Takaaki Kajita and Arthur MacDonald have won the 2015 Nobel Physics prize for their discovery of neutrino oscillations, which show that neutrinos — the second-most abundant particles in the universe, next to photons — have mass.
The Nobel Committee said in a statement that the research done by Kajita, of the University of Tokyo, and MacDonald, of Queen's University, Canada, has changed the world's understanding of the innermost workings of matter.
On Monday, the Nobel Committee announced the prize winners for medicine: scientists from Ireland, Japan and China.
William Campbell from Ireland and Satoshi Omura from Japan shared the prize for their discovery of a new therapy for infections caused by roundworm parasites.
And China's Tu Youyou discovered a drug that has significantly reduced the mortality rates for patients suffering from malaria, so she will also share in the prize.
Nobel Prizes are awarded each year in medicine, physics, chemistry, literature, peace, and economic sciences. The money comes from a bequest by swedish inventor Alfred Nobel and the awards, in existence since 1901, have become a top achievement award in each field.
Winners are awarded a monetary prize that varies slightly from year to year — in 2015, the Physics prize is $963,000, to be divided equally between the winners. They also receive a medal and a Nobel "diploma."
Prize winners are announced in October, and prizes are awarded at ceremonies in early December in Stockholm and Oslo, Norway.