Luis Alvarez was a Nobel Prize winning physicist, probably most famous for the discovery of the iridium layer and his theory that the mass extinction of dinosaurs was caused by an asteroid or comet colliding with Earth. Besides doing the normal work you might expect of a physics professor, Alvarez took on more unusual projects, like making use of cosmic rays to search for hidden chambers in an Egyptian pyramid.

Luis Alvarez was a highly talented and highly imaginative experimental physicist. He had a particular talent for devising experiments that asked questions in such a way that Mother Nature felt compelled to give a good answer.

Some of his achievements were:

Establishing K-electron capture

One of the ways radioactive atoms transform into new elements is capture of an orbiting electron by the nucleus. The electron combines with a proton to form a neutron. The atom now has one proton fewer than it used to, and so has become a new element.

This process had been predicted by theorists but never observed. In 1937 Alvarez devised a new experiment to ask Mother Nature whether the process really happened. He looked for the X-rays expected to be emitted by a nucleus when it captured an electron. The experiment worked and K-electron capture became an established phenomenon in physics.

The Cyclotron

Alvarez spent a lot of time at Berkeley working with the cyclotron (particle accelerator/atom smasher). He was able to prove that helium-3 is stable, although it had been predicted to be unstable.

Air Safety Improved by Ground-Controlled Approach

Alvarez was an enthusiastic pilot; he learned to fly in 1933.

In the early 1940s he invented the Microwave Phased Array Antenna. This was a form of radar that gave ground crew unparalleled precision in determining the position of an aircraft in flight. The invention allowed ground crew to give clear instructions to pilots as their aircraft approached runways preparing to land.

The system was particularly useful when visibility was poor, such as in fog, or other adverse weather, or when pilots were inexperienced. Alvarez’s invention was used by the military and civil authorities in various countries for decades, greatly enhancing air safety.

Detecting Nuclear Weapons Projects

In 1943, during World War 2, Alvarez was asked if it would be possible to tell scientifically if Germany had its own atom bomb project. He knew that research and development into atom bombs produces radioactive gases, such as xenon-133. These gases could be detected with the right equipment; and Alvarez was an equipment expert. He said aircraft should fly over Germany carrying radiation detectors to detect the telltale gases. The flights took place and found no evidence Germany had an atom bomb project. Alvarez’s method was used after the World War 2 to detect atomic research taking place around the world.

The Atomic Bomb

In 1944, Alvarez arrived at Los Alamos, New Mexico, to work on the Manhattan Project. There he devised an electrical detonation method for the plutonium bomb.

He and his graduate student Lawrence Johnston also designed equipment to measure the energy released by a nuclear explosion. The two scientists flew in an observation aircraft to Japan when the bombs were dropped to measure how powerful the nuclear explosions had been.