Granted. I mean, strictly speaking, we can't prove that the gravitational constant won't change tomorrow. :) But I would like a substantial enough body of evide

Granted. I mean, strictly speaking, we can't prove that the gravitational constant won't change tomorrow. :) But I would like a substantial enough body of evidence from competent and disinterested assessment(s) so that our societies can take the right long-terms risks on new materials (where "new" = less than 100 years). Obviously easier said than done; I like the idea of putting it in the same category as medical treatments (though let's be frank, even that process is hardly flawless).