60 Fun Facts About Niels Bohr

In which year was Bohr awarded the Nobel Prize in Physics?

The citation covered both his atomic model and his early leadership of the new quantum theory.

Bohr's Nobel Prize recognised his investigation of the structure of what?

His model had electrons in fixed orbits that could jump between energy levels, emitting quanta of light.

Bohr's father Christian was a university professor of which subject?

The young Bohr did his prize-winning experiments in his father's laboratory because the university had no physics lab.

Bohr's brother Harald, a mathematician, represented Denmark at the 1908 Olympics in which sport?

The brothers played together for the Akademisk Boldklub, and Denmark took silver at those London Games.

In which position did Niels play for the Akademisk Boldklub?

Legend has it he was once caught working out a maths problem against the goalpost while play was at the other end.

Bohr's prize-winning 1905 essay measured the surface tension of liquids using what?

He improved on Lord Rayleigh's method, allowing for viscosity, and submitted the essay at the last minute.

For his 1905 experiments Bohr had to make what himself, since none existed with the right shape?

An improved version of the paper went to the Royal Society's Philosophical Transactions.

Bohr's doctoral thesis was on the electron theory of what?

He concluded that electron theory could not fully explain their magnetic properties, a result later called the Bohr-Van Leeuwen theorem.

Why did Bohr's groundbreaking 1911 PhD thesis attract little attention outside Scandinavia?

It was a university requirement at the time; a Dutch physicist independently derived one of its theorems a decade later.

In 1911 Bohr went to Cambridge to work under which discoverer of the electron, whom he failed to impress?

He got on better with the younger crowd, including Rutherford, who invited him to Manchester.

Under which Manchester physicist did Bohr do post-doctoral work, building on his nuclear model?

There he met Charles Galton Darwin, whom he called 'the grandson of the real Darwin'.

Bohr's 1913 model of the atom married Rutherford's nucleus to whose quantum theory?

The result was electrons confined to 'stationary states' that could only jump between fixed orbits.

Bohr's three 1913 papers, 'the trilogy', appeared in which journal?

They were published in July, September and November of that year.

Whose 30-year-old formula for hydrogen's spectral lines did Bohr's model finally explain?

He derived it from first principles in the first paper of the trilogy.

Challenged over the Pickering series of spectral lines, Bohr correctly said they came from what?

Helium atoms with a single electron behave like heavy hydrogen, and his model handled them perfectly.

Einstein called Bohr's atomic model 'the highest form of' what 'in the sphere of thought'?

Older physicists such as Thomson, Rayleigh and Lorentz disliked the trilogy; the young ones saw a breakthrough.

When Bohr was presented as a new professor, King Christian X was delighted to meet such a famous what?

The king had confused him with his brother Harald, the Olympian.

Which brewery's foundation partly funded Bohr's 1911 trip to England and later his institute?

He later lived in the brewer's honorary mansion, reserved for Denmark's most eminent contributor to science or the arts.

Which element, predicted by Bohr to resemble zirconium, was discovered at his institute in 1923?

Named for the Latin name of the city where it was found, it turned out to be more common than gold.

Which French chemist challenged Bohr by claiming element 72 was a rare earth he called 'celtium'?

Coster and de Hevesy proved Bohr right by searching mineral samples for a zirconium-like metal.

The 'Bohr Festival' of June 1922, a series of seven lectures, took place in which German university town?

The talks coincided with the town's Handel festival, hence the nickname.

Bohr's correspondence principle says the new physics reproduces classical physics in the limit of what?

He laid it out in his Nobel lecture as part of a survey of what was then known about the atom.

The 1924 Bohr-Kramers-Slater theory proposed energy and momentum were conserved only how?

Experiments by Bothe and Geiger soon killed it; Bohr asked for the idea to be given 'as honourable a funeral as possible'.

Bohrium, the element named after Bohr, has which atomic number?

An asteroid and a lunar crater are also named for him.

Which philosophical principle did Bohr conceive to reconcile wave and particle descriptions?

It dominated his thinking in physics and philosophy alike, and he felt professional philosophers never quite grasped it.

Who first occupied the Danish honorary mansion Bohr moved into in 1932?

The philosopher had taught Bohr and been a friend of his father.

Bohr's 1936 theory of the compound nucleus pictured the nucleus as deformable like what?

The picture later let him work out which uranium isotope was splitting.

In 1939 Bohr worked out that fission with slow neutrons was mainly due to which isotope?

He announced 'I have understood everything' after a few minutes' thought; Dunning proved him right in 1940.

With whom did Bohr publish 'The Mechanism of Nuclear Fission' in September 1939?

Wheeler was later Richard Feynman's doctoral advisor at Princeton.

To hide two Nobel medals from the occupying Germans, Bohr had de Hevesy dissolve them in what?

The gold sat in solution on a shelf until after the war, then was precipitated and re-struck by the Nobel Foundation.

Bohr's own Nobel medal was auctioned in 1940 to raise money for what?

The buyer donated it to a Danish museum, and it later flew to the International Space Station.

Which astronaut took Bohr's Nobel medal to the International Space Station in 2023?

It normally lives at Frederiksborg Castle alongside August Krogh's medal.

Michael Frayn's 1998 play about the mysterious 1941 meeting between Bohr and Heisenberg is called what?

Historians have criticised it for adopting a pro-Heisenberg view; Bohr's unsent letters tell a very different story.

After fleeing to Sweden in 1943, Bohr persuaded King Gustaf V to make a public offer of what?

Swedish radio broadcast the offer on 2 October, and the mass rescue of Denmark's Jews followed swiftly.

Flying to Britain in the bomb bay of a Mosquito, Bohr passed out at high altitude. Why?

He could not hear the pilot's instruction to switch on his oxygen, and revived only when the plane descended over the North Sea.

Under what alias did Bohr travel in the United States during the Manhattan Project?

His son Aage, acting as his assistant, became 'James Baker'.

Which of Bohr's sons won the Nobel Prize in Physics in 1975?

Bohr and Margrethe had six sons; another, Ernest, played Olympic field hockey.

Which wartime leader wrote that Bohr 'ought to be confined', near 'the edge of mortal crimes'?

Bohr had argued for openness with the Soviets about the bomb; the two, he said, 'did not speak the same language'.

Which Supreme Court justice, a friend of Bohr, got him a 1944 meeting with President Roosevelt?

Roosevelt and Churchill later agreed to keep an eye on Bohr for 'leakage of information, particularly to the Russians'.

To which body did Bohr address his 1950 'Open Letter' on control of nuclear energy?

The International Atomic Energy Agency was later created along the lines he suggested.

In 1957 Bohr became the first ever recipient of which honour?

It recognised his post-war campaign for openness and international cooperation.

Bohr's Order of the Elephant, conferred in 1947, was normally reserved for whom?

The king said it honoured Danish science, not just Bohr.

Which symbol did Bohr put on the coat of arms he designed for himself?

The Latin motto beneath it reads contraria sunt complementa, 'opposites are complementary'.

Bohr wanted CERN based at his own institute. Which city was chosen instead in 1952?

Pierre Auger thought Bohr and his institute past their prime, though CERN's theory group stayed in Denmark until 1957.

Bohr died in November 1962 of what?

His ashes lie in the family plot at Assistens Cemetery with those of his parents, brother and eldest son.

The 1997 500-krone banknote showed Bohr doing what?

Google marked his birthday in 2012 with a doodle of the hydrogen atom.

Before marrying Margrethe in 1912, Bohr resigned his membership of what?

The couple married in a civil ceremony at Slagelse town hall; his brother later left the church before his own wedding.

How did Bohr's eldest son Christian die in 1934?

Another son, Harald, was institutionalised at four and died of meningitis six years later.

Bohr's son Ernest represented Denmark at the 1948 Olympics in which sport?

He followed his uncle Harald, the 1908 Olympic footballer, into the Games.

Which philosopher did Bohr read and send to his brother as a birthday gift in 1909?

He loved the style but disagreed with the philosophy, perhaps because Kierkegaard championed Christianity and Bohr was an atheist.

In a 1999 poll, Bohr was named the how-many-eth greatest physicist of all time?

Heisenberg said he was 'primarily a philosopher, not a physicist'.

Rutherford's nuclear atom, which Bohr built on, replaced which earlier picture of the atom?

The 1904 model had electrons embedded in a positive sphere.

Early in his university career, Bohr disliked being obliged to teach physics to which future professionals?

He admitted he was a poor lecturer, torn between clarity and truth, 'Klarheit und Wahrheit'.

Where in Copenhagen was Bohr educated from the age of seven?

He enrolled at the University of Copenhagen in 1903 to study physics under Christian Christiansen.

When did Bohr's Institute of Theoretical Physics, later the Niels Bohr Institute, open?

He had begun campaigning for it in April 1917 with backing from the Danish government and the Carlsberg Foundation.

Which two physicists met Bohr's train in Hamburg in 1925 to ask his opinion of electron spin?

Bohr was en route to Leiden for Lorentz's doctoral jubilee; spin had been introduced by Uhlenbeck and Goudsmit a month earlier.

With whom did Bohr open the fifth Washington Conference on Theoretical Physics in January 1939?

He had just brought news of Otto Hahn's discovery of nuclear fission to the United States.

Where was Bohr given an apartment while working with the British Tube Alloys team in 1943?

James Chadwick and Sir John Anderson welcomed him warmly but kept him out of sight for security reasons.

Bohr was the first chairman, from 1956, of which Danish atomic research establishment?

The next year he also chaired the new Nordic Institute for Theoretical Physics, Nordita.

Where in Copenhagen are Bohr's ashes buried in the family plot?

He lies in the Nørrebro district alongside his parents, his brother Harald and his son Christian.