Clock watcher

Demetrios Matsakis keeps America’s time.And so, when the man who maintains the most accurate timepieces in the world at the U.S. Naval Observatory in Northwest Washington notices that one of two clocks on the wall in his office is four minutes fast, he grabs the minute hand and takes it back a few clicks.

“Oh, well. It’s just a wall clock,” says Mr. Matsakis, who has been the director of the observatory’s Time Service Department the past seven years.

In practice, the day-to-day business of keeping the nation’s time is much more technical.

Mr. Matsakis, an administrator with a scientific background, leads a team of 24 scientists who maintain a cluster of atomic clocks that measure our days.

He and his team are the unseen influence that tell Americans when to go to work. They tell people when midnight on Jan. 1 arrives and it’s time to celebrate the New Year. They provide the time to the services that people call to find out how fast or slow their clocks are.

They move the hands of every clock without touching them.

The work of the Time Service Department takes place quietly among people with considerable math and computer skills.

The scientists are the keepers of 60 atomic clocks housed in temperature-controlled chambers behind panes of glass in two buildings on the observatory campus.

From the outside, the building where Mr. Matsakis and his team work looks like an old bank, with stone walls and barred windows. Security is tight. Each door of Building 78 is locked to prevent people from wandering in.

From the inside, Building 78 looks downright institutional. Narrow halls and bare walls indicate that keeping official time is serious, scientific business.

There are no hands of time here. The atomic clocks show time in red digital numbers.

The clocks look like computer servers.

There are no grandfather clocks. There is no ticking or tocking. Not even on the wrist of the head of the Time Service Department.

Mr. Matsakis, a 54-year old with curly black hair, doesn’t bother to wear a watch.

“I don’t own a watch. What do I need one for? I’ve got so many here,” he says.

He is surrounded by clocks and immersed in the challenge of keeping an accurate read of the time.

Although the effort is largely automated, the team of scientists constantly oversees the operation to ensure that the clocks run properly.

“We have set it up so the system is automated,” he says. “But we do have to intervene.”

The 60 atomic clocks at the observatory and 15 at the Schriever Air Force Base in Colorado keep time independently. Engineers use each clock’s reading to determine the average time, then feed that into the Master Clock.

The reading on the Master Clock represents the official time.

That definitive time-keeping device sits down the hall from Mr. Matsakis’ office in a temperature-controlled chamber and easily could be mistaken for a piece of computer hardware.

Atomic clocks are different from the quartz watch on your wrist because the oscillation in an atomic device is between the nucleus of an atom and the surrounding electrons. Those oscillations keep track of passing time.

While the clocks do their work, computers are checking up on them to ensure accuracy. Mathematical equations measure each clock’s time, checking it against every other clock.

One group of clocks is checked every 20 seconds to determine whether their times are accurate. A second group is checked every hour.

Time kept by the Time Service Department is so accurate that on a bad day, Mr. Matsakis says proudly, it is likely off by no more than one-billionth of a second, or one nanosecond, over the course of a day. The accuracy of the system is the single-most important responsibility that Mr. Matsakis and his team have, and their delicate work is done on behalf of the Defense Department.

The Defense Department relies on accurate time keeping to support military operations. Atomic clocks aboard the Defense Department’s satellite-based global positioning system are calibrated daily with the atomic clocks at the Time Service Department to ensure that the military clocks are accurate. If clocks on the satellites are wrong, missiles that get coordinates from them could miss targets.

GPS devices are the spatial reference points that guide tactical weapons, said Geoff Chester, spokesman for the Naval Observatory.

Myriad other functions rely on accurate time keeping, including the operation of the Internet, cell phone networks, financial transactions and distribution of energy over power grids.

“Almost everyone in the world relies on accurate time, even though people don’t know it,” Mr. Matsakis says.

Despite the accuracy of the atomic clocks, a team led by Christopher Ekstrom, director of the Clock Development Division at the observatory, is developing a new clock.

“What we have now works now,” Mr. Matsakis says. “But in five to 10 years, it will be absolutely crucial” to update the clocks.

And a margin of error of one nanosecond will be too great.

“We can be more accurate,” Mr. Matsakis says.

As long as they aren’t using the clock in his office, that is.