“The Royal Swedish Academy of Sciences has decided to award the 2015 Nobel Prize in Physics to Takaaki Kajita and Arthur B. McDonald for the discovery of neutrino oscillations, which shows that neutrinos have mass.”
Göran Hansson, secretary general of the academy, a few minutes before 6am Eastern time. Kajita is at the University of Tokyo. McDonald is with Queen’s University in Kingston, Canada.
“At this moment in this room there are more than a billion neutrinos, which travel almost at the speed of light.”
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Anne L'Huillier is the chair of the Nobel physics committee.
The world's first neutrino observation in a hydrogen bubble chamber was found Nov. 13, 1970, on this historical photograph from the Zero Gradient Synchrotron's 12-foot bubble chamber. The invisible neutrino strikes a proton where three particle tracks originate (right). The neutrino turns into a muon, the long center track. The short track is the proton. The third track is a pi-meson created by the collision. (Argonne National Laboratory/Wikimedia Commons)
“These elementary particles are the second most abundant in the universe, next to the photons, which are the particles of light. They are created in nuclear reactions, for example, in the sun, in stars. They interact very little with the environment, for example, they can go through Earth without being stopped.
There are three kinds of neutrinos. Electron-neutrinos, mu-neutrinos and tau-neutrinos. This year’s prize is awarded to the experimental discovery that neutrinos can change identity. For example, a mu-neutrino can become a tau-neutrino and vice versa. They oscillate.
The observations were made by two research groups, one at the Super-Kamiokande detector in Japan and the other at Sudbury Neutrino Observatory in Canada. The discovery implies that neutrinos, which were believed to be massless, do have a mass, even if very little. And since there are so many of them, it changes our view of the universe.
For an in-depth listen about the 2015 Nobel Prize in Physics, look for the Scientific American Science Talk podcast later this morning.
—Steve Mirsky
[The above text is a transcript of this podcast.]
