The Nobel prize in physics has been awarded to Takaaki Kajita and Arthur McDonald for their work on subatomic particles called neutrinos. The scientists from the University of Tokyo and Queen’s University, Kingston, Canada, have won the prize “for the discovery of neutrino oscillations, which shows that neutrinos have mass”. The Nobel committee said the discovery by Kajita and McDonald that neutrinos can alter their identities had “changed our understanding of the innermost workings of matter and can prove crucial to our view of the universe”.

For many years, the central enigma with neutrinos was that up to two-thirds fewer of them were detected on Earth than expected, based on how many should be flooding through the cosmos from our Sun and other stars or left over from the Big Bang. Around the turn of the millennium, Kajita and McDonald, using different experiments, managed to explain this by showing that neutrinos actually changed identities, or “flavors”, and therefore must have some mass, however small.

Nobel Prize Physics Winner

While McDonald and Kajita have cracked a key part of the puzzle, other questions remain, including the exact masses of neutrinos and whether different types exist beyond the electron-neutrinos, muon-neutrinos and tau-neutrinos identified so far.

The 8 million Swedish crown ($962,000) physics prize is the second of this year’s Nobels. Previous winners of the physics prize have included Albert Einstein, Niels Bohr and Marie Curie.