This looks like what Daniel Dennett calls a "deepity": something superficially deep that amounts to nothing more than a confusion. In this case, a confusion between map and territory, between "facts" (what we think is true) and "facts" (what is true).
The book might be worthwhile. If our maps keep changing in a more or less predictable way, then maps are themselves a territory which can be studied.
I was thinking more that it would be useful in popularising the fact that facts are contingent but still useful, and that scientific facts changing doesn't mean it's all politics and lies. (I might be a bit hopeful there, of course.)
Even in the stable camp, facts can mutate: An atom's weight, for example, varies depending on the isotope.
This is a non sequitur. "Atomic weight" has to refer, implicitly or explicitly, to a particular isotope to be meaningful. The weight of an isotope is not going to change over time, and it's very unlikely that we're significantly wrong about the weight of an isotope.
ETA: comments below explain my confusion. Thanks.
In practice "atomic weight" commonly refers to the average weight of the most common isotope mix.
I don't know the history of the discovery of isotopes. I wouldn't be surprised if atomic theory started with weights assigned by the most common isotopes, and further checking led to "Hey, what we thought was just one sort of atom for each element needs to be more sophisticated because we were almost cutting reality at the joints but not quite".
That's how it was. Atomic weights were known to be not in whole number ratios, although sometimes tantalisingly close to them, and a lot of effort went into determining them precisely. There was a certain amount of chagrin when scientists realised that these numbers had no fundamental significance, but were just the average weights of the distribution of the different isotopes.
Although you are right, as a nitpicker I don't think non sequitur, i.e. "doesn't follow", is correct to use here.
Well, as it turned out, I was mostly wrong: "atomic weight" refers to the average weight of the most common isotope mix of the element (on Earth), and our data about the isotope distribution changes. I didn't remember that, but that's probably what that original quote meant.
You seem to be right about the non sequitur.
In practice "atomic weight" commonly refers to the average weight of the most common isotope mix.
Everything you know will, in due course, be wrong. A review of Samuel Arbesman's The Half-Life of Facts: Why Everything We Know Has an Expiration Date in Slate:
Arbesman's book expands on a piece he wrote in 2010 for the Ideas section of the Boston Globe. That short essay, called "Warning: Your reality is out of date," laid out a theory of what Arbesman named the mesofact. "When people think of knowledge," he wrote, "they generally think of two sorts of facts." One includes the data that should never change, like the atomic weight of hydrogen, while the other comprises all the tidbits that shift from day to day, like the closing price of the Dow Jones Industrial Average. Even in the stable camp, facts can mutate: An atom's weight, for example, varies depending on the isotope. But Arbesman is more interested in a third category of knowledge, one that's nestled between the other two in terms of how amenable it is to change. These are the facts that shift too slowly for us to notice, but not so slowly that they'll only matter to our children. "Mesofacts," he says, evolve within our lifetimes but often out of view.