Evan James Williams
Physicist
Evan James Williams was born on 8 June 1903 at Cwmsychpant, a hamlet near Llandysul in Cardiganshire (now Ceredigion), and was educated at Llandysul County School. He went on to study at Swansea University before completing doctorates at both Manchester and Cambridge, working alongside some of the leading physicists of the twentieth century, including Ernest Rutherford, Patrick Blackett and Niels Bohr.
Williams became one of the foremost experimental physicists investigating cosmic rays and the newly theorised subatomic particles known as mesons. In 1939 he was the first person to observe and photograph experimentally the production process of the particle predicted by Hideki Yukawa's meson theory. The following year, using the cloud chamber method, he gave the first direct demonstration of a cosmic ray meson decaying into an electron — a landmark result in the physics of what would later be understood as the muon.
In 1939 Williams was elected a Fellow of the Royal Society in recognition of this work, and he was appointed Professor of Physics at University College, Aberystwyth. His research was interrupted by the Second World War, during which he contributed to operational research; he died in 1945, shortly before he was due to resume his professorship at Aberystwyth.