Dusty_Matter:

It is the estimates of the amounts of molecular H2 that is speculative.

Just a couple of questions here, doesn't the math associated with the Recombination era of the Big Bang predict the hydrogen/helium proportions across the universe?  And doesn't current observation agree with that prediction?  If so, wouldn't this enormous abundace of molecular hydrogen skew that proportion?

Yes...

I think that there are several strands here for me to reply to.

 Firstly, I think that the people who have reported the galactic molecular hydrogen results would not readily agree with your comments about the accuracy/reliability of their estimates that are based on real, quantitative measurements. This work has involved a good many contributors, using very much up to date space telescope spectroscopic data. Results of this kind keep on appearing. I have just come across a 2007 paper in the much-respected journal 'Science' by F. Bournaud et al, 25 May 2007, pp1166-1169, entitled 'Missing mass in collisional debris from galaxies.' These workers were surprised to find 2-3 times the amount of 'dark matter' compared to visible matter in dwarf galaxies arising from the collision of larger galaxies. And, guess what - these people don't believe that the dark matter here is the mysterious 'non-baryonic' matter, but rather cold molecular hydrogen (H₂). Perhaps the famous Bullet Cluster work would repay a study of this kind as well -  clearly there is a lot of 'missing mass' here that reveals itself in gravitational lensing from which the familiar red/blue picture has been deduced.Secondly, why shouldn't our galaxy, the Milky Way, be very much the same as other spiral galaxies in which much of the missing mass has been accounted for in terms of molecular hydrogen, as I indicated in my last post.Thirdly, I have re-read the article on Dark Matter in the November issue of Astronomy magazine, and it seems to me that it is largely about the techniques that scientists are currently using to search for non-baryonic dark matter. There isn't much evidence from anywhere, as yet, of what non-baryonic dark matter really is. Most claims for it also end with the caveat that 'we think that this is the real stuff, but it might not be'.So, I will keep an open mind on this unfolding story and see what hard evidence is reported. Science is about testing hypotheses, looking at the evidence and amending a hypothesis in the light of the evidence etc. Now is not the time to be too dogmatic about anything in cosmology - theories can change!!

 

At one time we didn't know what stars were made of, but we knew they existed. You are quite correct, we don't know what dark matter is made of, but we know that it exists. It will probably be some time before we really figure it out, and you could probably look at these initial experiments of their trying to find out what it is, as being in it's infancy stage. We know it's not molecular H2, however. If the gravitational lensing, as shown in the pictures from these galactic collisions, was from this hydrogen, then we would have been able to identify it by it's spectral readings. We don't know what dark matter is, but we know it's not molecular H2, as it would have to make up over 80% of the mass of all the galaxies, including ours, and it doesn't.