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We live in a global society with two standards of measurement, the so-called British system and the metric system. Although commonly used but not in the United Kingdom (which has adopted the metric system), the British gravitational system of measurement is not an easy system to work with, since there are no convenient or predictable ratios between units. For example, there are, for some non-scientific reason, 12 inches in 1 foot, 3 feet in a yard, and 5,280 feet in a mile. These units are largely based on non-reproducible standards and traditions.
For example, it is said that King Henry I established the yard by measuring the distance between the tip of his finger and the tip of his nose. An inch is the length of three dry, round barley corns laid end to end, by pronouncement of King Edward II. Interestingly, the system of shoe sizes we use today is based upon that definition. The shoemakers of King Edward's era found that the longest foot of that day was 30 barley corns, or 13 inches, long. They called this size 13, and graded sizes downward by one barley corn to a size. The same basic system is used today, and the difference between shoe sizes is one-third of an inch - the length of a grain of barley.
The mile comes from the Latin mille, or thousand, and was determined by the thousand double steps of the average Roman soldier. Edward Teller has commented humorously upon the historical bases for our British system of measurement. In Noah's time carpenters had a measurement called the cubit. This was the length of the forearm from the tip of the middle finger to the elbow. Teller observes that, assuming several carpenters worked on the same project, it is a wonder that the Ark floated. The wittiness of Teller, a great nuclear physicist, is seen through a story he tells about the historical development of our commonly Used Fahrenheit temperature scale. "There is a story that the erudite German, Gabriel Daniel Fahrenheit, once waited in Danzig until it had got as cold as he thought it could possibly get. Then, on that very cold day he stuck his thermometer out the window and that became zero. Then he put it under his arm. That became 100 degrees. So the history of the Fahrenheit scale of temperature supposedly goes back to the fact that there was once, in a rather cold town, a rather hot guy!"
As noted above, the metric system is a decimal system, that is, units are a certain power of 10 larger or smaller than other units describing the same physical property.
In the metric system different physical properties are linked by interrelated units. Imagine a hollow cube with sides measuring one tenth of a metre. Fill it with water and the volume of that water becomes one litre whilst its weight becomes one kilogram. The master kilogram, made from platinum, resides in Paris, whilst faithful copies, or witnesses, are held in major cities around the world, ensuring that a kilogram weighs exactly the same from Kilmarnock to Karachi.
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