SCIENCE

Potent particles

A Canadian scientist makes a key discovery

JAMES DEACON January 7 1991
SCIENCE

Potent particles

A Canadian scientist makes a key discovery

JAMES DEACON January 7 1991

Potent particles

SCIENCE

A Canadian scientist makes a key discovery

In the fall of 1984, John Simpson, a professor of physics at Ontario’s University of Guelph, carried out an experiment that produced results that could be crucial to scientists’ understanding of the universe—and its ultimate destiny. Simpson was trying to measure the mass of elementary particles called electron neutrinos, which are emitted from atoms during radioactive decay. In December of that year, Simpson made a discovery

that many other scientists said was probably erroneous: he found that some neutrinos had a much higher mass than scientists had previously believed possible.But last November, scientists at a laboratory in Berkeley, Calif., disclosed that they had duplicated Simpson’s results. Some physicists said that, as a result, theorists now may face the prospect of having to rethink some widely held theories about the creation and composition of the universe. Said Gerald Roy, a nuclear physicist at the University of Alberta in Edmonton: “If the theory is correct, it will tum a lot of things upside-down in the physics world.”

Simpson said that what he discovered in 1984 and in follow-up experiments were neutrinos with two different masses, including some with masses of 17 kiloelectronvolts (the mass of subatomic matter is quoted in units of energy). Scientists previously said that neutri-

nos have little or no mass. Simpson made his discovery with the help of a particle accelerator, a device that shoots atomic particles at one-tenth the speed of light, at McMaster University in Hamilton. But after Simpson published his findings in the New York Citybased journal Physical Review Letters in April 1985, scientists in Canada, the United States and Europe were unable to duplicate his findings in experiments of their own. As well,

Simpson, a 51-year-old native of North Bay, Ont., who won a scholarship in 1962 to England’s Oxford University, where he earned a PhD in physics, said that there was widespread skepticism about his discovery because it caused “some problems with physics as we know it.” He added, “People were not ashamed to tell me they did not believe it.”

Now, the experimental findings reported by scientists at the U.S. department of energy’s Lawrence Berkeley Laboratory in Berkeley could change that. Eric Norman, a nuclear physicist at that lab, disclosed at a physics conference held in Czechoslovakia in November that experiments carried out in the Berkeley laboratory appeared to confirm Simpson’s discovery. Norman told Maclean’s that he subsequently submitted a paper on his findings to Physical Review Letters, and editors at the Review said that Norman’s paper was being considered for publication early in 1991.

The confirmation of Simpson’s discovery could lead to a major revision of accepted theories about the nature, and eventual fate, of the universe. According to a body of scientific thought known as the big bang theory, the universe was created in a cosmic explosion about 15 billion years ago. Supporters of the big bang theory say that, ever since, all the matter in the universe, including stars and planets, has been moving away from the starting point and will continue to do so throughout eternity. But adherents of a rival theory contend that the expanding universe may reach a point at which, if the total mass of the universe is great enough, it will slow down, stop and then begin contracting again towards the centre. If that happens, some theorists say, the densely compacted mass at the centre of the universe will eventually heat up and destroy itself by exploding again—and set a new universe in motion.

Until recently, most physicists calculated that the total mass of the universe was not sufficient to cause it to stop expanding. But those calculations were based on the belief that neutrinos have virtually no mass. Although Simpson’s findings would only apply to about one-third of all neutrinos, Roy said that if heavy neutrinos exist, then previous calculations would mean that the effect of gravity on them would eventually cause the universe to contract. The discovery of the heavy neutrinos, said Clifford Hargrove, a physicist at the Ottawa-based Centre for Research in Particle Physics, “challenges the underpinnings of physics regarding the building blocks of matter.”

Roy added that if Simpson’s findings are widely verified, he could be in line for the Nobel Prize in physics, which is awarded annually to scientists who achieve major breakthroughs. Simpson’s discoveries, said Roy, “are that important.” For his part, Norman said that when he began his experiments in California two years ago, he was skeptical about the possibility of heavy neutrinos. But he added that the result of his laboratory work turned out to be “the most exciting thing I have ever been involved with.”

Simpson told Maclean’s that he had arranged for a leave from his teaching post for the 1990-1991 school year to work on the planned $61-million neutrino observatory under construction more than a mile underground in a mine shaft near Sudbury, Ont. There, according to Simpson and other scientists, by studying neutrinos that penetrate the Earth’s crust from outer space, they may be able to learn more about the tiny particles and the role they play in the unfolding of the universe. Despite the Sudbury commitment, Simpson said that he would continue to work on his neutrino mass experiments in an effort to confirm the existence of heavy neutrinos. If he succeeds, excitement over Simpson’s discovery would almost certainly be tempered by the questions they raise about the creation, and the future, of the universe.

JAMES DEACON