I’m amazed at the way people get strung out over units of measurement. I regularly swap between inch and metric sometimes even within a project, I have swapped units on a dro on a mill when I was doing a specific bolt circle. This is not complex. Good machinists do this all the time. Tool and die makers very often receive prints that have enchant metric dimensions. When I was the owner of an old school Land Rover I often had to deal with inch metric and Whitworth form at the same time as well.

The imperial system is very organic and grew up as a very organic system. The finer the dimensions had to be the more accurate the measurement devices had to be. When you’re making a piece of furniture and you need something to be a little over 14 inches but not quite 15 in there’s 14 and 1/2 in. When you find that it needs to be a little over 14 and 1/2 but not quite 15 that’s 14 and 3/4. This kind of insanity went as far as 64th but below that it’s almost impossible to read on any kind of a ruler. At this level of precision people needed something a little tighter and people made dividing engines capable of providing very fine accuracy. Somebody determined that if you can accurately cut a thread that has 40 threads per inch, each full revolution of that thread equals 0.025″, and the micrometer was born. Divide the symbol of that micrometer into 25 equal divisions and you can very accurately measure to a thousandth of an inch.

The origin of the imperial system? Yeah it was completely arbitrary. But once it was established it became a reference of course. And people stuck with that reference. This meant that everybody could do the same thing and get the same work done.

There’s no question the imperial system is more complex. But our brains adapt relatively easily to complex systems.

The metric system was intended to be a more logical system – and it is. But it is no less arbitrary in its origin. Originally the meter was defined as one ten millionth of the distance between the equator and the North Pole on a line drawn through Paris.

Okay tell me who has a tape measure that long so they can actually measure that and figure out what that distance is. I’ll wait.

The answer of course is nobody. You can’t physically measure that, you can pretty accurately approximate it, this is what geometry and mathematics are for, however it’s based on the idea that the Earth is a perfect sphere and it’s not. And the idea that doesn’t change and plate tectonics tells you that it does. And oh let’s back up a second.

Earth.

This dimension is only meaningful on earth. This dimension has no meaning for anybody else anywhere else. If aliens come and land on our planet they are not going to be using metric measurements because metric measurements rely on distances established on this planet. The same is true of our temperature measurement. Fahrenheit was supposed to be a measurement of human body temperature with 96 being the norm as measured-get this-by a thermometer stuck under fahrenheit’s wife’s armpit. The story I heard was that when that temperature was established Fahrenheit’s wife had been ill and had a lower body temperature. Which is why the body temperature is more like 98. Fahrenheit incidentally established zero as the temperature it took to melt ice in a bath of water using salt.

Yes these are odd and seemingly quite arbitrary measurements but they are or at least within the ability of his experimentation seems to be repeatable.

Celsius, or Centigrade (which literally means 100 graduations)
Attempts to clean this messy system up by establishing a scale that is 100° between the freezing point and boiling point of water.

At sea level

On Earth.

Once again we are establishing a measurement that can only really be reproduced on this planet and even then under only certain circumstances.

We cannot claim to have established a universal measurement when that universal measurement relies on features and conditions that can only exist on a specific planet in a specific solar system in a specific Galaxy in a specific universe.

And this is as exactly true of the metric system as it is of the imperial system. It is based on completely arbitrary measurements. The idea that the length of a royals pedal extremity is any less arbitrary than an imaginary measurement that can never be physically verified is ludicrous. Once that number is nailed down and a standard is established it works fine but the origin is still arbitrary. This is so much the case that at one point they had physically measured that the American inch was 25.4000508 mm long, but just decided to truncate that to 25.4 because it was easier. So there’s how important your sacred metric system is, they rounded it off for convenience.

No if you are going to establish a meaningful system of measurement, you’re going to have to do so based on things that should theoretically be the same anywhere in the universe regardless of location. We do maybe have one of those numbers although I’m not enough of a physicist to be sure of this. That is 0° kelvin. Absolute zero. The coldest any shit can ever get. And we have another one of those numbers although again I’m not enough of a physicist to know how accurate this is but I would suggest that the temperature at which a fusion reaction takes place is a potentially meaningful standard. The current measurements of temperature are based on human experience. Even that is arbitrary. Nailing down a temperature scale that goes from absolute zero to the temperature of nuclear fusion is arbitrary only in that it exists in this universe. And should theoretically be the same at all points in the universe.

We also know the speed of light. So the scale from no motion to the speed of light is another non-arbitrary scale that we can establish.

Having a meaningful scale for temperature and a meaningful scale for distance we can extrapolate other things. We have the ability to measure the vibration of a hydrogen atom and if we know what that frequency is we can say to ourselves, we are going to establish as a measurement of time, a round number of vibrations of the hydrogen atom. Let’s call it 1,000 vibrations of the hydrogen atom is the new second. And the new measurement of distance is the distance light travels in that second. Start that as a whole number and divided into pieces like the meter is. Then take those numbers and use them to extrapolate all of the other dimensions.

I sometimes feel there is a good deal of science especially physics that is hiding from us because we have settled ourselves with these arbitrary and frankly archaic measurement systems. I always wonder if we managed to establish a measurement system based on the laws of physics and not completely arbitrary BS that we have made up that pieces would fall into place and a lot more things would make sense. But I’m just a guy yapping on the internet. Pay no attention to the man behind the curtain who is telling you that the metric system is the superbest.