75 years ago at 5:29 a.m. on 7/16 1945 scientists gathered in the desert of NM to witness the first A-bomb test, code-named Trinity. The countdown began, followed by a burst of white light and a fireball that seemed to transform the sky. One of them thought, “Fermi was right.”

Three years before, as the scientists calculated the physics behind the atomic bomb, they had come upon a troubling possibility: that the chain reaction set in motion would not stop—that it would ignite all the hydrogen in the air and oceans and set the whole world aflame.

The calculations were uncertain, yet so serious was the risk that Robert Oppenheimer consulted the project director. They decided to continue the project while trying to prove that this catastrophe was impossible. That was never proved, but they decided the risk was negligible.

The night before the test, Enrico Fermi offered to accept odds on whether atmospheric ignition would occur. When Gen. Groves heard this he was upset, afraid such talk would upset the enlisted men. Some thought Fermi was joking--others who had done the math were not so sure.

The next day the explosion did not destroy the world or even New Mexico. Phew! And yet the effect was powerful enough to remind some of them of Fermi's "jest." As the fire rose in the sky, Oppenheimer thought of the Sanskrit text: “I am become death the destroyer of worlds.”