Driving home one recent evening on a narrow country road, the Old Man rounded a curve to see a turtle about 6 inches across (or was it a tortoise?) in the middle of the lane, heading for the other side. With no time to stop, and no room to pass on either side, the only alternative was to head straight for it, straddling it so it might survive between the wheels. The rear view mirror showed an intact but bewildered turtle motionless in the road.
Why did I estimate 6 inches and not 15 centimeters? Because this is a US website. We are world leaders, leading from behind. We lead the world in capital punishment, in citizens in prisons, in foreigners imprisoned without trial—but I digress.
Using the metric system is not just how you measure things. It’s, for instance, whether you sell milk and soda in quart bottles or liter bottles. More important, it’s what size screws you make and use. You can pour from a liter bottle into a 10-ounce glass, but you can’t fasten a metric screw with a US nut, or set a metric screw into a hole tapped with US threads.
The Old Man’s best guess as to why the US is still using inches is that it gives US makers of screws, nuts, wrenches and the like a captive market with no competition from the metric world. It will be a long time before the US really adopts the metric system.