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Portrait of Niels Bohr
Photo: The American Institute of Physics credits the photo [1] to AB Lagrelius & Westphal, which is the Swedish company used by the Nobel Foundation for most photos of its book series Les Prix Nobel., Niels Bohr's Nobel Prize biography, from 1922 · Public domain via Wikimedia Commons

Nobel Prize in Physics · 1922

Niels Bohr

His 1913 model of the atom helped launch quantum physics; he sheltered refugee scientists and pleaded for an open world after the bomb.

The Nobel citation: “for his services in the investigation of the structure of atoms and of the radiation emanating from them”
Born
October 7, 1885, Copenhagen, Denmark
Died
November 18, 1962, Copenhagen, Denmark
Affiliation at the time
Copenhagen University, Denmark

Physics prize

1922

Awarded alone.

Age that year

37years

Born in 1885.

Headline credited impact

18,400–30,600lives saved

Air-pollution deaths prevented by nuclear power replacing fossil fuels. How it was built

Sources cited

23

Fact-checked September 24, 2026.

  • In 1913 his atomic model let him calculate a key number in hydrogen's light spectrum from basic constants, matching experiment as closely as the data of the day allowed.
  • Between 1916 and 1961, 444 scientists from 35 countries came to Copenhagen to work with him for a month or longer.
  • After 1933 his institute became a refuge for physicists, mostly Jewish, forced out of Nazi Germany.
  • In 1939 he worked out that the rare isotope uranium-235 is what splits under slow neutrons, a key step toward the bomb dropped on Hiroshima.
  • Facing arrest in 1943, he fled to Sweden and urged its king to shelter Denmark's Jews; about 7,200 were soon ferried to safety.

The breakthrough

A quantum model of the atom (1913)

By 1911, experiments in Ernest Rutherford's lab in Manchester had shown that an atom has a tiny, heavy nucleus with light electrons around it. But the physics of the day said such an atom should be unstable, because circling electrons ought to keep giving off light and lose their energy. In 1913 Bohr, then 27, proposed a bold fix. He borrowed Max Planck's idea that energy comes in fixed packets, called quanta, and argued that electrons can move only in certain allowed orbits, each with its own fixed energy. While it stays in one of these orbits, an electron gives off no light. Light comes out only when an electron jumps from a higher orbit to a lower one, and the energy of that jump sets the exact color. Think of a staircase instead of a ramp: you can stand on any step but never between steps, so every drop is one of a fixed set of sizes. This explained why glowing hydrogen shines in only a few sharp colors, a pattern that had been measured but never explained. Using basic constants of nature, Bohr calculated a number that describes hydrogen's spectrum, and it matched the measured value as closely as those constants were then known. Full quantum mechanics, worked out in the mid-1920s partly at his own institute, later replaced his model, but its central idea of fixed energy levels survived. In the early 1920s he also used his theory to explain the layout of the periodic table.[2],[3],[5],[7],[8],[10],[11]

“The very fact that knowledge is in itself the basis for civilization points directly to openness as the way to overcome the present crisis.”
Niels Bohr, Open Letter to the United Nations, 9 June 1950, arguing that nations must share scientific and military information to avoid a nuclear arms race.[17]

What it meant for humanity

Bohr's atom opened the door to quantum physics, the science of the very small. Quantum mechanics, completed in the mid-1920s by physicists many of whom worked with him in Copenhagen, now underpins the lasers, transistors and chips that run modern society. His own model is no longer used by specialists, but its picture of electrons on fixed orbits is still the image of the atom that most people carry, and his explanation of the periodic table laid a foundation for quantum chemistry. It even pointed to a missing element: guided by his theory, Dirk Coster and George de Hevesy found hafnium in Copenhagen in 1922. His other great creation was a place. The Institute for Theoretical Physics, opened in 1921, became the world's leading center of theoretical physics in the 1920s and 1930s. Between 1916 and 1961, 444 scientists from 35 countries came to Copenhagen to work with him for a month or more, and about 1,200 physics papers came out of Copenhagen in his lifetime. Hevesy's isotope-tracer work at the institute helped found nuclear medicine. After 1933 the institute sheltered physicists, mostly Jewish, driven out of Nazi Germany. In nuclear physics, his liquid-drop picture of the nucleus helped explain fission in 1939, knowledge behind both nuclear power and nuclear weapons. After the war he was the leading voice for an open world, in which nations would share information to prevent an arms race. He helped launch CERN, hosting its theory group in Copenhagen from 1952 to 1957, drove the founding of the Nordic institute Nordita, and chaired Denmark's Atomic Energy Commission, which built the Risø research center for peaceful nuclear energy.

  • In the early 1920s Bohr used his atomic theory to explain the periodic table; guided by it, Dirk Coster and George de Hevesy discovered the element hafnium in Copenhagen.[5],[8]
  • Between 1916 and 1961, 444 scientists from 35 countries worked with him in Copenhagen for a month or more; about 1,200 physics papers came out of Copenhagen in his lifetime, some 200 of them his own.[5]
  • His institute was a refuge for German Jewish physicists after 1933; in 1940 Hevesy dissolved the Nobel medals of Max von Laue and James Franck there in acid to hide them from the Nazis.[6]
  • He chaired Denmark's Atomic Energy Commission and led the founding of the Risø research center, hosted CERN's theory group from 1952 to 1957, and drove the founding of Nordita.[2],[5]
  • In his 1950 Open Letter to the United Nations he argued that only an open world, with free access to information between nations, could head off a nuclear arms race.[2],[17]

Impact in numbers

Most of Bohr's influence is the kind numbers cannot capture: a new picture of the atom, a school of physicists trained in Copenhagen, refuge for scientists fleeing Nazism, and a moral argument for openness between nations in the nuclear age. We record three small claims, each crediting him 1% of a much larger outcome. Quantum mechanics underpins modern electronics, so we use cumulative world semiconductor sales as a conservative proxy for that economy and share it with Planck, Einstein, Heisenberg, Schrödinger, the inventors of the transistor and many others. His fission theory is one link in the chain behind nuclear power, which a NASA study estimates prevented about 1.8 million air-pollution deaths from 1971 to 2009. The same physics made the atomic bomb possible, so we record a share of the deaths at Hiroshima and Nagasaki as a harm. These shares are judgment calls; his work co-founding CERN and Nordita has no credible number.

Fundamental scienceTechnologyEconomyEnergyPeace

Each number is the laureate’s credited share of a real-world outcome, cumulative to 2025. The whole outcome, the share of credit, and the reasoning are shown so you can check the arithmetic. Outcomes shared with other laureates are counted once on the impact page.

  • Low confidenceRippleModeledEconomy

    Cumulative world semiconductor sales, a proxy for the quantum-based electronics economy

    $142–160

    billion in economic value, credited share

    That is 1% of $14.2–16 trillion in economic value since 1955.

    How this number was built

    Summing WSTS annual worldwide semiconductor billings for 1986-2025 gives $10.28 trillion nominal; converting each year to 2024 dollars with the US CPI (Minneapolis Fed table) gives $14.2 trillion (low). High ($16T): $14.2T + rough, unsourced allowances of ~$0.5T for pre-1986 chip sales and ~$1T for lasers and other quantum devices outside WSTS = ~$15.7T, rounded up. Sales revenue is only a proxy for value. NIST notes that quantum science underpins lasers and transistors. Share 0.01: quantum theory is one essential input alongside materials science and engineering, and within the theory Bohr's 1913 atom and Copenhagen school sit beside Planck, Einstein, Heisenberg, Schrödinger, Born, Dirac, Pauli and the band theorists; his own model was superseded.[18],[19],[20]

    Sources: National Institute of Standards and Technology (Taking Measure blog); World Semiconductor Trade Statistics (WSTS); Federal Reserve Bank of Minneapolis

  • Low confidenceRippleModeledEnergy

    Air-pollution deaths prevented by nuclear power replacing fossil fuels

    18,400–30,600

    lives saved, credited share

    That is 1% of 1.8–3.1 million lives saved since 1971.

    How this number was built

    Kharecha and Hansen (2013) calculate a mean of 1.84 million net deaths prevented by world nuclear power in 1971-2009 (low; counts nothing after 2009), averaging 76,000 a year in 2000-2009 (per the authors' NASA GISS science brief). High extends that 2000-2009 rate over 2010-2025: 16 x 76,000 = 1.22 million, so 1.84 + 1.22 = about 3.06 million. Share 0.01: Bohr's liquid-drop theory of fission (with Wheeler) and his uranium-235 insight are early links in a long chain that runs through Hahn, Meitner and Frisch, Fermi's reactor, reactor engineering and decades of industry; he also chaired Denmark's Atomic Energy Commission.[5],[21],[23]

    Sources: NobelPrize.org; NASA Goddard Institute for Space Studies; NASA Goddard Institute for Space Studies (Internet Archive copy)

  • HarmMedium confidenceRippleSourced totalPeace

    Deaths from the atomic bombings of Hiroshima and Nagasaki within two to four months

    1,500–2,460

    deaths caused, credited share

    That is 1% of 150,000–246,000 deaths caused since 1945.

    How this number was built

    The Radiation Effects Research Foundation estimates acute deaths within two to four months at 90,000-166,000 in Hiroshima and 60,000-80,000 in Nagasaki, so 150,000-246,000 in total. Share 0.01: Pais writes that Bohr's 1939 uranium-235 insight led to the Hiroshima bomb, Los Alamos theorists used his nuclear model, and he consulted on the bomb's initiator, but his wartime role was minor. The discovery of fission, the Manhattan Project's scientists and engineers, and the political and military decision to bomb the cities carry nearly all the responsibility.[5],[11],[22]

    Sources: NobelPrize.org; Encyclopedia.com; Radiation Effects Research Foundation (RERF)

The double edge

Bohr did not build the atomic bomb, but his science helped make it possible. In 1939 he worked out that fission with slow neutrons comes from the rare isotope uranium-235; the physicist and historian Abraham Pais wrote that this insight led to the uranium bomb dropped on Hiroshima. Los Alamos theorists used his liquid-drop model of the nucleus to estimate how nuclear reactions would go. After fleeing Denmark in 1943 he joined the British team attached to the Manhattan Project, visited Los Alamos under the alias Nicholas Baker and worked on the initiator that starts a bomb's chain reaction, though Pais judged his wartime role minor. The Hiroshima and Nagasaki bombs killed an estimated 150,000 to 246,000 people within two to four months. Bohr foresaw a postwar arms race and in 1944 urged Roosevelt and Churchill to seek international control of the weapon; neither leader took up his proposal, and his candor struck statesmen as strange and suspicious. His 1941 meeting with Werner Heisenberg, who was working on Germany's nuclear program, is still disputed.

  • Major

    A key insight behind the Hiroshima bomb

    In 1939 Bohr realized that slow-neutron fission of uranium comes from its rare isotope uranium-235. Pais traced the building of the uranium bomb used on Hiroshima back to this insight. That bomb and the Nagasaki bomb together killed an estimated 150,000 to 246,000 people within two to four months. Los Alamos theorists also used his liquid-drop model to estimate nuclear reaction probabilities.[5],[11],[22]

  • Moderate

    Consultant to the atomic bomb project

    After escaping occupied Denmark in 1943, Bohr joined Britain's Tube Alloys bomb project as a consultant and made extended visits to Los Alamos under the name Nicholas Baker, where he worked on the bomb's neutron initiator. He saw the project as a hedge against a Nazi bomb, and the physicist and historian Abraham Pais judged his role minor.[5],[11],[16]

  • Minor

    The disputed 1941 Heisenberg meeting

    In September 1941 Werner Heisenberg, a leader of Germany's uranium project, visited Bohr in occupied Copenhagen. Heisenberg later said he had hinted that scientists on both sides should hold back; unsent letters by Bohr, published in 2002, describe Heisenberg as confident of German victory and of a German bomb. What was said remains disputed.[12]

Against the odds

By European standards, Denmark was a safe country for Jews. Danish Jews gained civic equality in 1814 and full citizenship in 1849, and Bohr's Jewish grandfather, David Adler, rose high in banking and politics. Bohr's own rise was swift: at 30 he became Copenhagen's first professor of theoretical physics, and the university built an institute for him. Hitler changed everything. From 1933 Bohr helped scientists, mostly Jewish, who were forced out of Nazi Germany, giving them temporary posts at his institute. Germany occupied Denmark on 9 April 1940. For three years the Danish government did not single out Jews, but the occupiers distrusted Bohr for his opinions and his mother's Jewish family, and he knew he was being watched. In the autumn of 1943, as Germany prepared to deport Denmark's Jews, Bohr faced imminent arrest. In September he fled with his family by fishing boat to Sweden, where he urged the Swedish king to grant asylum to Danish Jews. Within weeks, Danish fishermen and helpers carried about 7,200 Jews, with 680 non-Jewish family members, across to neutral Sweden; about 470 Jews from Denmark were caught and deported to the Theresienstadt ghetto. Bohr went on to Britain and the United States and did not return home until August 1945.

  • 1940

    Persecution

    Danish Jews had held equal rights since the 19th century, but after Germany occupied Denmark in April 1940 the Nazi authorities distrusted Bohr for his political views and his mother's Jewish family. He knew he was being spied on.[10],[12],[14],[15]

  • 1943

    Exile

    Facing imminent arrest in September 1943, Bohr escaped with his family by fishing boat to Sweden. In October he was flown to Britain in the bomb bay of an unarmed Mosquito aircraft, and he did not return to Denmark until August 1945.[9],[11],[12]

  • 1943

    War

    When the Germans moved to deport Denmark's Jews in October 1943, about 7,200 reached safety in Sweden with Danish help, but about 470 were seized and deported to the Theresienstadt ghetto.[13]

Jewish background

Jewish motherDistant from Jewish identity

Bohr's mother, Ellen Adler, was born into a well-off Danish Jewish family active in banking, politics and education; her father, David Adler, was a prominent Jewish banker and politician. His father, the physiologist Christian Bohr, was not Jewish. Niels was christened in the Christian church and did not practise Judaism. Under the German occupation, the Nazi authorities distrusted him for his political views and his mother's Jewish family, and in 1943 he fled Denmark to avoid arrest. In later life he followed the physics work of Israel's Weizmann Institute of Science and visited it several times.[10],[11],[12]

Key dates

  1. October 7, 1885

    Born in Copenhagen to the physiologist Christian Bohr and Ellen Adler, who came from a wealthy Jewish family.[1],[2],[11]

  2. 1911

    Earns his doctorate in Copenhagen, then goes to England to work with J.J. Thomson in Cambridge and, from 1912, Ernest Rutherford in Manchester.[2],[7]

  3. 1913

    Publishes his quantum model of the atom in three papers, explaining the spectrum of hydrogen.[2],[7]

  4. 1916

    Becomes the first professor of theoretical physics at the University of Copenhagen.[2],[5]

  5. March 3, 1921

    His Institute for Theoretical Physics opens in Copenhagen, with Bohr as director for the rest of his life.[2],[5]

  6. December 10, 1922

    Receives the 1922 Nobel Prize in Physics in Stockholm; Einstein's delayed 1921 prize is announced the same autumn.[1],[3],[4],[8]

  7. 1933

    After the Nazis take power, opens his institute as a temporary refuge for physicists, mostly Jewish, forced out of Germany.[5],[6]

  8. 1939

    Shows that slow-neutron fission comes from rare uranium-235 and, with John Wheeler, publishes a theory of nuclear fission.[5],[11]

  9. April 9, 1940

    Germany occupies Denmark; at his institute George de Hevesy dissolves the Nobel medals of Max von Laue and James Franck in acid to hide them.[6],[14]

  10. September 1943

    Facing arrest, flees with his family by fishing boat to Sweden and urges the Swedish king to give asylum to Denmark's Jews.[11],[12]

  11. October 1943

    Flown to Britain in a Mosquito's bomb bay; joins the British team in the Manhattan Project and later visits Los Alamos as 'Nicholas Baker'.[9],[11],[16]

  12. June 9, 1950

    Publishes his Open Letter to the United Nations, calling for an open world to prevent a nuclear arms race.[2],[17]

  13. October 24, 1957

    Receives the first Atoms for Peace Award, in Washington.[5],[11]

  14. November 18, 1962

    Dies in Copenhagen at age 77.[1],[2],[9]

Sources

  1. 1.Niels Bohr - Facts · NobelPrize.org (Nobel Prize Outreach)
  2. 2.Niels Bohr - Biographical · NobelPrize.org (from Nobel Lectures, Physics 1922-1941, Elsevier, 1965), 1965
  3. 3.The Nobel Prize in Physics 1922 - Presentation Speech by S.A. Arrhenius · NobelPrize.org, 1922
  4. 4.Niels Bohr - Nobel Lecture: The Structure of the Atom (11 December 1922) · NobelPrize.org, 1922
  5. 5.Physics in Denmark: the first four hundred years, by Abraham Pais · NobelPrize.org
  6. 6.A unique gold medal (The Nobel medals and the medal for the Prize in Economic Sciences) · NobelPrize.org
  7. 7.Bohr's atomic model (Niels Bohr's career) · Niels Bohr Institute, University of Copenhagen, 2012
  8. 8.The Nobel Prize (Niels Bohr's career) · Niels Bohr Institute, University of Copenhagen, 2012
  9. 9.Nuclear physics and war (Niels Bohr's career) · Niels Bohr Institute, University of Copenhagen, 2012
  10. 10.Niels Henrik David Bohr, by J J O'Connor and E F Robertson · MacTutor History of Mathematics, University of St Andrews
  11. 11.Bohr, Niels Henrik David (Complete Dictionary of Scientific Biography entry by Leon Rosenfeld; Encyclopaedia Judaica entry by Samuel Aaron Miller; and other reference entries) · Encyclopedia.com
  12. 12.Bohr & Heisenberg: Two Physicists in Occupied Copenhagen, by Susanne Dambeck · Lindau Nobel Laureate Meetings, 2015
  13. 13.Rescue in Denmark · United States Holocaust Memorial Museum, Holocaust Encyclopedia
  14. 14.Denmark · United States Holocaust Memorial Museum, Holocaust Encyclopedia
  15. 15.Denmark Virtual Jewish History Tour · Jewish Virtual Library
  16. 16.Niels Bohr · Atomic Heritage Foundation, National Museum of Nuclear Science & History
  17. 17.Open Letter to the United Nations, by Niels Bohr (9 June 1950) · atomicarchive.com (reprinted from Bulletin of the Atomic Scientists 6, no. 7, 1950), 1950
  18. 18.A Quantum Leap Forward: How Tiny Particles Can Bring Us Exciting New Tech, by Corey Stambaugh · National Institute of Standards and Technology (Taking Measure blog), 2025
  19. 19.Historical Billings Report (WSTS Blue Book monthly data, 1986 to date) · World Semiconductor Trade Statistics (WSTS), 2026
  20. 20.Consumer Price Index, 1913- · Federal Reserve Bank of Minneapolis
  21. 21.Prevented mortality and greenhouse gas emissions from historical and projected nuclear power, by P.A. Kharecha and J.E. Hansen (Environmental Science & Technology 47, 4889-4895) · NASA Goddard Institute for Space Studies, 2013
  22. 22.Frequently Asked Questions: How many people died as a result of the atomic bombings? · Radiation Effects Research Foundation (RERF)
  23. 23.Coal and Gas are Far More Harmful than Nuclear Power, by Pushker Kharecha and James Hansen (Science Brief, April 2013) · NASA Goddard Institute for Space Studies (Internet Archive copy), 2013

Fact-checked on September 24, 2026 by a separate AI fact-checking pass that re-opened the sources, with 11 corrections made. How we check

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