ASTR 340 Lecture Notes - Lecture 16: Low Mass, Cosmic Distance Ladder, Energy Density
Document Summary
Evidence for dark matter: high speed for galaxies in clusters, hot gas around galaxy clusters, galaxy rotation curves. Large scale structure of universe: bullet cluster, cmb. Dark matter: must be different from what we already know. Does not interact with forces other than gravity. May be new particle of nature / our models of particle physics must be incomplete. Segue 1: 1 milllion x fainter than the milky way. More than 50x faster than it should be due to its visible mass. Cmb implies flat geometry: can only account for about 30% . Expansion of universe should tell us about matter. Need to find a standard candle (supernova) Measure redshift to find relationship between distance and r. New force must explain this, drives expansion. Doesn"t change with scale factor of universe. Universe goes from homogeneous structure via a few small disturbances at a very early time. Perturbations grow slowly until matter dominates energy density of universe, then grew faster.
