1) In the film "A Window to Creation" we saw the results of two space-based experiments to measure the properties of the Cosmic Background Radiation (CBR). The rocket-borne experiment by Lang, Matsumoto and their colleagues had problems with electrical noise, so they couldn't confirm their earlier results.

a) (7 pts) Explain how Lang's earlier results seemed to contradict the Big Bang theory or at least suggested some new thinking was necessary. Explain what the more sophisticated COBE (Cosmic Background Explorer) discovered about the nature of the CBR.

b) (7 pts) The discovery of COBE proves what about the early Universe? Explain.

2) For each of the following facts about quasars, describe the supporting evidence that proves that fact:

1 - Quasars have absolute luminosities thousands of times brighter than galaxies.

2 - Quasar light doesn't come from galaxies or collections of stars.

3 - Quasars are much smaller than galaxies.

3) Most Astronomers think that quasars are probably just a phase that normal galaxies go through as part of their life cycle.

a) (7 pts) Explain the evidence that supports this view.

b) (7 pts) A related object is a blazar. What is one primary difference between a quasar and a blazar, and why do quasars and blazars appear differently despite the fact that they are probably, in fact, the same kind of object?

4) Suppose we know that throughout the history of the Universe, there is an element "X" whose abundance has slowly been increasing over time since the formation of the first stars and galaxies, about a billion years after the Big Bang.

a) (7 pts) Sketch a graph of the abundance of "X" vs distance from Earth, and explain why you drew the graph the way you did.

b) (7 pts) In the future, we would like to be able to determine whether the Universe will expand forever or collapse. Explain how and why we can determine the answer to this question.

5) Below is a Hubble Law diagram for a 14-billion-year-old Universe in which gravity is negligible and there is no cosmological constant.

a) (7 pts) On the same graph, draw what the Hubble diagram must have looked like to Astronomers when the Universe was only 7 billion years old. If it would look the same, just write "no change" on the diagram. Explain your answer in the space to the right.

b) (7 pts) Below, draw a Hubble diagram for the Universe if it were not expanding at all. Again, explain your answer in the space to the right of your graph.

6) According to Hubble's Law, almost all of the galaxies in the Universe are moving away from the Milky Way galaxy (our home galaxy) at very high speeds. The further away they are, the faster they are moving, while we don't seem to be moving.

a) (8 pts) Explain what the Copernican Principle is and why Hubble's Law is not a violation of the Copernican Principle.

b) (6 pts) Why is it that some galaxies do not "obey" Hubble's Law? In other words, why do some galaxies appear to be moving toward us, contrary to the expanding Universe theory?

7) Two concepts that have recently gotten the attention of researchers in Astronomy are Gamma-Ray Bursters (GRB's) and the Cosmological Constant (CC).

a) (6 pts) Explain how we know that GRB's are at very great distances, similar to quasars.

b) (8 pts) Why did Einstein originally propose the idea of a CC? Explain the evidence that leads Astronomers to think a CC may exist in the Universe.

8) In the movie "Contact", Astronomers were listening for radio signals from extraterrestrials, and they ended up pointing at a star in the constellation Lyra.

a) (7 pts) What is the name of a bright star in Lyra, and where can Lyra be found in the sky at about 10pm tonight?

b) (7 pts) Some Astronmomers feel that we should be looking at optical rather than radio wavelengths for SETI signals. Explain their reasoning.