And with that, I mourn the obsolescence of my last remaining "absolute unit" joke and will have to develop something equally satisfying based on dressed lumber to replace it.
Definition of mole changes too.<p><i>One mole contains exactly 6.022 140 76×10²³ elementary entities</i> (as opposed to the number of atoms in 12 grams of ¹²C). Effective 20 May 2019.
For the next revision: remove the mole from the SI. It's completely pointless. A number is not a unit!
Instead replace it by the bit, the fundamental unit of information.
I've always been mildly irritated that the name of the SI mass base unit has a prefix. Second, liter, meter, Newton, kilogram. Were I emperor of the world I would slide the name scale up so the mass equal to 2.205lbs was called a gram.
Reading about standard kilogram always reminds me 2014 movie "1001 grams" [0]. Not sure how accurate it reflects how the things are actually run there, but was interesting to watch it nevertheless.<p>[0] <a href="https://www.imdb.com/title/tt3346824/" rel="nofollow">https://www.imdb.com/title/tt3346824/</a>
Confused, so how do they measure 1 kilo of something now when they need to calibrate the most precise instruments? They count 10^40 photons? How? And how does that translate into a physical mass they want to carry around?<p>Edit: Seems I completely missed a paragraph somehow. Thanks!
>Despite the greatest of precautions, every time the standard kilo was handled — for example, to compare it to another unit that could then be used to calibrate instruments — it would shed some atoms and its mass would be slightly changed. Over its lifetime, that standard kilo is estimated to have lost about 50 micrograms.<p>Why did the standard kilo ever need to be handled? Just store it on a balance and only handle the comparison unit.
This article sounds like it got written by a scientist but got butchered through a PR department.<p>It talks about the "Mass of a photon" and weighing them directly, rather than the energy-equivalent mass, which is presumably what they are intending to talk about?
Veritasium has a video back in 2017 explaining kibble balance
<a href="https://youtu.be/Oo0jm1PPRuo" rel="nofollow">https://youtu.be/Oo0jm1PPRuo</a>
I wonder if there is a process that has to be gone through to now update the pound avoirdupois. It is defined as 453.59237 grams but given the formal definition of the gram has changed could there be a need for a formal acknowledgement, or does the law encompass changes in methods so it just happens automagically?
Change is scheduled for 20 May 2019.<p><i>checks date</i><p>fake news... the artifact is still the official reference for the standard kilogram for another 72 hours... ;)
The new reference kilogram is an engineering marvel, but I’ve always wondered this: why didn’t they just build a reference gram instead? Seems like that would be at least a thousand times easier to pull off.