Sometimes you look at the world a different way.<p>It's a trope in fantasy books that <i>elves are sensitive to iron</i>, and humans can easily defeat them by using "cold iron" or steel weapons and armour.<p>So... what is humanity's "cold iron"?<p>Two that come to mind are beryllium and cadmium, both used almost nowhere in bulk outside of... military aerospace... because they're poisonous to humans.<p>Beryllium is the ultimate aerospace engineering metal. Extremely light, very strong, and doesn't expand much when heated. It's commonly used in missiles and the like.<p>Cadmium is the ultimate anti-corrosion coating because it's so soft that it <i>reflows</i> to cover microscopic cracks. That gold colour you see on the undercarriage and landing gear of some military aircraft is cadmium. Its use is banned for most civilian purposes, but <i>special dispensation</i> is available for military use. It's <i>just that good</i>, which justifies lightly poisoning a few airmen.
A coworker pointed out to me that all the crew chiefs in his (Marine Corps) aviation unit only had daughters.<p>They worked on aircraft with radioactive emitters designed to detect bullet holes in the rotors without electronics going through a rotating joint.
Previous discussion on the topic: <a href="https://news.ycombinator.com/item?id=35225181" rel="nofollow">https://news.ycombinator.com/item?id=35225181</a>