75 years ago, the Trinity atomic bomb test changed the world forever
July 16 marks the 75th anniversary of the first detonation of an atomic bomb. Now famous as the Trinity Test, the giant explosion was the culmination of the ultra-secret Manhattan project and would within weeks lead to the end of the Second World War and usher in the Atomic Age.
On July 16, 1945, at 5:29 AM, the predawn darkness on what was then the United States Army Air Force (USAAF) Alamogordo Bombing and Gunnery Range in the Jornada del Muerto desert about 35 miles southeast of Socorro, New Mexico, was suddenly lit up with the light of a thousand suns. As a collection of the world's leading scientists looked on from a safe distance, an ordinary-looking steel tower vanished in a fraction of a second as the world's first plutonium bomb instantaneously converted matter into energy.
That day was the sharp end of three years of hard work carried out in a boomtown that is now the Los Alamos National Laboratory. Back then it had a population of 6,000 living in a collection of mud streets and hastily erected wooden buildings with just five bathtubs, and it was the center of the Manhattan project – the highly secret Allied effort to build the atomic bomb.
It began life originally as a British weapons project, but with the British Isles under constant German bomber attack, and every factory turned over to cranking out conventional weapons, it was decided to pool Britain's efforts with America's, resulting in the Manhattan project coming to life in June 1942.
Today, weapon development is highly evolutionary, building on the work that has been done by others going back decades, if not centuries, but the Manhattan project was about as close to starting from scratch as one can imagine. When the project began under the leadership of Brigadier General Leslie R. Groves and physicist J. Robert Oppenheimer, they were working almost entirely on theoretical work and a few laboratory experiments. To give an idea of how far they had to go, in those days, there was only enough plutonium in the world to cover the head of a pin – nowhere near enough to build a bomb, even if they were sure it could be done.
Fast forward to 1945 and the physicists and engineers at Los Alamos had produced two prototype nuclear devices. One was a simple design that worked by an explosive charge in a tube that slammed two plugs of uranium-235 together, resulting in a critical mass that set off a chain reaction as the uranium atoms burst apart, spewing out neutrons that split more uranium atoms in a cascade of destruction.
The uranium bomb was so simple that the scientists didn't feel it necessary to test it, but the second bomb, called the Gadget, was much more sophisticated. The Gadget used the man-made radioactive element plutonium instead of uranium. Instead of a simple tube, the plutonium was formed into a near-solid sphere surrounded by explosives, a web of detonators, and acoustic lenses to make sure the resulting explosive wave imploded the plutonium sphere correctly to start the chain reaction.
Some sort of test would be needed to make certain that the plutonium bomb, which was subsequently used against the Japanese city of Nagasaki, would work. At first, the idea was to do a low-power explosion, but Oppenheimer opted for a full-scale test, which was code-named "Trinity."
By May, a 100-foot tall steel tower was set up at the Alamogordo site along with a base for 160 people, which swelled to 450 on the day of the test. Because of the high level of secrecy, the US Army accidentally bombed the area twice.
Like a Hollywood spectacle where the big scene means destroying the set, the test could only be done once. The Manhattan team set up cameras and instruments, including a lead-lined tank, to make sure that every millisecond of the test and every scrap of data was recorded. As the scheduled test time loomed, atop the tower and shrouded in tarps, the globe-like Gadget was assembled by seven men and the intricate networks of wires were connected to the detonators. Then the entire bomb was sealed inside a steel container called Jumbo that would prevent the plutonium from scattering if the test proved a dud.
As if there wasn't enough tension, there were also a string of electrical storms passing through the area, raising the prospect of the tower being hit by lightning.
About 10,000 yards away from the tower, shelters were set up. Among the Army personnel and the civilian scientists and technicians were Groves, Oppenheimer, and VIPs Richard Tolman, Vannevar Bush, James Conant, Brigadier General Thomas F. Farrell, Charles Lauritsen, Isidor Isaac Rabi, Sir Geoffrey Taylor, and Sir James Chadwick.
While waiting for the explosions, the scientists took dollar bets on how big the yield from the bomb would be. Edward Teller took 45,000 tons of TNT, Oppenheimer bet 3,000 tons, Rabi bet 18,000 tons, Hans Bethe had 8,000 tons, and Enrico Fermi took side bets on incinerating the state of New Mexico or the entire planet.
When the bomb went off, few actually saw the explosion. Most did as they were ordered and turned their backs. Others, like Teller, saw it using goggles and suntan lotion for protection. Meanwhile, a young Richard Feynman reasoned that the only real danger from the bomb at that distance was from hard ultraviolet rays, so he sat in an Army truck and watched from behind the protective glass windscreen, making him the only one to see the test with the naked eye.
The Gadget detonated as planned, releasing a yield of 22 kilotons. The tower was vaporized, and a 5-foot-deep crater was blasted out of the desert floor, which was converted into glass by the tremendous heat flash, creating a new mineral called trinitite. Above the site, the first atomic mushroom cloud turned golden, purple, violet, gray and blue, rising 7.5 miles into the sky as a pair of B-29 bombers circled to record the event at a distance. On the ground, the observers felt a wave of heat like the open door of an oven.
"We knew the world would not be the same," said Oppenheimer in a 1965 interview. "A few people laughed, a few people cried. Most people were silent. I remembered the line from the Hindu scripture, the Bhagavad Gita; Vishnu is trying to persuade the Prince that he should do his duty and, to impress him, takes on his multi-armed form and says, 'Now I am become Death, the destroyer of worlds.' I suppose we all thought that, one way or another."
Today, the Trinity Site is a National Historic Landmark marked by a simple lava-rock plinth bearing a plaque that reads, "Trinity Site Where the World's First Nuclear Device Was Exploded on July 16, 1945."
As to what became known as the Bomb (with a capital B), it went on to end World War II and became the centerpiece of the Cold War, reshaping our world forever.