2015 Noble Prize in Physics

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The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2015 to Takaaki Kajita (Japan) and Arthur B. McDonald (Canada)

“for the discovery of neutrino oscillations, which shows that neutrinos have mass”


Neutrinos are one of the fundamental particles which make up the universe. They are also one of the least understood. Neutrinos are similar to the more familiar electron, with one crucial difference: neutrinos do not carry electric charge. Because neutrinos are electrically neutral, they are not affected by the electromagnetic forces which act on electrons.

Neutrinos are affected only by a “weak” sub-atomic force of much shorter range than electromagnetism, and are therefore able to pass through great distances in matter without being affected by it. If neutrinos have mass, they also interact gravitationally with other massive particles, but gravity is by far the weakest of the four known forces.

Three types of neutrinos are known; there is strong evidence that no additional neutrinos exist, unless their properties are unexpectedly very different from the known types. Each type or “flavor” of neutrino is related to a charged particle (which gives the corresponding neutrino its name).


The Nobel Prize in Physics 2015 recognises Takaaki Kajita in Japan and Arthur B. McDonald in Canada, for their key contributions to the experiments which demonstrated that neutrinos change identities. This metamorphosis requires that neutrinos have mass. The discovery has changed our understanding of the innermost workings of matter and can prove crucial to our view of the universe.

Around the turn of the millennium, Takaaki Kajita presented the discovery that neutrinos from the atmosphere switch between two identities on their way to the Super-Kamiokande detector in Japan.

Meanwhile, the research group in Canada led by Arthur B. McDonald could demonstrate that the neutrinos from the Sun were not disappearing on their way to Earth. Instead they were captured with a different identity when arriving to the Sudbury Neutrino Observatory.

A neutrino puzzle that physicists had wrestled with for decades had been resolved. Compared to theoretical calculations of the number of neutrinos, up to two thirds of the neutrinos were missing in measurements performed on Earth. Now, the two experiments discovered that the neutrinos had changed identities.

The discovery led to the far-reaching conclusion that neutrinos, which for a long time were considered massless, must have some mass, however small.

For particle physics this was a historic discovery. Its Standard Model of the innermost workings of matter had been incredibly successful, having resisted all experimental challenges for more than twenty years. However, as it requires neutrinos to be massless, the new observations had clearly showed that the Standard Model cannot be the complete theory of the fundamental constituents of the universe.

The discovery rewarded with this year’s Nobel Prize in Physics have yielded crucial insights into the all but hidden world of neutrinos. After photons, the particles of light, neutrinos are the most numerous in the entire cosmos. The Earth is constantly bombarded by them.

Many neutrinos are created in reactions between cosmic radiation and the Earth’s atmosphere. Others are produced in nuclear reactions inside the Sun. Thousands of billions of neutrinos are streaming through our bodies each second. Hardly anything can stop them passing; neutrinos are nature’s most elusive elementary particles.

Now the experiments continue and intense activity is underway worldwide in order to capture neutrinos and examine their properties. New discoveries about their deepest secrets are expected to change our current understanding of the history, structure and future fate of the universe.

Also read 2015 Noble Prize in Medicine


Youngest Physics Laureate

To date, the youngest Nobel Laureate in Physics is Lawrence Bragg, who was 25 years old when he was awarded the Nobel Prize together with his father in 1915.

Oldest Physics Laureate

The oldest Nobel Laureate in Physics to date is Raymond Davis Jr., who was 88 years old when he was awarded the Nobel Prize in 2002.

Female Nobel Laureates in Physics

Of the 198 individuals awarded the Nobel Prize in Physics, only two are women.
1903 – Marie Curie (also awarded the 1911 Nobel Prize in Chemistry.)
1963 – Maria Goeppert-Mayer

Multiple Nobel Laureates in Physics

John Bardeen is the only person who has received the Nobel Prize in Physics twice. Marie Curie was awarded the Nobel Prize twice, once in Physics and once in Chemistry.

Posthumous Nobel Prizes in Physics

There have been no posthumous Nobel Prizes in Physics. From 1974, the Statutes of the Nobel Foundation stipulate that a Prize cannot be awarded posthumously, unless death has occurred after the announcement of the Nobel Prize. Before 1974, the Nobel Prize has only been awarded posthumously twice: to Dag Hammarskjöld (Nobel Peace Prize 1961) and Erik Axel Karlfeldt (Nobel Prize in Literature 1931).

Family Nobel Laureates in Physics

Married couples:
Marie Curie and Pierre Curie were awarded the Nobel Prize in Physics in 1903. Marie Curie was awarded the Nobel Prize a second time in 1911, this time receiving the Nobel Prize in Chemistry.

(One of Marie and Pierre Curie’s daughters, Irène Joliot-Curie , was awarded the Nobel Prize in Chemistry in 1935 together with her husband Frédéric Joliot.)

Father & son:
(All awarded the Nobel Prize in Physics.)
William Bragg and Lawrence Bragg, 1915
Niels Bohr, 1922 and Aage N. Bohr, 1975
Manne Siegbahn, 1924 and Kai M. Siegbahn, 1981
J. J. Thomson, 1906 and George Paget Thomson, 1937


  • Shuji Nakamura-2014
  • Hiroshi Amano-2014
  • Isamu Akasaki-2014
  • Peter Higgs-2013
  • François Englert-2013
  • David J. Wineland-2012
  • Serge Haroche-2012
  • Adam Riess-2011
  • Brian Schmidt-2011
  • Saul Perlmutter-2011
  • Andre Geim-2010
  • Konstantin Novoselov-2010
  • George E. Smith-2009
  • Willard Boyle-2009
  • Charles K. Kao-2009
  • Yoichiro Nambu-2008
  • Toshihide Maskawa-2008
  • Makoto Kobayashi-2008
  • Peter Grünberg-2007
  • Albert Fert-2007
  • George Smoot-2006
  • John C. Mather-2006
  • Roy J. Glauber-2005
  • Theodor W. Hänsch-2005
  • John L. Hall-2005

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