Unit 6 Sample Test Cosmology

True/False

Indicate whether the sentence or statement is true or false.

____ 1. The night sky is dark because the universe is neither static nor infinitely old.

____ 2. Homogeneity is the assumption that the universe looks the same in all directions.

____ 3. The cosmological principle states that any observer in any galaxy will see the same general features of the universe.

____ 4. The red shifts of the galaxies imply that the universe is expanding and that we are at the center.

____ 5. During its early history, the universe was dominated by matter.

____ 6. Most of the elements heavier than helium were made during the first few minutes after the big bang.

____ 7. If the average density of the universe is less than the critical density, the universe is open.

____ 8. The deuterium in Earth's oceans and in the interstellar medium suggests that the universe is open.

____ 9. According to the steady state theory, the universe did not expand.

____ 10. The inflationary theory of the universe may explain why the background radiation is so isotropic.

Multiple Choice

Identify the letter of the choice that best completes the statement or answers the question.

11. The assumption of isotropy states that

a.	the universe looks the same at all epochs.
b.	the universe looks the same in all locations.
c.	the universe looks the same in all directions.
d.	all of the above
e.	none of the above.

12. The universe is said to be closed if

I.	gravity is strong enough to stop the expansion in a finite time.
II.	the density of the universe is less than the critical density.
III.	the universe is finite.

a.	I & II
b.	I & III
c.	II & III
d.	I, I, & III
e.	none of the above

13. If the universe is closed, then its age will be

a.	less than two-thirds of 1/H.
b.	more than two-thirds of 1/H.
c.	equal to 1/H
d.	equal to H squared.
e.	equal to the square-root of H.

14. The steady state theory was abandoned because of evidence such as

a.	The discovery of the Hubble law.
b.	The discovery of quasars as very distant and luminous active galaxies.
c.	The discovery of dark matter in clusters of galaxies.
d.	The discovery of the primordial background radiation.
e.	The discovery of a super massive black hole at the center of the Milky Way.

15. Measurements of the amount of deuterium interstellar medium and very little lithium-7 tells us that

a.	the universe is closed.
b.	the universe is open.
c.	the universe is flat
d.	the universe formed more than 13 billion years ago
e.	there is not enough baryonic matter in the universe for the universe to be closed.

16. ______________ cause sudden brightening of distant stars by gravitationally lensing the light from those stars. This processes causes the distant stars to grow brighter over a period of a few tens of days.

a.	WIMPs
b.	neutrinos
c.	globular clusters
d.	MACHOs
e.	none of the above

17. Measured ages of globular clusters and a study the time required for massive stars to build up the present abundance of heavy elements suggests that the universe is

a.	no more than 20 billion years old.
b.	no more than 10 billion years old
c.	at least 14 billion years old
d.	flat
e.	closed

18. If the universe is flat

a.	its age will be equal to 1/H.
b.	its age will be equal two-thirds of 1/H
c.	the density of the universe is less than the critical density
d.	the density of the universe is greater than the critical density.
e.	dark matter accounts for a small fraction of the density of the universe

19. The flatness problem and horizon problem

a.	are solved if there was a sudden inflation of the universe at a very early time.
b.	show that the universe cannot be described by the steady state theory.
c.	show that dark matter must be a small fraction of the total mass of the universe.
d.	imply that the universe was once much hotter than it is now.
e.	imply that the inflationary theory is incorrect.

20. Galaxy seeds around which galaxies, clusters and walls grew may be

a.	caused by hot dark matter.
b.	baryons.
c.	the result of the separation of the electromagnetic and weak forces.
d.	the result of freezing water molecules shortly after the universe became transparent to photons.
e.	defects in space-time.

21. The best data and models suggest that the universe is

a.	open, expanding and accelerating.
b.	open, expanding, but decelerating.
c.	closed, expanding and accelerating.
d.	closed, expanding, but decelerating.
e.	flat, expanding and accelerating.

22. If a two dimensional universe has a negative curvature

a.	the area of a circle will be greater than pr^2.
b.	the area of a circle will be equal to pr^2.
c.	the universe is infinite.
d.	the universe is finite but bounded
e.	the universe will have a center

23. The ______________ proposes that matter was created continuously so that the density of the universe never changes as the universe expands

a.	open big bang theory
b.	flat big bang theory
c.	closed big bang theory
d.	steady state theory
e.	inflationary universe theory

24. The age of the universe can be determined if

a.	the universe is flat.
b.	the amount of dark matter in the universe can be accurately determined
c.	the rate of recession of the galaxies in the Local Group can be accurately determined.
d.	the temperature of the cosmic background radiation can be accurately determined.
e.	the Hubble constant and density of the universe can be accurately determined.

25. The flatness problems is that

a.	the density of the universe is very close to the critical density.
b.	the density of the universe is much larger than the critical density.
c.	the flat universe would expand forever and we could never measure the density of the universe
d.	the laws of physics may not be different at different times in the history of the universe.
e.	the red shift of a distant galaxy is caused by the curvature of space-time.

26. The cosmic microwave background radiation contains small variations in temperature that are about a degree in size. What does the size and distribution of these variations tell us?

a.	That the universe is closed.
b.	That the universe is open.
c.	That the universe is flat.
d.	That the universe is expanding.
e.	That Olbers' paradox implies that the universe is finite and bounded.

27. What evidence supports an acceleration in the expansion rate of the universe?

a.	The discovery of super massive black holes at the center of quasars.
b.	The discovery that Type Ia supernova in distant galaxies are 25 percent fainter than expected.
c.	The discovery of MACHOs
d.	The discovery of the grand unified theory.
e.	none of the above

28. If a galaxy is located at a distance of 18 Mpc and it is found to have recessional velocity of 1170 km/sec, what is Hubble's constant based only on this galaxy?

a.	65 km/sec
b.	75 km/sec
c.	55 km/sec
d.	85 km/sec
e.	95 km/sec

29. If a galaxy is found receding from us at 894 km/sec and it is located at a distance of 12 Mpc, what is the age of the universe if it is flat?

a.	about 20 billion years
b.	about 1.4 billion years
c.	about 14 billion years
d.	about 9 billion years
e.	about 90 billion years

30. If gravity is unimportant and H equal 75 km/sec/Mpc, then the age of the universe is about

a.	8.9 billion years.
b.	13 billion years.
c.	16.6 billion years.
d.	26 billion years
e.	74 billion years

Completion

Complete each sentence or statement.

31. The _______________ states that the universe is both isotropic and homogeneous.

32. The _______________ are theories that unify the electromagnetic, weak and strong forces at extremely high energies

33. A(n) ____________________ universe is infinite an would have a density equal to the critical density.

34. _____________________ are a form of dark matter that consists of very low mass stars and planets too faint to be seen.

35. COBE measure the temperature of the cosmic background radiation to be ____________.

Essay

36. How can the big bang still be visible? In what form has it been detected?

37. Why would a value of 100 km/sec/Mpc for the Hubble constant cause a revision in theories of stellar evolution?

38. How could the measurement of the Hubble constant at great distances tell us whether the universe is open or closed?

Unit 6

Answer Section

TRUE/FALSE

1. T

2. F

3. T

4. F

5. F

6. F

7. T

8. T

9. F

10. T

MULTIPLE CHOICE

11. C

12. B

13. A

14. D

15. E

16. D

17. C

18. B

19. A

20. E

21. E

22. C

23. D

24. E

25. A

26. C

27. B

28. A

29. D

30. B

COMPLETION

31. cosmological principle

32. grand unified theories or GUTs

33. flat

34. MACHOs or Massive Compact Halo Objects

35. 2.7 K

ESSAY

36. Answer not provided.

37. Answer not provided.

38. Answer not provided.