Talk:Atomic mass

Equivalent vs equal

I have a reason for whatever I do. If you ask, I can answer. I understand that the reason may not be valid, but discussion helps to ascertain the validity so please feel free to ask me.

From enWP:

[One unified atomic mass unit] is defined as one twelfth of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of 1.660538921(73)×10-27 kg. The CIPM has categorised it as a non-SI unit accepted for use with the SI, and whose value in SI units must be obtained experimentally.

1.660538921(73)×10-27 kg is not the definition – it is an approximation that must be obtained experimentally – so is not equal. The definition is one twelfth of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state.

For me, I see it similar to saying ${\sqrt {2}}=1.41421356237$. Square roots of positive whole numbers that are not perfect squares are always irrational numbers. It is inaccurate to say that it equals 1.41421356237 and it gives the reader the wrong idea.

Why did I change it to equivalent?

From www.differencebetween.com:

When two things cannot be compared directly, it is better not to call them equal. There is another word labeled equivalent that echoes this sentiment. When two things are same in some specific way, they can be called equivalents. In geometry, a circle can be equivalent to a square if they have same areas, but they cannot be treated as equal.

Here, 1.660538921(73)×10-27 kg is a completely different way of looking at the definition. It fixes the value in SI units like a constant, whereas the value in SI units must be obtained experimentally. The definition and 1.660538921(73)×10-27 kg cannot be treated as equal. Thus, I changed equal to equivalent to reflect this.

As I said above, this may not be a good change but this is my thinking. Most likely, there is a better way of expressing this using different wording, but I think equals gives the wrong idea. --Thrasymedes (talk) 09:16, 9 January 2014 (UTC)

How about, "1 u has a value of 1.660538921 × 10⁻²⁷ kg."? --Thrasymedes (talk) 08:16, 10 January 2014 (UTC)

Sorry for the delay, I've been travelling w/o computer. I think we cannot reduce 'equivalent' to 'equal' here, because the latter is not accurate. An earlier discussion with science people, including Barras, Ep, and others, left us with an agreement which encouraged Simple English so long as the science pages were accurate. An encyclopedia just cannot say things which are not true or not accurate (you will recall other occasions recently). It is necessary to use some technical terms, and some more difficult general words. Therefore, the question becomes whether an explanation can be given for 'equivalent' in a footnote. I would see equivalent as "not identical or equal, but in practice having the same effect as...". You can probably find a better definition in some dictionary. The guideline I developed for my articles was: "a technical term should be linked to a page which explains it or explained in a footnote". One cannot have science without such words, because the technical terms are an important part of any science (as I explained re the Earth article). The present case is slightly different because it uses an exceptional ordinary language word because the simpler word would be inaccurate. If 'equal' was used one would need a footnote to explAain why it was the wrong word, which would seem a bit odd. Macdonald-ross (talk) 13:38, 21 January 2014 (UTC)

OK. I don't understand this particular case, but I'll take your word for it. Go ahead and change the word back if you think that's best. --Auntof6 (talk) 13:55, 21 January 2014 (UTC)

I have changed the article to "1 u has a value of 1.660538921(73) × 10⁻²⁷ kg" in the hope that this is both simple and accurate. --Thrasymedes (talk) 09:24, 22 January 2014 (UTC)