CHAPTER 18—COSMOLOGY IN THE 21ST CENTURY
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
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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 faster
b. 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.
II.
III.
a.
b.
c.
d.
gravity is strong enough to stop the expansion in a finite time.
the density of the universe is less than the critical density.
the universe is finite.
I & II
I & III
II & III
I, I, & III
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7.
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8.
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9.
____ 10.
e. none of the above
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.
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.
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.
Baryonic matter includes
I.
II.
III.
IV.
V.
protons
neutrons
WIMPs
neutrinos
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. WIMPs
b. 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.
____ 14.
____ 15.
____ 16.
____ 17.
____ 18.
____ 19.
____ 20.
b. no more than 9 billion years old.
c. at least 13 billion years old.
d. flat.
e. closed.
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.
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.
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.
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.
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/Mpc
b. 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.
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.
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 theory
b. 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 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
____ 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/Mpc
b. 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 years
b. 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
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