Non-technical summary of the Physics Nobel Prize
The 2002 Nobel Prize in Physics has been awarded to three physicists for their work in exotic astronomy. All three published the landmark papers for which the Nobel was awarded in the American Physical Society journal Physical Review Letters.
Neutrino astronomy
Ray Davis and Masatoshi Koshiba win the prize for their work in detecting neutrinos, elusive particles that rarely interact with anything. Trillions of them pass through our bodies every second almost always undisturbed. Neutrinos are the only detectable particle that come from the active energy-producing center of the Sun and are a key to understanding how it works. They also play an important role in many other reactions that occur both on Earth and throughout the universe.
Davis, who did a significant part of his work while based at Brookhaven National Lab, detected neutrinos coming from the nuclear fusion processes that power the Sun. Over 30 years, he was able to detect a mere 2000 neutrinos in 600 tons of cleaning fluid in a tank sitting at the bottom of the Homestake Mine in South Dakota. Many physicists thought this detection was too hard to even attempt but Davis persisted and succeeded. His feat has been compared with finding a single specific grain of sand somewhere in the Sahara desert. (The sign of a neutrino is a single argon atom appearing in the 600 tons of chlorine-based fluid.) The data he collected was the first hard evidence that nuclear processes do occur in the center of the Sun. Davis now lives on Long Island, near Brookhaven Lab. He turns 88 on Monday.
Koshiba, at the University of Tokyo, ran the Kamiokande neutrino detector in a mine in Japan and improved on Davis' experiment because it showed the direction the neutrinos came from and gave results instantly. In February 1987, the Kamiokande detector registered 12 neutrino observations over a 17-minute period. They came from a supernova (an exploding star) in another galaxy. This is actually a huge number of neutrinos compared to the usual number that are detected, so it indicated a particularly violent cosmic event.
X-ray astronomy
Riccardo Giacconi was the first person to discover x-rays hitting the Earth from space. These x-rays are absorbed by the Earth's atmosphere and not detectable at ground level so he sent a rocket up above the atmosphere. He was specifically looking to see if the Moon gave off x-rays after being bombarded with energy from the Sun. He found no evidence for that but as the rocket tumbled through its six-minute flight, he detected a strong burst of x-rays from elsewhere in space. He also discovered a weak background of x-rays coming from all directions. Later, he launched the Uhuru, a satellite specifically designed for looking at these cosmic x-rays. It was followed by the Einstein X-ray Observatory and the Chandra satellite. The field of x-ray astronomy has vastly improved our understanding of the universe and some of its more exotic inhabitants, like black holes. It has also provided some of our most spectacular images of the universe.
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