CHAPTER 18—COSMOLOGY IN THE 21ST CENTURY
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
____ 1. The resolution of Olbers' paradox suggests that it gets dark at night because
a. / the universe is not infinite in age.b. / the universe is accelerating.
c. / the universe is closed.
d. / the universe is flat.
e. / the universe is isotropic
____ 2. 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.
____ 3. 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.
____ 4. If galaxy A is four times more distant than galaxy B, then according to the Hubble Law, galaxy A will recede ______than galaxy B.
a. / 16 times fasterb. / 4 times faster
c. / 2 times faster
d. / 1.2 times faster
e. / 0.25 times faster
____ 5. During the first moments of the big bang, nuclear fusion reactions made few heavy elements because
a. / all heavy nuclei are unstable.b. / no stable nuclei exist with masses of 5 or 8 hydrogen masses.
c. / the helium nucleus was unstable
d. / the temperature and density were too low.
e. / no nuclei heavier than helium could form since there weren't any electrons formed.
____ 6. 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
____ 7. 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.
____ 8. The steady state theory was abandoned primarily due to the discovery of
a. / the Hubble law.b. / quasars as very distant and luminous active galaxies.
c. / dark matter in clusters of galaxies.
d. / the primordial background radiation.
e. / a super massive black hole at the center of the Milky Way.
____ 9. If the Hubble constant, H, is smaller for extremely distant galaxies than it is for nearby galaxies, then
a. / the universe is closed.b. / we must be located near the edge of the universe.
c. / the expansion is accelerating.
d. / we must be located near the center of the universe.
e. / dark matter cannot exist between galaxies.
____ 10. Baryonic matter includes
I. / protonsII. / neutrons
III. / WIMPs
IV. / neutrinos
V. / MACHOs
a. / I, II, & V
b. / III & IV
c. / I & II
d. / I, II & III
e. / I, II, III, IV, & V
____ 11. Measurements of the amount of deuterium and the presence of very little lithium-7 in the gas clouds near quasars tell 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 can not be enough protons and neutrons to make the universe flat.
____ 12. ______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. / WIMPsb. / neutrinos
c. / globular clusters
d. / MACHOs
e. / none of the above
____ 13. Measured ages of globular clusters and a study of the time required for massive stars to build up the present abundance of heavy elements suggests that the universe is
a. / at least 20 billion years old.b. / no more than 9 billion years old.
c. / at least 13 billion years old.
d. / flat.
e. / closed.
____ 14. The cosmic background radiation comes from the time in the evolution of the universe
a. / when protons and neutrons were first formed.b. / when the big bang first began to expand.
c. / known as the inflationary period.
d. / when gamma rays had enough energy to destroy nuclei.
e. / when electrons began to recombine with nuclei to form atoms.
____ 15. If the universe is flat and not accelerating,
a. / the universe's age will be equal to 1/H.b. / the universe's age will be equal two-thirds of 1/H.
c. / the universe it not isotropic.
d. / the density of the universe is greater than the critical density.
e. / dark energy accounts for a small fraction of the critical density of the universe.
____ 16. 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.
____ 17. 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.
____ 18. The best determination of the Hubble constant, using Cepheid variables found in distant galaxies by the Hubble telescope, suggests that the
a. / Hubble constant is less than 50 km/sec/Mpcb. / Hubble constant is greater than 100 km/sec/Mpc.
c. / age of the universe is between 8 and 12 billion years.
d. / age of the universe is greater than 20 billion years.
e. / dark matter in the universe must be composed primarily of baryonic matter.
____ 19. The best scientific 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.
____ 20. If a two-dimensional universe has a negative curvature,
a. / the area of a circle will be greater than r2.b. / the area of a circle will be equal to r2.
c. / the universe is infinite.
d. / the universe is finite but bounded.
e. / the universe will have a center.
____ 21. The ______proposes that matter was created continuously so that the density of the universe never changes as the universe expands
a. / open big bang theoryb. / flat big bang theory
c. / closed big bang theory
d. / steady state theory
e. / inflationary universe theory
____ 22. 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.
____ 23. The flatness problem 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.
____ 24. What evidence supports an acceleration in the expansion rate of the universe?
a. / The discovery of super massive black holes at the center of quasarsb. / 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
____ 25. 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/Mpcb. / 75 km/sec/Mpc
c. / 55 km/sec/Mpc
d. / 85 km/sec/Mpc
e. / 95 km/sec/Mpc
____ 26. 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 yearsb. / about 1.4 billion years
c. / about 14 billion years
d. / about 9 billion years
e. / about 90 billion years
____ 27. 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
True/False
Indicate whether the sentence or statement is true or false.
____ 28. The night sky is dark because the universe is neither static nor infinitely old.
____ 29. Homogeneity is the assumption that the universe looks the same in all directions.
____ 30. The cosmological principle states that any observer, in any galaxy, will see the same general features of the universe.
____ 31. The red shifts of the galaxies imply that the universe is expanding, and that we are at the center.
____ 32. During its early history, the universe was dominated by matter.
____ 33. Most of the elements heavier than helium were made during the first few minutes after the big bang.
____ 34. If the average density of the universe is less than the critical density, the universe is open.
____ 35. The deuterium in Earth's oceans and in the interstellar medium suggests that the universe is open.
____ 36. If the density of the universe is equal to the critical density, and H equals 50 km/sec/Mpc, then the true age of the universe is 13.3 billion years.
____ 37. According to the steady state theory, the universe did not expand.
____ 38. The inflationary theory of the universe may explain why the background radiation is so isotropic.
CHAPTER 18
Answer Section
MULTIPLE CHOICE
1. ANS: A
2. ANS: C
3. ANS: C
4. ANS: B
5. ANS: B
6. ANS: B
7. ANS: A
8. ANS: D
9. ANS: C
10. ANS: A
11. ANS: E
12. ANS: D
13. ANS: C
14. ANS: E
15. ANS: B
16. ANS: A
17. ANS: E
18. ANS: C
19. ANS: E
20. ANS: C
21. ANS: D
22. ANS: E
23. ANS: A
24. ANS: B
25. ANS: A
26. ANS: D
27. ANS: B
TRUE/FALSE
28. ANS: T
29. ANS: F
30. ANS: T
31. ANS: F
32. ANS: F
33. ANS: F
34. ANS: T
35. ANS: T
36. ANS: T
37. ANS: F
38. ANS: T