News from the world of maths: Mathematical Moments - Harald Bohr

Died 56 years ago: Harald August Bohr

Born: 22nd of April 1887 in Copenhagen, Denmark
Died: 22nd of Jan 1951 in Copenhagen, Denmark

Harald Bohr must be the only mathematician who came to fame through football: as a member of the Danish national team he won a silver medal at the 1908 Olympics in London. Although it's hard to imagine these days, back then you could still pursue a sports career in your spare time, and by the time Bohr took part in the Olympics, he had already spent four years doing a maths degree at the University of Copenhagen. His sporting success gained him celebrity status in Denmark and when he defended his doctoral thesis after the games, the audience reportedly contained more football fans than mathematicians.

Eventually, though, his interest in maths gained the upper hand and he became a professor of mathematics at the Polytechnic Institute in Copenhagen in 1915, moving on to the University of Copenhagen in 1930. He was interested mainly in the application of analysis to number theory. Together with Edmund Landau he proved some major results about the Riemann zeta function, which lies at the heart of the famous Riemann hypothesis. Although their work contributed two important steps towards its solution, no-one has yet been able to fill in the remaining details — the problem is still unsolved and bugs mathematicians to this day.

But if Bohr's name rings a bell in your brain, it's probably not because of his football stardom, or because of his own excellent contribution to maths, but because of his famous brother Niels. Niels Bohr won the 1922 Nobel Prize for physics for his insights into the structure of atoms and for his work on radiation, and was one of the founding fathers of quantum mechanics. Although Niels takes most of the posthumous limelight, Harald's contribution to maths was nonetheless remarkable, gaining him international recognition as one of the most prominent Danish mathematicians of the twentieth century.

But Harald Bohr's life wasn't all maths. His generosity towards people in need, especially those fleeing the Nazi regime in Germany, gained him just as much international acclaim as his work.

You can read more about the brothers Bohr on the MacTutor History of Mathematics Archive:

• Harald Bohr
• Niels Bohr.

Find out more about the Riemann hypothesis in the following Plus articles:

• A whirlpool of numbers;
• The prime number lottery ;
• The music of the primes.