Which makes the humble neutrino stand out. Two physicists, Takaaki Kajita of the University of Tokyo and Arthur B. McDonald of Queen’s University in Canada, shared the Nobel today for showing that neutrinos have mass.
That means a lyrical John Updike poem needs an official correction:
Neutrinos, they are very small.
They have no charge; they have
no mass; a tiny amount of mass;
They do not interact at all.
The earth is just a silly ball
To them, through which they pass
Like dustmaids down a drafty hall.
If a poet can get excited about neutrinos, so can we. Here's my case for why we, like physicists, should celebrate the neutrino:
1) A figment of physicists' imaginations
The neutrino was invented to fix a loophole in an equation. Who hasn't stared at a math problem and not been able to figure out why the numbers don't add up? That happened for physicists in 1930, who were trying to figure out why there was some troubling missing energy in radioactive decay. Enrico Fermi and Wolfgang Pauli invented an imaginary particle to solve the problem.
"Dear radioactive ladies and gentlemen," Pauli wrote to fellow scientists. "I have come to a desperate way out. ... I admit that my solution may appear to you not very probable a priori, since one would probably have seen the neutrons a long time ago if they exist. But only one who dares wins."
Pauli suggested "the neutrons" be called neutrinos instead -- little neutral ones.
2) The poltergeist particle
Science can often seem quite dry, its results presented as if their certitude was never in doubt. But science is a risky business, more a process of continuously being wrong about stuff and troubleshooting experiments than it is about enjoying moments of lucid insight. As if an admission of that fact, the first Nobel Prize-winning experiment that confirmed the neutrino was real in 1956 was called Project Poltergeist. If ever one needed a reminder that even physicists pondering the smallest components of matter or the biggest questions about the universe are just like us, that name is a powerful piece of evidence.
3) Today's Nobel is the answer to a longstanding scientific mystery
In the 1960s, a physicist named Ray Davis set up a huge detector 4,850 feet underground in an active gold mine in South Dakota. It was a massive vat, filled with 100,000 gallons of perchlorethylene, to catch neutrinos that might interact with the chemical. The miners in the gold mine called it "the tank." Which, by the way, means that miners in a tiny South Dakota town were aware of a major scientific experiment to capture a mysterious particle that a German and Italian scientist had proposed a couple decades earlier.
The mile of rock above would act like a filter and Davis would measure the interactions between the neutrino and the particle inside. This detector identified neutrinos created from the sun, but far too few.
"That was where the hint came from that there weren’t enough neutrinos coming from the sun," said Kate Scholberg, a physicist at Duke University. "That lasted forever; it started in the '60s, when they detected less than predicted by the model. Is something wrong with the model? Something wrong with the detector?"
Davis would win the Nobel for his work, but also set off several decades of scientific soul-searching.
"Solar Neutrinos: Where are They?" a 1972 article in Science magazine asked.
The answer would come from the work that led to this year's Nobel prize.
Neutrinos, physicists figured out, came in three flavors. Davis's detector was sensitive to only one -- the electron neutrinos produced by the sun. That meant maybe he was finding so few because the neutrinos could switch identities. But for that to be true, the particles would have to have a mass and everyone had assumed they didn't. The experiments that McDonald and Kajita led -- cavernous underground detectors in Canada and Japan -- were able to finally show that neutrinos have mass and were changing identity. The particles weren't disappearing -- they were changing flavors.
4) The people's particle
Perhaps more than any other particle, the neutrino is also the people's particle. It was a daring fiction concocted in the mind of a scientist, confirmed a quarter century later, that has continued to tease the scientific world with its elusive nature for another half century. Even knowing it has mass doesn't solve things, because that simple fact chips away at a canonical framework in physics, called the Standard Model. Further experiments on neutrinos may help us crack an existential philosophical conundrum: why the universe is made up of matter and not anti-matter.
I called Mayor Jerry Apa of the little town of Lead, S.D., where the conundrum about neutrinos that was ultimately solved by scientists today first began, to ask him how he felt about his town's role in this ongoing mystery of the universe. Lead isn't a university town or even a very big place -- its population hovers a little over 3,000 people. But it recently put up a statue, made of the actual metal of the original detector, he said, to honor Ray Davis, the scientist who started the head-scratching solved by today's prize-winning work.
"I don't know the exact year that Dr. Davis started his neutrino project down in the Homestake Gold Mine at the 4,850 level. But I know that prior to that, all Dr. Davis had was a theory. And when he set up his initial project, that proved his theory," Apa said. "We're especially proud and very excited that we do have now a long-term based neutrino project going in. ... They're going to do further experimentation on the mass and makeup of the neutrino, and we're very excited about this. We're very happy. And we're very proud that we're basically the home of the neutrino."