Wikipedia:Reference desk/Archives/Science/2022 July 23

= July 23 =

How high were the "gross CO2e emissions" in 2021
I'm having trouble finding the correct values. I find values of 34.9 GtCO2 (probably only CO2?), 36.3 (the same) etc. But I need CO2 equivalents (CO2e) and I would prefer "gross" emissions. The reason is that I want to compare the value in an essay to that of a company. The company has given the values as gross CO2e. 80.71.142.166 (talk) 08:25, 23 July 2022 (UTC)

isotopes of Helium
Hopefully someone here can fix this. According to our article on Helium, "The shortest-lived heavy helium isotope is helium-5 with a half-life of 7.6×10−22 s." But then Isotopes of helium says that "The shortest-lived isotope is helium-10 with a half-life of 260(40) yoctoseconds", and it doesn't mention helium-5 at all. —scs (talk) 11:50, 23 July 2022 (UTC)
 * The 'fact' in the Helium article is cited to a 1968 publication, while that in the Isotopes of helium is cited to a current online encyclopaedia which is presumably much more up to date (though I don't have full access to it). It looks to me as if more comprehensive details are needed on all the 'heavy helium' (i.e. n>4) isotopes, by someone with access to relevant academic sources. {The poster formerly known as 87.81.230.195} 90.201.73.20 (talk) 12:38, 23 July 2022 (UTC)
 * It looks to me as if they're both cited to the same 1968 encyclopedia? I mean Isotopes_of_helium only has that one reference. (Though I searched inside that book a bit, and didn't find any any mention of helium-5 or helium-10. In fact page 260 is cited, which discusses isotopes, but not either of those two, unless I'm missing it.) Both isotopes are given half-lives in List of radioactive nuclides by half-life. Looks like The NUBASE2020 evaluation of nuclear physics properties is the source. Page 22 gives the year 1994 for the discovery of 10He, and the 260 ys 40 halflife. (What is that 40, a margin of error?) Card Zero  (talk) 13:43, 23 July 2022 (UTC)
 * NUBASE2020 is the most complete and recent source for isotopes and their decay properties and it gives helium-10 as the shortest-lived isotope, so I'll check that this is consistently described. yes, the 40 is a margin of error: the half-life is $260 ys$, but it is expressed more concisely with parentheses. ComplexRational (talk) 15:17, 23 July 2022 (UTC)
 * Just an observation: I must admit that I had to look up yocto- to understand that the numbers scs cites for helium 5 and 10 were of the same order of magnitude. --174.95.81.219 (talk) 23:30, 23 July 2022 (UTC)
 * Rule of thumb: (1) recognize the transmogrified Latin or Greek numeral (here octo); (2) take the numerical value (here 8); (3) multiply it by 3 (here giving 8×3 = 24); and bingo!, you have the absolute value of the 10 exponent. For lower case symbols, use minus that value. --Lambiam 02:17, 24 July 2022 (UTC)