A RESPECTED SCIENTIST AND A BELOVED TEACHER

Author: By Richard Saltus, Globe Staff

Date: Friday, October 13, 1989
Page: 3
Section: NATIONAL/FOREIGN

Speaking to reporters at a news conference yesterday, the new Nobelist was making a homely analogy to an atom, with its nucleus and a cloud of surrounding electrons locked in a counter-rotating pas de deux.

The nucleus and the electrons are both surrounded by magnetic fields that interact as the particles whirl -- like two magnetized toy tops.

As a result, the atom emits energy at extraordinarily regular intervals, energy that can be picked up and measured in cycles per second like a radio station, explained the 74-year-old Ramsey, who shared the Nobel Prize for physics yesterday.

"You learn a lot about the structure of the atom and the molecule" by studying this emission of energy from the magnetic interaction, said Ramsey, who won the prize for an extremely precise method of measuring the energy.

"And incidentally," he added, "it also makes the world's most stable clock."

It was this kind of pithy explanation, toy tops and all, that made Ramsey a beloved teacher as well as a leading research scientist, said Geoffrey Greene, a former student.

"He was always pointing with his fingers," Greene recalled with a smile. ''His great strength is that he has a deep, intuitive understanding of physics, not just a complicated mathematical one."

"And his students all absolutely adore him," added Greene, now a scientist with the National Institute of Standards and Technology.

Ramsey has spent much of his career devising ways to make the most precise possible measurements of the way basic particles behave. The technique for which the Nobel committee cited him, called the "separated oscillatory fields" method, is the basis of the cesium clock, the present worldwide standard of time.

The basis of timekeeping has always been a periodic motion of some kind, whether it is the swing of a pendulum or -- the most basic measure of time -- the rotation of the earth.

All these movements have slight variations that erode their accuracy. But the regular spurts of energy from an atom, like that of the element cesium, are "very, very stable and are not affected by temperature and other things," explained Ramsey.

These measurements, made possible by Ramsey's technique, are the basis of ''atomic clocks." The second, for example, is defined as a 9,192,631,770 cycles of energy from a cesium atom.

Using the same principle with hydrogen atoms, Ramsey was the principal inventor of the atomic hydrogen maser, a device used to amplify extremely faint signals such as radiation from space.

West German Wolfgang Paul and University of Washington researcher Hans G. Dehmelt, who shared the prize with Ramsey, have done work that will make even more accurate atomic clocks possible. The prize committee cited them for developing different versions of the "ion trap," a technique for separating electrically charged atoms and measuring them in such a way that no physical forces interfere.

Despite his retirement from Harvard, Ramsey is continuing to work on one of the central problems of physics, trying to determine if the fundamental particle called the neutron has a property called the electric dipole moment.

If so -- and it has not yet been detected -- it would be a sign of ''symmetry breaking," a concept related to the creation of matter in the
universe after the primordial Big Bang. A major puzzle is why the universe contains so much matter compared with its invisible mirror-image counterpart: antimatter.

According to some scenarios, the universe could have vanished in a huge explosion of energy as matter and antimatter anihilated each other, but for some reason matter predominated.

SALTUS;10/12 NKELLY;10/13,11:22 CLOCK13