Astro 2nd Canadian Edition By Shohini Ghose – Test Bank

1. What does the resolution of Olbers’s paradox say about why it gets dark at night?
a. It gets dark at night because the universe is not infinite in age.
b. It gets dark at night because the universe is static.
c. It gets dark at night because the universe is closed.
d. It gets dark at night because the universe contains dust.
ANSWER: a

2. Which of the following statements best describes Olbers’s paradox?
a. The night sky should glow in predominantly X-ray wavelengths.
b. The night sky should glow bright.
c. The night sky should be always dark.
d. The night sky should glow in predominantly infrared wavelengths.
ANSWER: b

3. Why is there a limit to the size of the observable universe?
a. because the universe has a finite radius
b. because galaxies appear to be moving away from us
c. because the sky is dark at night
d. because the universe has a finite age
ANSWER: d

4. What is the point of the raisin bread analogy for the expanding universe?
a. to show that all observers see other raisins (galaxies) expanding away from them
b. to show that the raisins (galaxies) at the centre of the loaf have a special viewpoint
c. to show that there is an edge to the universe (the crust)
d. to show that the expansion is faster near the edges and slower in the centre
ANSWER: a

5. What is the Hubble time?
a. the time it takes a galaxy moving at 1000 km/sec to move 1 Mpc
b. the time it takes the galaxy to double its distance from us
c. the time remaining before the universe stops expanding and begins to contract
d. an estimate of the age of the universe based on the Hubble constant
ANSWER: d

6. If we lived in a static, unchanging universe, which of the following would you expect to see?
a. detection of the cosmic microwave background (CMB)
b. dark sky at night
c. galaxy properties that are constant with distance
d. redshift of galaxies that change with distance
ANSWER: c

7. Where did the cosmic microwave background (CMB) come from?
a. photons emitted from the first stars
b. photons released from hydrogen in our galaxy
c. light scattered by dust in our solar system
d. photons released when electrons and nuclei combined for the first time
ANSWER: d

8. When people hear the phrase “big bang,” they often think of an explosion. What word would be a better description than “explosion”?
a. expansion
b. compression
c. combustion
d. extension
ANSWER: a

9. What is quintessence?
a. the name of the force that led to the inflationary period of the universe
b. the name of the theoretically-hypothesized five-dimensional space of the universe
c. the name of the force suspected to cause the current acceleration in universe’s expansion
d. the name of one of the particles of dark matter related to WIMPs
ANSWER: c

10. Why is the cosmic microwave background (CMB) so cold, if the early universe was so hot?
a. Enough time has passed for matter in the universe to release enough heat to cool down.
b. The CMB constantly interacts with atoms, which effectively cools down the photons.
c. The big bang was initially hot but the CMB was released from cold material much later on.
d. The expansion of the universe has redshifted those photons to an effectively cooler temperature.
ANSWER: d

11. During the first moments of the big bang when elements could be created, nuclear fusion reactions made few heavy elements. Why not?
a. because all nuclei with masses greater than 4 hydrogen masses are unstable
b. because no stable nuclei exist with masses of 5 or 8 hydrogen masses
c. because the helium nucleus is unstable
d. because the temperature and density were too low
ANSWER: b