To help unravel the mysteries of the universe, a University of Delaware scientist literally went to the ends of the earth.
Tom Gaisser has been searching for the tiniest of space travelers in Antarctica for nearly 10 years as part of an international expedition of scientists.
In November, the team formally announced it had discovered 28 high-energy neutrinos - nearly massless subatomic particles, many from outside our solar system - at the IceCube South Pole Neutrino Observatory.
Physics World proclaimed it the "Breakthrough of the Year." Dave Goldberg, a writer and Drexel University astrophysicist who was not on the South Pole team, called the results "absolutely breathtaking."
Best-selling author Ray Jayawardhana, whose book Neutrino Hunters serendipitously was published last Tuesday, hailed the discoveries as the "beginnings of a new kind of astronomy."
Gaisser's appraisal is more humble. "It's a new window on the universe because you're looking at the cosmos with neutrons, not photons or light," he said.
It's not the first time high-energy neutrinos have been found. Jayawardhana said a handful were detected when a supernova outside the Milky Way exploded in 1987.
The neutrinos arrived on Earth before light, because they could escape from a dying star unhindered. Photons, or light, can be pulled into the gravitational sink of a black hole. Not the neutrino.
"Neutrinos are special because they can - and mostly do - pass through just about anything," said Goldberg. "It's not just that they've traveled so far to reach us. It's that they're so different than almost anything else that we've been able to detect after making the same trip."
Rather than relying on random explosions of supernova, the IceCube station takes a methodical approach to neutrino detection. It's essentially a colossal telescope buried under a mile of ice. And it's a remarkable feat unto itself, said Gaisser, who was on the crew that set up neutrino detectors on the surface, dubbed IceTop.
Beginning in 2003, teams drilled dozens of holes a mile deep into the ancient glacial ice using hot water under high pressure. Thirty engineers worked around the clock during the brief austral summer, when temperatures in January reach an average high of 20 degrees below zero.
"And managing water at the South Pole is not easy, because you have to have insulated hoses," he said.
Though the inhospitable cold might discourage less committed researchers, Gaisser thrived under the completely clear sky and a sun that never set.
"I quite enjoyed it," he said. "Being outside, which I was quite a bit, is not that bad. The only discomfort that comes up is because your goggles are always fogging over."
The 86 holes are drilled into a cubic kilometer of ice at regular intervals. Sixty sensitive monitors, each about the size of a basketball, were lowered on a cable into each hole, he said. Each of the 5,000 monitors streams information to a computer farm on the surface located in a long blue building on stilts.
Neutrinos rarely interact with matter. In fact, trillions of neutrinos zip through a human being every second, said author Jayawardhana. "The only more common are particles of light, photons. They're all around us."
But to detect the rarest form of neutrino - the high-energy variety - you need a massive target. "That's why IceCube is so big," Gaisser said. "It's a gigaton of target matter."
But couldn't an enormous target be built closer to home? Not something that works like this. The South Pole's ice is extraordinarily dense and clear. It not only filters out cosmic rays and other noise, but it allows staff to make use of a bizarre phenomenon.
When a neutrino interacts with matter, it produces a muon, a high-energy particle that travels close to the speed of light. But in ice, the behavior of muons and photons - the component of light - gets really weird: The muon goes faster than light in the ice.
The muon creates a cascade, a faint blue flicker, that can be sensed by the detectors in sequence.
The neutrinos' origin remains a mystery.
"We don't know yet, and that's the outstanding question of the moment," Gaisser said.
Some scientists think they may be jets of particles accelerating from supermassive black holes.
Gaisser says he doubts the research at IceCube will have any practical applications.
Some are more hopeful. Jayawardhana suggests that the neutrino work may one day produce new ways of communicating through the Earth, detecting nuclear proliferation, or finding oil.
Derrick Pitts, chief astronomer of the Franklin Institute Science Museum, takes a more poetic view.
"Astronomers are developing another tool to peek behind nature's curtain of extreme distance and time to see the intimate details of activity of the most energetic events of the universe," he said.
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