[Phys-L] new kilogram, mole, kelvin, and ampere

[John Denker <jsd@av8n.com>]

The new definitions take effect Monday May 20th.
Happy world metrology day.

In practice, nobody but ultra-experts will notice any change,
but conceptually this is a reeeeally big deal.

Here's a nice easy-to-read writeup:
  https://www.latimes.com/science/la-sci-new-definition-kilogram-mole-ampere-kelvin-20190517-story.html

Some more background:
  https://www.nist.gov/si-redefinition/redefining-mole

I've been teaching for years that a mole was just a number,
like a dozen only bigger, even though officially that wasn't
true.  As of Monday it will actually be true.