## Monday, September 10, 2007 ... //

### Arthur Compton: 115th birthday

Arthur Holly Compton was born in 1892. He shared the Nobel prize in 1927 for the Compton scattering. This story shows how long time it took for photons to become a part of our thinking about the electromagnetic radiation.

In 1900, Planck has found everything he really needed in order to develop a complete theory of photons and all phenomena that depend on the particulate nature of the electromagnetic radiation. Nevertheless, the world had to wait for Einstein who took photons somewhat more seriously in 1905 and explained the photoelectric effect.

The question was clearly not settled intellectually. Compton started to work on X-rays in 1918 and observed his effect in 1923. It was nothing else than elastic scattering involving particles that had been known - or should have been known - for 18 or 23 years. Nevertheless, people were still thrilled because his discovery shows the particle concept of electromagnetic radiation. Once again.

I am convinced that science historians in 2050 will say the very same thing about strings. They will say that it has been clear since the mid 1970s that string theory had to be the underlying theory of gravity but many people were continuing to dismiss its explanation of gravity as a mathematical coincidence for decades, just like Max Planck did.

Compton was an eminent physicist but he was actually also an official. It was him who appointed Robert Oppenheimer as the top theorist of the Manhattan project: Compton was actually above Oppenheimer. Compton was the leader of uranium and plutonium research in various contexts.

After the war, he led physicists in St Louis. His department became the last one that opened the door to African Americans but Compton became the first local department boss who hired a female physicist in the early 1950s - something that hasn't been a shocking act at least for 50 years.

George Paget Thomson

This experimenter who discovered the wave properties of the electron by electron diffraction (Nobel prize in 1937) died on September 10th, 1975.

Felix Bloch

On September 10th, 1983, this Swiss American citizen died. This Gentleman who gave the name to Bloch waves worked mostly on nuclear physics and received the 1952 Nobel prize with Edward Purcell for new methods to measure magnetic properties of the nuclei.