> We know the number of photons in the universe (most of them are in the CMB), and we therefore know the number of protons. If the strongest argument for DM wa

> We know the number of photons in the universe (most of them are in the CMB), and we therefore know the number of protons. If the strongest argument for DM was fixing a particular model of nucleosynthesis, most people who care about this hypothesis would not care for it. In my opinion, extrapolating our standard theories back in time to "big bang" and drawing consequences such as "DM had to be created so that our model of nucleosynthesis can be preserved" is not a credible science. But no, DM was introduced to explain observations of celestial motions. And it works. Too well, it is too accommodating to any observations to be a great insight of what is going on with celestial motions.