Apart from detonators, what else is Luis Alvarez famous for? 

If you are a science lover, you would know that American physicist and Nobel Laureate Luis Alvarez is famous for his contribution in creating detonator, a blasting cap used to detonate an explosive device for the atomic bomb. However, did you know that he and his son discovered the asteroids responsible for the extinction of dinosaurs? We are unaware of many such contributions of Luis Alvarez, who born in San Francisco in 1911. Let us take you through some of them.  
 
Ground-Controlled Approach (GCA) system 
Alvarez joined the newly established Radiation Laboratory at the Massachusetts Institute of Technology during World War II, where he invented microwave radar applications for the military. He worked on creating a radar system for controlling anti-aircraft fire. There, he realized that the aircraft-tracking components, which were used to shoot down opponent aircraft, could be used to assist the landing of planes in low visibility situations, such as night or fog. He became famous for developing this Ground-Controlled Approach (GCA) system, which helps pilots safely land in exceptionally bad weather. The guiding principles of this system were subsequently adopted by air traffic control systems all over the world. In simple words, this system enables the ground observer to monitor the track and angle of an aircraft during landing. 

Pyramid chamber search 
The concept of using cosmic rays to map dense constructions, like the Great Pyramid of Giza, was developed by Luis Alvarez. But what exactly are cosmic rays? Cosmic rays are high-energy particles (mainly protons or neutrons) that move through space at nearly the speed of light. When they hit earth's atmosphere, these rays produce showers of secondary particles. Some of them enter the earth, but most of them are scattered into space. When these cosmic rays collide with particles in the atmosphere, muons (elementary particles) are created.  
 

In 1965, Luis suggested that muon tomography, a technique that uses cosmic ray muons to generate three-dimensional (3D) images, can be used to look for previously undiscovered chambers in the Egyptian Pyramids. Alvarez and his interdisciplinary team of physicists and archaeologists from USA and Egypt installed detectors inside one of the known chambers beneath the second largest pyramid in the Egyptian city of Giza, made by an ancient Egyptian pharaoh, Chephren. The detectors could track the incoming cosmic rays and gauge their deflections when they hit the solid bricks of the pyramid. Luis and his team surprisingly discovered that muons could simply cross through a chamber and leave a visible vacuum in the 3D image. 

The experiment was momentarily put on hold during the 1967 Arab-Israeli Six-Day War, but it quickly got back on track. Alvarez's team continued collecting cosmic ray data over the following two years. By 1969, they had successfully scanned around 19% of the pyramid, but had not discovered any secret chambers.  

Alvarez's theory on the death of dinosaurs 
As a geologist, Luis Alvarez's son Walter Alvarez was drawn to a tiny layer of clay found in a limestone gorge in central Italy. This mud layer marked the exact point between the Cretaceous and Paleogene boundary, which is a thin band of rock from a time period that marks the end of the Cretaceous period (145-66 million years ago) and beginning of the Paleogene period (66 million and 23 million years ago). This is also the beginning and end of the dinosaurs era! Based on the finding from the mud layer, Alvarez came up with a hypothesis. The hypothesis states that the collision of a huge asteroid with the Earth during this period led to the mass extinction of dinosaurs and many other types of organisms around 66 million years ago. Evidence suggests that the asteroid fell in Chicxulub, Mexico, on the Yucatán Peninsula.  

Initially, geologists were harshly critical. But further testing of the clay revealed that it included uncommon minerals that can only form in extreme pressure and temperature conditions. Subsequently, the Dutch palaeontologist Jan Smit also suggested a similar theory. In March 2010, an international group of scientists agreed that the Chicxulub impact, caused by an asteroid, was the reason for the extinction.