In article , jacobnavia
writes:

Le 19/05/2018 à 11:09, Phillip Helbig (undress to reply) a écrit:
Maybe primordial black holes coalesced.

This hasn't been observed.

What did LIGO observe? Of course, it is hard to prove that a black hole
is primordial. However, if its mass is such that no other known
mechanism could form it, then this increases faith in the primordial
idea.

Primordial black holes are very hypothetical

They are an idea which has been around for a long time. Yes,
hypothetical, but not really "very".

and micro lensing observations rule them out as you said when discussing
with Mr Oldershaw...

Microlensing observations rule out a significant proportion of the dark
matter being in the form of black holes (primordial or otherwise) of
about a solar mass, which is what Mr Oldershaw was claiming. However, I
have also mentioned the paper by Bernard Carr and Swedish collaborators
here, which shows that very small and very large primordial black holes
are not ruled out, particularly if they don't have all the same mass.

Strange, now you think that they exist.

Not strange at all; see above. I don't think that they exist, but
rather point out that this is an explanation which has not yet been
ruled out.

Do you have any observations
that point to those primordial black holes?

Not directly, but see LIGO. However, I was reasonably certain that
extrasolar planets exist before the first one was discovered.

Also, define "observation". In some sense, if other means of growth are
ruled out, observation of a large black hole might be evidence of
primordial black holes.