4.6. Dark Matter Candidates
The preceding sections have established that there is some evidence for dark matter in the Universe but whether or not 90% of 99% of the Universe is made up in this form is still unresolved. The order of magnitude difference between these numbers has important implications with respect to the nature of the dark matter. There are two broad classes of dark matter to consider: baryonic and non-baryonic. In addition to important physical differences there may be an important philosophical difference. Astronomers want to build big telescopes in order to probe over vast distances and solve cosmological problems. But astronomers can only detect and measure baryons. If the mass of the Universe is mostly non-baryonic, then its fundamental nature will not be revealed through telescopic observation, but rather in some high energy accelerator experiment on the Earth. It is thus highly regrettable that continued funding of the Superconducting Super Collider was denied as this might have been the grandest cosmological experiment ever done.