Richard Feynman claimed to be the only observer to see the explosion without dark glasses, protecting himself from harmful ultraviolet rays only behind the glass of a truck. About 260 people witnessed the test, none within a distance of less than 9 kilometers.
Just now 75 years ago, on July 16, the Trinity test , the first explosion of a nuclear weapon, by the United States, took place in a remote enclave of the New Mexico desert.
The detonated bomb used plutonium as fissile material, like the one dropped weeks later on Nagasaki, Japan. At 05.29.45 local time on July 16, the device exploded with an energy equivalent to 19 kilotons, equivalent to 19,000 tons of TNT .
It left a crater in the desert floor 3 meters deep and 330 meters wide. After the explosion, in the crater, the desert sand, composed mainly of silica, melted into a light green glass, which was called trinitite .
Trinitite, also known as Alamogordo glass , is a glass created by the vitrification of the sands of the Alamogordo desert. The glass is composed mainly of arcosic sand, with the majority of quartz and feldspar with traces of plagioclase, calcite, hornblende and augite in a matrix of sandy clay, melted by the explosion. Trinitite is usually light green , but can be found in various colors. It is slightly radioactive, although it can be handled safely.
The boom from the explosion took 40 seconds to reach the observers and the shock wave could be felt 100 miles away. The mushroom cloud reached 12 kilometers .
The area was declared a National Historic Landmark in 1975 and is accessible to the public during the first Saturday of April and October. There is still a small residual radiation at the site. The Trinity Monument , made up of a rough, dark obelisk-shaped rock about 3.6 meters high, marks the hypocenter of the blast.