Francis Birch

Albert Francis Birch, known as Francis Birch, was an American geophysicist who lived from 1903 to 1992 and was considered one of the founders of solid Earth geophysics. He established what became known as Birch law in 1961, a linear relationship between compressional wave velocity and density in rocks and minerals, and in 1947 adapted the isothermal Murnaghan equation for finite strain into the widely used Birch-Murnaghan equation of state for high-pressure research. Through experimental work published in 1952 he demonstrated that the mantle of the Earth consists primarily of silicate minerals overlying an inner and outer iron core, conclusions still accepted as correct. During the Second World War he contributed to the Manhattan Project, overseeing the design and manufacture of the uranium gun-type weapon Little Boy and personally supervising its assembly and loading onto the Enola Gay. He spent his entire career at Harvard University, publishing over one hundred papers, and received the National Medal of Science in 1967. He received the Penrose Medal in 1969.