Were you among the physicists? :) Notability is not an intrinsic property of articles: it's like weight, not like mass. Your argument fails at the "if seriously engaged in by enough people" point, since it's simply false (by definition) that at time T1 the first uninteresting thing is sufficiently popular, at T1. It's also false that people will a) notice and b) care enough to make it sufficiently popular even at time T2.
Same goes for numbers. The fallacy is in confusing intrinsic and extrinsic properties.
Now, one could reasonably argue that merely being the answer to this question would not, by itself, be enough to make a subject notable. However, the act of arguing this point, if seriously engaged in by enough people, would, in fact, make the question (and the answer) notable, and thus the answer to the question would deserve inclusion in Wikipedia.
Inductively, you can use this argument to show every subject is notable enough for inclusion in Wikipedia. Take that, deletionists!
(Inspired by a lunchtime conversation with a group of physicists and philosophers.)