Edwin Mattison McMillan was born in Redondo Beach, California, on 18 September 1907. At 119 years from his birth, his recognition remains tied to transuranic elements and an acceleration principle, not to a laboratory name popularised by Hollywood.

He studied at Caltech and Princeton, then worked at the Radiation Laboratory in Berkeley. In 1940, with Philip Hauge Abelson, he isolated neptunium, the first transuranic element produced and identified in the laboratory. Plutonium followed in the team led by Glenn T. Seaborg. McMillan did not work alone.

During the war years he contributed to applied physics in the American nuclear programme. After 1945 he returned to accelerators. The principle of phase stability, which he published, allowed particles to be kept in step on expanding orbits. Vladimir Veksler published the same idea independently; credit is shared.

The synchrocyclotron and then the synchrotron became standard instruments. McMillan directed the Berkeley laboratory in the 1950s–1970s. The 1951 Nobel Prize in Chemistry was awarded jointly with Seaborg for the transuranium discoveries. Abelson did not share the prize; laboratory histories note the omission.

The cover shows the 184-inch cyclotron magnet at Berkeley, with McMillan and colleagues beside it, not a studio portrait. It is a laboratory photograph from the Lawrence Berkeley archive.

The anniversary marks a large-group physicist, not a solitary inventor. Transuranics and synchronous accelerators remain team results, with priorities split between Berkeley and other centres.

18 September 2026 does not “close” the priority file. It recalls that neptunium, plutonium and phase stability have names attached to several people, not to a single laureate.

Image: Lawrence Berkeley National Laboratory / U.S. Department of Energy, public domain. 184-inch cyclotron magnet, with Robert Thornton (right) and Edwin McMillan. Laboratory photograph, not a studio portrait. Cropped to 16:9.

Source consulted: Edwin M. McMillan — biographical | Nobel Prize; Edwin M. McMillan | Lawrence Berkeley National Laboratory; Edwin Mattison McMillan | National Park Service.