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Too bad US doesn't use them.
It does actually, US measurements are legally defined in terms of metric units. https://en.wikipedia.org/wiki/United_States_customary_units
What surprised me reading that wiki page is that apparently the metric system was opposed in the US based on religious reasons. That is mind-boggling.
This is probably the dumbest thing I'll type on HN. In university I just gave up trying to understand why we even needed the Avogadro constant / mole as a fundamental constant. It still confuses me. Why have a difference between molar mass and mass? Why couldn't it just be "1" and everything else change around it?
> the Avogadro number was initially defined by Jean Baptiste Perrin as the number of atoms in one gram-molecule of atomic hydrogen, meaning one gram of hydrogen. (from Wikipedia)
(It's since been refined to be 12 grams of carbon-12.)
So a mole is defined to be approximately one gram worth of protons and neutrons. We use it because grams are a significantly easier unit of mass for humans to work with, than like individual particles.
https://www.bipm.org/utils/en/pdf/CGPM/Draft-Resolution-A-EN...
Too bad US doesn't use them.
(Just making up a number here) 3.937" stroke? Why on Earth... Ah. 100.0mm. That's why.
This is probably the dumbest thing I'll type on HN. In university I just gave up trying to understand why we even needed the Avogadro constant / mole as a fundamental constant. It still confuses me. Why have a difference between molar mass and mass? Why couldn't it just be "1" and everything else change around it?
On the rare chance that anyone here missed today's XKCD: https://xkcd.com/2073/
> a cylinder of a platinum alloy stored at the BIPM in France, will now be retired. It will be replaced by the Planck constant – the fundamental constant of quantum physics. I thought they did that long time ago.
I did too, but apparently they only defined it for the second, meter and candela. Are other units still tied to physical measures, or is this all of them?
As you stroll Paris, you can still find various meter secondary standards - bolted onto public buildings to aid in commerce back in the day.
This is probably the dumbest thing I'll type on HN. In university I just gave up trying to understand why we even needed the Avogadro constant / mole as a fundamental constant. It still confuses me. Why have a difference between molar mass and mass? Why couldn't it just be "1" and everything else change around it?