- Speed of galaxies depends on their distances - Most often used to determine distance based on speed
H(0) = (70km/s)/MPC = 22(km/s)/Mly
Shortcomings of Hubble’s Law
(1) Gives exact distance for galaxies that move away only b/c of expansion of universe - does not work for galaxies in MW Locale Group b/c they are gravitationally tied to MW; better for very distant galaxies w/ large recession speeds
(2) Only as accurate as Hubble’s constant
Hubble & Age of Universe
Hubble’s constant inverted gives the age of the Universe!