Famous Scientists

  • Home
  • Top 100 Scientists
  • List of Scientists
  • Blog

Aage Bohr

Aage Bohr

Lived 1922 – 2009.

Aage Bohr was awarded the Nobel Prize in Physics in 1975 for his work detailing the structure of the atomic nucleus.

Early Life and Education

Aage Niels Bohr was born in Denmark’s capital city, Copenhagen, on June 19, 1922.

In the same year as Aage was born, his father, Niels Bohr, was awarded the Nobel Prize in Physics for his explanation of the structure of atoms and the radiation emitted by them.

Aage’s mother, Margrethe Nørlund, gave birth to six children – all boys; Aage was the fourth. Margrethe was well educated; she assisted Niels Bohr with his paperwork and discussed his scientific research with him in detail.

Aage Bohr’s education was both conventional and, from a scientific point of view, extraordinarily privileged. Like many other students of high school age in Copenhagen, he attended grammar school – the Sortedam Gymnasium. Unlike other students, he also enjoyed conversations with some of the world’s most outstanding physicists, including his father, of course.

In later life Aage recalled some of the giants of science who had worked in Copenhagen with his father; he met them so regularly that they became his ‘uncles’ – including Uncle Werner Heisenberg (Nobel Prize in Physics 1932) and Uncle Wolfgang Pauli (Nobel Prize in Physics 1945).

Advertisements

World War 2

In April 1940, when Aage was 17, Denmark was invaded by the armed forces of Nazi Germany.

This was a worrying time for the Bohr family. Aage’s mother and father were both baptized Christians, but Aage’s grandmother (Niels Bohr’s mother) was Jewish, and this connection meant there could be trouble from the Nazis.

At first, however, there were no problems and, aged 18, Aage enrolled at Copenhagen University intending to obtain a degree in physics. He also became a scientific assistant to his father, with gradually increasing input to his father’s research.

In September 1943, the Nazis decided to deport Denmark’s Jews to concentration camps.

The Bohr family fled in fishing boats across the short stretch of water separating Denmark from Sweden. Sweden was officially neutral and had not been invaded by the Nazis. Nearly all of Denmark’s 7000 Jews fled over the sea to Sweden in 1943.

In October 1943, one week apart, Niels and Aage Bohr flew from Sweden over Nazi-occupied Norway to the United Kingdom. They flew in British warplanes, which came to Sweden to collect them. Margrethe Bohr decided to remain in Sweden, where she stayed until the war ended.

Mosquito

At the age of 21, Aage Bohr was flown from Sweden over Nazi-occupied Norway and the North Sea to Scotland in a de Havilland Mosquito. Such a flight was not free of risk!

Once safely in the UK, father and son began scientific research for the British Government, working in the atomic bomb project headed by James Chadwick.

In 1944 father and son became involved in the Manhattan Project, spending significant amounts of time in the United States as well as London. To keep their presence in America secret, they traveled under the names “Nicholas Baker” and “James Baker.”

Los Alamos Tech Area

The Tech Area at Los Alamos became very familiar to father and son “Nicholas Baker” and “James Baker” as they helped with the Manhattan Project.

Copenhagen – USA – Copenhagen

When the war ended, the Bohr family reunited in Copenhagen in August 1945.

In 1946 Aage Bohr completed his masters degree in physics, in which he considered the interaction of charged particles with matter. He then carried out research work at the University of Copenhagen’s Institute for Theoretical Physics. (This is now the Niels Bohr Institute.)

In 1948 he moved to the Institute for Advanced Study in Princeton, USA, where he tried to model the behavior of the atomic nucleus in a magnetic field, spending considerable amounts of time working at Columbia University.

While in America, he married Marietta Soffer in March 1950, returning with her to Copenhagen at the end of 1950. He was awarded a Ph.D. degree in 1954. Aage Bohr then worked in Copenhagen until he retired, becoming director of the Niels Bohr Institute in 1962. He resigned as director in 1967 to dedicate his time to research work and retired in 1981.

Aage Bohr’s Scientific Work

Like his father, Aage Bohr was intrigued by the structure of the atom. The atomic nucleus in particular; that tiny, densely packed, positively charged mass at the heart of every atom interested him intensely.

What was the nucleus really like – were there any structural details, and if so, what were they?

The Nucleus as a Drop of Liquid

One idea, which had been developed most fully by Niels Bohr and John Archibald Wheeler in the late 1930s, was the liquid-drop model. The liquid-drop model pictured the nucleus as a rotating drop of incompressible liquid held together by surface tension.

The drop of liquid could be deformed from its basic spherical shape and a large drop of liquid could fall apart to form two new drops. Similarly a large atomic nucleus, like uranium, could fall apart to form two new atomic nuclei – this is nuclear fission, the energy source behind both the uranium atom bomb and the uranium power plant.

liquid drop

The tiny atomic nucleus was modeled as a drop of liquid held together by surface tension. Just like a liquid, the shape of the drop was spherical, but could be deformed from this shape.

The liquid drop model had its greatest successes in explaining the properties of heavy nuclei, such as uranium.

By 1950, however, the liquid drop model was in danger of being pushed aside by the newer shell model of the nucleus.

The Nucleus with Energy Shells

Much like electrons are said to occupy shells of different energy outside the nucleus, the shell model of the nucleus says protons and neutrons occupy distinct energy shells inside the nucleus.

shell model of nucleus

Shell model of an atomic nucleus, showing different energy levels. Image by Schunck.

By 1950, most physicists had decided the shell model looked more promising than the liquid-drop model.

In particular, the shell model explained why atomic nuclei with so-called magic numbers of protons+neutrons are particularly stable. This is similar to the concept taught in high school chemistry, where atoms with complete electron shells, for example, 2 or 8 electrons in their outermost shells are particularly stable, leading to the unreactive behavior of the noble gases.

In the case of atomic nuclei, the magic numbers of 2, 8, 20, 28, 50, 82 and 126 protons+neutrons result in particularly stable nuclei.

The shell model was particularly good at explaining the properties of lighter nuclei and magic-number nuclei, but was less successful with heavy nuclei such as uranium.

“Today, it is difficult to fully imagine the great impact of the evidence for nuclear shell structure on the physicists brought up with the concepts of the liquid-drop.”

Aage Bohr, 1975
Nobel Lecture
 

Unification

In fact, the liquid-drop model and the shell model both had advantages and disadvantages – indicating that neither could be the full story.

In 1949, James Rainwater, a Columbia University physicist, decided to combine the best aspects of the liquid-drop and shell models into a single unified model of the nucleus. Rainwater shared an office at Columbia with Bohr and explained his ideas to him. Bohr was captivated, seeing the potential of Rainwater’s ideas to explain the behavior and structure of the atomic nucleus.

Bohr returned to Copenhagen, determined to pursue the unified model further. There he worked with Ben Mottelson, who had completed his Ph.D. at Harvard University and was now in Copenhagen on a Harvard Traveling Fellowship.

Together, Bohr and Mottelson worked out in intricate detail how a unified model could explain a huge number of experimental observations from different atomic nuclei. In 1953 they published a 173-page report describing their unified model and in 1954 Bohr published The Rotational States of Atomic Nuclei. Crucially, predictions they made about how nuclei would behave were verified in experiments.

One of their key findings was that some of the behavior of nuclei could be explained by nuclei having different amounts of energy resulting from rotation. Furthermore, nuclei do not rotate as rigid objects but, instead, a surface wave travels around the nucleus. They also found that nuclei vibrate, changing their shape around an average value.

At first Bohr had trouble convincing his father that the liquid-drop model should be dropped – after all, Niels Bohr was one of the liquid-drop model’s main architects – but eventually he won his father over.

The unified model – often called the collective model – is sometimes likened to a swarm of bees, where each bee is a neutron or proton and the swarm is the nucleus. The swarm acts as a single entity, even though each bee within it is moving around independently with its own, individual energy. In the Bohr-Mottelson model, the outside of the swarm rotates and wobbles inward and outward.

Each neutron or proton has its own orbital energy within the nucleus. These orbits can sometimes deform the nucleus so that it is no longer truly spherical. For example, the nucleus of heavier atoms can become an oblate spheroid (discus shaped) or prolate spheroid (football shaped).

spheroids

An oblate and a prolate spheroid. Images by AugPi, modified by this site.

Of course, we need to remember that atomic nuclei have a diameter of between 1.7 x 10-15 m for hydrogen and about 15 x 10-15 m for uranium.

The fact that Bohr and others were able to mathematically model such incredibly small objects, produce fine structural detail, and predict their behavior in agreement with experimental data is remarkable.

In 1975, Aage Bohr, Ben Mottelson, and James Rainwater shared the Nobel Prize in Physics for their model of the nucleus. In the words of the award committee, the prize was:

“for the discovery of the connection between collective motion and particle motion in atomic nuclei and the development of the theory of the structure of the atomic nucleus based on this connection.”

Despite the huge strides taken by the trio of physicists, even today, the structural details of atomic nuclei have still not been fully resolved.

The End

Aage Bohr died on September 8, 2009, aged 87. He was buried in the Mariebjerg Cemetery, Copenhagen. His first wife, Marietta, died in 1978.

Bohr was survived by his second wife, Bente Meyer Scharff, whom he had married in 1981, and by two sons and a daughter from his marriage to Marietta. One of his sons, Tomas, became a Professor of Physics at the Technical University of Denmark.

“The constant questioning of our values and achievements is a challenge without which neither science nor society can remain healthy.”

Aage Bohr, 1975
Nobel Banquet Speech
 
Advertisements

Author of this page: The Doc
Images of Bohr digitally enhanced and colorized by this website.
© All rights reserved.

Cite this Page

Please use the following MLA compliant citation:

"Aage Bohr." Famous Scientists. famousscientists.org. 27 Mar. 2015. Web.  
<www.famousscientists.org/aage-bohr/>.

Published by FamousScientists.org

More from FamousScientists.org:
  • Abdus Salam
    Abdus Salam
  • Niels Bohr
    Niels Bohr
  • James Chadwick
    James Chadwick
  • Chen-Ning Yang
    Chen-Ning Yang
Advertisements

Search Famous Scientists

Scientist of the Week

  • Linda Buck: Discovered how we smell things

Recent Scientists of the Week

  • Jan Ingenhousz: Discovered photosynthesis
  • Barry Marshall: Overturned the Medical Establishment
  • Linus Pauling: Maverick Giant of Chemistry
  • William Röntgen: The Discovery of X-rays
  • Howard Florey: Brought penicillin to the world
  • Henrietta Leavitt: The key to the size of the universe
  • Archimedes: A mind beyond his time
  • Stanley Milgram: The infamous Obedience Experiments
  • C. V. Raman: Color change allows harm-free health check of living cells
  • Rosalind Franklin: Shape-shifting DNA
  • Robert Boyle: A new science is born: chemistry
  • Carl Woese: Rewrote Earth’s history of life
  • Alfred Wegener: Shunned after he discovered that continents move
  • Henri Poincaré: Is the solar system stable?
  • Polly Matzinger: The dog whisperer who rewrote our immune system’s rules
  • Otto Guericke: In the 1600s found that space is a vacuum
  • Alister Hardy: Aquatic ape theory: our species evolved in water
  • Elizebeth Friedman: Became the world’s most famous codebreaker
  • Evangelista Torricelli: We live at the bottom of a tremendously heavy sea of air
  • Eudoxus: The first mathematical model of the universe
  • James Black: Revolutionized drug design with the Beta-blocker
  • Inge Lehmann: Discovered our planet’s solid inner core
  • Chen-Ning Yang: Shattered a fundamental belief of physicists
  • Robert Hooke: Unveiled the spectacular microscopic world
  • Barbara McClintock: A Nobel Prize after years of rejection
  • Pythagoras: The cult of numbers and the need for proof
  • J. J. Thomson: Discovered the electron
  • Johannes Kepler: Solved the mystery of the planets
  • Dmitri Mendeleev: Discovered 8 new chemical elements by thinking
  • Maurice Hilleman: Record breaking inventor of over 40 vaccines
  • Marie Curie: Won – uniquely – both the chemistry & physics Nobel Prizes
  • Jacques Cousteau: Marine pioneer, inventor, Oscar winner
  • Niels Bohr: Founded the bizarre science of quantum mechanics
  • Srinivasa Ramanujan: Untrained genius of mathematics
  • Milutin Milankovic: Proved Earth’s climate is regulated by its orbit
  • Antoine Lavoisier: The giant of chemistry who was executed
  • Emmy Noether: The greatest of female mathematicians, she unlocked a secret of the universe
  • Wilder Penfield: Pioneer of brain surgery; mapped the brain’s functions
  • Charles Nicolle: Eradicated typhus epidemics
  • Samuel Morse: The telegraph and Morse code
  • Jane Goodall: Major discoveries in chimpanzee behavior
  • John Philoponus: 6th century anticipation of Galileo and Newton
  • William Perkin: Youthful curiosity brought the color purple to all
  • Democritus: Atomic theory BC and a universe of diverse inhabited worlds
  • Susumu Tonegawa: Discovered how our bodies make millions of different antibodies
  • Cecilia Payne: Discovered that stars are almost entirely hydrogen and helium

Top 100 Scientists

  • Our Top 100 Scientists

Our Most Popular Scientists

  • Astronomers
  • Biologists & Health Scientists
  • Chemists
  • Geologists and Paleontologists
  • Mathematicians
  • Physicists
  • Scientists in Ancient Times

List of Scientists

  • Alphabetical List

Recent Posts

  • Perfect Numbers and our Tiny Universe
  • What Happens when the Universe chooses its own Units?
  • Hipparchus and the 2000 Year-Old Clue
  • Darwin Pleaded for Cheaper Origin of Species
  • You Will Die For Showing I’m Wrong!
  • Getting Through Hard Times – The Triumph of Stoic Philosophy
  • Johannes Kepler, God, and the Solar System
  • Charles Babbage and the Vengeance of Organ-Grinders
  • Howard Robertson – the Man who Proved Einstein Wrong
  • Susskind, Alice, and Wave-Particle Gullibility




Alphabetical List of Scientists

Louis Agassiz | Maria Gaetana Agnesi | Al-BattaniAbu Nasr Al-Farabi | Alhazen | Jim Al-Khalili | Muhammad ibn Musa al-Khwarizmi | Mihailo Petrovic Alas | Angel Alcala | Salim Ali | Luis Alvarez | Andre Marie Ampère | Anaximander | Carl Anderson | Mary Anning | Virginia Apgar | Archimedes | Agnes Arber | Aristarchus | Aristotle | Svante Arrhenius | Oswald Avery | Amedeo Avogadro | Avicenna

Charles Babbage | Francis Bacon | Alexander Bain | John Logie Baird | Joseph Banks | Ramon Barba | John Bardeen | Charles Barkla | Ibn Battuta | William Bayliss | George Beadle | Arnold Orville Beckman | Henri Becquerel | Emil Adolf Behring | Alexander Graham Bell | Emile Berliner | Claude Bernard | Timothy John Berners-Lee | Daniel Bernoulli | Jacob Berzelius | Henry Bessemer | Hans Bethe | Homi Jehangir Bhabha | Alfred Binet | Clarence Birdseye | Kristian Birkeland | James Black | Elizabeth Blackwell | Alfred Blalock | Katharine Burr Blodgett | Franz Boas | David Bohm | Aage Bohr | Niels Bohr | Ludwig Boltzmann | Max Born | Carl Bosch | Robert Bosch | Jagadish Chandra Bose | Satyendra Nath Bose | Walther Wilhelm Georg Bothe | Robert Boyle | Lawrence Bragg | Tycho Brahe | Brahmagupta | Hennig Brand | Georg Brandt | Wernher Von Braun | J Harlen Bretz | Louis de Broglie | Alexander Brongniart | Robert Brown | Michael E. Brown | Lester R. Brown | Eduard Buchner | Linda Buck | William Buckland | Georges-Louis Leclerc, Comte de Buffon | Robert Bunsen | Luther Burbank | Jocelyn Bell Burnell | Macfarlane Burnet | Thomas Burnet

Benjamin Cabrera | Santiago Ramon y Cajal | Rachel Carson | George Washington Carver | Henry Cavendish | Anders Celsius | James Chadwick | Subrahmanyan Chandrasekhar | Erwin Chargaff | Noam Chomsky | Steven Chu | Leland Clark | John Cockcroft | Arthur Compton | Nicolaus Copernicus | Gerty Theresa Cori | Charles-Augustin de Coulomb | Jacques Cousteau | Brian Cox | Francis Crick | James Croll | Nicholas Culpeper | Marie Curie | Pierre Curie | Georges Cuvier | Adalbert Czerny

Gottlieb Daimler | John Dalton | James Dwight Dana | Charles Darwin | Humphry Davy | Peter Debye | Max Delbruck | Jean Andre Deluc | Democritus | René Descartes | Rudolf Christian Karl Diesel | Diophantus | Paul Dirac | Prokop Divis | Theodosius Dobzhansky | Frank Drake | K. Eric Drexler

John Eccles | Arthur Eddington | Thomas Edison | Paul Ehrlich | Albert Einstein | Gertrude Elion | Empedocles | Eratosthenes | Euclid | Eudoxus | Leonhard Euler

Michael Faraday | Pierre de Fermat | Enrico Fermi | Richard Feynman | Fibonacci – Leonardo of Pisa | Emil Fischer | Ronald Fisher | Alexander Fleming | John Ambrose Fleming | Howard Florey | Henry Ford | Lee De Forest | Dian Fossey | Leon Foucault | Benjamin Franklin | Rosalind Franklin | Sigmund Freud | Elizebeth Smith Friedman

Galen | Galileo Galilei | Francis Galton | Luigi Galvani | George Gamow | Martin Gardner | Carl Friedrich Gauss | Murray Gell-Mann | Sophie Germain | Willard Gibbs | William Gilbert | Sheldon Lee Glashow | Robert Goddard | Maria Goeppert-Mayer | Thomas Gold | Jane Goodall | Stephen Jay Gould | Otto von Guericke

Fritz Haber | Ernst Haeckel | Otto Hahn | Albrecht von Haller | Edmund Halley | Alister Hardy | Thomas Harriot | William Harvey | Stephen Hawking | Otto Haxel | Werner Heisenberg | Hermann von Helmholtz | Jan Baptist von Helmont | Joseph Henry | Caroline Herschel | John Herschel | William Herschel | Gustav Ludwig Hertz | Heinrich Hertz | Karl F. Herzfeld | George de Hevesy | Antony Hewish | David Hilbert | Maurice Hilleman | Hipparchus | Hippocrates | Shintaro Hirase | Dorothy Hodgkin | Robert Hooke | Frederick Gowland Hopkins | William Hopkins | Grace Murray Hopper | Frank Hornby | Jack Horner | Bernardo Houssay | Fred Hoyle | Edwin Hubble | Alexander von Humboldt | Zora Neale Hurston | James Hutton | Christiaan Huygens | Hypatia

Ernesto Illy | Jan Ingenhousz | Ernst Ising | Keisuke Ito

Mae Carol Jemison | Edward Jenner | J. Hans D. Jensen | Irene Joliot-Curie | James Prescott Joule | Percy Lavon Julian

Michio Kaku | Heike Kamerlingh Onnes | Pyotr Kapitsa | Friedrich August Kekulé | Frances Kelsey | Pearl Kendrick | Johannes Kepler | Abdul Qadeer Khan | Omar Khayyam | Alfred Kinsey | Gustav Kirchoff | Martin Klaproth | Robert Koch | Emil Kraepelin | Thomas Kuhn | Stephanie Kwolek

Joseph-Louis Lagrange | Jean-Baptiste Lamarck | Hedy Lamarr | Edwin Herbert Land | Karl Landsteiner | Pierre-Simon Laplace | Max von Laue | Antoine Lavoisier | Ernest Lawrence | Henrietta Leavitt | Antonie van Leeuwenhoek | Inge Lehmann | Gottfried Leibniz | Georges Lemaître | Leonardo da Vinci | Niccolo Leoniceno | Aldo Leopold | Rita Levi-Montalcini | Claude Levi-Strauss | Willard Frank Libby | Justus von Liebig | Carolus Linnaeus | Joseph Lister | John Locke | Hendrik Antoon Lorentz | Konrad Lorenz | Ada Lovelace | Percival Lowell | Lucretius | Charles Lyell | Trofim Lysenko

Ernst Mach | Marcello Malpighi | Jane Marcet | Guglielmo Marconi | Lynn Margulis | Barry Marshall | Polly Matzinger | Matthew Maury | James Clerk Maxwell | Ernst Mayr | Barbara McClintock | Lise Meitner | Gregor Mendel | Dmitri Mendeleev | Franz Mesmer | Antonio Meucci | John Michell | Albert Abraham Michelson | Thomas Midgeley Jr. | Milutin Milankovic | Maria Mitchell | Mario Molina | Thomas Hunt Morgan | Samuel Morse | Henry Moseley

Ukichiro Nakaya | John Napier | Giulio Natta | John Needham | John von Neumann | Thomas Newcomen | Isaac Newton | Charles Nicolle | Florence Nightingale | Tim Noakes | Alfred Nobel | Emmy Noether | Christiane Nusslein-Volhard | Bill Nye

Hans Christian Oersted | Georg Ohm | J. Robert Oppenheimer | Wilhelm Ostwald | William Oughtred

Blaise Pascal | Louis Pasteur | Wolfgang Ernst Pauli | Linus Pauling | Randy Pausch | Ivan Pavlov | Cecilia Payne-Gaposchkin | Wilder Penfield | Marguerite Perey | William Perkin | John Philoponus | Jean Piaget | Philippe Pinel | Max Planck | Pliny the Elder | Henri Poincaré | Karl Popper | Beatrix Potter | Joseph Priestley | Proclus | Claudius Ptolemy | Pythagoras

Adolphe Quetelet | Harriet Quimby | Thabit ibn Qurra

C. V. Raman | Srinivasa Ramanujan | William Ramsay | John Ray | Prafulla Chandra Ray | Francesco Redi | Sally Ride | Bernhard Riemann | Wilhelm Röntgen | Hermann Rorschach | Ronald Ross | Ibn Rushd | Ernest Rutherford

Carl Sagan | Abdus Salam | Jonas Salk | Frederick Sanger | Alberto Santos-Dumont | Walter Schottky | Erwin Schrödinger | Theodor Schwann | Glenn Seaborg | Hans Selye | Charles Sherrington | Gene Shoemaker | Ernst Werner von Siemens | George Gaylord Simpson | B. F. Skinner | William Smith | Frederick Soddy | Mary Somerville | Arnold Sommerfeld | Hermann Staudinger | Nicolas Steno | Nettie Stevens | William John Swainson | Leo Szilard

Niccolo Tartaglia | Edward Teller | Nikola Tesla | Thales of Miletus | Theon of Alexandria | Benjamin Thompson | J. J. Thomson | William Thomson | Henry David Thoreau | Kip S. Thorne | Clyde Tombaugh | Susumu Tonegawa | Evangelista Torricelli | Charles Townes | Youyou Tu | Alan Turing | Neil deGrasse Tyson

Harold Urey

Craig Venter | Vladimir Vernadsky | Andreas Vesalius | Rudolf Virchow | Artturi Virtanen | Alessandro Volta

Selman Waksman | George Wald | Alfred Russel Wallace | John Wallis | Ernest Walton | James Watson | James Watt | Alfred Wegener | John Archibald Wheeler | Maurice Wilkins | Thomas Willis | E. O. Wilson | Sven Wingqvist | Sergei Winogradsky | Carl Woese | Friedrich Wöhler | Wilbur and Orville Wright | Wilhelm Wundt

Chen-Ning Yang

Ahmed Zewail

Return to top of page

Famous Scientists - Privacy - Contact - About - Content & Imagery © 2023