Ralph Baldwin
The astronomer who made the case in 1949, in The Face of the Moon, that the Moon's craters were blasted out by impacts.
Key facts
- Born
- 1912
- Died
- 2010
- Nationality
- American
- Field
- Astronomer
Ralph Belknap Baldwin studied astronomy at the University of Michigan. During the Second World War he worked on the proximity fuse, a device that made shells explode near their targets, and this gave him a close knowledge of explosions and the craters they made.
After the war he went into his family's machinery business, but he kept studying the Moon in his spare time. He compared the sizes and depths of lunar craters with craters made on Earth by bombs, shells and explosions, and found that they followed the same smooth relationship, from small pits to the largest basins. Volcanic craters did not fit the pattern.
In 1949 he published his evidence in a book, The Face of the Moon. He argued that almost all lunar craters were made by impacts, and that the great dark plains, the maria, were lava that later filled huge impact basins. He also showed how the Imbrium basin had sprayed long streaks of debris across the Moon.
The book persuaded many younger scientists, including Eugene Shoemaker, who later proved that Meteor Crater was made by an impact. When Apollo astronauts brought back lunar rocks, they confirmed Baldwin's picture. He received the Meteoritical Society's Barringer Medal and lived to 97.