Question 1

What is the "cosmological redshift"?

Accepted Answer

A)  stretching of the wavelengths of photons as they travel through expanding space 
B)  stretching of the wavelengths of photons by the Doppler shift because they are emitted by galaxies that are moving away from Earth 
C)  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 Earth through space 
D)  stretching of the wavelengths of photons as they pass through absorbing matter in galaxies between Earth and the emitting galaxy 
A)  stretching of the wavelengths of photons as they travel through expanding space 
B)  stretching of the wavelengths of photons by the Doppler shift because they are emitted by galaxies that are moving away from Earth 
C)  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 Earth through space 
D)  stretching of the wavelengths of photons as they pass through absorbing matter in galaxies between Earth and the emitting galaxy

Question 2

Why is the universe expanding?

Accepted Answer

A)  The energy from all the stars is heating the universe, making it expand like a gas that is heated. 
B)  Spacetime itself is expanding, carrying the galaxies (or superclusters of galaxies) with it. 
C)  The universe is not expanding-it is the Galaxy that is getting smaller, making the universe seem bigger and bigger. 
D)  An infinitely dense clump of matter exploded, sending the galaxies (or superclusters of galaxies) hurtling out through space. 
A)  The energy from all the stars is heating the universe, making it expand like a gas that is heated. 
B)  Spacetime itself is expanding, carrying the galaxies (or superclusters of galaxies) with it. 
C)  The universe is not expanding-it is the Galaxy that is getting smaller, making the universe seem bigger and bigger. 
D)  An infinitely dense clump of matter exploded, sending the galaxies (or superclusters of galaxies) hurtling out through space.

Question 3

Why did the formation of particle-antiparticle pairs (such as protons and antiprotons) from gamma rays come to an end in the first second after the start of the Big Bang?

Accepted Answer

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. 
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.

Question 4

Astronomers studying the cosmic microwave background have recently inferred the existence of another relic of the Big Bang that pervades the universe. What makes up this other background?

Accepted Answer

A)  gamma rays 
B)  cosmic rays 
C)  magnetic fields 
D)  neutrinos 
A)  gamma rays 
B)  cosmic rays 
C)  magnetic fields 
D)  neutrinos

Question 5

When the Big Bang began, all the fundamental forces were unified and behaved like a single force. As the universe expanded and cooled during the Big Bang, when did gravity first become a separate force?

Accepted Answer

A)  at the start of quark confinement, when the universe was about 10-6 s old 
B)  at the start of the inflationary period, when the universe was about 10-35 s old 
C)  at the end of the inflationary period, when the universe was about 10-33 s old 
D)  at the Planck time, when the universe was about 10-43 s old 
A)  at the start of quark confinement, when the universe was about 10-6 s old 
B)  at the start of the inflationary period, when the universe was about 10-35 s old 
C)  at the end of the inflationary period, when the universe was about 10-33 s old 
D)  at the Planck time, when the universe was about 10-43 s old

Question 6

If the early universe had been perfectly uniform, galaxies could not have formed. As it is, cosmologists believe the variations observed in the cosmic microwave background which were sufficient to produce the galaxies and other structures now seen were only about 3 parts in

Accepted Answer

A)  10. 
B)  1000. 
C)  100,000. 
D)  10 million. 
A)  10. 
B)  1000. 
C)  100,000. 
D)  10 million.

Question 7

Because of the travel time of light, astronomers see more distant parts of the universe as they were when the universe was younger, but they cannot see back "into" times when the universe was opaque and light could not travel freely. Using photons, then, what is the furthest back in time that astronomers can when they look out into the universe?

Accepted Answer

A)  1/1 millionth seconds after the start of the Big Bang 
B)  380,000 years after the start of the Big Bang 
C)  3 minutes after the start of the Big Bang 
D)  3000 years after the start of the Big Bang 
A)  1/1 millionth seconds after the start of the Big Bang 
B)  380,000 years after the start of the Big Bang 
C)  3 minutes after the start of the Big Bang 
D)  3000 years after the start of the Big Bang

Question 8

How was the cosmic microwave background radiation discovered?

Accepted Answer

A)  using a microwave detector on the Hubble Space Telescope 
B)  using the Cosmic Background Explorer (COB
E)  spacecraft 
C)  using a communications antenna on Earth's surface 
D)  using the Ulysses spacecraft observing from above the Sun's north pole 
A)  using a microwave detector on the Hubble Space Telescope 
B)  using the Cosmic Background Explorer (COB
E)  spacecraft 
C)  using a communications antenna on Earth's surface 
D)  using the Ulysses spacecraft observing from above the Sun's north pole

Question 9

How does the observed total amount of matter in the universe, including dark matter, compare with the amount of matter required to make its geometry flat?

Accepted Answer

A)  The observed total amount of matter equals the amount needed, to within observational uncertainty. 
B)  The observed total amount of matter is about 1/3 the amount needed. 
C)  The observed total amount of matter is about twice the amount needed. 
D)  The observed total amount of matter is about 1/25 of the amount needed. 
A)  The observed total amount of matter equals the amount needed, to within observational uncertainty. 
B)  The observed total amount of matter is about 1/3 the amount needed. 
C)  The observed total amount of matter is about twice the amount needed. 
D)  The observed total amount of matter is about 1/25 of the amount needed.

Question 10

Many of the small temperature fluctuations in the cosmic microwave background are a result of

Accepted Answer

A)  galaxy formation. 
B)  symmetry breaking. 
C)  sound waves. 
D)  polarization. 
A)  galaxy formation. 
B)  symmetry breaking. 
C)  sound waves. 
D)  polarization.

Question 11

What observations have MOST clearly revealed the geometry of the universe?

Accepted Answer

A)  the brightnesses of supernovae 
B)  the apparent sizes of features in the cosmic microwave background 
C)  gravitational?-lensing near galaxy clusters 
D)  galaxy rotation curves 
A)  the brightnesses of supernovae 
B)  the apparent sizes of features in the cosmic microwave background 
C)  gravitational?-lensing near galaxy clusters 
D)  galaxy rotation curves

Question 12

Which element(s) was (were) created during the Big Bang?

Accepted Answer

A)  hydrogen and helium 
B)  hydrogen, helium, lithium, and beryllium 
C)  hydrogen 
D)  hydrogen, helium, and lithium 
A)  hydrogen and helium 
B)  hydrogen, helium, lithium, and beryllium 
C)  hydrogen 
D)  hydrogen, helium, and lithium

Question 13

During the first one-ten-thousandth of a second (10-4 s) of the life of the universe, antiprotons were very common. For every billion antiprotons, how many protons were there?

Accepted Answer

A)  exactly 1 billion since protons and antiprotons were created in equal numbers 
B)  slightly more than 1 billion, thus producing the matter seen today 
C)  totally unknown number since the early universe was opaque and astronomers cannot see what conditions were like then 
D)  10 billion, thus producing the dark matter seen today 
A)  exactly 1 billion since protons and antiprotons were created in equal numbers 
B)  slightly more than 1 billion, thus producing the matter seen today 
C)  totally unknown number since the early universe was opaque and astronomers cannot see what conditions were like then 
D)  10 billion, thus producing the dark matter seen today

Question 14

What is "dark energy"?

Accepted Answer

A)  energy associated with the matter that has fallen into a black hole 
B)  matter-energy needed to bridge the gap between the energy seen or inferred and the energy needed to make the universe flat 
C)  energy associated with dark matter 
D)  an unusual form of energy that creates a universewide repulsive force 
A)  energy associated with the matter that has fallen into a black hole 
B)  matter-energy needed to bridge the gap between the energy seen or inferred and the energy needed to make the universe flat 
C)  energy associated with dark matter 
D)  an unusual form of energy that creates a universewide repulsive force

Question 15

The conditions in the early universe at the time matter became decoupled from radiation were (in terms of age t, peak background wavelength $\lambda$, and equivalent temperature T)

Accepted Answer

A)  t = 2 * 1011 years, $\lambda$ = 1 mm, microwaves, T = 3 K 
B)  The universe was never radiation-dominated since matter has always dominated by generating the gravitational field into which the universe has expanded. 
C)  t = 3 minutes, $\lambda$ = 0.3 $\mu$m, near UV, T = 107 K 
D)  t = 380,000 years, $\lambda$ = 1 $\mu$m, infrared, T = 3000 K 
A)  t = 2 * 1011 years, $\lambda$ = 1 mm, microwaves, T = 3 K 
B)  The universe was never radiation-dominated since matter has always dominated by generating the gravitational field into which the universe has expanded. 
C)  t = 3 minutes, $\lambda$ = 0.3 $\mu$m, near UV, T = 107 K 
D)  t = 380,000 years, $\lambda$ = 1 $\mu$m, infrared, T = 3000 K

Question 16

What is the difference between a proton and a neutron in terms of their constituent quarks?

Accepted Answer

A)  A proton is made of two "up" quarks and a "down" quark, and a neutron is made of two "down" quarks and an "up" quark. 
B)  A proton is made of two "down" quarks and an "up" quark, and a neutron is made of two "up" quarks and a "down" quark. 
C)  A proton is made of three "up" quarks, and a neutron is made of three "down" quarks. 
D)  A proton is made of three "down" quarks, and a neutron is made of three "up" quarks. 
A)  A proton is made of two "up" quarks and a "down" quark, and a neutron is made of two "down" quarks and an "up" quark. 
B)  A proton is made of two "down" quarks and an "up" quark, and a neutron is made of two "up" quarks and a "down" quark. 
C)  A proton is made of three "up" quarks, and a neutron is made of three "down" quarks. 
D)  A proton is made of three "down" quarks, and a neutron is made of three "up" quarks.

Question 17

In relation to the universe, what does "isotropy" mean?

Accepted Answer

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. 
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.

Question 18

When the Big Bang began, all the fundamental forces were unified and behaved like a single force. As the universe expanded and cooled during the Big Bang, when did the strong nuclear force first become a separate force?

Accepted Answer

A)  at the start of quark confinement, when the universe was about 10-6 s old 
B)  when pair production ceased, when the universe was about 1 s old 
C)  at the Planck time, when the universe was about 10-43 s old 
D)  at the start of the inflationary period, when the universe was about 10-35 s old 
A)  at the start of quark confinement, when the universe was about 10-6 s old 
B)  when pair production ceased, when the universe was about 1 s old 
C)  at the Planck time, when the universe was about 10-43 s old 
D)  at the start of the inflationary period, when the universe was about 10-35 s old

Question 19

What appears to be the relationship between the distribution of dark matter and the distribution of luminous matter?

Accepted Answer

A)  There seems to be no correlation at all. 
B)  There seems to be a separate distribution of dark matter-dark-matter galaxy clusters, voids in the dark matter, and so on. But these formations all occur in regions of space far from luminous matter. 
C)  The distribution of dark matter seems to coincide with the distribution of luminous matter. 
D)  The distribution of dark matter seems to be just the reverse of the distribution of luminous matter: Dark-matter galaxy clusters occur in the voids of luminous matter; luminous galaxy clusters occur in the voids of dark matter. 
A)  There seems to be no correlation at all. 
B)  There seems to be a separate distribution of dark matter-dark-matter galaxy clusters, voids in the dark matter, and so on. But these formations all occur in regions of space far from luminous matter. 
C)  The distribution of dark matter seems to coincide with the distribution of luminous matter. 
D)  The distribution of dark matter seems to be just the reverse of the distribution of luminous matter: Dark-matter galaxy clusters occur in the voids of luminous matter; luminous galaxy clusters occur in the voids of dark matter.

Question 20

If the Hubble constant is 75 km/s/Mpc, then the age of the universe is 13 billion years. Suppose it were discovered that the Hubble constant is actually larger than 75 km/s/Mpc. What effect would this fact have on the estimated age of the universe?

Accepted Answer

A)  The estimated age could be increased or decreased, depending on the recession velocity of the galaxy being investigated. 
B)  The estimated age would be the same. 
C)  The estimated age would be decreased. 
D)  The estimated age would be increased. 
A)  The estimated age could be increased or decreased, depending on the recession velocity of the galaxy being investigated. 
B)  The estimated age would be the same. 
C)  The estimated age would be decreased. 
D)  The estimated age would be increased.

What is the "cosmological redshift"?

Why is the universe expanding?

Why did the formation of particle-antiparticle pairs (such as protons and antiprotons) from gamma rays come to an end in the first second after the start of the Big Bang?

Astronomers studying the cosmic microwave background have recently inferred the existence of another relic of the Big Bang that pervades the universe. What makes up this other background?

When the Big Bang began, all the fundamental forces were unified and behaved like a single force. As the universe expanded and cooled during the Big Bang, when did gravity first become a separate force?

If the early universe had been perfectly uniform, galaxies could not have formed. As it is, cosmologists believe the variations observed in the cosmic microwave background which were sufficient to produce the galaxies and other structures now seen were only about 3 parts in

How was the cosmic microwave background radiation discovered?

How does the observed total amount of matter in the universe, including dark matter, compare with the amount of matter required to make its geometry flat?

Many of the small temperature fluctuations in the cosmic microwave background are a result of

What observations have MOST clearly revealed the geometry of the universe?

Which element(s) was (were) created during the Big Bang?

During the first one-ten-thousandth of a second (10^-4 s) of the life of the universe, antiprotons were very common. For every billion antiprotons, how many protons were there?

What is "dark energy"?

The conditions in the early universe at the time matter became decoupled from radiation were (in terms of age t, peak background wavelength $\lambda$ , and equivalent temperature T)

What is the difference between a proton and a neutron in terms of their constituent quarks?

In relation to the universe, what does "isotropy" mean?

When the Big Bang began, all the fundamental forces were unified and behaved like a single force. As the universe expanded and cooled during the Big Bang, when did the strong nuclear force first become a separate force?

What appears to be the relationship between the distribution of dark matter and the distribution of luminous matter?

If the Hubble constant is 75 km/s/Mpc, then the age of the universe is 13 billion years. Suppose it were discovered that the Hubble constant is actually larger than 75 km/s/Mpc. What effect would this fact have on the estimated age of the universe?

Discovering the Night Sky

Gravitation and the Motion of the Planets

Light and Telescopes

Atomic Physics and Spectra

Exoplanets and the Formation of Planetary Systems

Formation of the Solar System

Earth and the Moon

The Other Terrestrial Planets

The Outer Planets

Vagabonds of the Solar System

The Sun: Our Extraordinary Star

Characterizing Stars

The Lives of Stars From Birth Through Middle Age

The Death of Stars

Black Holes: Matters of Gravity

The Milky Way Galaxy

Galaxies

Quasars and Other Active Galaxies

Astrobiology

Filters

Exam 19: Cosmology

What is the "cosmological redshift"?

Why is the universe expanding?

Why did the formation of particle-antiparticle pairs (such as protons and antiprotons) from gamma rays come to an end in the first second after the start of the Big Bang?

Astronomers studying the cosmic microwave background have recently inferred the existence of another relic of the Big Bang that pervades the universe. What makes up this other background?

When the Big Bang began, all the fundamental forces were unified and behaved like a single force. As the universe expanded and cooled during the Big Bang, when did gravity first become a separate force?

If the early universe had been perfectly uniform, galaxies could not have formed. As it is, cosmologists believe the variations observed in the cosmic microwave background which were sufficient to produce the galaxies and other structures now seen were only about 3 parts in

How was the cosmic microwave background radiation discovered?

How does the observed total amount of matter in the universe, including dark matter, compare with the amount of matter required to make its geometry flat?

Many of the small temperature fluctuations in the cosmic microwave background are a result of

What observations have MOST clearly revealed the geometry of the universe?

Which element(s) was (were) created during the Big Bang?

During the first one-ten-thousandth of a second (10-4 s) of the life of the universe, antiprotons were very common. For every billion antiprotons, how many protons were there?

What is "dark energy"?

The conditions in the early universe at the time matter became decoupled from radiation were (in terms of age t, peak background wavelength λ\lambdaλ , and equivalent temperature T)

What is the difference between a proton and a neutron in terms of their constituent quarks?

In relation to the universe, what does "isotropy" mean?

When the Big Bang began, all the fundamental forces were unified and behaved like a single force. As the universe expanded and cooled during the Big Bang, when did the strong nuclear force first become a separate force?

What appears to be the relationship between the distribution of dark matter and the distribution of luminous matter?

If the Hubble constant is 75 km/s/Mpc, then the age of the universe is 13 billion years. Suppose it were discovered that the Hubble constant is actually larger than 75 km/s/Mpc. What effect would this fact have on the estimated age of the universe?

Discovering the Night Sky

Gravitation and the Motion of the Planets

Light and Telescopes

Atomic Physics and Spectra

Exoplanets and the Formation of Planetary Systems

Formation of the Solar System

Earth and the Moon

The Other Terrestrial Planets

The Outer Planets

Vagabonds of the Solar System

The Sun: Our Extraordinary Star

Characterizing Stars

The Lives of Stars From Birth Through Middle Age

The Death of Stars

Black Holes: Matters of Gravity

The Milky Way Galaxy

Galaxies

Quasars and Other Active Galaxies

Astrobiology

Filters

During the first one-ten-thousandth of a second (10^-4 s) of the life of the universe, antiprotons were very common. For every billion antiprotons, how many protons were there?

The conditions in the early universe at the time matter became decoupled from radiation were (in terms of age t, peak background wavelength $\lambda$ , and equivalent temperature T)