The light of a nuclear explosion is unlike anything else on Earth. This is because the heat of a nuclear explosion is unlike anything else on Earth. Seventy years ago today, when the first atomic weapon was tested, they called its light cosmic. Where else, except in the interiors of stars, do the temperatures reach into the tens of millions of degrees? It is that blistering radiation, released in a reaction that takes about a millionth of a second to complete, that makes the light so unearthly, that gives it the strength to burn through photographic paper and wound human eyes. The heat is such that the air around it becomes luminous and incandescent and then opaque; for a moment, the brightness hides itself. Then the air expands outward, shedding its energy at the speed of sound—the blast wave that destroys houses, hospitals, schools, cities.
The test was given the evocative code name of Trinity, although no one seems to know precisely why. One theory is that J. Robert Oppenheimer, the head of the U.S. government’s laboratory in Los Alamos, New Mexico, and the director of science for the Manhattan Project, which designed and built the bomb, chose the name as an allusion to the poetry of John Donne. Oppenheimer’s former mistress, Jean Tatlock, a student at the University of California, Berkeley, when he was a professor there, had introduced him to Donne’s work before she committed suicide, in early 1944. But Oppenheimer later claimed not to recall where the name came from.
The operation was designated as top secret, which was a problem, since the whole point was to create an explosion that could be heard for a hundred miles around and seen for two hundred. How to keep such a spectacle under wraps? Oppenheimer and his colleagues considered several sites, including a patch of desert around two hundred miles east of Los Angeles, an island eighty miles southwest of Santa Monica, and a series of sand bars ten miles off the Texas coast. Eventually, they chose a place much closer to home, near Alamogordo, New Mexico, on an Army Air Forces bombing range in a valley called the Jornada del Muerto (“Journey of the Dead Man,” an indication of its unforgiving landscape). Freshwater had to be driven in, seven hundred gallons at a time, from a town forty miles away. To wire the site for a telephone connection required laying four miles of cable. The most expensive single line item in the budget was for the construction of bomb-proof shelters, which would protect some of the more than two hundred and fifty observers of the test.