Think “you wake up in the woods naked,” Dr. Stone-style tech reset. How could humans acquire a 1-gram weight, a centimeter ruler, an HH:MM:SS timekeeping device, etc. starting with natural resources?
My best guess was something involving calibrating a mercury thermometer (after spending years developing glassblowing and finding mercury, lol) using boiling water at sea level to mark 100 ° C and then maybe Fahrenheit’s dumb ice ammonium chloride brine to mark -17.7778 ° C, then figuring out how far apart they should be in millimeters on the thermometer (er, somehow). I can already think of several confounding variables with that though, most notably atmospheric pressure.
I feel like the most important thing to get would be a length measurement since you can then get a 1 gram mass from a cubic centimeter of distilled water.
That’s as far as I got with this thought experiment before deciding to ask the internet. I actually asked on Reddit a while back but never got any responses.
Guess what? You get to reinvent modern metrology!
I’d start with making a surface plate using Whitworth’s 3 plate method.
Next, make a perfectly square block, pick two opposing faces of that block, that’s your unit of length. Use your surface plate to make more and measure things against it.
If you’re really smart you would have made that block out of some sort of homogeneous material like steel and made it a perfect cube, not just perfectly square. That’s going to be your prototype weight.
Temperature is the easy one, make a thermometer. Mark where the liquid is at based on two different repeatability phenomenons. Subdivide as desired. Someone will come up with a “better” way later.
Time is another easy one, just build a pendulum and start counting.
That sould get you through most of the neo-industrial revolution.
The rest of the base units will come later for now focus on building a lathe.