Today is the 65th anniversary of Trinity.
We all remember J. Robert Oppenheimer's reaction ("Now I am become Death, the destroyer of worlds" from the Bhagavad Gita) but I think the lesser known words of the lesser known Kenneth Bainbridge do the job a little bit better: "Now we are all sons of bitches."
Humans have a tendency to overuse superlatives when it comes to history. Browse the non-fiction section of your bookstore and you will find dozens, perhaps hundreds, of accounts of things that "changed the world" or were "turning points in history." This is almost always bunk, but the events of July 16, 1945 at White Sands are among the few that can accurately be described that way. I could talk for hours and maybe days about this subject but I will be as brief as I can: the moment "The Gadget" detonated, the world changed. What happened at 5:29 AM Mountain Time on that day became the dominant topic of conversation and thought for the next forty years and forever altered the way the nations of the world interact. It made World War III unthinkable and, as a result, introduced proxy wars and Marx Brothers-like misadventures of industrialized nations in isolated and unpronounceable places.
Not being a historian by trade, I can only think of a few analogous events. The invention of electricity. The printing press. The Protestant Reformation – Treaty of Westphalia combo. The conversion of Constantine I of Rome to Christianity. Marco Polo shaking hands with Kublai Kahn.
What else? I'm sure I've only scratched the surface of the list of events that legitimately altered the course of human history. There must be more, such as the historic and planet-changing election of Barack Obama.