Name: __________________________  Date: _____________

1.	Why is the universe expanding?	
A)	Because the energy from all the stars is heating the universe, making it expand like a gas that is heated	
B)	Because spacetime itself is expanding, carrying the galaxies (or superclusters of galaxies) with it	
C)	It's not expanding—it is we who are getting smaller, making the universe seem bigger and bigger.	
D)	Because an infinitely dense clump of matter exploded, sending the galaxies (or superclusters of galaxies) hurtling out through space	

2.	What is the "cosmological redshift"?	
A)	The stretching of the wavelengths of photons as they travel through expanding space	
B)	The stretching of the wavelengths of photons by the Doppler shift because they are emitted by galaxies that are moving away from us	
C)	The loss of energy from photons interacting with virtual particles in the vacuum, resulting in the wavelength of the photons gradually increasing as they travel toward us through space	
D)	The stretching of the wavelengths of photons as they pass through absorbing matter in galaxies between us and the emitting galaxy	

3.	In the expansion of the universe, the expansion takes place	
A)	only between objects separated by vacuum; as a result, our bodies do not expand, but the Earth-Moon system does.	
B)	between all objects, even between the atoms in our bodies, although the expansion of a person is too small to be measured reliably.	
C)	only over distances about the size of a galaxy or larger; consequently, our Galaxy expands, but the solar system does not.	
D)	primarily in the huge spaces between clusters of galaxies; “small” objects like galaxies or the Earth do not expand.	

4.	According to Hubble's law, how old is the universe (H0 = Hubble's constant)?	
A)	Age = v/H0 (where v = recession velocity in km/s)	
B)	Age = r/H0 (where r = distance in Mpc)	
C)	Age = H0	
D)	Age = 1/H0	

5.	If Hubble's constant is 75 km/s/Mpc, then the age of the universe is 13 billion years. Suppose it were discovered that Hubble's constant is actually larger than 75 km/s/Mpc. What effect would this have on the calculated age of the universe?	
A)	It could increase or decrease the calculated age, depending on the recession velocity of the galaxy being investigated.	
B)	It would have no effect on the calculated age.	
C)	It would decrease the calculated age.	
D)	It would increase the calculated age.	

6.	How does the universe behave, according to the steady-state theory?	
A)	As the universe expands, new matter is created from which new galaxies form, thus maintaining a “steady state.”	
B)	New matter is being continuously created, which adds to the absorption of light in the universe and makes distant galaxies seem farther and farther away.	
C)	The universe is static, not expanding or contracting, but new matter is being created so that as old galaxies die and new galaxies form to take their place.	
D)	The universe is static, neither expanding nor contracting, thus maintaining a “steady state” in which no change takes place.	

7.	The cosmic background radiation is	
A)	the flux of visible radiation in empty space, contributed by all visible stars in the universe.	
B)	the radio noise generated by Earth-bound transmitters, spreading out into space since about 1920.	
C)	the beam of atomic nuclei known as cosmic rays that continuously rain down upon the Earth from all directions in space.	
D)	low-intensity radio noise, with a 3 K blackbody temperature, almost uniform in intensity in all directions.	

8.	In relation to the universe, what does “isotropy” mean?	
A)	The universe has the same expansion speed at all distances.	
B)	The universe is the same at all distances.	
C)	The universe at any given distance is the same at all times.	
D)	The universe looks the same in all directions.	

9.	What do we mean when we say that the universe is homogeneous?	
A)	At any given time, the universe looks the same at all locations.	
B)	There are no mass concentrations anywhere in the universe.	
C)	The universe is static and unchanging.	
D)	At any given time, the universe looks the same in all directions.	

10.	What do superstring theories try to explain?	
A)	The forces holding superclusters of galaxies together	
B)	The apparent acceleration of the expansion of the universe	
C)	The behavior of matter during the Planck time when all four fundamental forces were unified	
D)	The behavior of matter during the inflationary epoch	

11.	How many fundamental forces are there in nature at the present time under normal conditions?	
A)	Three: strong, electromagnetic, and gravitational	
B)	Six: color, strong, weak, magnetic, electric, and gravitational	
C)	Four: strong, weak, electromagnetic, and gravitational	
D)	Five: strong, weak, magnetic, electric, and gravitational	

12.	What are the particles that make up protons and neutrons?	
A)	Quarks	
B)	Muons	
C)	Gravitons	
D)	Neutrinos	

13.	How do we know that the fundamental forces become unified as the energy of particle interactions increases?	
A)	Only because the theory that says that they do is a very elegant one, and it would be nice if it were right	
B)	Because experiments have actually been done with high-energy particle accelerators where all four forces have been unified	
C)	Because, although it is not possible to see unification in the laboratory, the theory of unification agrees with many of the observed properties of the universe	
D)	Because we have actually seen the start of it in high-energy particle accelerators, where the electromagnetic and weak forces become unified	

14.	Within which time frame from the initial Big Bang do we believe all four fundamental forces of nature were united into a single force?	
A)	t = 0 to 106 years, when radiation dominated the universe	
B)	t = 0 to 1 sec, when photons interchanged freely with electron-positron pairs	
C)	t = 0 to 10–35 sec, when the strong nuclear force “froze out” of the universe	
D)	t = 0 to 10–43 sec, the Planck time, when gravity “froze out” of the universe	

15.	What is the isotropy (or horizon) problem?	
A)	The universe is not as uniform as the standard cosmological model predicts it should be.	
B)	If the universe expanded at the rate originally predicted, then the parts we see in opposite directions would never have been in equilibrium with each other and should not exhibit the degree of isotropy we observe.	
C)	Without modification, the standard theory suggests that an observer on a distant galaxy would not be able to see our Galaxy because of the intense cosmological redshift.	
D)	As we observe galaxies on the “horizon,” the farthest distance obtainable, the standard theory predicts that the recessional velocity should approach the speed of light.	

16.	If the universe had expanded at its original rate beyond the time when the strong nuclear force became a distinct force (about 10–35 sec after the Big Bang), the isotropy problem would have arisen:  Parts of the universe we see in opposite directions would never have been in equilibrium with each other and should not exhibit the degree of isotropy we observe.  The proposed solution to this problem is	
A)	the cosmological redshift.	
B)	quark confinement.	
C)	cosmic inflation.	
D)	the Grand Unified Theory (GUT).	

17.	In cosmology, what is the “inflationary period”?	
A)	A period when the cost of living rose faster than astronomers' salaries	
B)	The first 500,000 years of the life of the universe, when matter and radiation interacted vigorously	
C)	The period of universal expansion from the Big Bang to the present	
D)	A short period of extremely rapid expansion when the universe was very young	

18.	Why did the formation of particle-antiparticle pairs (such as protons and antiprotons) from gamma rays come to an end within the first second after start of the Big Bang?	
A)	Expansion of the universe carried the gamma rays too far apart for them to collide and form particle-antiparticle pairs.	
B)	The gamma-ray energy decreased as the universe expanded.	
C)	The universe became transparent to radiation, so gamma rays and particles no longer interacted.	
D)	The formation of particle-antiparticle pairs exhausted the supply of gamma rays, preventing further formation of particle-antiparticle pairs.	

19.	Where was most of the helium in the universe created?	
A)	By nuclear reactions in the cores of stars, and was then thrown out into space by supernovae	
B)	By high-energy processes during the collapse of pregalactic clouds during the formation of galaxies	
C)	By nuclear reactions during the first three minutes following the Big Bang	
D)	By the collision of cosmic rays with hydrogen nuclei in interstellar gas clouds	

20.	At an age of 300,000 years, the temperature of the universe had fallen to 3000 K, and electrons could then combine with protons to produce neutral hydrogen gas. What major transition took place in the universe at this time?	
A)	The present laws of physics began to apply for the first time.	
B)	The universe suddenly lost its electrical charge and become neutral.	
C)	Nuclear fusion no longer occurred below this temperature.	
D)	It became transparent to light for the first time.	

21.	Why does the observable universe have an “edge”?	
A)	Because we cannot see any farther out into space than the distance that light has traveled over the lifetime of the universe	
B)	Because the density of neutrinos at the “edge” becomes so large that photons cannot penetrate this barrier, and this prevents us from seeing beyond this point	
C)	Because absorbing matter prevents us from seeing beyond a certain distance	
D)	Because there are so many galaxies in the universe that every line of sight eventually hits a galaxy, stopping us from seeing any farther	

22.	During the formation of the universe, where did the density enhancements come from that subsequently collapsed to form superclusters of galaxies?	
A)	From turbulence during the time when the universe was opaque, which left denser regions that were free to collapse when the universe became transparent	
B)	From quantum fluctuations in the density of matter during the early Big Bang, which were later expanded by inflation	
C)	From spatial variations in the rate heating from pair annihilation after the first second of the Big Bang	
D)	From a random gravitational fragmentation of the matter in the universe after the era of recombination	

23.	The very small detected irregularities in the uniformity of the cosmic microwave background are considered to be very important in the study of the evolution of our universe because	
A)	they show us that the Big Bang explosion was very nonuniform.	
B)	they were the seeds of supermassive black holes around which the earliest superclusters of galaxies then formed.	
C)	they are thought to have led to the development of the present concentrations of matter and energy in superclusters of galaxies.	
D)	they are thought to contain most of the elusive “missing matter” in the form of energy concentration in the universe.	

24.	For how long did continuous star formation last in spiral galaxies?	
A)	For about the first 8–10 billion years of the galaxy's life	
B)	For about the first billion years of the galaxy's life	
C)	For about the first million years of the galaxy's life	
D)	Continuously throughout the galaxy's life, right to the present day	

25.	In which of the following universe scenarios will the present universe evolve to a Big Crunch at some time in the future?	
A)	An open universe	
B)	A Newtonian universe	
C)	A closed universe	
D)	A flat universe	

26.	What kind of curvature (geometry of space) does the universe have if the universe is open?	
A)	Hyperbolic	
B)	Parabolic	
C)	Spherical	
D)	Flat	

27.	What kind of curvature (geometry of space) does the universe have if the universe is just on the boundary between being open and being closed?	
A)	Parabolic	
B)	Hyperbolic	
C)	Spherical	
D)	Flat	

28.	What kind of curvature (geometry of space) does the universe have if the universe is closed?	
A)	Parabolic	
B)	Flat	
C)	Hyperbolic	
D)	Spherical	

29.	Which parameter of the present universe, more than any other, is considered to be critical in determining the ultimate fate of the universe?	
A)	The amount of mass in black holes in the universe	
B)	The number of neutrinos in the universe	
C)	The amount of matter and energy in the universe	
D)	The number of photons of radiation in the universe	

30.	Recent results from very bright supernovae in very distant galaxies seem to indicate that the expansion of the universe	
A)	has now stopped and the universe will shortly begin to contract again toward a Big Crunch.	
B)	is decelerating (slowing down).	
C)	is continuing at a constant rate and has done so since just after the Big Bang.	
D)	is accelerating (speeding up).	

31.	What is the difference between dark matter and dark energy?	
A)	Dark matter exists today, whereas dark energy existed only until the strong nuclear force became a separate force at the Planck time.	
B)	Dark energy is the energy emitted by dark matter, much as luminous energy (light) is emitted by visible matter.	
C)	There is no difference: Energy has mass by E = mc2, and dark matter and dark energy are two names for the same effect.	
D)	Dark matter is attractive and slows the universal expansion, whereas dark energy is repulsive and accelerates the universal expansion.	

32.	In a primordial, pre-galactic gas cloud, what is believed to have been the most important condition that caused the cloud to become an elliptical galaxy?	
A)	The initial rate of star formation was high.	
B)	The cloud started off with a lot of dust and heavy elements.	
C)	The cloud started off flattened and disk-shaped before it collapsed.	
D)	The initial rate of star formation was low.	

Answer Key

1.	B	
2.	A	
3.	D	
4.	D	
5.	C	
6.	A	
7.	D	
8.	D	
9.	A	
10.	C	
11.	C	
12.	A	
13.	D	
14.	D	
15.	B	
16.	C	
17.	D	
18.	B	
19.	C	
20.	D	
21.	A	
22.	B	
23.	C	
24.	D	
25.	C	
26.	A	
27.	D	
28.	D	
29.	C	
30.	D	
31.	D	
32.	A