It’s sometimes said you ought to look backward before you can look forward. This week, we’re showing how one very specific moment in American history has had knock-on effects for scientific instruments the world over.
* July 16, 1945: The world’s first nuclear device is detonated over New Mexico, under the direction of J. Robert Oppenheimer. That successful test, of course, had implications far beyond the scope of this episode.
* The problem we’re talking about involves background radiation. We’re constantly bombarded by cosmic radiation, but on Earth, it can naturally be found in soil and rocks, in the air we breathe, in the water we drink, in extremely low concentrations — mostly uranium, potassium, and thorium. Most nuclear contamination is localized after an explosion, but as soon as all those isotopes, like cobalt-60, were unleashed upon the atmosphere, the fallout was diluted and blown around the world with different concentrations depending on the wind and geography.
* Before that fateful day, your global average dose of natural background radiation was 2.4 “milli-Sieverts” with units named after a Swedish physicist. The average dose climbed with each new artificial aboveground test, peaking in 1963 about 4-7% above the background. That year, the “Limited Test Ban Treaty” was signed by the US, UK, and USSR, prohibiting aboveground nuclear testing — and wouldn’t you know it, that global average began to drop.
* For instruments like Geiger counters, sensors on spacecraft, medical imagers, or other particle detectors, any contamination is unwelcome… and there’s your problem. Steelmaking involves compressing atmospheric oxygen to maintain a certain level of carbon… so any steel produced after 1945 would still have traces of that nuclear fallout, and that’s where “looking backward” comes in.
* Calling it “pre-war steel” ignores every war before the end of World War II, but in any case, “low-background steel” became highly sought after once our tech started catching up. Where’s your greatest source of low-background steel? How about below the waves? Shipwrecks and scrap heaps from both World Wars have been legally recovered or illegally scavenged for their nuke-free properties.
* One big source lies off the coast of Scotland, or at least used to. Not wanting to surrender their ships at the end of the First World War, the Imperial German Navy scuttled 52 ships, exactly a week before the Treaty of Versailles was signed. All but 7 ships have since been raised or partially salvaged, with some of that going toward radiosensitive scientific projects.
* NASA has never confirmed or denied its use in the Apollo or Voyager missions, though the rumors are still floating out there. There’s even an Italian particle detector that uses ancient Roman lead salvaged from a wreck to shield the experiment from outside influence — though melting down history to power the future will always be met with a good dose of controversy.
* These days, it’s almost a moot point, with background radiation WAY down from decades ago, largely thanks to that 1960s treaty. Still, it’s a fascinating window into one (or several types of one) experiment leading to cascading effects for generations.
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