The Hubble constant, which relates distance to observed redshift, is about 70 km/sec per Megaparsec. Given this value, what is the observed recession velocity of a very distant galaxy that is 13 billion light-years away? What fraction of the speed of light is this recession velocity?
Please describe the importance of pigeons in discovering the cosmic microwave background.
There are a variety of ways of estimating the ages of various objects in the universe. Describe two of these ways and indicate how well they agree with one another and with the age of the universe itself as estimated by its expansion.
Assume that the average galaxy contains 10^11 Msun and that the average distance between galaxies is 10 million light-years. Calculate the average density of matter (mass per unit volume) in galaxies. What fraction is this of the critical density we calculated in the chapter?