How a so-so physics student finally won his Nobel4 min read . Updated: 22 Nov 2020, 02:36 PM IST
Masatoshi Koshiba, who built an underground water tank to detect neutrinos, has died at 94
TOKYO—The events of a single day—Feb. 23, 1987—made Masatoshi Koshiba’s career and advanced the quest of physicists and astronomers for the universe’s secrets.
On that day, countless neutrinos, elementary particles of vanishingly small mass, arrived on earth from a supernova explosion and made their way through 3,000 tons of water in a Japanese mineshaft. About a dozen of them crashed into electrons, leaving traces that were picked up by 1,000 sensor tubes Dr. Koshiba and his team had set up.
It was further proof of the existence of the long-theorized particles and a demonstration of how they were emitted by the stars. Soon after, Dr. Koshiba found neutrinos emanating from the nuclear reactions in our closest star, the sun. It was the basis for the Nobel Prize in physics earned in 2002 by Dr. Koshiba, who died at a hospital in Tokyo on Nov. 12 at the age of 94.
Katsumi Funasaka, former mayor of the town where the experiment was set up, recalled that people told Dr. Koshiba he was lucky because the big discovery happened just a month before his mandatory retirement from the University of Tokyo.
The physicist retorted that he had been working on the deep-underground experiments for decades and didn’t consider himself lucky. “This result was born from all my unrelenting effort," he said, according to Mr. Funasaka.
Effort had marked Dr. Koshiba’s life from his early days. Born on Sept. 19, 1926, in the central Japanese city of Toyohashi, he was initially destined to follow in the footsteps of his father, an officer in the Imperial Army.
In an autobiography, Dr. Koshiba recalled an incident as a toddler when he spilled a bowl of soup and tried to squirm behind a food tray. “What is this, a son of a samurai trying to hide?" his father bellowed. His mother, as he remembered it, tried to protect him. Soon after, she died of tuberculosis.
At 13, when he was preparing to take the entrance exam for the army cadet school, he contracted polio and for a time had to be carried to his bath by a maid. He had to give up his plans for the army. To get to his regular school, he said, “I could no longer take the steps of the bus because they were too high for me." He wobbled to school every day for nearly two hours, eventually training himself to walk at the same pace as others, although he never regained much use of his right arm.
As he prepared to enter the University of Tokyo in December 1947, he was in his school dormitory’s bath one day and heard another student and a teacher gossiping about him. They couldn’t see each other because of the steam, he recalled.
The teacher, so the story went, said he didn’t know what young Masatoshi would study, “but the one certain thing is he will not apply for the physics department. He would never pass." The future Nobel Prize winner, who had been considering German literature, decided he would go into physics.
Working odd jobs to support his family, since his father had little work as an ex-army officer in defeated Japan, Dr. Koshiba earned mediocre grades. A half-century later, when he made a speech at the university’s graduation ceremony, Dr. Koshiba projected those grades on a screen and told students that drive to succeed, not grades on paper tests, were what mattered.
After earning a Ph.D. at the University of Rochester in New York state, he started a career trying to tease out the fundamental particles that make up the universe. That led him to set up the giant apparatus in the mine, shielded from solar radiation, with 1,000 photomultiplier tubes for detecting particles that he enlarged after hearing the specifications of a competing project in the U.S. He named it Kamiokande after the town of Kamioka where it was located, and initially studied the decay of protons.
As the Far Eastern Economic Review later wrote, Dr. Koshiba’s proposal for government funding included two sentences, almost as an afterthought, that the tank might also be able to observe neutrinos from a massive stellar explosion.
Neutrinos are “the most elusive and the weirdest of all known denizens of the subatomic world," wrote Ray Jayawardhana in “The Neutrino Hunters." A hundred trillion neutrinos from the sun are estimated to pass through one’s body every second, “yet they do no harm and leave no trace," he wrote.
On that February day in 1987, Dr. Koshiba didn’t realize at first that neutrinos from a supernova in the Large Magellanic Cloud, about 160,000 light-years away, were arriving. He recalled that a colleague got a fax asking whether the Kamiokande detector had picked up anything.
Dr. Koshiba’s team quickly sent magnetic tapes to colleagues in Tokyo, and Keiko Hirata, a master’s student, detected the first signs of a neutrino’s hit. Weeks later, the publication was ready, headlines went out around the world, and Dr. Koshiba became Japan’s most distinguished physicist.
A protégé of Dr. Koshiba helped prove in this century using a successor apparatus called Super-Kamiokande that neutrinos have tiny mass. They can change form in ways that eventually may help physicists grasp secrets of the universe.
Dr. Koshiba believed universities should conduct research with an eye 50 or 100 years into the future, said Shoji Asai, director of the particle physics institute at the University of Tokyo founded by Dr. Koshiba.
When Dr. Koshiba was asked what good his studies were, “he always answered, ‘It will be good for nothing,’" recalled Dr. Asai. “By saying, ‘Good for nothing,’ he paradoxically meant it ought to be useful sometime in the future."
Dr. Koshiba is survived by his wife, Kyoko; a son, Shyun; a daughter, Mari Fujii, and two granddaughters.
This story has been published from a wire agency feed without modifications to the text