I have often participated in MO with serious concerns about set theory. All my questions and answers have been downvote and deleted. But when I posted the following text, I got 5 upvotes, and the text remained over two months until today and gathered 300 views.
=========================================================================== We have found that, in an oscillating universe, some massless classical gauge fields in a Friedmann-Robertson-Walker universe necessarily involve a quantized massless gauge field of Planckian distribution which cannot be established by a countable set of elementary particles and photons. In order to satisfy the Bekenstein Bound near the final singularity when the entropy is taken as CR^2 (C a constant, R the always finite radius of the universe) we need the cardinal number of the continuum for the required particle density.
It appears as if the proof of Cantor's original claim about the existence of uncountable sets in the real universe is no longer out of reach.
This text is easily recognized by any expert including good mathematicians as the summit of nonsense. But also more serious approaches to seek real applications of Cantor's invention are necessarily condemned to fail - in particular because set theory is depending on a certain clever kind of indexing and therefore cannot have any application to consistent reality which is always independent of the choice of indices.
But it was nice to check the level of the "professional research mathematicians" of MO.
Note: They are not very clever there but very fast: The above text existed only for 3 minutes, gathered 6 views and only one downvote.