Harold Metcalf is one of the pioneers of laser cooling, a technique in which a laser beam is shined on atoms and cools them down to temperatures of microkelvins (millionths of a degree above absolute zero), where quantum mechanical properties can be experimentally observed. In fact, he and a colleague wrote the book on it, "Laser Cooling and Trapping," published in 1999. His role in the development of this vital scientific work is considered so significant that when William D. Phillips was jointly awarded the Nobel Prize in Physics in 1997 for "developments of methods to cool and trap atoms with laser light," he recognized Metcalf in his Nobel autobiography. Phillips wrote: "I had worked with Hal a little at MIT, and I knew that his unbounded enthusiasm and his effervescent creativity were priceless qualities. My collaborating with Hal on laser cooling was the first and one of the most important among many valuable interactions with colleagues who came to NIST, or whom I met elsewhere."
The two began their collaboration at MIT, when Phillips was still a student and Metcalf was on sabbatical from Stony Brook. Metcalf, now a Distinguished Teaching Professor in the Department of Physics & Astronomy at Stony Brook University, clearly remembers those first few moments of their partnership. Phillips "had ideas, and I told him he was crazy," he remarks. Crazy? "It was a simple argument," he recalls thinking at the time. "If you shine laser light onto something, you can't cool it."
But that is the beauty of science - hypotheses often lead scholars in unexpected directions. And discord among scientists often leads to the greatest of discoveries. "You make a hundred mistakes and then something works and then finally you get enough to work," he says. "The only way this can work is if the scientists remain in friendly contention, and I work best when there are different viewpoints. There always has to be a little bit of cooperative contention and an enormous respect for each other." He says that the friendly disagreement he encounters is often orchestrated by a bet: "Many times, I'll say (to a colleague) 'I'll bet you a Coke that you're wrong,'" and he jokes that the outcome of the scientific gambling is "I owe enough people Cokes to fill a railroad car."
Because of their tendency to see things in different ways, their eventual resolution made Metcalf and Phillips into excellent research partners, and in fact their fruitful alliance yielded the first two published papers on laser cooling. "It became clear after that -- we got along very well," Metcalf says with a laugh. Although in the beginning, when they first discovered the ability to cool atoms with lasers, he admits he was uncertain what the scientific value was. "Gee, this is pretty...his is good, but I wonder what we'll do next," he remembers thinking. But soon, he and Phillips were staying up all night tweaking their experiments, adjusting the lasers and before long, the aesthetic quality of the laser gave way to the ability to be able to observe quantum activity of atoms while they were cooled and trapped.
On the morning of one of their monumental discoveries they finished at the lab in the early hours, and went back to Phillips' house at 5am. They immediately went to the freezer, and started eating ice cream out of the carton. When Phillips' wife walked in, they told her about the atoms they had trapped. "She just shrugged,...and said that the ice cream was for the kids."
Despite all of his research successes, Metcalf states that that the relationship he has with his students is the facet he values most in his career. "My best moments are when a student says to me 'Look, Metcalf, you're wrong, and you're going to stand at this blackboard until I prove it.'" His educational philosophy is based on the fundamental notion that students should be required to study other areas of physics in addition to the subject on which they are focusing their thesis. "A significant number of students get jobs outside the area of their specialty," he explains. "An educated professional physicist must know about other areas of physics...It's all a matter of not being narrow."
To further his educational goals, Metcalf helped launch the Laser Teaching Center at Stony Brook over 12 years ago, which hosts undergraduate and high school students to conduct hands-on optics and laser research projects. "Hold on to your socks when you look at the students' projects," he proclaims with pride. "We have had students who live in another state and spend three hours traveling to the Center to work for a few hours on their projects. They get really very involved." The advantage of the youngsters pursuing their own original laser research is tremendous, he says. Students know that when they "will have learned something they will be the only person who knows this in the world, and that's very exciting."