Francis Birch

Who was Francis Birch?

Francis Birch was an American geophysicist. He is considered one of the founders of solid Earth geophysics. He is also known for his part in the atomic bombing of Hiroshima and Nagasaki.

During World War II, Birch participated in the Manhattan Project, working on the design and development of the gun-type nuclear weapon known as Little Boy. He oversaw its manufacture, and went to Tinian to supervise its assembly and loading into Enola Gay, the Boeing B-29 Superfortress tasked with dropping the bomb.

A graduate of Harvard University, Birch began working on geophysics as a research assistant. He subsequently spent his entire career at Harvard working in the field, becoming an Associate Professor of Geology in 1943, a professor in 1946, and Sturgis Hooper Professor of Geology in 1949, and professor emeritus in 1974.

Birch published over 100 papers. He developed what is now known as the Birch-Murnaghan equation of state in 1947. In 1952 he demonstrated that Earth's mantle is chiefly composed of silicate minerals, with an inner and outer core of molten iron. In two 1961 papers on compressional wave velocities, he established what is now called Birch's law.