2(A) We know   that Sun is roughly in the center of the disk because the galaxy’s dust lane bisects the Milky Way.


Chapt 16.

  1. A redshift due to the Doppler effect is due to the motion pf the object with some reference point, for example, the Doppler shift in a binary star system may be measured with respect to the center of mass of the binary stars. In the case of redshift due to the expansion of the universe, the redshift is not due the galaxy’s motion through space, but rather due to the galaxy being carried along due to the expansion of space itself.
  1. (a) We would conculed that we lived in a static universe, and that the observed redshifts were due to the random motion of the galaxies in the universe.


(b) This would suggest that we lived in a collapsing universe, and that the blueshifts of galaxies was primarily to the contraction of the space in which the galaxies are embedded.


(c) From this we can conclude that our galaxy were moving through a static universe.


  1. The didtribution of the galaxies on large scales resembles a network of soap bubbles, where galaxies are distributed along the surfaces of the bubbles, which surround large voids that are largely free of galaxies. The universe begines to look featureless and smooth on scales of 300 Mpc and greater.


Chpt 17


6.   If the Hubble constant were 65 km/s/Mpc and density parameter were 1, such  high values of the constant and density parameter would imply that an age of the universe  using the big bang model of significantly less than 14 billion years measured for the oldest known stars.