Hacker News Reader

Comment by kiernanmcgowan | Hacker News Reader

The kilogram is not the only unit that will be redefined based on universal constants. The seven base units[0] will transition to being based on elementary charge and the Planck, Boltzmann, and Avogadro constants[1].

[0] https://en.wikipedia.org/wiki/SI_base_unit#Seven_SI_base_uni...

[1] https://en.wikipedia.org/wiki/Proposed_redefinition_of_SI_ba...

View on HN

Four of the seven physical constants used to define the seven base SI units will change, so a bunch of physical constants that currently have exactly defined values will start being subject to measurement uncertainty. So μ_0 will no longer be exactly 4π × 10^-7 H/m, k_C = 1/4πε_0 will no longer be exactly 8,987,551,787.3681764 N m^2/C^2, and 1 mol of carbon-12 will no longer have a mass of exactly 12 g.

Why can't they update the Avogadro constant and keep having 1 mole weight 12g of carbon 12?

And for that matter, isn't it a bit frivol to call it a constant, if it's based on something mutable? Perhaps "the Avogadro number" would be a more appropriate name.

I don't actually know what any of that means (this is either impostor syndrome or I'm just dumb), but it reminds me of why I love Hacker News so much.

Now to Google to figure out what the heck you just said...:)

Slightly off-topic, but looking at the temperature section in your second link reminded me of the latest video from Linus Tech Tips[1] where he gets bashed for using the expression "degrees Kelvin". Personally, I don't see the problem. Since a kelvin is a hundredth of the difference between boiling and freezing temperatures of water, there is a notion of scale so the term "degrees" makes sense.

1. https://www.youtube.com/watch?v=60OkanvToFI

Battles over being "technically correct" are the most fierce, because the stakes are so low.

Yes, in the same way that a half-marathon is 13 degrees mile long.

The half-marathon is a race that commemorates the Greek soldier who ran halfway from Marathon to Athens after the Battle of Marathon.

Your username is "analog31".

Reply on news.ycombinator.com