To Err … You Know the Rest
Wednesday, August 05, 2009 by Sarah Elbert.
Our editor maintains that, in general, a third of a magazine’s readers know less than its editors, a third know just about the same amount and a third know more than they (OK, we) do. Of course, some know more about certain fields than others, and our sources and writers come almost exclusively from the last, smarty-pants category. Occasionally (though not often), we also happen upon readers who also fall into this last category, finding nuggets that escaped even our tenacious fact-checkers.
Take Mark Powell, a Delta customer from Arlington, Virginia, a vigilant error-buster who alerted us to some issues in our June issue. The most notable was in a sidebar about some lesser-known facts about gold, in which we state that “in all of history, about 161,000 tons of gold have ever been mined—enough to fill just two Olympic-size swimming pools.” Turns out, if you’re planning on collecting all the gold in the world and filling up a couple of Olympic pools, just for the heck of it, you’ll want to make sure you’ve got three empty ones waiting (and perhaps a baby pool as well). As Powell says:
That sounded “off” to me despite gold’s high density, I thought 161K tons would equal more than two Olympic pools. And simple math shows it does:
First note that 161K “tons” here does refer to standard or “short” avoirdupois tons of 2K lb., as most readers would assume at least at this point. Further, the figure is correct, at least as far as the knowledge-world is concerned and as far as anyone could have faith in any figure for so historically vast and hard-to-track a datum, at least before modern times. I confirmed this from moments of research, which found a moderately/correspondingly lower figure of “long” tons for all-time gold mined.
So, we have (161,000)(2,000)=322,000,000 lb. And (322M)(454g/lb)=146.2 billion grams. Gold’s density is 19.32 g/cm³, so we have 7,567,287,785 cm³ of gold. (That’s way too precise given the obvious approximation of 161K tons, but we could be way too precise or even way too loose here and still have decisive conclusion.) Simply divide by 1M (100³ cm³ per m³) to reduce to 7,567 m³. (Still too precise, but ditto.)
And guess how many m³ of volume are in an Oly pool, folks? 2,500. So we have a fair bit more than three Oly pools worth of gold pulled from the Earth.
He also found some explanation lacking in point number 6: “An ounce of gold is based on troy weight; a pound of gold is 12 ounces, not 16 ounces.” Says Powell:
It’s right, even necessary to note the troy/avoirdupois difference. But you leave readers thinking an avoir. pound is simply 12/16 or .75 a “regular” pound. It’s not; it’s a bit more than that, since a troy ounce is more than a “regular” ounce, just less than 1.1 oz (compare grain- or gram-weights, as I did, if you don’t find this ratio expressed directly.) So an avoir. pound is just more than 14.5 troy ounces, and a troy pound is about 13.2 avoir. oz.
He also noted that while the story got it right, a timeline placed the U.S. removal from the gold standard at 1973 rather than 1971. We are not going to make it a habit to print letters from our readers in this blog (although luckily, most of them are very positive about the magazine, so that would just look self-serving), but I did promise Mr. Powell that I would correct these numbers for the public record. So, let me revise that sidebar:
In all of history, about 161,000 tons of gold have ever been mined—enough to fill more than three Olympic-size swimming pools.
An ounce of gold is based on troy weight; a troy pound of gold is 12 troy ounces, which translates to13.2 avoirdupois ounces.
* And, as a bonus, if you’re into corrections, check out this recent one in The New York Times (at the bottom of the article).
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