Would it be possible for all the missing matter to be just unseen baryonic matter? How are we sure that most of this is exotic dark matter?
My question is, how do we know that the "dark matter" we assume to be littered all over the universe isn't just clear baryonic matter?
I know that we infer the existence of dark matter through gravity so how do we know that this dark matter isn't just "clear" baryonic matter?
Any astronomers care to share their expertise?