winner of the Nobel Prize for Physics in 1948 for his discoveries in the field of cosmic radiation, which he accomplished primarily with cloud-chamber photographs that revealed the way in which a stable atomic nucleus can be disintegrated by bombarding it with alpha particles (helium nuclei). Although such nuclear disintegration had been observed previously, his data explained this phenomenon for the first time and were useful in explaining disintegration by other means.

After graduating from Cambridge University in 1921, Blackett spent 10 years as a research worker in the Cavendish Laboratory. There he began to develop the Wilson cloud chamber—a device that detects the path of ionizing particles—into an automatic instrument for the study of cosmic radiation. He received the Nobel Prize for his interpretation of the data he obtained from this device.

Blackett became professor of physics at the University of London in 1933 and Langworthy professor of physics at the University of Manchester in 1937. He established a school of cosmic-ray research and stimulated the development of other research interests, which led to the creation of the first chair of radio astronomy, at the University of Manchester, and to the building of the Jodrell Bank Experimental Station for Radio Astronomy. In 1953 he was appointed professor and head of the physics department of the Imperial College of Science and Technology in London, where he became senior research fellow in 1965. That year he was named president of the Royal Society. He was created a life peer in 1969.