If the alternate universes implied by the mainstream MWI (as opposed to
variants like consistent histories) are "actual" in some sense, with
even the slightest chance of communication between universes, then why
have we not seen solid evidence of such communication?
Amongst the universes, many ("many" is a huge number, obviously) of
them will be way ahead of us. Some will have had galactic civilizations
for a billion years. Some will be versions of Earth except that the
Egyptians pioneered electronics and hence the world is a few thousand
years "ahead" of our world...even assuming time is commensurate with
And so on. You can all imagine the rich possibilities.
If these universes are even remotely able to affect each other, through
perhaps enormously advanced technology, then the vast number of such
possible worlds would suggest that at least some of them have figured
out how to do so.
And yet they aren't here. No visitors from alternate universes. No
signals sent in, a la Benford's "Timescape."
Perhaps we don't know how to listen. Perhaps there are so many possible
universes to potentially visit that we just haven't been gotten to yet.
Perhaps in a multiverse of so many possibilities, ours is just not an
interesting destination. Maybe there's a kind of MWI censorship going
on: since we are still debating the validity of MWI, we obviously are
in a universe where MWI has not been proved through such a visit.
(There are many divergent series here, making even crude estimates
difficult and probably worthless.)
--Tim May Prime, resident of Earth Prime