The Telegraph
Since 1st March, 1999
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Physics Nobel for star research

Stockholm, Oct. 8 (Reuters): Raymond Davis and Riccardo Giacconi of the US and Masatoshi Koshiba of Japan won the 2002 Nobel Prize in Physics today for proving why the sun shines and making the discovery of distant stars possible.

The Royal Swedish Academy of Sciences said Davis, 87, and Koshiba, 76, would share half of the $1 million prize for their pioneering work in astrophysics which laid the foundations for a new field of science called neutrino astronomy.

Italian-born Giacconi, 71, would receive the other half of the coveted award for work that helped launch X-ray astronomy.

“This year’s Nobel laureates in physics have used (the) very smallest components of the universe to increase our understanding of the very largest: the sun, stars, galaxies and supernovae,” the academy said in a statement. “The new knowledge has changed the way we look upon the universe.”

Davis and Koshiba proved the existence of tiny particles, called neutrinos, which are created in a nuclear reaction transforming hydrogen into helium — confirming the theory that this reaction was the source of the sun’s energy.

Thousands of billions of solar neutrinos are estimated to pass through our bodies every second without our noticing them, because the tiny particles react weakly with matter. It is therefore very difficult to capture them.

Davis, who has Alzheimer’s disease according to the University of Pennsylvania where he is emeritus professor, designed a way to catch neutrinos by placing a 615 tonne tank of common cleaning fluid in a mine to keep out sun rays.

High-energy neutrinos passing through the tank in the 30-year study turned atoms of chlorine from the cleaning liquid into atoms of argon, which Davis counted — “an achievement considerably more difficult than finding a particular grain of sand in the whole of the Sahara desert”, the academy said.

Koshiba, in a separate experiment using a water tank in a mine in Japan, recorded the small flashes of light created when a neutrino interacts with atomic nuclei in water.

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