Recitation 10: Big Bang Cosmology

A. What is the difference between a Doppler shift in the frequency of light and the reddening of light by the cosmological red shift?

B. In the Lambda-CDM model of cosmology, the so called "standard model," 70% of matter is the mysterious dark energy and 25% is the dark matter in galaxies. We have no independent evidence of the existence of these two forms of matter other than through their gravitational effects. Should this worry us?

C. How sure can we be that the assumptions of Hawking's theorem are correct?

D. Some theorists find a singularity, such as the big bang, an affront to science and feel a strong need to find reformulated theories that will eliminate them. Are singularities to be avoided or eliminated from theories if possible? Why?