Good Things, Bad Things: Measurements and Distances

This post is the last and belated part of the Good Things, Bad Things series.

The USA is the only industrialized country to be using a systems of units that differs from the international standardized, or metric, system. In fact, the World Factbook by the CIA, in Appendix G, states that:

At this time, only three countries - Burma, Liberia, and the US - have not adopted the International System of Units (SI, or metric system) as their official system of weights and measures. Although use of the metric system has been sanctioned by law in the US since 1866, it has been slow in displacing the American adaptation of the British Imperial System known as the US Customary System. The US is the only industrialized nation that does not mainly use the metric system in its commercial and standards activities, but there is increasing acceptance in science, medicine, government, and many sectors of industry

This issue about units of measurements causes many differences, both for the good and for the worse. The system now called American Customary Units was derived from the English and later Imperial Units, but even that is not entirely correct or accurate. For example, an American Wet Pint is much smaller than its British counterpart (and even the Amreican dry Pint for that matter, but who the hell drinks a dry beer?!), and the only explanation for that might be that no one wants to drink more than an American pint of domestic beer, especially when compared to a nice smooth pint of Guiness. Anyway, I digress.

One problem with American Customary Units is that they hold true only at a certain location on Earth, specifically at latitude 45, which is roughly where the USA is. This is so typical of Americans: to invent a set of units that can be true only at a certain location in the universe. As usual, as long as Americans keep to themselves and don't try to meddle with the affairs of others that is not a problem. However, they rarely do, and at some point they even decided to venture to space. Now, on space, as everyone knows, there is no gravity. As a result, there is also no definition of weight, which is the force that stems from the product of mass and gravity, hence no gravity - no weight. Since the American Customary Units assume a weight of 1 lb as its basic unit of measurement, and calculates the mass that produces this weight at latitude 45 and sea-level, this entire system of units is useless in space. Thus, for scientific purposes, it makes more sense to use Standard International units, i.e. the metric system, whose base unit is the Kg for mass, and not weight. Mass is invariant no matter what the gravity acceleration is. Why am I telling you all this? For two reasons: 1) it's virtually impossible to teach American students to distinguish between mass, weight and the units used for both. They know that some multiplication or division is required, but not exactly which is what. 2) it's the cause of one of the most colossal failures in NASA's history.

There are also positive sides to using American units. For example, we still think about temperature in Celsius, but if you look at Fahrenheit it makes more sense: the weather in Cincinnati this year ranged from really cold when it was zero Fahrenheit to hot when it was 100 Fahrenheit. On the other hand, spatial distances are shrunk or expanded as needed: for example it's much nicer to live in a 1000 sq. ft. apartment than in a 100 sq. meters apartment. It's easier to drive 500 miles to a party than it is to drive 800 Kms, as we did on the weekend of the 4th of July. ;-)