Japanese scientist Takaaki Kajita of University of Tokio, and Canadian colleague Arthur McDonald of Queen’s University in Canada, are the winners of the 2015 Nobel Prize in physics. The physicists were awarded for their discoveries on the nature of neutrinos that ”can prove crucial to our view of the universe”, said the Royal Swedish Academy of Sciences.
Neutrinos are subatomic particles that, until now, were believed to have zero mass. Kajita and McDonald discovered neutrinos can spontaneously switch between the three kinds of “flavours” there are, as they move through space. These oscillations prove they do have mass.
This solves the “solar neutrino problem”, a discrepancy between measurements of the number of neutrinos flowing through the Earth that has puzzled physicists for decades. There were up to two thirds of neutrinos missing in measurements performed on Earth, compared to theoretical calculations. Now, thanks to Kajita and McDonald, it is known that the neutrinos were not disappearing, but switching identities.
How much do neutrinos weight? This is yet to be discovered
Experts at the Karlshrune Institute of Technology in Germany plan to start working on determining the weight of neutrinos. However, because these particles are so abundant in the universe (they are the second most common particle species in the Universe), it’s estimated that the combined weight of neutrinos may equal the weight of all visible stars in the universe.
Many neutrinos have their origin in the big bang, others in radioactive decay inside the Earth, and some others are created thanks to nuclear processes in the sun and other stars. They were first detected in 1930, and their three “flavours” or species were discovered in 1956. Now, Kajita and McDonald’s discovery is “one of the milestones in our understanding of nature”, said Antonio Ereditato, director of the Albert Einstein Center for Fundamental Physics at the University of Bern, Switzerland.
Image credit: Nobel Prize on Twitter
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