Explorations: Introduction to Astronomy (Arny), 6th Edition

Chapter 18: Cosmology

Online Quiz

1
Why do astronomers believe the Universe is expanding?
A)They see a redshift in the spectral lines of distant galaxies.
B)They can see the disks of galaxies getting smaller over time.
C)They can see distant galaxies dissolve, pulled apart by the expansion of space.
D)All of the above.
2
What is the cosmic horizon?
A)The place where the Big Bang occurred.
B)The average distance between galaxies.
C)The distance beyond which astronomical objects are invisible -- even in principle -- because the Universe is not old enough for their light to have had time to reach us.
D)The diameter of the Universe.
3
If the Universe is infinitely large, infinitely old, and expanding, the night sky should be bright. But in fact it is not. What do we call this?
A)The Einstein Anomaly.
B)Olbers Paradox
C)The Hubble Law.
D)The Neutrino Discrepancy.
4
What is the cosmic microwave background?
A)It is radio noise from Seyfert galaxies.
B)It is radiation from hot gas in intergalactic space.
C)It is radiation from the first stars formed when the Universe was young.
D)It is radiation created in the young Universe.
5
Which of the following is evidence that the early Universe was hot and dense?
A)Intense x-ray emission from gas in galaxy clusters.
B)The ratio of helium to hydrogen is approximately the same in all old stars.
C)The cosmic microwave background.
D)Both B and C.
6
How do astronomers estimate the approximate age of the Universe?
A)It is equal to the Hubble constant (H).
B)Age = 1/H
C)Age = 10/H
D)It is not possible to calculate the age of the Universe.
7
Where did helium come from the early Universe?
A)The early Universe was so hot and dense that fusion of protons (hydrogen) into helium could occur.
B)Helium was formed in the cores of stars formed in the early Universe.
C)Photons bombarded hydrogen atoms and broke them up into helium atoms.
D)Helium was not formed in the early Universe, because only neutrons were present.
8
The Big Bang theory can explain
A)The expansion of the Universe.
B)The cosmic background radiation.
C)The amount of helium in the Universe.
D)All of the above.
9
What is inflation all about in cosmology? This is the idea that
A)The force of gravity suddenly grew stronger in the distant past.
B)The Universe increased dramatically in size in an extremely brief period of time.
C)The number of galaxies we see at large distances is greater than the number we can see near us.
D)The diameters of distant galaxies are much greater than those of galaxies near us.
10
Which Big Bang "puzzles" does the inflationary model resolve?
A)The energy of expansion is almost exactly equal to the collective gravitational force between galaxies.
B)The Universe is all ordinary matter with almost no antimatter.
C)The cosmic background radiation is smooth, but the distribution of matter in the Universe is lumpy.
D)All of the above.
11
What is the critical density?
A)The density of the Universe.
B)The density of the most massive black hole in the Universe.
C)The density that determines whether the Universe expands forever or recollapses.
D)None of the above.
12
If its density is less than the critical density, then a universe
A)expands forever.
B)will recollapse.
C)contains only anti-matter.
D)never expands
13
Astronomers have found evidence that the expansion of the Universe is accelerating. Such acceleration
A)is evidence for a cosmic repulsion related to the cosmological constant of relativity theory.
B)is deduced because distant galaxies are receding more slowly than expected from the Hubble Law.
C)is deduced because distant galaxies are receding faster that expected from the Hubble Law.
D)Both A and B
14
Approximately how long after the Big Bang did proto-galaxies form?
A)10 min.
B)1 million years (106 years)
C)1 billion years (109 years)
D)10 billion years (1010 years)
15
In a GUT (Grand Unified Theory), what is "unified"?
A)Matter.
B)The fundamental forces.
C)Galaxies.
D)Subatomic particles.
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