We continued through a gate and down a path lined with barbed wire, Keep Out signs and warnings about rattlesnakes, to a fenced-in area littered with glassy gravel, sand and tufts of sagebrush and sparse grass. It was here at 5:29:45 a.m. on July 16, 1945, that arguably the most consequential physics experiment of the 20th century took place.
The bomb would use explosives to squeeze a softball-size lump of plutonium to critical density, ideally resulting in a soul-rattling explosion. It worked, lighting up the New Mexico landscape a few minutes before dawn and causing Dr. Oppenheimer to mutter to himself a verse from the Bhagavad Gita: “Now I am become death, destroyer of worlds.”
Three weeks later, on Aug. 6, 1945, a bomb of slightly different design was dropped on Hiroshima, killing an estimated 140,000 people. It shot two hunks of uranium together, creating the critical mass needed for a chain reaction to occur; scientists were so certain the design would work that they did not even bother testing it before it was deployed. Fat Man, a plutonium bomb of the kind tested at Trinity, was used on Nagasaki on Aug. 9, and the end of World War II soon followed.
Trinkets of the Apocalypse
At Trinity’s ground zero, hundreds of people were milling around as if at a county fair, but there was little to see. The detonation created a crater eight feet deep, a half-mile wide and lined with glassy pebbles called trinitite: sand that had been swept up in the fireball, vaporized and then fell back down in molten radioactive droplets. But gradually the pebbles were shoveled out and the hole filled with scrubby sand, weeds and rocks. Now display stands sold snacks and souvenirs; at one table, docents were using a Geiger counter to show off mildly radioactive rocks.
The Gadget was detonated atop a 100-foot tower. All that remained was an inch-long stub of metal sticking out of the ground. An obelisk of black rocks, with a plaque commemorating the event, marked the exact point of ground zero; we took turns posing in front of it and a life-size model of Fat Man, which resembled a short, bulbous submarine with enormous tail fins.