On Luis Alvarez

Posted by jns on 21 November 2007

From this week’s Physics News Update^* a note about physicist Luis Alvarez, to whom all things were interesting. In case you’ve ever wondered about the source of the hypothesis that the dinosaurs were wiped out by a meteorite, read on.

EGYPTIAN PYRAMIDS, DINOSAUR EXTINCTION, THE JFK ASSASSINATION: all were studied by Berkeley physicist Luis Alvarez. Alvarez won a Nobel Prize for his discovery of new particles using a bubble chamber, but some of his fame comes from his work applying physics principles and methods outside the normal physics-research world. In the November issue of the American Journal of Physics, Charles Wohl of the Lawrence Berkeley National Lab looks at three notable examples of Alvarez*s extracurricular effort.

(1) To search for possible hidden chambers in the Chephren pyramid in Cairo-one of the three great pyramids built in the third millennium BCE-Alvarez designed an experiment in which cosmic rays would strike a detector set up inside a known chamber beneath the pyramid. Observing the penetrating muons from cosmic-ray showers, this detector would discern any intervening empty spaces in the overlying pyramid structure. The upshot: no hidden chambers.

(2) In scrutinizing the so called “Zapruder film”, a short filmed sequence that caught the assassination in progress, experts had been puzzled by the backwards jerk of President Kennedy’s head after one of the bullet impacts. Some took this to be evidence for another assassin shooting from in front of the president’s car. Alvarez and some of his colleagues performed impromptu experiments at a shooting range, and also considered the conservation of momentum and the forward-moving matter from the wound. From this they concluded that the movie sequence was consistent with a shot coming from the rear.

(3) Most famous of all was Alvarez’s hypothesis, made in collaboration with his son Walter Alvarez, that a thin but conspicuous layer of the otherwise rare element iridium in numerous places around the world, all at a geological stratum corresponding to the era just around the boundary between the Cretaceous and Tertiary periods (the KT boundary), signified a large asteroid impact at that time. This impact, it was further thought, cast enough dust into the air from a long enough time as to kill off many living things, including a large portion of dinosaurs.

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^* Phillip F. Schewe, Physics News Update, The American Institute of Physics Bulletin of Physics News, Number 847, 20 November 2007.