Feb. 16, 2004 Neutrinos are about the tiniest things in existence, but developing a greater understanding of what they are and how they function is likely to have a huge impact in the next few years.
The subatomic particles, created in the nuclear furnaces of the sun and other stars, have no electrical charge and only recently has it been found that they have any mass at all, yet billions pour through each human body every second with no discernable effect or interaction.
Still, the very slight mass each neutrino possesses is enough for all of them together to be comparable to the mass of all the stars and planets of the universe, said John F. Wilkerson, a University of Washington physicist who is working at the forefront of neutrino research. He will discuss the future of neutrino physics research Sunday during a symposium at the American Association for the Advancement of Science meeting in Seattle.
While neutrino research might seem esoteric to some, Wilkerson believes it has broader impact.
"You can never predict the future of what the spinoffs will be," he said. "We're trying to have a better understanding of the universe, and because we're pushing the technology there are some interesting technological spinoffs."
He concedes that current neutrino experiments and ones that follow are unlikely to have much direct impact on most people's daily lives, but they will bring technological advances. For instance, neutrino science is improving techniques for making clean materials, since the laboratories are among the cleanest places in the world in terms of background radiation.
Inside those labs are neutrino detectors – huge tanks filled with hundreds of thousands of gallons of ultrapure water or other liquid ideal for observing ionizing particle reactions. But those detectors also keep vigil, watching for a star in our galaxy that explodes into a supernova. A sudden burst of neutrinos, lasting less than a minute, can let scientists know of the supernova in time to make astronomical observations.
Technologies developed for neutrino detectors also can be adapted for security needs, such as detecting clandestine nuclear weapons tests or possibly detecting nuclear material being smuggled through a seaport.
Neutrinos come in three types, or flavors: electron, tau and muon. One project in which Wilkerson has played a major role, the Sudbury Neutrino Observatory in Ontario, two years ago provided definitive evidence that not only do neutrinos have mass, but that they change willy-nilly from one flavor to another as they flit through air or matter.
This answered a question that had puzzled scientists for decades – why there seemed to be fewer neutrinos coming from our sun than theory predicted. The answer was that the neutrinos were there, but only one type could be detected. Finding the other types solved that problem, and led to the realization that neutrinos do have mass, contrary to the accepted rules of physics.
"Science, in answering one question, has opened up a whole area of new and interesting questions," Wilkerson said – questions such as what role neutrinos played in the early universe, how stars explode and how those explosions create heavy elements such as copper and lead.
"If we want to understand the way these elements are created, as we are trying to do, there's no way to do that without understanding neutrinos," he said.
That lends greater importance to an upgrade of the Sudbury experiment that will allow it for the first time to be able to differentiate in real time between types of neutrino reactions. It also shows the significance of an experiment in Japan called KamLAND, which examines the properties of antineutrinos generated by a number of nuclear reactors at Japanese power plants.
Wilkerson believes the work at Sudbury and KamLAND in the next few years will emphasize a growing need for an underground science laboratory in the United States. Currently there are a handful of major dedicated underground labs in the world, but the deepest is less than a mile below the surface and new experiments need depths of perhaps 7,000 feet or more.
There are several proposals to build an underground lab in the United States, including a closed gold mine in South Dakota, beneath Washington state's Cascade Range and next to an old iron mine in Minnesota. There are many advantages for the U.S. to have an underground lab, Wilkerson said: it would be a boon to education on all levels, would help train a future force of scientists, and would let the work of U.S. scientists be accomplished here, he said.
"There's been a long history in the last 30 or more years that there have been good ideas in the United States, and they've been done at underground labs around the world but not in the United States because we didn't have a facility," he said. "There's a real compelling need based on the science, and there are a lot of potential benefits."
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