The effectiveness of the atomic bomb would stay in question until it could be tested. There had never been a nuclear explosion, and predictions for the amount of energy that would be released ranged considerably. There were still some scientists at Los Alamos who quietly questioned whether it would even function.

Because there was only enough weapons-grade uranium for one bomb and there was high confidence in the gun-type design, most of the uranium bomb (“Little Boy”) started traveling to the Pacific on July 14, 1945, without ever having undergone a complete test of its design.

However, a test of the plutonium weapon seemed essential to verify its novel implosion design and compile information on nuclear explosions.

There were currently some plutonium bombs “in the pipeline,” and they would be accessible over the coming weeks and months. Therefore, it was agreed to try out one of these.

Exposed wiring of “The Gadget,” the nuclear device that exploded as part of Trinity, the first test of an atomic bomb. At the time of this photo, the device was being prepared for its detonation, which took place on July 16, 1945.


Robert Oppenheimer gave the “Trinity” test this moniker in honor of John Donne’s poetry. The location picked was the “Jornada del Muerto,” or “Journey of Death,” an isolated area of the Alamagordo Bombing Range located 210 miles south of Los Alamos.

On May 7, a significant quantity of conventional explosives was used in an explosion to test the complex instrumentation surrounding the site. By the beginning of July, the preparations had been completed throughout May and June.

The firing tower at ground zero was 5.6 miles to the north, west, and south of three observation bunkers that would measure the response. In particular, researchers would look at the symmetry of the implosion and the energy unleashed.

Additional measurements would be made to assess the damage, and equipment would be used to document the fireball’s behavior. Controlling the radioactivity that the test gadget would emit was the main worry.

The Army was prepared to evacuate the local population because it was not completely satisfied with depending on good weather to carry the radioactivity into the upper atmosphere.

On July 12, an army car transported the plutonium core to the test site. In the early hours of Friday the 13th, the non-nuclear components departed for the test location.

The “Gadget “‘s” final construction took place in the McDonald ranch home on the thirteenth during the day. The weapon was assembled and placed atop the 100-foot firing structure by 5:00 p.m. on the 15th.

It was raining when Leslie Groves, Vannevar Bush, James Conant, Ernest Lawrence, Thomas Farrell, James Chadwick, and others arrived at the test site.

Standing in front of the S-10,000 control bunker, Groves and Oppenheimer reviewed their options in case the weather did not clear in time for the test at 4:00 a.m.

Los Alamos director J. Robert Oppenheimer is seen in silhouette as he oversees the final assembly of the Gadget at the Trinity test site in July of 1945.

Fermi started by inviting anyone listening to place a bet on “whether or not the bomb would ignite the atmosphere, and if so, whether it would simply destroy New Mexico or destroy the world” to relieve the stress. Oppenheimer had personally wagered ten dollars that the bomb would not function, wagering against George Kistiakowsky’s full month’s salary.

In the dark hours before daybreak, Edward Teller was applying liberal amounts of sunscreen and offering to spread it around, making everyone tense.

Groves and Oppenheimer advanced the schedule to 5:30 at 3:30. The rain ceased at 4:00. Shortly after 5:00, Kistiakowsky and his crew armed the apparatus and fled to S-10,000. Groves left Oppenheimer and joined Bush and Conant at base camp by his rule that everyone watches from a different position in case of an accident.

The countdown was broadcast over the public address system to those in shelters, and observers at base camp heard it over an FM radio transmission.

Most of the watchers merely waited during the last few seconds, lying on the ground with their feet facing the Trinity site. Isidore Rabi asked Kenneth Griesen, lying next to him, “Aren’t you nervous?” as the timer neared one minute. Griesen answered, “Nope.

“As I lay there in the last seconds, I thought only of what I would do if the countdown got to zero and nothing occurred,” wrote Groves in a later essay.

Conant claimed he had no idea that a second could last so long. Griesen suddenly blurted out to his next-door neighbor Rabi, “Now I’m scared,” as the timer hit 10 seconds. “Now!” exclaimed Sam Allison, counting down from three to two to one.

Jumbo is a 200-ton steel canister designed to recover the plutonium used in the Trinity test if the explosives used could not trigger a chain reaction. In the end, Jumbo wasn’t used for recovery but was placed near ground zero to help gauge the effects of the blast. It survived intact, but its support tower did not.

A longer-exposure photograph of the Trinity explosion seconds after detonation on July 16, 1945.

The nuclear era started on Monday, July 16, 1945, at 5:30 a.m. The device detonated over the New Mexico desert as Manhattan Project employees nervously watched, vaporizing the tower and turning the asphalt surrounding its base into green sand. A massive detonation wave and sweltering heat wave swept the desert seconds after the explosion.

The radiation produced by the detonation was invisible to the naked eye, but everyone knew it existed. Even though it was standing half a mile from ground zero, the steel container “Jumbo,” which weighed over 200 tons and was moved to the desert only to be disqualified from the test, was knocked open.

A second, narrower than the first column, rose and flattened into a mushroom shape like the orange. Yellow fireball stretched up and spread, giving the atomic age a visual image ingrained in human consciousness as a symbol of power and awesome destruction.

Surprise, joy, and relief were the most frequent initial responses to the explosion. Lawrence was stepping from his vehicle when, in his words, everything went “from darkness to brilliant sunshine in an instant”; he was “momentarily stunned by surprise.”

The long hair has let it get away from them, yelled a military guy. Hans Bethe, staring at the detonation directly, was totally blinded for almost 30 seconds. The atom bomb “did not fit into any preconceptions held by anybody,” according to Norris Bradbury.

The expanding fireball and shockwave of the Trinity explosion were seen .053 seconds after detonation on July 16, 1945.

Kistiakowsky was knocked to the ground by the blast wave despite being more than five miles distant. He instantly jumped to his feet and told Oppenheimer, “Oppie, you owe me ten dollars,” as he patted him on the back. Our initial emotion was one of joy, according to physicist Victor Weisskopf.

Isidor Rabi used the term “jubilant”. Rabi was handing around a bottle of whiskey in no time. Bush, Conant, and Groves shook palms at base camp.

Groves told Oppenheimer, “I am glad of you,” when they first met. Groves’s assistant, Thomas Farrell, told his supervisor that “the war is over,” Groves responded, “Yes, after we dropped two bombs on Japan.

Fermi’s reaction was probably the most routine of all; he had anticipated how much the blast wave might move the released bits of paper.

Fermi stood up about 40 seconds after the detonation, threw some of his prepared slips of paper into the atomic wind, and calculated the deflection of those slips to determine that the test had released the energy of 10,000 tons of TNT.

More than twice as much as Fermi had predicted with this experiment and four times more than most at Los Alamos had predicted, the actual result, as it was ultimately calculated, was 21,000 tons (21 kilotons).

A fireball begins to rise, and the world’s first atomic mushroom cloud forms nine seconds after Trinity detonated on July 16, 1945.

The initial astonishment and euphoria soon gave way to more sobering thoughts. According to Rabi, a chill quickly descended upon those in attendance after the initial elation.

“Now we are all sons of bitches,” test head Kenneth Bainbridge said to Oppenheimer after describing the explosion as a “foul and awesome display.” In the later works of those who were there, expressions of horror and regret are particularly prevalent.

The experience, according to Oppenheimer, reminded him of the myth of Prometheus, who Zeus punished for giving man fire. He also briefly remembered Alfred Nobel’s fruitless belief that dynamite would stop wars.

Most notably, Oppenheimer remembered that the explosion had made him think of the verse “Now I have become Death, the destroyer of worlds” from the Bhagavad-Gita, a sacred text in Hinduism.

Many of the Manhattan Project scientists would live with the debilitating, destructive power of atomic bombs and their potential applications for the rest of their lives.

The Trinity test’s success meant that both types of bombs—the uranium design, which had not yet been tested but was believed to be trustworthy, and the plutonium design, which had just undergone a successful test—were now ready for use in the fight against Japan.

The uranium bomb Little Boy was detonated first at Hiroshima on August 6, and the plutonium bomb Fat Man was dropped at Nagasaki three days later on August 9. Within a few days, Japan made a surrender deal.

U.S. military observers watched the explosion during Operation Crossroads Baker, a nuclear test conducted on Bikini Atoll on July 25, 1946. This was the fifth nuclear explosion after two other tests and the two bombs dropped on Hiroshima and Nagasaki.

A massive column of water rises from the sea as the U.S. detonated an atomic bomb at Bikini Atoll in the Pacific in the first underwater test of the device on July 25, 1946. The blast and the enormous wave of water immediately overwhelmed several abandoned ships, which were part of the site’s dummy fleet of former warships.

A huge mushroom cloud rises above Bikini Atoll in the Marshall Islands on July 25, 1946, following an atomic test blast, part of the U.S. military’s Operation Crossroads. The dark spots in the foreground are ships placed near the blast site to test what an atomic bomb would do to a fleet of warships.

On November 16, 1952, a B-36H bomber dropped a nuclear bomb over a point north of Runit Island in the Enewetak atoll, resulting in a 500-kiloton explosion as part of a test code-named Ivy.

Operation Greenhouse occurred in the spring of 1951, consisting of four explosions at the Pacific Proving Grounds in the Pacific Ocean. This photo is from the third test, George, on May 9, 1951: the first thermonuclear bomb test, yielding 225 kilotons.

“Rope tricks” are seen in this image of a nuclear explosion taken less than one millisecond after detonation. During Operation Tumbler-Snapper in 1952, this nuclear test device was suspended 300 feet above the Nevada desert floor and anchored by mooring cables. As the ball of plasma expanded, the radiating energy superheated and vaporized the cables just ahead of the fireball, resulting in the “spike” effect.

Mannequins that represent a typical American family will soon experience the fury of an atomic blast with the power of 40,000 tons of TNT at Yucca Flat, Nevada, on April 24, 1955. The test is being conducted to determine the survival chances of an atomic attack. Visible through the window is the tower 4,700 feet away, where the detonation will occur.

(1 of 2) In Operation Doorstep, conducted during the larger Operation Upshot-Knothole nuclear bomb test, mannequins are seated at a table in the dining room of House No. 2, attending a “dinner party” thrown by Civil Defense officials who are testing the effects of an atomic explosion on houses and occupants on March 15, 1953.

(2 of 2) After the blast, mannequins lie strewn about the room, their “dinner party” interrupted violently by an atomic blast on March 17, 1953.

(1 of 2) Stretched on a bed in an upstairs bedroom of House No. 2 is a mannequin ready to test the effects of an atomic explosion at the atomic proving grounds near Las Vegas, Nevada, March 15, 1953. Through the window, a mile and a half away, stands a 300-foot steel tower atop which the bomb will be detonated. The purpose of the test blast is to show Civil Defense officials what would happen in an American city if it were subjected to an atomic attack.

(2 of 2) After the blast, a damaged bedroom, window, and blankets were missing after the blast, resulting from a test during an atomic blast on March 17, 1953.

(1 of 2) Mannequins representing a typical American family gathered in a living room are pictured on March 15, 1953, in House No. 2, awaiting an atomic test explosion on the Nevada Proving Grounds.

(2 of 2) After the blast, a damaged living room, members of the mannequin family were tossed about or missing after an atomic blast on March 17, 1953.

During the Plumbbob test at the Nevada Test Site on August 30, 1957, the Franklin Prime shot was detonated from a balloon in Yucca Flat at 750 feet.

The test explosion of a hydrogen bomb during Operation Redwing over the Bikini Atoll on May 20, 1956.

Ionization glow surrounds the cooling fireball of the Diablo shot, fired in Yucca Flat at 4:30 a.m. on Monday, July 15, 1957.

Operation Upshot-Knothole Grable was a test by the U.S. military in Nevada on May 25, 1953. A 280mm nuclear shell was fired 6 miles into the desert by the M65 Atomic Cannon, detonating in the air, about 500 feet above the ground, with a resulting 15-kiloton explosion.

The flash of the exploding nuclear warhead of an air-to-air rocket is shown as a bright sun in the eastern sky at 7:30 a.m. on July 19, 1957, at Indian Springs Air Force Base, some 30 miles away from the point of detonation. A Scorpion, the sister ship of the launching aircraft, is in the foreground.

The fireball of the Priscilla shot was fired on June 24, 1957, as a part of the Operation Plumbbob series.

NATO observers watched the detonation of Operation Plumbbob Boltzmann on May 28, 1957.

The tail section of a U.S. Navy blimp is shown with the Stokes cloud in the background at the Nevada Test Site on August 7, 1957. The blimp was on a temporary free flight over five miles from ground zero when it collapsed from the shock wave from the blast. The airship was unmanned and was used in a military effects experiment.

Observers view atmospheric testing during Operation Hardtack I, a thermonuclear detonation during the Pacific tests in 1958.

A view of the Arkansas test, part of Operation Dominic, a series of over 100 nuclear test explosions in Nevada and the Pacific in 1962.

The rising fireball of the Aztec test, part of Operation Dominic, a series of over 100 nuclear test explosions in Nevada and the Pacific in 1962.

Shot during Operation Fishbowl Bluegill, this is an image of an explosion of a 400-kiloton nuclear bomb taking place in the atmosphere, 30 miles above the Pacific, as viewed from above in October 1962.

Expanding rings surround a mushroom cloud during the Yeso test explosion, part of Operation Dominic, a series of over 100 nuclear test explosions in Nevada and the Pacific in 1962.

Sedan Crater was formed when a 100-kiloton explosive buried under 635 feet of desert alluvium was fired at the Nevada Test Site on July 6, 1962, displacing 12 million tons of earth. The crater is 320 feet deep and 1,280 feet in diameter.

A 1971 photo of a nuclear bomb detonated by the French government at the Moruroa atoll, French Polynesia.

A photo of a nuclear bomb detonated by the French government at the Moruroa atoll, French Polynesia.

This “Survival Town” house, photographed recently, was built some 7,500 feet from a 29-kiloton nuclear detonation—it remained essentially intact. Survival Town comprised houses, office buildings, fallout shelters, power systems, communications equipment, radio broadcasting stations, and trailer homes. The Apple II test was fired on May 5, 1955.

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