All of this debate overlooks the fact that use the metric (SI) system is much more widespread in the United States than people often assume. In the medical and pharmaceutic fields, for instance, it is used exclusively. A growing number of everyday items are now packaged or designated in SI units, and Americans have accepted them without any problems or objections. (Just try to buy bottled water by the pint or quart anywhere in this country; it can't be done. You can only find it in liters.) Weather forecasts frequently report the temperature in Celsius, sometimes exclusively in that scale. If you mention a millimeter, a meter or a kilometer, most people in the US have an immediate intuitive grasp of what those distances look like. The gram unit of mass is becoming more and more widely recognized. In our own hobby, we long ago converted our force measurements to Newtons without any difficulty, and I am beginning to hear that term mentioned on occasion in popular media and in news reports. These are all just a few examples. But as Zeus-Cat illustrated in his original post, the process of conversion is not yet complete here. But it is happening, bit by bit, and at an ever-increasing rate, I think. Our children are taught it in school, and I, too, was taught it in grade school some 45 years ago. But back then, I never heard metric units used for anything in my everyday world. Now, I encounter it all the time. So the question, "why doesn't the United States use the SI system" is a false one. The plain truth is, we already do! It is just not used exclusively yet, but it will be, eventually, and probably sooner than many critics think. Our government isn't forcing it down our throats, though; instead, we Americans are adopting it on our own without requiring any mandate from a central authority to do so. Has any other country ever done that?