Guest: Dr. Ethan Siegel was the guest for this Space Show program. Dr. Siegel is an astrophysicist at the University of Arizona and thus was highly qualified for the cosmological discussion which made up most of this program. We began our discussion with good working definitions for both cosmology and astrophysics. As you will hear, Dr. Siegel is a superb teacher and the use of humor weighs in strongly in how he presents his information, including from his website http://startswithabang.com.