Dave Knott writes with news that the 2015 Nobel Prize in physics has been awarded to Takaaki Kajita (of the University of Tokyo in Japan) and Arthur McDonald (of Queens University in Canada), for discovering how neutrinos switch between different "flavours." As the linked BBC article explains: In 1998, Prof Kajita's team reported that neutrinos they had caught, bouncing out of collisions in the Earth's atmosphere, had switched identity: they were a different "flavour" from what those collisions must have released. Then in 2001, the group led by Prof McDonald announced that the neutrinos they were detecting in Ontario, which started out in the Sun, had also "flipped" from their expected identity. This discovery of the particle's wobbly identity had crucial implications. It explained why neutrino detections had not matched the predicted quantities — and it meant that the baffling particles must have a mass. This contradicted the Standard Model of particle physics and changed calculations about the nature of the Universe, including its eternal expansion.