Question 1

The cosmic background radiation is

Accepted Answer

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

Question 2

If space has a hyperbolic geometry (open universe), what will happen to two initially parallel laser beams as they traverse billions of light-years of space?

Accepted Answer

A)  The beams will gradually diverge (move apart). 
B)  The beams will remain parallel. 
C)  The beams will gradually diverge (move apart) to a maximum separation, then gradually approach and cross. 
D)  The beams will gradually approach each other and eventually cross. 
A)  The beams will gradually diverge (move apart). 
B)  The beams will remain parallel. 
C)  The beams will gradually diverge (move apart) to a maximum separation, then gradually approach and cross. 
D)  The beams will gradually approach each other and eventually cross.

Question 3

At what time did the universe cool to a temperature of about 3 K?

Accepted Answer

A)  end of the inflationary era 
B)  end of the Planck time 
C)  very recently 
D)  era of recombination 
A)  end of the inflationary era 
B)  end of the Planck time 
C)  very recently 
D)  era of recombination

Question 4

Measurement of the sizes of hot spots in the temperature distribution of the cosmic microwave background suggests that the universe is flat. Yet the combined density of all the normal matter seen, plus the dark matter inferred, is only about one-quarter of the critical density. What conclusion have cosmologists drawn from this discrepancy?

Accepted Answer

A)  The universe is not flat after all. 
B)  There must be a large amount of luminous matter and radiation in the universe, which cosmologists have not yet found. 
C)  The universe is smaller than cosmologists have been assuming and thus the measured density is larger. 
D)  There is an entity to which cosmologists have given the name "dark energy" that contributes to the total density but that cannot be detected by the usual methods. 
A)  The universe is not flat after all. 
B)  There must be a large amount of luminous matter and radiation in the universe, which cosmologists have not yet found. 
C)  The universe is smaller than cosmologists have been assuming and thus the measured density is larger. 
D)  There is an entity to which cosmologists have given the name "dark energy" that contributes to the total density but that cannot be detected by the usual methods.

Question 5

Physicist's equations can describe the evolution of the universe since

Accepted Answer

A)  before the Big Bang. 
B)  a fraction of a second after the Big Bang. 
C)  30,000 years after the Big Bang. 
D)  380,000 years after the Big Bang. 
A)  before the Big Bang. 
B)  a fraction of a second after the Big Bang. 
C)  30,000 years after the Big Bang. 
D)  380,000 years after the Big Bang.

Question 6

What are quarks?

Accepted Answer

A)  particles of zero electric charge and zero mass that are emitted by nuclear reactions in the Sun's core 
B)  component particles making up electrons 
C)  antielectrons (the antimatter form of electrons) 
D)  component particles making up protons and neutrons 
A)  particles of zero electric charge and zero mass that are emitted by nuclear reactions in the Sun's core 
B)  component particles making up electrons 
C)  antielectrons (the antimatter form of electrons) 
D)  component particles making up protons and neutrons

Question 7

In the present theory of the Big Bang, what significant event occurred at about 400,000 years after the universe started expanding?

Accepted Answer

A)  The primordial helium in the universe was produced. 
B)  The universe became transparent to neutrinos. 
C)  The temperature of the cosmic background radiation had cooled to its present level of about 3 K. 
D)  The universe became transparent to photons. 
A)  The primordial helium in the universe was produced. 
B)  The universe became transparent to neutrinos. 
C)  The temperature of the cosmic background radiation had cooled to its present level of about 3 K. 
D)  The universe became transparent to photons.

Question 8

What condition is necessary for the universe to be closed?

Accepted Answer

A)  The universe must have no mass in it. 
B)  The density of the universe must be large. 
C)  The density of the universe must be small. 
D)  The cosmological constant must be large. 
A)  The universe must have no mass in it. 
B)  The density of the universe must be large. 
C)  The density of the universe must be small. 
D)  The cosmological constant must be large.

Question 9

What is the period of quark confinement?

Accepted Answer

A)  Because of the very large pressure in early times, all the quarks were confined to a small volume. After the inflationary epoch, the pressure dropped and the quarks were able to spread out to assume the distribution found today. 
B)  During the period of quark confinement, the energy of the photons was sufficiently high that conglomerations of quarks, such as neutrons and protons, could not exist and quarks were free. 
C)  During the period of quark confinement, the energy of the photons was sufficiently low that conglomerations of quarks, such as neutrons and protons, could exist without being blasted apart as soon as they were formed. 
D)  The period of quark confinement was the very early period in the universe when all matter and energy were confined to a region the size of a single quark. 
A)  Because of the very large pressure in early times, all the quarks were confined to a small volume. After the inflationary epoch, the pressure dropped and the quarks were able to spread out to assume the distribution found today. 
B)  During the period of quark confinement, the energy of the photons was sufficiently high that conglomerations of quarks, such as neutrons and protons, could not exist and quarks were free. 
C)  During the period of quark confinement, the energy of the photons was sufficiently low that conglomerations of quarks, such as neutrons and protons, could exist without being blasted apart as soon as they were formed. 
D)  The period of quark confinement was the very early period in the universe when all matter and energy were confined to a region the size of a single quark.

Question 10

How was MOST of the helium in the universe created?

Accepted Answer

A)  by nuclear reactions in the cores of stars and 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 3 minutes following the Big Bang 
D)  by the collision of cosmic rays with hydrogen nuclei in interstellar gas clouds 
A)  by nuclear reactions in the cores of stars and 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 3 minutes following the Big Bang 
D)  by the collision of cosmic rays with hydrogen nuclei in interstellar gas clouds

Question 11

What is the difference between dark matter and dark energy?

Accepted Answer

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. 
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.

Question 12

Why would cosmologists expect the rate of expansion of the universe to be slowing down?

Accepted Answer

A)  The gravitational pull of all objects in the universe on each other would lead to slowdown. 
B)  All expansions after explosions naturally slow down with time. 
C)  Galaxies feel a kind of friction as they move through space, which slows them down. 
D)  The greater the distance between two objects (such as galaxies or superclusters), the harder it is to push them farther apart. 
A)  The gravitational pull of all objects in the universe on each other would lead to slowdown. 
B)  All expansions after explosions naturally slow down with time. 
C)  Galaxies feel a kind of friction as they move through space, which slows them down. 
D)  The greater the distance between two objects (such as galaxies or superclusters), the harder it is to push them farther apart.

Question 13

Newton reached the conclusion that the universe must consist of an infinite expanse of stars because

Accepted Answer

A)  he and his colleagues had observed the uniform distribution of stars all over the sky. 
B)  he was unable to detect the movement of stars around a common center, which his theory required for stability against collapse in a finite universe. 
C)  of his religious conviction that the creator would create nothing less than an infinite universe. 
D)  he reasoned that if stars were not uniformly distributed everywhere, then denser portions of the universe would clump together under their own gravity. 
A)  he and his colleagues had observed the uniform distribution of stars all over the sky. 
B)  he was unable to detect the movement of stars around a common center, which his theory required for stability against collapse in a finite universe. 
C)  of his religious conviction that the creator would create nothing less than an infinite universe. 
D)  he reasoned that if stars were not uniformly distributed everywhere, then denser portions of the universe would clump together under their own gravity.

Question 14

During the formation of the universe, where did the density enhancements come from that subsequently collapsed to form superclusters of galaxies?

Accepted Answer

A)  turbulence during the time when the universe was opaque, which left denser regions that were free to collapse when the universe became transparent 
B)  quantum fluctuations in the density of matter during the early Big Bang, which were later expanded by inflation 
C)  spatial variations in the rate heating from pair annihilation after the first second of the Big Bang 
D)  random gravitational fragmentation of the matter in the universe after the era of recombination 
A)  turbulence during the time when the universe was opaque, which left denser regions that were free to collapse when the universe became transparent 
B)  quantum fluctuations in the density of matter during the early Big Bang, which were later expanded by inflation 
C)  spatial variations in the rate heating from pair annihilation after the first second of the Big Bang 
D)  random gravitational fragmentation of the matter in the universe after the era of recombination

Question 15

For how long did vigorous star formation last in elliptical galaxies?

Accepted Answer

A)  continuously throughout the galaxy's life, right to the present day 
B)  about the first million years of the galaxy's life 
C)  about the first billion years of the galaxy's life 
D)  about the first 8-10 billion years of the galaxy's life 
A)  continuously throughout the galaxy's life, right to the present day 
B)  about the first million years of the galaxy's life 
C)  about the first billion years of the galaxy's life 
D)  about the first 8-10 billion years of the galaxy's life

Question 16

What is the range of the strong nuclear force compared with the size of a large atomic nucleus, 10-14 m?

Accepted Answer

A)  the same since it is the strong force that holds the nucleus together 
B)  10 times larger than the size of an atomic nucleus 
C)  infinite; it has no limit 
D)  10 times smaller than the size of an atomic nucleus 
A)  the same since it is the strong force that holds the nucleus together 
B)  10 times larger than the size of an atomic nucleus 
C)  infinite; it has no limit 
D)  10 times smaller than the size of an atomic nucleus

Question 17

As astronomers look at more distant regions of space, they see the regions as they existed at earlier times, but their farthest views are blocked by a "wall" beyond which the universe is opaque. What event occurred at the time marked by this wall?

Accepted Answer

A)  Quarks combined to form neutrons and protons. 
B)  Electrons and protons combined to form neutral hydrogen atoms. 
C)  Protons combined with neutrons to form helium nuclei. 
D)  Gravity froze out as a separate force. 
A)  Quarks combined to form neutrons and protons. 
B)  Electrons and protons combined to form neutral hydrogen atoms. 
C)  Protons combined with neutrons to form helium nuclei. 
D)  Gravity froze out as a separate force.

Question 18

At the start of the Big Bang, all the fundamental forces were unified and behaved like a single force. As the universe expanded and cooled during the Big Bang, which was the first force to become a separate force?

Accepted Answer

A)  strong nuclear force 
B)  weak nuclear force 
C)  electromagnetic force 
D)  gravity 
A)  strong nuclear force 
B)  weak nuclear force 
C)  electromagnetic force 
D)  gravity

Question 19

At the present time cosmologists believe the structure and behavior of the universe are dominated by

Accepted Answer

A)  radiation. 
B)  ordinary matter. 
C)  dark matter. 
D)  dark energy. 
A)  radiation. 
B)  ordinary matter. 
C)  dark matter. 
D)  dark energy.

Question 20

What is the range of the electromagnetic force (the maximum distance over which it acts)?

Accepted Answer

A)  10-15 m (1 femtometer, or roughly the size of a proton) 
B)  10-9 m (1 nanometer, or roughly the size of a hydrogen atom) 
C)  a few thousand meters, or roughly the size of Earth 
D)  infinity 
A)  10-15 m (1 femtometer, or roughly the size of a proton) 
B)  10-9 m (1 nanometer, or roughly the size of a hydrogen atom) 
C)  a few thousand meters, or roughly the size of Earth 
D)  infinity

The cosmic background radiation is

If space has a hyperbolic geometry (open universe), what will happen to two initially parallel laser beams as they traverse billions of light-years of space?

At what time did the universe cool to a temperature of about 3 K?

Physicist's equations can describe the evolution of the universe since

What are quarks?

In the present theory of the Big Bang, what significant event occurred at about 400,000 years after the universe started expanding?

What condition is necessary for the universe to be closed?

What is the period of quark confinement?

How was MOST of the helium in the universe created?

What is the difference between dark matter and dark energy?

Why would cosmologists expect the rate of expansion of the universe to be slowing down?

Newton reached the conclusion that the universe must consist of an infinite expanse of stars because

During the formation of the universe, where did the density enhancements come from that subsequently collapsed to form superclusters of galaxies?

For how long did vigorous star formation last in elliptical galaxies?

What is the range of the strong nuclear force compared with the size of a large atomic nucleus, 10^-14 m?

As astronomers look at more distant regions of space, they see the regions as they existed at earlier times, but their farthest views are blocked by a "wall" beyond which the universe is opaque. What event occurred at the time marked by this wall?

At the start of the Big Bang, all the fundamental forces were unified and behaved like a single force. As the universe expanded and cooled during the Big Bang, which was the first force to become a separate force?

At the present time cosmologists believe the structure and behavior of the universe are dominated by

What is the range of the electromagnetic force (the maximum distance over which it acts)?

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

The cosmic background radiation is

If space has a hyperbolic geometry (open universe), what will happen to two initially parallel laser beams as they traverse billions of light-years of space?

At what time did the universe cool to a temperature of about 3 K?

Physicist's equations can describe the evolution of the universe since

What are quarks?

In the present theory of the Big Bang, what significant event occurred at about 400,000 years after the universe started expanding?

What condition is necessary for the universe to be closed?

What is the period of quark confinement?

How was MOST of the helium in the universe created?

What is the difference between dark matter and dark energy?

Why would cosmologists expect the rate of expansion of the universe to be slowing down?

Newton reached the conclusion that the universe must consist of an infinite expanse of stars because

During the formation of the universe, where did the density enhancements come from that subsequently collapsed to form superclusters of galaxies?

For how long did vigorous star formation last in elliptical galaxies?

What is the range of the strong nuclear force compared with the size of a large atomic nucleus, 10-14 m?

As astronomers look at more distant regions of space, they see the regions as they existed at earlier times, but their farthest views are blocked by a "wall" beyond which the universe is opaque. What event occurred at the time marked by this wall?

At the start of the Big Bang, all the fundamental forces were unified and behaved like a single force. As the universe expanded and cooled during the Big Bang, which was the first force to become a separate force?

At the present time cosmologists believe the structure and behavior of the universe are dominated by

What is the range of the electromagnetic force (the maximum distance over which it acts)?

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

What is the range of the strong nuclear force compared with the size of a large atomic nucleus, 10^-14 m?