After 1945, nuclear testing filled Earth’s atmosphere with trace radiation that contaminated all newly produced steel. This means that steel made after WWII is too radioactive for use in highly sensitive equipment, like Geiger counters, space instruments, and medical scanners. Instead, scientists use “low-background steel,” forged before 1945, often salvaged from sunken warships resting on the ocean floor. It’s a strange twist of history the weapons of war now serve science and healing. | Just F

43K views · 258 reactions | THE MYSTERIOUS DICTATOR: Kim Jong Un, the 36-year-old “Supreme Leader” of North Korea, has a ruthless history that includes executing his own family members and a series of nuclear weapons tests that has kept the entire world on edge. David Muir reports from Singapore. https://abcn.ws/2HCFiQD | ABC World News Tonight with David Muir | Facebook