Astronomy 123
Test 1
April 27, 2017
NAME ___________________________________________________________________

Multiple Choice Questions -- 15 questions @ 2 points per question → 30 total points. Select and circle the letter of the best answer for each question.

1. An important assumption made by Friedmann when he developed his models for expanding universes was _ .

a. that the Perfect Cosmological Principle held
b. the Principle of Mediocrity was not a law and so could be ignored
c. that the Anthropic Principle removed the need to postulate a birth for the Universe
d. that the Cosmological Principle was valid
e. that the Milky Way galaxy, our home, sat at the center of the Universe
2. Today, the make-up of the Universe is dominated by _ .

a. the elements hydrogen and helium
b. dark matter
c. normal matter
d. radiation
e. dark energy
3. The redshifts of distant galaxies _ .

a. have shown that our Universe is only one of many universes, each of the other universes moving away from us according to their distance
b. have shown that the Universe has stopped expanding and is now starting to collapse
c. have shown that the Universe started its evolution with a huge explosion centered on the Milky Way galaxy
d. arise simply because the Universe is expanding in size
e. are produced right after inflation has ended

4. When we observe galaxies that are 1 billion light years from the Earth, _ .

a. we see them as they were around 1 billion years ago
b. it verfies the validity of the Perfect Cosmological Principle
c. we show that the Principle of Mediocrity is invalid
d. we see what the Milky Way galaxy will look like in 1 billion years
e. we see them as they will be in 1 billion years
5. A galaxy whose redshift is twice as great as the redshift for the galaxy M87 in the Virgo cluster of galaxies, _ .

a. is at twice the distance from the Milky Way as is M87
b. is four times as far away from the Milky Way as is M87
c. is at half the distance from the Milky Way as is M87
d. is at one-fourth the distance from the Milky Way as is M87
e. may be closer or farther than M87 depending upon whether the Universe is open or closed
6. Our location in the Milky Way galaxy was determined by Harlow Shapley from _ .

a. studies of the redshifts of nearby stars
b. extensive star counting studies in the Solar neighborhood
c. observations of the star clusters known as Globular Clusters
d. the determination of the redshifts of distant galaxies
e. studies of the cosmic microwave background
7. _ is the concept that all large samples of the universe, on average, appear the same anywhere in the universe.
a. Conformity
b. Cosmology
c. Homogeneity
d. Isotropy
e. Universality
8. The Anthropic Principle states: _ .

a. What we observe the Universe to be is determined by the condition that the Universe is unchanging in time
b. We live in one universe in a multiverse of universes
c. The Universe must be dominated by Dark Energy
d. We, as observers in the Universe, do not exist at a preferred place or time, or in a preferred Universe
e. What we can expect to observe must be restricted by the conditions necessary for our presence as observers
9. The redshift of the light from distant galaxies is correctly interpreted as _ .

a. space is expanding with time; the wavelengths of light are stretched while they travel through expanding space
b. an "aging" of light as it travels from distant galaxies to us
c. the effect of intergalactic dust
d. differences in temperatures of distant and nearby galaxies
e. resulting from a giant explosion in the early Universe in which we happened to sit at the center of the explosion
10. The Sun sits roughly _ from the center of the Milky Way galaxy.
a. 600,000 light years
b. 3,000 light years
c. 25,000 light years
d. 150,000 light years
e. 2,100,000 light years
11. Which of the following about the cosmic microwave background radiation (CMBR) is not
a correct statement?
a. The CMBR has a temperature of about 2.73 Kelvin
b. The CMBR is a mixture of the light from many astrophysical sources, such as stars and galaxies
c. The CMBR had a much higher temperature in the past
d. The CMBR was discovered in the 1960s by Penzias and Wilson
e. The CMBR appears essentially the same in all directions (it is isotropic)
12. Cosmologists have determined that the Universe _ .

a. started expanding 13.7 billion years ago
b. is unchanging, it had no beginning and will have no end
c. is only one of a large number of universes
d. is slowly slowing in its expansion and one day will collapse into a single atom
e. is oscillating in size, we are currently in a phase of contraction
13. Cosmology is _ .

a. currently more driven by philosophical ideas than empirical data
b. the study of how objects such as stars form in the universe
c. the study of the structure and evolution of the universe
d. the idea that the Universe appears the way it does because we are the observer
e. based on the idea that Principle of Mediocrity is implausible
14. The expansion rate of the Universe is currently increasing. The universal accelerating force responsible for this speed-up may ___ .

a. be the force postulated by Einstein, his cosmological constant force
b. result from the material known as dark energy
c. be a consequence of dark matter in the Universe
d. a and b are possibilites for the accelerating force but not c.
e. All are possibilites for the universal accelerating force.
15. Which of the following is true for a scientific model?
a. It makes predictions and so can be disproven
b. It obeys the Mediocrity (Cosmological) Principle
c. It applies to the Universe as a whole in a uniform fashion
d. Only a and b are correct.
e. a, b, and c are correct.

Short Answer Questions -- Your score for this section will be based on the 3 highest scoring of the 4 following questions. Each scored question will be worth 10 points → 30 total points for this section. You may choose to answer only 3 questions or to answer all 4 questions.
1. The Big Bang Theory

a. Cite the three primary observations which led to and/or supported the validity Big Bang theory.

b. Explain why each of the pieces of evidence listed in Part b support the Big Bang theory.

2. Friedmann Models of the Universe

a. Briefly what are the three types of Friedmann models for the evolution of the Universe?

b. Describe a geometric test that may be performed to determine which of the Friedmann models best describes our Universe. What is the current indication for the type of Friedmann universe in which we live?

3. Cosmological Modeling and Philosophical Notions

a. Explain how Einstein's embrace of the Perfect Cosmological Principle led him to suggest the existence of a universal repulsive force in the Universe which he incuded in his theory through the Cosmological constant, Λ.

b. What caused Einstein to withdraw his suggestion?

4. Cosmic Puzzles

a. Briefly describe the Horizon Problem. What suggests we have a Horizon Problem?

b. Briefly describe the Flatness Problem. What suggests we have a Flatness Problem?

Part
Points

Multiple Choice

Short Answer

Total