Feb 26, 2010

Originally posted on Half an Hour, February 26, 2010.

I normally wouldn't blog my response to this post, but the circumstances are such that the comment might not survive moderation, and I would like there to be a record (I draw a lesson from all this at the end).

Andrew Pass writes:

My response:

Umâ€¦ donâ€™t teach math.

You shouldnâ€™t need to look up 40,000 times 58. Because 4 x 6 is 24, 4 x 2 = 8, you know the amount is 2,400,000 â€“ 80,000 = 2,320,000. No calculator needed.

You might not know that your silver is a bit more than 10 grams per cubic centimeter (CC) http://en.wikipedia.org/wiki/Silver , so you may have to look up the fact that just under a million kilograms of silver (1 kg = 2.5 pounds, roughly) is just under 100 cubic meters.

But there is no excuse for saying that 96.4 cubic meters is close to a cubic kilometer. First of all, a kilometer is 1,000 meters, not 100. Second, a cubic kilometer = 1000 meters x 1000 meters x 1000 meters = 1,000,000,000 cubic meters. One billion cubic meters, not 100 cubic meters.

The value of silver is generally around 15 dollars per ounce (today itâ€™s about $16.50 â€“ http://silverprice.org/silver-price-history.html ) and there are 12~~avoirdupois~~ troy ounces to a pound, so a pound of silver is worth $180. Say, about $200 today.

200 x 2 million = 400 million, so thereâ€™s no way $200 x 2,320,000 is $2.6 billion. More like $464 million. Silver would have to be priced at $60 per ounce to be worth that much. Silver peaked at about $50 an ounce once in 1980, but has otherwise never been close.

To put things in perspective, if I had a 1 gram dime to sell, your calculations would result in it being 1 million grams, which you would buy from me for $12,000.

(Just as an aside - this was not part of my response - I have often argued that 'knowing' is an act of

Such a person looks at 40K x 60 and

I normally wouldn't blog my response to this post, but the circumstances are such that the comment might not survive moderation, and I would like there to be a record (I draw a lesson from all this at the end).

Andrew Pass writes:

For the last several days, Iâ€™ve been wondering about Arrianâ€™s assertion in his life of Alexander the Great, that at the capture of Persepolis, Alexander and his army captured 40,000 talents of silver.

Now, a talent is a measure from ancient times, about 58 pounds of silver or gold. So Iâ€™ve been wondering, how much is that?

Iâ€™ve asked a few colleagues, and it turns out that people are curious. Not as curious as I am perhaps, but curious. But itâ€™s been gnawing at my insides for a few days, and I didnâ€™t know how to solve the problem.

Then I realized, I DID know. I used Wolfram|Alpha. It turns out that 40,000 talents of silver is about 2,320,000 pounds. And that weight of silver is 96.4 cubic meters â€“ not quite a cubic kilometer of silver, but close.

And its current street value? Around 2.6 billion dollars.

So maybe Arrian is exaggerating. Itâ€™s possible. Itâ€™s even likely. Maybe itâ€™s not pure silver.

But say that he isnâ€™t?

My response:

Umâ€¦ donâ€™t teach math.

You shouldnâ€™t need to look up 40,000 times 58. Because 4 x 6 is 24, 4 x 2 = 8, you know the amount is 2,400,000 â€“ 80,000 = 2,320,000. No calculator needed.

You might not know that your silver is a bit more than 10 grams per cubic centimeter (CC) http://en.wikipedia.org/wiki/Silver , so you may have to look up the fact that just under a million kilograms of silver (1 kg = 2.5 pounds, roughly) is just under 100 cubic meters.

But there is no excuse for saying that 96.4 cubic meters is close to a cubic kilometer. First of all, a kilometer is 1,000 meters, not 100. Second, a cubic kilometer = 1000 meters x 1000 meters x 1000 meters = 1,000,000,000 cubic meters. One billion cubic meters, not 100 cubic meters.

The value of silver is generally around 15 dollars per ounce (today itâ€™s about $16.50 â€“ http://silverprice.org/silver-price-history.html ) and there are 12

200 x 2 million = 400 million, so thereâ€™s no way $200 x 2,320,000 is $2.6 billion. More like $464 million. Silver would have to be priced at $60 per ounce to be worth that much. Silver peaked at about $50 an ounce once in 1980, but has otherwise never been close.

To put things in perspective, if I had a 1 gram dime to sell, your calculations would result in it being 1 million grams, which you would buy from me for $12,000.

(Just as an aside - this was not part of my response - I have often argued that 'knowing' is an act of

*recognizing*and not remembering. This is a case in point. A person that merely remembers must execute a series of calculations, in which there is a lot of room for error. But a person who*knows*can*recognize*errors that are that large.Such a person looks at 40K x 60 and

*just sees*2.4 million. Such a person looks at 96 cubic meters and*just sees*that it is not remotely a cubic kilometer (it is actually roughly 10 meters long by 3 meters wide by 3 meters high - roughly the size of a semi-trailer). When you learn math - or anything! - by rote, you do not learn to 'just see' - you do not develop 'knowledge as recognition'.)