More Than a Clock Watcher

A Nobel Prize winner in physics, William D. Phillips has done more than just improve the accuracy of clocks-he's an ambassador for public service.

For a world-renowned scientist, William D. Phillips is surprisingly easy to talk to. In 1997, he became the first government employee to receive the Nobel Prize in physics (which he shared with two other scientists) for research conducted in pursuit of an agency mission-namely, using lasers to cool atoms and improve the accuracy of clocks-at the National Institute of Standards and Technology.

Ask Phillips, who leads NIST's laser cooling and trapping group, to explain his work (How, for example, do lasers cool atoms? And what do chilled atoms have to do with clocks?), and he cheerfully launches into an explanation that starts, quite literally, at the most basic level. "Everything is made of atoms and molecules," he says in a patient tone that implies there are no stupid questions, and that nothing could be more important to him than helping you understand. "The temperature of anything is related to how fast those atoms and molecules are moving."

The velocity of atoms is important in measuring time because the international definition of a second is based on the frequency of cesium atoms, which at normal temperatures bounce around at approximately the speed of sound, making them difficult to observe and measure.

In the late 1970s, Phillips set out to slow atoms down. How and why he did so is a much more complicated story involving Einstein's theory of relativity, lasers tuned to a frequency that creates an "optical molasses," a fountain that sprays atoms, and many years of hard work. Suffice to say that Phillips and his collaborators managed to slow cesium atoms from the speed of sound to the comparatively glacial pace of less than one centi- meter per second. The temperature? Within one-millionth of a degree of absolute zero-about 100 times colder than anyone had predicted-or, as Phillips says, "more than a million times colder than outer space."

His work transcends the realm of time measurement, opening new ways to study the interaction between radiation and matter. And one emerging application, called quantum computing, could prove invaluable for national security. "What he has done is to introduce a whole new field of physics," says Katharine B. Gebbie, director of NIST's physics laboratory. Gebbie received the Service to America Medal for Career Achievement in 2002.

But that's not why she nominated Phillips for the Career Achievement Medal. Since receiving the Nobel Prize, he has made it his mission to give as many public talks as possible-not just before elite scientific societies and promising graduate students, but also at elementary schools, senior centers, churches, science fairs and Girl Scout gatherings. "I just don't see how in good conscience you can refuse to do that," Phillips says. His willingness to accept invitations to speak has required nearly constant travel. "It has changed his whole life," Gebbie says. "He is an ambassador not only for science and physics, but also for government."

Receiving the Nobel Prize was "an almost unimaginable honor," says Phillips, who spent much of his childhood experimenting with household chemicals and putting anything and everything under a microscope his parents gave him. He felt that the award came with a responsibility. "People will come to listen to you simply because they want to hear a Nobel laureate," he says. "As scientists, it's very important for us to try to interpret science to the general public and to convey to young people how exciting science is."

Indeed, Phillips-who was a member of his high school debate team-can pack a room even in bad weather. "His audiences are always excited," says Gebbie, who has observed many of his talks. "He has the ability to make people feel they understand." And the fact that Phillips performed his groundbreaking work at NIST flies in the face of a common academic prejudice-that curiosity-driven research is more interesting than practical research. "All of his research has been in support of the NIST mission," Gebbie says.

"I get a chance to be an example of what public servants do," Phillips says. "We watch the clock-to make it better." So how accurate are the clocks that make use of Phillips' research? They're off by less than one second every 60 million years. As Phillips says: "That's what we call close enough for government work."