The Nature of Dark Matter
Can dark matter be composed of normal matter?
If so, then its mass
would mostly come from protons and neutrons = baryons
The density of baryons
right after the big bang leaves a unique imprint in the abundances of deuterium
and
lithium.
Density of baryonic
matter is only ~ 4 % of critical density.
Most dark matter must be non-baryonic!
