Luis Alvarez
The Nobel prize-winning physicist who, with his son Walter, proposed in 1980 that an asteroid impact wiped out the dinosaurs.
Key facts
- Born
- 1911
- Died
- 1988
- Nationality
- American
- Field
- Physicist
Luis Walter Alvarez was one of the most inventive physicists of the twentieth century. He worked on radar and the atomic bomb during the Second World War, and in 1968 he won the Nobel Prize in Physics for discoveries made with the bubble chamber, a device for photographing the tracks of subatomic particles.
In the late 1970s his son Walter, a geologist, showed him a thin layer of clay in rocks near Gubbio in Italy. It marked the boundary between the Cretaceous and Paleogene periods, about 66 million years ago, when the dinosaurs and many other forms of life died out. Walter wanted to know how long the clay had taken to form.
Luis suggested measuring iridium, a metal that is very rare in Earth's crust but much more common in meteorites, which fall steadily as dust. With the chemists Frank Asaro and Helen Michel they found far more iridium in the clay than expected, hundreds of times the normal amount in some samples. In 1980 they proposed that an asteroid about 10 kilometres across had struck the Earth, throwing up dust that darkened the sky and caused the extinction.
The idea was fiercely debated. It was strongly supported when the buried Chicxulub crater in Mexico was identified in 1991, three years after Luis Alvarez died.