Weighing the Universe
Neta Bahcall (Princeton University)
How do we weigh the Universe? Where is the Dark Matter?
I will discuss these questions and show that several independent
methods, including the observed abundance of rich clusters , the
baryon-fraction in clusters, the observed Mass-to-Light function from
galaxies to superclusters, and other large-scale structure observations,
all reveal a universe with a low mass density of ~20% of the critical
density. The data suggest that the mass in the Universe, including the
dark-matter, follows light on large scales, and most of the mass resides
in huge dark halos around galaxies. I will review the combined
observational evidence for dark-matter and for dark-energy in the
universe and their cosmological implications.