If anybody says he can think about quantum physics without getting giddy, that only shows he has not understood the first thing about them.

He also appears on a banknote in 1997 when the Danish National Bank started circulating the 500-krone banknote with the portrait of Bohr smoking a pipe. In Kalckar Jørgen. He helped develop quantum mechanics in which electrons move from one energy level to another in discrete steps instead of continuously.

Later the element Bohrium was named after him. After Denmark was occupied by the Germans he had a dramatic meeting in Copenhagen with Heisenberg who had become the head of the German nuclear energy project. He conceived the principle of complementarity: that items could be separately analysed as having contradictory properties like behaving as a wave or a stream of particles.