University research professor Raymond Davis was recently awarded the National Medal of Science for his innovative work in the field of neutrino physics.
This honor acknowledges Davis' cutting-edge research in discovering the properties of neutrinos -- particles that are generated from reactions in the core of the sun.
Davis is very pleased with the award and actually did not expect to receive such an honor.
"I was quite surprised. I knew about the award but didn't think that I would ever receive it because I was busy doing science," Davis said.
Davis' research forced scientists to reconstruct the standard solar model -- which describes the composition of the sun and is derived from the conservation and energy laws of physics.
This work has also helped create the field of neutrino astronomy.
Davis' most significant academic achievement was developing an experiment in the early 1960's to catch neutrino particles coming from the core of the sun.
"It was really a unique experiment," Penn physics professor Ken Lande said. "What [Davis] did is absolutely pioneering -- to be so audacious as to say, 'I'm going to look at the center of the sun.'"
In order to catch the solar neutrino particles, Davis designed a detector -- which contains a 100,000 gallon tank containing the same chemical that is used in dry cleaning fluid -- in Homestake Gold Mine in Lead, South Dakota.
Although Davis's experiment proved that reactions in the sun generated neutrinos, his findings showed that there were only one-third of the number of neutrinos predicted by scientists.
"The important thing was that [Davis] found that the flux of neutrinos was one-third of what was predicted by the solar models," Physics Department Chair Tom Lubensky
The results from Davis's experiment caused scientists to question whether his findings were actually valid.
"There was a meeting in 1972 in Irvine, California to discuss the result of Ray's experiment and the fact that the theoreticians didn't expect it to give what they thought it should," retired chemist at Brookhaven National laboratory Keith Rowley said.
Verification experiments were launched in 1965 and confirmed Davis's findings; however the results were still boggling.
Scientists were left to face the fact that the only explanation of the discrepancy between Davis's findings and the expected amount of neutrinos was that they did not fully understand all the properties of neutrinos.
"The only possibility is that [the scientists] didn't understand something about neutrinos," Lubensky said.
It was not until last year that neutrinos -- "the mysterious particles" -- became less opaque to scientists.
The Sudbury Neutrino Observatory in Ontario, Canada announced in April 2001 that scientists international collaboration of scientists determined that there were actually three types of neutrinos -- electron, muon and tau -- instead of one.
Davis' detector had only captured electron neutrinos, which explained his neutrino deficit.
Data about the neutrinos was compiled from four different neutrino detectors around the world.
"We combined data from all these detectors and combined data to form the picture of the center of the sun," Lande said.
The finding implies that neutrinos have mass -- they were formerly thought to have had none -- and is a break through discovery.
"The first publication is very significant and impacts the details of nuclear physics of the sun and fundamental properties of the sun," physics and astronomy professor Gene Beier said.
Beier, along with a group of scientists conducted an experiment in the mid-1980's that confirmed Davis's experiment.
Lande applies the results from the 2001 findings a step further.
"We're addressing a more fundamental question of our existence than just how our sun generates energy," Lande commented.
Lande believes that the anti-matter in the universe may come from the way neutrinos disperse themselves from the sun.
Even though the discovery that neutrinos can change, Rowley believes that Davis's experiment was the first sign that neutrinos can change as they travel through space.
"Ray's experiment was the first hint that neutrinos oscillate," Rowley said.
Despite the cutting edge discoveries, scientists still have much more to learn about the properties of neutrinos.
While there are three different kinds of neutrinos, there are three different energy levels of them as well. And scientists have just begun to understand only the highest energy level of neutrinos.
However, Davis's colleagues are not only still in awe of Davis's detection of neutrinos -- they also feel that he is much more than a scientist.
"Besides being a great scientist, he is also a wonderful human being," Lande said.
