the 2006 Nobel Prize, shared by George Smoot and John Mather.) Alvarez proposed Muon tomography in 1965 to search the Egyptian pyramids for unknown chambers. Using naturally occurring cosmic rays, his plan was to place spark chambers, standard equipment in the high-energy particle physics of this time, beneath the Pyramid of Khafre in a known chamber. By measuring the counting rate of the cosmic rays in different directions the detector would reveal the existence of any void in the overlaying rock structure. Alvarez assembled a team of physicists and archeologists from the United States and Egypt, the recording equipment was constructed and the experiment carried out, though it was interrupted by the 1967 Six-Day War. Restarted after the war, the effort continued, recording and analyzing the penetrating cosmic rays until 1969 when he reported to the American Physical Society that no chambers had been found in the 19% of the pyramid surveyed. In November 1966 Life published a series of photographs from the film that Abraham Zapruder took of the Kennedy assassination. Alvarez, an expert in optics and photoanalysis, became intrigued by the pictures and began to study what could be learned from the film. Alvarez demonstrated both in theory and experiment that the backward snap of the President's head was consistent with his being shot from behind being called the "jet-effect" theory. Prominent conspiracy theorists attempted to refute his experiment – see Last Second in Dallas by Josiah Thompson, however, doctor Nicholas Nalli, Ph.D. supports Alvarez's theory which is consistent with a shot from behind. He also investigated the timing of the gunshots and the shockwave which disturbed the camera, and the speed of the camera, pointing out a number of things which the FBI photo analysts either overlooked or got wrong. He produced a paper intended as a tutorial, with informal advice for the physicist intent on arriving at the truth. Dinosaur extinction In 1980 Alvarez and his son, geologist Walter Alvarez, along with nuclear chemists Frank Asaro and Helen Michel, "uncovered a calamity that literally shook the Earth and is one of the great discoveries about Earth's history". During the 1970s, Walter Alvarez was doing geologic research in central Italy. There he had located an outcrop on the walls of a gorge whose limestone layers included strata both above and below the Cretaceous–Paleogene boundary. Exactly at the boundary is a thin layer of clay. Walter told his