Elonoshi's Weird Knowledge Series

Some of the steel used in our most sensitive scientific instruments has to be salvaged from sunken WWI and WWII battleshipbecause no steel made after 1945 is “clean” enough.
Here’s why:
When you make steel, you blast air through molten iron. That’s fine… until humanity started detonating nuclear bombs in the atmosphere. The Trinity test in 1945 and the decades of testing that followed seeded the entire planet’s air with faint radioactive isotopes like cobalt-60. Every breath of air pulled into a steel furnace since then carries a whisper of that fallout
so all modern steel is very slightly radioactive.
For most things, who cares. But for Geiger counters, deep-space radiation sensors, medical body scanners, and particle physics detectors, that trace radioactivity is loud enough to ruin the readings. The instrument can’t measure faint radiation if its own body is humming with it.
The solution is almost poetic: go find steel forged before the nuclear age. The richest source is the German Imperial Navy fleet that was deliberately scuttled at Scapa Flow, Scotland in 1919, dozens of warships sitting on the seabed, their hulls made of pristine pre-atomic steel.
Divers have been quietly cutting them up for decades to feed cutting-edge science. So a battleship sunk by sailors who’d never heard the word “atom” ends up inside the machines we use to study the universe.
This is called low-background steel, and there’s a beautiful footnote to it:
because atmospheric testing was banned in 1963, the air has slowly been cleaning itself, and modern steel keeps getting purer.
Future generations may not need the shipwrecks at all, problem is literally fading away on its own.