Isotopes produced in the original Manhattan Project reactors seeded decades of research and even a few Nobel Prizes. //

On July 16 this year, on what marks the 75th anniversary of the first nuclear bomb test, a patient may go to the doctor for a heart scan. A student may open her textbook to study the complex chemical pathways green plants use to turn carbon dioxide in the air into sugar. A curious grandmother may spit into a vial for a genetic ancestry test and an avid angler may wake up to a beautiful morning and decide to fish at one of his favorite lakes.

If any of these people were asked to think about this selection of activities from their days, it would likely strike them as totally unrelated to the rising of a mushroom cloud above the New Mexico desert three-quarters of a century ago. But each item from the list has been touched by that event.

The device that was detonated at dawn on that fateful day unleashed the energy of around 20,000 tons of TNT from a plutonium core roughly the size of a baseball. It obliterated the steel tower on which it stood, melted the sandy soil below into a greenish glass -- and launched the atomic age. //

The scan, the textbook, the genetic test and the favorite lakeside retreat represent elements of the Manhattan Project’s forgotten legacy. They are connected through a type of atom called an isotope, which was deployed in scientific labs and hospitals before World War II, but whose overwhelming prevalence in the decades after the war was enabled and pushed by the government apparatus that was a direct heir of the effort to build the bomb.

“Generally when both ordinary people and scholars have thought about the legacy of the Manhattan Project, we thought about the way in which physics and engineering were put to military use,” said Angela Creager, a science historian at Princeton University whose book “Life Atomic” chronicles the history of isotopes in the decades after WWII. “Part of what I discovered was that atomic energy had just as much of a legacy in some of the fields that we think of as peaceable as it did in military uses. … A lot of the postwar advances in biology and medicine that have really been taken for granted owe a lot to the materials and policies that were part of the Cold War U.S.”