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Trinity site

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An early stage in the "Trinity" fireball.
An early stage in the "Trinity" fireball.

The Trinity site is the site of the first testing of a nuclear weapon, on July 16, 1945. A plutonium bomb was tested, the type of weapon later dropped on Nagasaki, Japan (the weapon used against Hiroshima was powered by uranium, a type not tested prior to its war use).

The site was part of the Alamogordo Bombing Range, now the White Sands Missile Range. The test site is at the northern end of the Range, between the towns of Carrizozo and Socorro, New Mexico in the Jornada del Muerto Desert in the southwestern United States. The culmination of the Manhattan Project, the event was code-named "Trinity", using the device code-named "Gadget".

The exact origin of the name is not known, but it is often attributed to laboratory leader J. Robert Oppenheimer as a reference to the poetry of John Donne. Oppenheimer had been exposed to Donne primarily through his former girlfriend Jean Tatlock, who had committed suicide in July 1944. In 1962, General Leslie Groves wrote to Oppenheimer on the origin of the name, asking if he had chosen it on the basis that it was a common name to rivers and peaks in the West and would not attract attention. "I did suggest it, but not on [that] ground... Why I chose the name is not clear, but I know what thoughts were in my mind. There is a poem of John Donne, written just before his death, which I know and love. From it a quotation: 'As West and East / In all flatt Maps—and I am one—are on, / So death doth touch the Resurrection.'" ("Hymn to God My God, in My Sicknesses"). Oppenheimer continued, "That still does not make a Trinity, but in another, better known devotional poem Donne opens, 'Batter my heart, three person'd God;—.' Beyond this, I have no clues whatever." (Holy Sonnets XIV).

There was a pre-test explosion of 100 tons of TNT on May 7 to calibrate the instrumentation. For the actual test, the plutonium core nuclear weapon, nicknamed the gadget, was placed on the top of a 20-metre steel tower for detonation. It had been assembled at the nearby McDonald Ranch House , the components arriving on July 12. It was assembled on the 13th and winched up the tower the following day. In case of failure, a huge steel canister code-named "Jumbo" was prepared to recover the plutonium; it was shipped to the test site but not used. The detonation was planned for 4 a.m. but postponed due to poor weather.

At 05:29:45 local time (Mountain War Time), the device exploded with an energy equivalent to 19 kilotons of TNT (87.5 TJ). It left a crater in the desert 3 metres deep and 330 metres wide. The shock wave was felt over 160 km away, and the mushroom cloud reached 12 km. As Los Alamos director J. Robert Oppenheimer watched the demonstration, he misquoted a line from the Hindu scripture, the Bhagavad Gita, "Now I am become Death, the Destroyer of worlds." Test director Kenneth Bainbridge , in an attempt to be less poetic or perhaps more so, stated "Now we are all sons of bitches." Richard Feynman claimed to be the only person to see the explosion without the dark glasses provided, relying on a truck windshield to screen out harmful ultraviolet wavelengths.

A monument now stands at what was originally the "Trinity" target point.
A monument now stands at what was originally the "Trinity" target point.

In the crater the desert sand, which is largely made of silica, melted and became glass of a light green color; this was named trinitite. The crater was filled in soon after the test. The military reported it as an accidental explosion at a munitions dump, and the actual cause was not publicly acknowledged until the August 6 attack on Hiroshima. The Manhattan Project's official journalist, William L. Laurence , had previously put multiple press-releases on file with his office at the New York Times, to be released in case of emergency, ranging from a successful test (the one which was used) to more macabre scenarios explaining why all of the scientists had perished in a single freak accident.

Around 260 personnel were present, none closer than 9 km. At the next test series, Operation Crossroads in 1946, over 40,000 people were present.

The area was declared a National Historic Landmark in 1975; the public is admitted on the first Saturdays of April and October. There is still a little residual radiation at the site. The Trinity monument, a rough sided dark stone obelisk around 12 ft (3.65 m) high, marks the explosion hypocenter.


  • Richard Rhodes, The Making of the Atomic Bomb (New York: Simon and Shuster, 1986). Quotes regarding the naming of the test from p. 571-572.

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