In case you missed it, "standard atomic weights are not constants of nature" (doi:10.1351/PAC-REP-10-09-14)! Wow, chemistry upside down. This is bigger than the new arsenic life they found!
Calm down, calm down. Nothing to see here, move on.
It was actually news a some weeks back, but a tweet by @MatToddChem and a question by Antony on the Blue Obelisk eXchange, made me write up this post.
Facts: 1. atomic weights have never been constant; 2. isotopic weight are constants of nature. The difference is simple, but the public was amazed last month and reaffirmed that science is just another religion. (In fact, the Dutch political wizard Wilders calls religion just a politic ideology, so, science is just politics; Q.E.D. :).
Atomic weights are used to calculate the weight of samples, or, the other way around, how many molecules we have in 1 mg of some organic sample. Now, at this macroscopic level, and looking at carbons, we have actually to do with a mix of, mostly I guess, 12C and 13C, more or less 99% and 1% each. Now, these percentage reflect a mixture. Mixture composition has never been natural constants, so the claim by the authors of the paper is weird, to say the least. In fact, it has been know for years that the isotope ratios vary around the world. Hence, the molecular weight of compound X is not the same here as somewhere else. That's all.
Now, the Blue Obelisk has been making this information aggregated by IUPAC available under a permissive license. The most recent release still has a MIT license, but the next release will be even more permissive an have the CC0 waiver.