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Comment by eck | Hacker News Reader

Another interesting story about precious metals in bank vaults:

During the Manhattan project they needed to build something with a ridiculous amount of copper coils, and copper was scarce due to the war. So they used silver instead. Who cares if it's more expensive, if that machine is going to be more heavily guarded than any bank anyway and you can always melt it back into ingots when you're done?

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Since you bring up the Manhattan Project... Feynman described during the Manhattan Project they were testing different metals to find one with the right neutron properties. At one point they wanted to test gold, so they ordered a 6 inch gold sphere. The powers-that-be pointed out that the sphere would be 80 pounds of gold and would cost a fortune, but they ended up delivering it from Fort Knox. Gold didn't have the required properties, so the scientists ended up using the sphere as a doorstop for a while. The other interesting part of the story is the librarian who received the gold amused herself by asking people to move the small package for her - they failed, not expecting a small package to weigh 80 pounds; gold is much heavier than you'd expect.

http://articles.latimes.com/1985-08-05/news/mn-3468_1_manhat...

> Gold didn't have the required properties, so the scientists ended up using the sphere as a doorstop for a while.

If I remember the story correctly, it was the door stop to a room that held fissible material - gold wasn't expensive compared to the materials they were working with!

When I started working in Investment Banks, I was sent on an Introduction to Finance course. Next to me was an older guy (50's) with a massive bruised thumbnail. I asked him how he did it and told me he worked in the vaults and had dropped a gold bar on it.

a question i like to ask bright kids - "do you think gold is approximately half as heavy, as heavy, or twice as heavy as lead?"

Gold is quite close to tungsten in density (19320 kg/m^3 for gold vs 19300 kg/m^3 for tungsten). The criminal mind has found use for that factoid: they coat tungsten bars with gold and pass them off all gold (after all, they come close to passing the Archimedes test). However, the speed of sound in tungsten is significantly different than in gold. This fact allows ultrasonic thickness meters† to be used to verify nondestructively that a gold bar is golden thru-and-thru.

†http://sensorsblog.com/uncategorized/counterfeit-gold-detect...

They didn't take it out of the treasury, on a technicality: The room the machine was in was declared a bank vault, and 99.9% of the silver was recoverable, so it never really left!

What are silver and gold, when you're making enriched uranium?

Col. Nichols from the Manhattan Project went to the director of the Treasury and said that they needed to borrow 6000 tons of silver. Who replied frostily: "We measure silver in troy ounces here."

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