April 19, 2001

Physics Expert Breaks Down Tiny Neutrinos

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Approximately ten trillion cosmic neutrinos penetrate every square centimeter of our skin every second of every day, yet we cannot feel them. In fact, the possibility of their existence had not entered anyone’s mind until 70 years ago, and these particles have been puzzling scientists ever since.

The history of the neutrino and recent scientific findings concerning the particle were the subject of “Neutrinos: John Updike and the Big Bang,” a talk given yesterday by Wick Haxton, a physics professor from the University of Washington in Seattle.

Haxton, introduced as “an interesting fellow, but not quite as interesting as neutrinos,” is the director of the National Institute for Nuclear Theory in Seattle and has served on staff of the Los Alamos Scientific Laboratory.

The idea of the neutrino, or “little neutral one,” was proposed by Wolfgang Pauli in 1930 to explain the missing energy in the products of beta decay, Haxton said. Because Pauli proposed a particle that rarely interacts with other matter, he thought he had done a terrible thing, thinking he had postulated a particle that cannot be detected, Haxton said.

“If you threw a neutrino at the Milky Way, it would leave unchanged,” Haxton said. “Pauli felt that neutrinos could not be measured in the laboratory, [but] Pauli was only right for 25 years.”

The first discovery of the neutrino by experiment was performed in 1956 near the nuclear plant of Savannah River, S.C.

Haxton discussed John Updike’s poem “Cosmic Gall,” calling it ‘nerd poetry’ because of its subject — neutrinos. Updike wrote that neutrinos “have no mass/And do not interact at all./ The earth is just a silly ball/To them, through which they simply pass.”

But it turns out that although the standard model of particle physics describes neutrinos as massless, recent experiments have shown that at least one of the three types of neutrinos has a mass of approximately one tenth eV (electron-volt).

“It is entirely possible that the mass density of neutrinos totally dominates the universe,” Haxton said.

“We now know that neutrino mass is part of the dark matter,” he said.

According to Haxton, the most plentiful sources of neutrinos are the early universe and the sun. He described neutrinos as time capsules that cross the universe, having emerged one second after the Big Band.

This talk was part of the Hans A. Bethe Lectures, which were established by the Cornell physics department and the College of Arts and Sciences in 1977 to honor Bethe, winner of the 1967 Nobel Prize in physics. The John Wendell Anderson Professor of Physics Emeritus, Bethe won the Nobel Prize for describing the nuclear processes that power the sun.

Archived article by Inna Bruter