Critical mass with disambiguation bonus

While 'critical mass' is first and foremost a scientific term having to do with nuclear fission, I've always used it in the social context, to designate that arrival at a sufficient level of jollification which is achieved by any number of independent factors. In reference to a party, for instance, critical mass would occur with the arrival of whichever guest really kicks things off. It may not be a characteristic specific to that particular guest, but rather an inevitable happening considering the other guests present and that particular concatenation of events. (I've just begun reading the Foundation Trilogy aloud to Michael, so I'm feeling rather psycho-historic, vague, and inevitable these days.)

On a far grander scale, I'm beginning to realise that we are in the process of achieving critical mass within our own family, and it's a thrilling and delightful discovery. For many a day after the arrival of Jane, the avoidance of collapsing into a blue funk of drudgery and boredom was a chief concern, to which end I sought out adequate outside activities sufficient to divert us without running us ragged. The logistical difficulties of pursuing such interests with three children in tow had been a bit of a worry, but I'm finding more and more that Jane and Ella provide their own diversion, both to me and to each other. Their activities are more independent and self-contained than ever, their conversations infinitely more amusing, their intellectual rapport growing ever more engaging. If I go for days without experiencing much adult conversation, as the cliche goes, my psyche hardly suffers anymore, because the precocious child conversation is almost as stimulating. Food, money, and other economic considerations prevent us from dropping out of society altogether, but it's nice to know that we're well on our way to forming what could be, in a pinch, an independent and self-sustaining society for rainy days.

(On a side note, I couldn't remember whether the term 'critical mass' had to do with nuclear fusion or fission, so I popped onto Wikipedia to find out, and found myself on some page describing a cycling movement. The 'critical mass' term that I was after was found on a different page, all such pages tagged with the appellation 'disambiguation.' I love reading interesting articles with lots of hyperlinks, for this led me down a charming rabbit hole of rhetorical metonymy, Naive Bayes Classifiers, and Yarowsky Algorithms. This is as close to mathematics as I get.)