The year was 1964. I was a student in Mrs. Seiler’s elementary-school class in a school in rural Iowa. Mrs. Seiler introduced a new topic that we students would be learning about for the next few weeks — the metric system!
What we learned during those few weeks was that although the US was a bit behind most of the other countries of the world that had already adopted the metric system, it was by now settled that the US would now get up to date and would be in harmony with the rest of the world. We would be switching to the metric system.
We learned that a liter was around the same size as a quart.
We learned that a meter was roughly the same length as a yard.
We did exercises where we would add up, say, three measurements to arrive at a total, followed by calculating where the midpoint would be of the resulting length. We would do it once using our familiar units like sixteenths of an inch and inches and feet. And again using millimeters and centimeters and meters. We would work out how long it took to do the adding-up and the dividing-by-two in the two systems.
Even now, more than fifty years later, I find myself having to spend quite some time working out the midpoint of a length if the entire length is so many inches and so many eighths of an inch. And then having to double-check it.
Oh, and in this class in third grade, we memorized conversion constants. An inch is 2.54 centimeters. A meter is 39.37 inches. Even now, more than fifty years later, I do find myself using such conversion constants in daily life, I regret to realize.
And we learned that “a kilogram is 2.2 pounds”. But then maybe eleven years later, in first-year physics in college, there was the sort of abrupt realization that this is almost never true, except in a few very special cases for example where you happen to be on the surface of the earth. One of those units is measuring mass and the other of those units is measuring weight, and mass and weight are not the same thing. (This distinction had not been explored in detail in our third-grade elementary school class.)
Alas, the US lost its resolve from 1964 and did not ever actually convert to the metric system (except in science classes).
This discussion does remind me that when I first became a car owner, which was in high school in about 1973, the only car that I could afford to buy was a used Volkswagen. It was of course all metric. I had to buy a set of metric sockets for my socket wrench set and I had to buy metric combination wrenches. Where I lived, in those days, almost nobody had a car with metric fittings. At that time, and for some years thereafter, there was only one auto mechanic anywhere nearby who worked on metric cars! Looking back on it, I realize that this auto mechanic must have been looked at by many other mechanics in town as being subversive or crypto-Communist or something, with his shop filled with metric tools, and with his vaguely un-American customers whose cars did not use normal red-blooded American inch-type sockets and wrenches.
Maybe the most embarrassing example of this failure by the US came in September of 1999, when the Mars Climate Orbiter burned and broke into pieces after almost ten months of travel to Mars. The explanation, it turned out, was that there were two teams of engineers that had needed to cooperate to get some maneuver to work correctly. One team was in Europe and used metric units. The other team was in the US and, you know where this is going, was using inches and pounds. And the Americans, you know where this is going, failed to pay attention to the problem of metric and non-metric units being involved.
Saying this differently, if only the US had maintained its resolve in 1964 and carried out the conversion to the metric system, the Mars Climate Orbiter would not have burned and broken into pieces in 1999. It would have orbited Mars and returned valuable climate data.