong.
Most Washingtonians probably think of official US time, if they think of it at all, as that clock with red numbers outside the Naval Observatory on Massachusetts Avenue, Northwest. You might have adjusted your dashboard clock to it at a stoplight. But that’s one of the least precise pieces of equipment the Time Service Department runs. The real time-geek goodies sit behind the guard depot and wrought-iron fence.
The security checkpoints protect not the Time Service Department—though it does house classified military equipment—but the Vice President, who also resides on the USNO campus. (Al Gore often dropped by the observatory to peer through telescopes.) Beyond the security, the campus is bucolic—full of trees, meandering roads, and occasional deer. The low buildings would look almost like an old-fashioned town but for the gargantuan satellite dishes out front that push time signals into space.
The devices that keep official US time sit in environmentally controlled chambers down the hall from Matsakis’s office. They look nothing like typical wall clocks with gears and springs. Some of the devices are hydrogen masers, which are similar to lasers. They look like an airplane drink cart might if it were designed by Brink’s—thick, black, imposing, and on wheels. They weigh more than 500 pounds, and only a time display in front betrays them as clocks.
The other main type of timepieces, cesium clocks, are stacked in a separate room in what look like refrigerators with glass doors. Both devices keep time essentially by counting. In cesium clocks, a beam of light strums a certain electron inside some cesium atoms, causing the electron to oscillate back and forth unthinkably quickly—9,192,631,770 times a second. Scientists know it takes 9,192,631,770 flip-flops because they’ve defined one second as that many flip-flops—which explains why Matsakis can rattle that number off in roughly a nanosecond himself.
Masers are sprinters, best at keeping time over the short term—a few days—while cesium clocks keep better time over weeks and months. Official US time incorporates readings from both—around a dozen masers and a few dozen cesiums. But because each clock ticks ever so slightly differently, the Time Service Department has picked one maser as the clock and uses other devices to tweak its output every hour.
This ensemble of devices, collectively called Master Clock 2, keeps official US time, and it has ticked continuously, every second of every minute of every hour, since 1995. (There used to be a Master Clock 1 as well, and the Time Service Department alternated between the two. When the decision was made to stop doing that, Master Clock 2 happened to be running things, so it stayed on as the official clock.) Backup master clocks sit in other buildings around campus, Matsakis says, “so if one building burns down, another keeps ticking.”
Defining time with MC2 is only half the job. The department also pushes time out to the public so the rest of us can at least approximate its precision. The least precise method of disseminating time is the telephone. If you dial 202-762-1401, Fred Covington will read the time to you. He’s best known as the auctioneer in Roots, but the movie website IMDb does credit him with reading USNO time. Reciting the entire 24-hour day in five-second intervals took Covington multiple days of taping in 1978; his voice does sound smoother than typical call-in services. Dialing in and listening for beeps might seem archaic—too imprecise for a digital age—but Americans still ring Fred up 4 million times every year. It might be the most repeated performance in history.
For higher precision, USNO disseminates time over the Internet. If left unchecked, internal computer and server clocks can drift by several minutes a month, which could lead to quarrels over, say, when stock trades went through or whether someone submitted his taxes on time. For that reason, most computers and servers synchronize with official US time every hour or so.
Even more sophisticated is the equipment that helps set time for GPS. (The GPS Master Control Station—located on Schriever Air Force Base in Colorado—keeps its own clock, but USNO corrects and updates it.) GPS devices detect signals from multiple satellites and use the time differences among those signals to calculate position. For every nanosecond of uncertainty in when the signals arrive, that accuracy drops. USNO also provides time information for military satellites that need even higher resolution, but Matsakis declines to elaborate.
The various clocks that define US time mostly tick along without intervention. They certainly don’t need winding. Still, there’s a chronic, smoldering fear that something will go awry—that time will be lost.