Our founding fathers were Penny Wise. They created the world's first decimal currency.

Sadly, we remain Pound Foolish. The rest of the world uses simple metric systems of measurement, while we Americans continue to struggle with yards, pounds, and tablespoons.

Penny Wise and Pound Foolish. Time to wise up, America!

Wednesday, January 4, 2012

A True Span

My dad taught me to use my hand’s span as a useful approximation of length. His span, when he stretched his thumb and his pinky as far as they could reach, was 9 inches. Before he moved a dresser, he’d measure the dresser in handspans and then measure the wall space to see how well it would fit. If he wanted an accurate measurement, he’d use a tape measure. But for “ballpark” calculations, he used his hand.
When I was growing up, I often measured my handspan. As I grew, it grew. I went from skip-counting by 6 to 7 to 8 inches. By the time I was 14, my handspan was 9 inches, just like my dad’s was. For a woman, I have huge hands with very long fingers. Excellent measuring devices. I often skip count by 9’s as I measure.

But saying, “This table is 5 handspans long” does not provide useful information unless everyone agrees on the definition of one handspan. Since human hands vary tremendously, how could there be a single accurate measurement called a span? Or a finger? A palm? A foot? Someone had to define each measure, and make sure that the relationship between them was constant.
I just discovered that the handspan I inherited from my dad is 27 barleycorns in length: a true span in the English Imperial System.

Knowing that, I could calculate the length of a fathom, a furlong, or even a league. But I’d probably make an error in calculation.

Look at those simple metric measures along the righthand side of the chart. Each level increases by a power of ten.

My handspan is 23 centimeters long. I could learn to count by 23’s.

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