… expansion and contraction are natural consequences of the homogeneity and isotropy of the Universe. (Chap 1)
A distribution is called homogeneous if it is uniformly distributed, and it is called isotropic if it has the same properties in all spatial directions. Thus in a homogeneous and isotropic space the distribution of matter would look the same to observers located anywhere—no point would be preferential. (Chap 1)
The conclusive demonstration that the Milky Way is an average-sized galaxy, in no way exceptional or central, was given only in 1952 by Walter Baade. This we may count as the third breakdown of the anthropocentric world picture. (Chap 1)
On a cosmological scale we are not really interested in objects smaller than a galaxy! We generally measure cosmic distances in parsec (pc) units (kpc for 103 pc and Mpc for 106 pc). A parsec is the distance at which one second of arc is subtended by a length equalling the mean distance between the Sun and the Earth. （Chap 1)
