The Trinity Test

Conrad Ukropina
February 25, 2015

Submitted as coursework for PH241, Stanford University, Winter 2015


Fig. 1: Trinity Test Site Map. (Source: Wikimedia Commons)

The first detonation of a nuclear weapon on United States soil occurred on July 16, 1945, code named "The Trinity Test." Located in the Jornada del Muerto in New Mexico, the test occurred in a safe, flat area, with the closest buildings vacated approximately 2 miles southeast of the bombsite and 120 miles south of Albuquerque. [1] All of the land was government owned, with grazing rights from local farmers suspended. Base camp was located ten miles outside the center of the explosion, with a safe-radius created thirty miles from the blast site (see Fig. 1).


By the start of July 1945, 250 people were employed at Trinity. On the day of the test, there were 425 individuals present to witness the explosion. [1] The project name "Trinity" was created by J Robert Oppenheimer, the current director of the Los Alamos Laboratory, one of the largest nuclear and fundamental science institutions in the world, after the poem "A Litany" by John Donne. [2] The test itself experimented with a plutonium implosion fission device, nicknamed "The Gadget."

Fig. 2: Present Day Historical Landmark. (Source: Wikimedia Commons)


On July 16, 1945, "The Gadget" was set to detonate. However, due to initial weather delays of rain and lightning, the test was postponed until the afternoon. Later in the afternoon, a sunny weather forecast came in at 4:45pm, starting the twenty-minute countdown at 5:10pm. Then, at 5:29:21 (± 2 seconds) MWT, the device was detonated, equivalent to twenty kilotons of trinitrotoluene, flashing the local mountains with incredibly bright light for approximately one and a half seconds. [3] The desert sand was melted into radioactive light green glass, afterwards given the name trinitite. A five-foot deep, thirty-foot wide crater was dug into the ground at the site of the bomb. Following the detonation, a mushroom cloud expanded 7.5 miles high, and a shockwave could be felt over 100 miles away.

Present Day

Today, there is a Trinity Site open house that is available to the general public, declared a national historic landmark in 1965. A Trinity monument was constructed thereafter, dubbed the Trinity Site Obelisk, marking the explosion's hypocenter (see Fig. 2). More than sixty years after the test there is still residual radiation, measured at about ten times higher than the normal radiation in the neighboring area. In fact, the amount of radioactive exposure received during a one-hour visit is about half of the total radiation exposure in which a U.S. adult receives on an average day. [1]

© Conrad Ukropina. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] L. Hoddeson et al.,. Critical Assembly: A Technical History of Los Alamos during the Oppenheimer Years, 1943-1945. (Cambridge U. Press, 2004).

[2] J. Donne, Poems of John Donne (Lawrence Bullen, 1896).

[3] B. Gutenberg, "Interpretation of Records Obtained From the New Mexico Atomic Bomb Test, July 16, 1945," B. Seismol. Soc. Am. 36, 327 (1946).