75 years ago today—at 5:29:45 AM (Mountain War Time)—about 35 miles SE of Socorro, New Mexico, the nuclear age began with a big bang. Contrary to popular belief, the area surrounding the Trinity test site was not uninhabited, and the fallout did not harmlessly drift away. 
In fact, some 40,000 people lived in the vicinity. Manhattan Project scientists tracked the radioactive cloud from that first 21-kiloton test (left). The Los Alamos Historical Document Retrieval and Assessment Project created a more recent graphic (right) using the same data.
Although ignored for decades, Trinity's radioactive fallout had significant immediate and long-term consequences. Last year, this @BulletinAtomic article revealed infant mortality in the downwind region increased dramatically in the months after the test. thebulletin.org/2019/07/trinit…
Those present at Trinity had a variety of reactions. Los Alamos director Robert Oppenheimer famously quoted the Bhagavad Gita: "Now I am become Death, the destroyer of worlds." Physicist Kenneth Bainbridge, the test director, was more blunt: "Now we are all sons of bitches."
Lacking familiar objects in the frame, it's very difficult to gauge how large the Trinity explosion was in photos or film. Fortunately, @wellerstein created this composite image which stacks photos at a consistent scale and includes the Empire State Building as a reference.
Last year, @atomcentral released stunning, restored, black-and-white HD footage of the Trinity test, which was conducted in New Mexico's aptly-named Jornada del Muerto desert. The cleaned-up film reveals a remarkable amount of detail previously unseen.
Also via @atomcentral is this extremely rare view of the Trinity test from a 16-mm high-speed Eastman camera shooting through a prism. As filmmaker Peter Kuran notes, "it displays some interesting anomalies not seen in other footage of the Trinity test."
