By The Metric Maven
My friend Pierre spends a lot of time browsing for backpacks and such. I suspect he has always wanted to runaway from home, but just never has found exactly the right luggage. One day he came across a backpack with a capacity of 1700 cubic inches or 28.7 liters. This caused him to think about a new unit which is appropriate for storing Jimmy Hoffa or other expired homo sapiens. Pierre saw no reason that he should not suggest a new unit for SI because he had discovered how compromised the liter is:
“So for that one moment in time, I thought about how we communicate volume to others. Moving hand gestures seem to work, but that doesn’t help in print advertising. Usually, we use “cubic inches,” or “cubic feet.”
But, the French get wet. They use quarts/liters/litres/litrons and cubic decimetres for everything, apparently. …”
Then Pierre goes for the jugular:
“Speaking of which, liters aren’t actually an SI unit? I’ve been lied to? Maybe you should get on that with your foreign pals. Or just toss it and use quarts like everybody else does.
As an example, note this bag on sale on Amazon this week, specifically the part I highlighted en rouge:
Unlike an insanely hot, but, hairy-armpitted, chain-smoking French girl, we smartly measure volume by linear methods cubically applied. They just go right to liquids. How funny would it sound for us to say this bag could contain 108 cups of coffee (real cups, not “coffee cups”) . One could kind-of picture that. But saying “this bag holds 27,000,000 cubic millimeters?” Not so useful.
Even a mostly dim marketer can immediately see that metric isn’t good for advertising AT ALL.
Unless this is a “wet bag” of some sort, isn’t the metric system inappropriate here?
Who uses wet measurements to measure dry things? Besides luggage and motorcycle/car engine manufacturers. Those goose-feeding, croissant-eating French, that’s who. Well, and baking measurements too. But that’s just wrong.”
The good news is that Pierre’s understated, quiescent and measured questioning provides me with an excuse to explain the importance of the liter—otherwise known as the Rodney Dangerfield of the metric system. First one must realize that wet and dry volumes are equivalent, and no distinction is necessary. In cooking, wet measurement cups have a line below the top, and are generally clear. Dry measures are made so that the exact measure is at the rim of the cup. One can scrape them flat with a knife and have the exact same volume as the wet value, but in a way that works better for dry stuff. It was Isaac Newton who changed cooking forever by defining mass. After that point, much like the metric system, the English creation was adopted by the French. They realized that dry ingredients were best weighted in the Earth’s gravitational field, which allows one to back out the mass in grams. I think we know what happened to English versus French cooking at that point.
There is no distinction between wet and dry volume in reality; but in the imagination of English speaking people, somehow a magical change occurs. Exhibit A is the US Gallon (Wikipedia):
The US liquid gallon
- The US gallon, which is equal to approximately 3.785 litres, is legally defined as 231 cubic inches. A US liquid gallon of water weighs about 8.34 pounds or 3.78 kilograms at 62 °F (17 °C), making it about 16.6% lighter than the imperial gallon. There are four quarts in a gallon, two pints in a quart and 16 fluid ounces in a US pint, which makes a US gallon equal to 128 fl. oz. In order to overcome the effects of expansion and contraction with temperature when using a gallon to specify a quantity of material for purposes of trade, it is common to define the temperature at which the material will occupy the specified volume. For example, the volume of petroleum products and alcoholic beverages are both referenced to 60 °F (16 °C) in government regulations.
The US dry gallon
- This gallon is one-eighth of a US Winchester bushel of 2150.42 cubic inches; it is therefore equal to exactly 268.8025 cubic inches or 4.40488377086 L. The US dry gallon is not used in commerce, and is not listed in the relevant statute, which jumps from the dry quart to the peck.
The liter is fixed in value. It is a 100 mm x 100 mm x 100 mm cube. The gallon?—-not so much.
The liter was clearly designed by Father Nature (wait till Mother Nature finds out) as it is a cube with edges which are very close to the width of an average man’s hand. This allows an average man to estimate a liter of volume very quickly.
SI, in its semi-infinite wisdom, made the cubic meter the official unit of volume, and the liter was relegated to second class citizen status. When the Australians decided to become a metric nation, they were apparently far enough away from the bad influences of the US, Canada and the UK to realize (from Metrication in Australia):
Yes, even applications that involve describing the volume of a backpack. The backpack could be described as 28 700 milliliters (or 28 700 – 10 mm cubes), but any person slightly acquainted with the metric system will immediately see 28.7 liters, and would not understand the importance of extra numbers for marketing purposes. When actually attempting to present numbers in an understandable way, the liter is excellent. Water has a density of 1000 grams/L. If any SOLID object has a density higher than this it sinks, if it’s lower it floats. Wet and dry coexisting in harmony, without an artificial separation, because of the liter.
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