The Trinity Nuclear Test on 16 July 1945 is a key incident in the blockbuster Oppenheimer movie and in the history of humankind. Many scientists think it marks the beginning of the Anthropocene, a new geological era characterized by humanity’s influence on the Earth. That’s because Trinity’s radioactive fallout will forever appear in the geological record, creating a unique signature of human activity that can be precisely dated.
But there’s a problem. In 1945, radioactive monitoring techniques were in their infancy so there are few direct measurements of fallout beyond the test site. What’s more, weather patterns were also less well understood so the spread of fallout could not be easily determined.
As a result, nobody really knows how widely Trinity’s fallout spread across the U.S. or indeed, how the fallout dispersed from other atmospheric nuclear tests on the U.S. mainland.
