•Not nearly enough normal matter to provide critical
density
•We keep seeing effects of gravity from “dark
matter”
–Higher rotation speeds in our own galaxy
–Higher relative velocities of galaxies in
clusters
–Rate at which matter clumps together to form galaxy
clusters
–Gravitational lensing from galaxies, clusters
–May be 10 to 100 times as much “dark
matter” as visible matter
•
–
•What
might make up the “dark matter”? Possibilities include
•but
2H, Li, Be abundance suggest no more than 5% can be
“baryonic”
–WIMPs
(weakly interacting massive particles) predicted by some GUT’s
–Mass
of neutrinos
–Mass equivalent of “cosmological constant” energy