The flash of light was blinding. The explosion, gigantic. The shock waves, earth-shattering.
Jay Weschler has vivid memories of that first fireball. He measured the force of explosions for the top-secret government Manhattan Project where a group of scientists created the bomb. He was 15 kilometers from the Trinity Site when the nuclear bomb went off. "It was like a regular explosion but you began to get a feeling for the scale as it rose higher and higher. It stayed bright for so long and it was pretty luminous and it was like no other explosion I'd seen," he said.
Now 81, Peggy Shephard saw the rainbow of colors from the blast at her home 200 kilometers away. But she didn't know until about a month later that she'd witnessed a nuclear explosion. She described events that morning. "And I had gotten up that morning, and it was brighter, much brighter than it is right now, for just a few seconds. And then you saw that cloud come with all those colors in it. Beautiful. Beautiful."
The first atomic test bomb, and the first use of the bomb, came during World War II. The United States was in a race against time, trying to develop a nuclear device before the Nazis in Germany, who never perfected the process.
In 1945, the plutonium core of the first atomic bomb was assembled at a former ranch house, and then taken to the nearby site, code-named Trinity. The bomb was placed on top of a 30-meter steel tower and detonated just before 5:30 in the morning.
A huge crater was formed during the blast more than 700 meters long. Intense heat vaporized most of the steel tower, and melted the desert sand into a hard, glassy, radioactive substance that was named trinitite. Later, most of the crater was filled in and the trinitite was buried under the sand. Visitors still find small pieces of trinitite today.
The substance used to be highly radioactive. But as some high school science students show, 60 years later, the radioactivity of the remaining trinitite is so low it's no longer dangerous.
"From what I measured earlier, this does seem to be marginally radioactive," remarked one of the students.
Today, not much is left at the Trinity Site, except for a few legs from the steel tower, and a shed covering a small section of the remaining crater containing pieces of trinitite. A memorial stands at the spot where the bomb exploded.
About a month after the blast, the U.S. military dropped nuclear bombs on two Japanese cities -- Nagasaki and Hiroshima, causing widespread destruction. Soon after, the Japanese government surrendered, and the Second World War was over.
Jerry DuBois, an American bomber pilot during World War II, was relieved when the Japanese surrendered. "We knew that if we had to continue to do the regular bombing in Japan there would be more and more destruction. Naturally, with the two bombs the mortality was high -- in Nagasaki and Hiroshima. But if it hadn't been for that, we would have had a widespread massacre on any potential landing (on the ground) or anything."
Tom Nathan was a U.S. soldier who was about to be part of an allied land invasion of Japan where casualties were expected to be high. After the nuclear bombs were dropped on Japan, he didn't have to go. He says, "I resent when people are anti-nuclear bomb, because I figure it saved my life."
John Hunner, a history professor at New Mexico State University, took a tour group to the Trinity Site. He's concerned about nuclear arms in the future. "But hopefully there will be an international effort to contain and control nuclear proliferation, so that weapons aren't developed, because sooner or later, as the weapons proliferate they will be used in anger or combat or an act of terrorism," he fears.
Jay Weschler says the scientists who developed the nuclear bomb didn't know for sure what they were unleashing. But for better or worse, the world changed with the explosion of the first atomic bomb that ushered in the nuclear age.