[FOM] "Mathematician in the street" on AC
Vaughan Pratt
pratt at cs.stanford.edu
Wed Aug 26 00:57:34 EDT 2009
Daniel Méhkeri wrote:
> For that matter, could the real numbers be the union of a countable family
> of countable sets?
No, because the latter is a countable union of null sets and hence
itself null.
A better question would be, could the Cantor middle-third set be a
countable union of countable sets?
(In both sentences, "could be" means "holds in some equiconsistent
extension of ZF.")
Vaughan Pratt
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