Re: [Phys-L] The kilogram and Planck's constant

[John Denker <jsd@av8n.com>]

On 06/30/2017 08:08 PM, Bob Sciamanda wrote:

> https://www.nist.gov/news-events/news/2017/06/new-measurement-will-help-redefine-international-unit-mass

The story just made the front page of the Gomorrah Post web site:
  https://www.washingtonpost.com/news/speaking-of-science/wp/2017/07/05/scientists-are-about-to-change-what-a-kilogram-is-thats-massive/

See also the roadmap and discussion here:
  http://www.bipm.org/en/news/full-stories/2017-06-ccm-pilot.html
  http://www.bipm.org/en/measurement-units/rev-si/

========

Also note that the kilogram isn't the only base unit on the menu.
In fact the kilogram, the mole, the kelvin, and the ampere are
all scheduled for redefinition.

I always tell students that a mole is a number, like a "dozen"
only much larger.  Alas the official SI definition is something
else, something IMHO very strange.  However, they are about to
fix that.

In accordance with Stigler's law of eponymy, Avogadro died without
ever knowing the value of Avogadro's number.  If you had given him
a number that was an order of magnitude too high or too low, he
would not have known the difference.

Einstein's Brownian motion paper refers to Loschmidt's number,
which seems more logical.

===

Planck's constant is part of the story, but it is not a base unit.