# Talk:2019 revision of the SI

Make Redefinition of SI base units as a disambiguation page for all redefinitions.
2A02:C7F:31CF:6400:F4DF:CC40:B26C:BA04 (talk) 19:09, 26 August 2021 (UTC)

Link: Redefinition of the SI base units. At least at the moment the 2019 one is by far the most important one. That's generally what readers will look for. The other redefinitions, which were much smaller, don't even have their own articles. --mfb (talk) 10:29, 27 August 2021 (UTC)

What happened to all the IPKs? They didn't just throw them away, did they? Recycle them?  I would suspect that they are still around, though maybe in museums. Gah4 (talk) 19:40, 8 June 2022 (UTC)

It is clear form the Mole part of the Appendix 2 of the SI brochure 9th edition that Molar mass constant is infact calculated from unified atomic mass. Why don't you guys remove the discussion around ambiguity of whether unified atomic mass is defined from Molar mass constant or Molar mass constant is defined from unified atomic mass?? Aakash6022 (talk) 09:07, 10 November 2023 (UTC)

The title "2019 redefinition of the SI base units" is misleading. The reform of 2019 was NOT just about the base units. There have been various redefinitions of base units before (metre prototype => wave length => speed of light; freezing and boiling point of water => triple point; rotation of earth => tropical year => period of Cs radiation)  and, yes, the new one is now built on fundamental contants.
But the key change is: the concept of base units (= 7 units, from which all others are derived) was abandoned. There are no base units anymore. (the word was just kept "for historical reasons"). Instead, the base are the 7 constants. [1] and all units are directly derived from these. The fact, that e.g. kg has a new definition, is just a side effect.
“Prior to the definitions adopted in 2018, the SI was defined through seven base units from which the derived units were constructed as products of powers of the base units. Defining the SI by fixing the numerical values of seven defining constants has the effect that this distinction is, in principle, not needed […] Nevertheless, the concept of base and derived units is maintained because it is useful and historically well established […]” (SI brochure, chapter 2.3)
I strongly recommend that the article be renamed to "2019 revision of SI" -- Wassermaus (talk) 12:47, 9 September 2024 (UTC)

The title of the 2018 Resolution 1 supports the proposed renaming:
"On the revision of the International System of Units (SI)"
Other refs use similar wording:
Davis, R. (2019). An introduction to the revised international system of units (SI). IEEE Instrumentation & Measurement Magazine, 22(3), 4-8.
Schlaudt, O. (2019). The reform of the International System of Units (SI). Measurement, 9, 26.
Giunta, C. J. (2019). What chemistry teachers should know about the revised International System of Units (Système International). Journal of Chemical Education, 96(4), 613-617.
I think the title should be
2019 revision of the SI
or possibly
2019 revision of the international system of units.
Any objections, comments from @Quondum @Gah4? Johnjbarton (talk) 15:23, 9 September 2024 (UTC)
I strongly endorse the need for a renaming to something that does not reference base units.  The only thing that is distinctive about the base units now is that they are the units associated with the conventional reference basis for the space of dimensions – nothing more.  They get used for easily figuring out a form to put a product of units in.  That they figure in the definition of the SI at all is historical and possibly even transitional.  Their unnecessary nature being pointed out in the SI Brochure itself makes this very plain.  I would support either title suggested by Johnjbarton, with the proviso that the latter would capitalize the full name of the SI appropriately.  —Quondum 17:37, 9 September 2024 (UTC)

I presume I was mentioned because of my notes above about the confusion of base and derived units. Often enough, base units are derived from other units. So, yes, I am find with removing base from the article title. Gah4 (talk) 19:30, 9 September 2024 (UTC)
 Done I changed a few of the incoming links. I might try an auto browser tool on the rest if I get brave. Johnjbarton (talk) 22:15, 9 September 2024 (UTC)
I have updated the link in two templates, and this has reduced the number of remaining mainspace pages to 52, as listed by "What links here".  This is manageable in time, whether by AWB or manually; it is the kind of thing I pick away at.  Even with AWB, there will likely be a bunch of review and editing, because the text must change accordingly.   —Quondum 20:44, 10 September 2024 (UTC)
All incoming links have been cleaned up.  —Quondum 16:29, 13 September 2024 (UTC)