Question 1

In the present universe, the "mass density" of radiation, using Einstein's equation E = mc2 for the photons, is

Accepted Answer

A)  essentially zero since there is very little radiation left in the universe at the present time. 
B)  much greater than the mass density of matter leading to a radiation-dominated universe. 
C)  equal to the mass density of matter, since these parameters have remained balanced throughout the evolution of the universe as a consequence of the equipartition of energy. 
D)  much less than the mass density of matter, leading to a matter-dominated universe. 
A)  essentially zero since there is very little radiation left in the universe at the present time. 
B)  much greater than the mass density of matter leading to a radiation-dominated universe. 
C)  equal to the mass density of matter, since these parameters have remained balanced throughout the evolution of the universe as a consequence of the equipartition of energy. 
D)  much less than the mass density of matter, leading to a matter-dominated universe.

Question 2

Physicists speculate that, early in its history, the universe shifted from a "false vacuum" state to a "true vacuum" state. What is the significance of this transition?

Accepted Answer

A)  The "false vacuum" describes the state of the universe before the Planck time, 10-43 s. During this time the laws of physics as are currently understood did not apply. 
B)  The transition was from a high-energy state to a low-energy state. The transition caused the inflationary epoch. 
C)  The transition was one from a low-energy state to a high-energy state. The consequent intake of energy caused the universe at the end of the inflationary epoch to be much cooler than it had been at the beginning of the inflationary epoch. 
D)  In its transition to the true vacuum, the universe became trapped in a state of minimum energy, unable to expand or contract. 
A)  The "false vacuum" describes the state of the universe before the Planck time, 10-43 s. During this time the laws of physics as are currently understood did not apply. 
B)  The transition was from a high-energy state to a low-energy state. The transition caused the inflationary epoch. 
C)  The transition was one from a low-energy state to a high-energy state. The consequent intake of energy caused the universe at the end of the inflationary epoch to be much cooler than it had been at the beginning of the inflationary epoch. 
D)  In its transition to the true vacuum, the universe became trapped in a state of minimum energy, unable to expand or contract.

Question 3

Suppose new experimental evidence were to point to a Hubble constant value of H0 = 50 km/s/Mpc. A calculation of the age of the universe using this value would give

Accepted Answer

A)  the same value now calculated, namely 13.4 billion years. 
B)  an age younger than 13.4 billion years. 
C)  an age older than 13.4 billion years. 
D)  a different value of the age, but more information is needed to estimate what it would be. 
A)  the same value now calculated, namely 13.4 billion years. 
B)  an age younger than 13.4 billion years. 
C)  an age older than 13.4 billion years. 
D)  a different value of the age, but more information is needed to estimate what it would be.

Question 4

Suppose an object is at rest and that it is emitting radiation. An observer at rest with respect to the object observes the radiation to be blueshifted from its original frequency. This blueshift can be caused by

Accepted Answer

A)  the Doppler shift only. 
B)  the gravitational wavelength shift only. 
C)  the cosmological wavelength shift only. 
D)  either the gravitational or the cosmological wavelength shift 
A)  the Doppler shift only. 
B)  the gravitational wavelength shift only. 
C)  the cosmological wavelength shift only. 
D)  either the gravitational or the cosmological wavelength shift

Question 5

Astronomers detect the slight anisotropy in the cosmic microwave background by making redshift measurements: wavelengths coming from the direction of Aquarius are slightly longer and those from the direction of Leo are slightly shorter. This redshift is a

Accepted Answer

A)  Doppler shift. 
B)  gravitational redshift. 
C)  cosmological redshift. 
D)  Doppler shift, gravitational redshift, or cosmological redshift since all three are one and the same thing. 
A)  Doppler shift. 
B)  gravitational redshift. 
C)  cosmological redshift. 
D)  Doppler shift, gravitational redshift, or cosmological redshift since all three are one and the same thing.

Question 6

Which of these statements correctly describes the universe for the entire first 380,000 years of its life?

Accepted Answer

A)  The universe was filled with free quarks (not confined inside neutrons or protons). 
B)  All the fundamental forces of nature were unified into one force. 
C)  The universe was filled with a sea of nuclear particles undergoing violent reactions. 
D)  The universe was opaque. 
A)  The universe was filled with free quarks (not confined inside neutrons or protons). 
B)  All the fundamental forces of nature were unified into one force. 
C)  The universe was filled with a sea of nuclear particles undergoing violent reactions. 
D)  The universe was opaque.

Question 7

When the isotropy of the cosmic microwave radiation was first realized, what effect did this discovery have on the contemporary theories of cosmology?

Accepted Answer

A)  The discovery was a great support for the Big Bang cosmology that predicts this isotropy. 
B)  The discovery was a great support for the steady-state cosmology that predicts this isotropy. 
C)  The discovery was a great problem because it was prohibited by all the main cosmologies. 
D)  The discovery was a puzzle because the Big Bang cosmology does not predict this isotropy, although it does not prohibit it either. 
A)  The discovery was a great support for the Big Bang cosmology that predicts this isotropy. 
B)  The discovery was a great support for the steady-state cosmology that predicts this isotropy. 
C)  The discovery was a great problem because it was prohibited by all the main cosmologies. 
D)  The discovery was a puzzle because the Big Bang cosmology does not predict this isotropy, although it does not prohibit it either.

Question 8

Cosmologists presently consider the universe to be matter dominated. In this stage the number of photons

Accepted Answer

A)  vastly outnumbers the number of particles. 
B)  is vastly outnumbered by the number of particles. 
C)  is greatly outnumbered by the number of particles, but is less than the number of particles plus antiparticles. 
D)  is close to being equal to the number of particles. 
A)  vastly outnumbers the number of particles. 
B)  is vastly outnumbered by the number of particles. 
C)  is greatly outnumbered by the number of particles, but is less than the number of particles plus antiparticles. 
D)  is close to being equal to the number of particles.

Question 9

Within which time frame from the initial Big Bang do cosmologists believe all four fundamental forces of nature were united into a single force?

Accepted Answer

A)  t = 0 to 106 years, when radiation dominated the universe 
B)  t = 0 to 1 s, when photons interchanged freely with electron-positron pairs 
C)  t = 0 to 10-35 s, when the strong nuclear force "froze out" of the universe 
D)  t = 0 to 10-43 s, the Planck time, when gravity "froze out" of the universe 
A)  t = 0 to 106 years, when radiation dominated the universe 
B)  t = 0 to 1 s, when photons interchanged freely with electron-positron pairs 
C)  t = 0 to 10-35 s, when the strong nuclear force "froze out" of the universe 
D)  t = 0 to 10-43 s, the Planck time, when gravity "froze out" of the universe

Question 10

The physical force that controls the structure of the nucleus and binds together protons and neutrons is the

Accepted Answer

A)  gravitational force. 
B)  weak nuclear force. 
C)  electromagnetic force. 
D)  strong nuclear force. 
A)  gravitational force. 
B)  weak nuclear force. 
C)  electromagnetic force. 
D)  strong nuclear force.

Question 11

Astronomers can determine the amount of mass in a cluster of galaxies by observing its gravitational interactions. How much of this mass is luminous matter?

Accepted Answer

A)  1-2% 
B)  10-20% 
C)  50% 
D)  80-90% 
A)  1-2% 
B)  10-20% 
C)  50% 
D)  80-90%

Question 12

Because of the general expansion of space, all distant galaxies appear to be moving away from Earth, with speeds that increase with distance from the Milky Way Galaxy. What would an observer in one of these distant galaxies see?

Accepted Answer

A)  same thing as seen from Earth: all galaxies moving away, with more distant galaxies moving faster 
B)  all galaxies moving nearer, with more distant galaxies moving faster 
C)  all galaxies moving away, with closer galaxies moving faster 
D)  all galaxies on one side of the sky moving nearer and all galaxies on the other side moving away, with more distant galaxies moving faster 
A)  same thing as seen from Earth: all galaxies moving away, with more distant galaxies moving faster 
B)  all galaxies moving nearer, with more distant galaxies moving faster 
C)  all galaxies moving away, with closer galaxies moving faster 
D)  all galaxies on one side of the sky moving nearer and all galaxies on the other side moving away, with more distant galaxies moving faster

Question 13

At an age of 380,000 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?

Accepted Answer

A)  The present laws of physics began to apply for the first time. 
B)  The universe suddenly lost its electrical charge and became neutral. 
C)  Nuclear fusion no longer occurred below this temperature. 
D)  The universe became transparent to light for the first time. 
A)  The present laws of physics began to apply for the first time. 
B)  The universe suddenly lost its electrical charge and became neutral. 
C)  Nuclear fusion no longer occurred below this temperature. 
D)  The universe became transparent to light for the first time.

Question 14

What do superstring theories try to explain?

Accepted Answer

A)  forces holding superclusters of galaxies together 
B)  apparent acceleration of the expansion of the universe 
C)  behavior of matter during the Planck time when all four fundamental forces were unified 
D)  behavior of matter during the inflationary epoch 
A)  forces holding superclusters of galaxies together 
B)  apparent acceleration of the expansion of the universe 
C)  behavior of matter during the Planck time when all four fundamental forces were unified 
D)  behavior of matter during the inflationary epoch

Question 15

How does the universe behave, according to the steady-state theory?

Accepted Answer

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, 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. 
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, 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.

Question 16

Measurement of structure in the cosmic microwave background radiation has recently indicated that the universe is flat (on the cusp between a closed and an open universe), but the measured density of detected matter and radiation is only 20-40% of the critical density required for a flat universe. In what form is the other 60-80% of the "matter" thought to be?

Accepted Answer

A)  myriads of small primordial black holes whose gravitational effects are spread throughout the universe and which emit no radiation 
B)  dark energy emitting no visible radiation 
C)  antimatter, which generates a negative gravitational effect and emits radiation only if it meets matter and is annihilated 
D)  neutrinos, which have very little rest mass and are very difficult to detect, but are very abundant 
A)  myriads of small primordial black holes whose gravitational effects are spread throughout the universe and which emit no radiation 
B)  dark energy emitting no visible radiation 
C)  antimatter, which generates a negative gravitational effect and emits radiation only if it meets matter and is annihilated 
D)  neutrinos, which have very little rest mass and are very difficult to detect, but are very abundant

Question 17

In what way does the study of the collisions of very high-speed nuclear particles with other matter at particle accelerator laboratories help in the understanding of the early universe?

Accepted Answer

A)  The temperature of the early universe was so high that mutual collisions of particles occurred at energies equivalent to those in nuclear particle accelerators. 
B)  Nuclear accelerators generate enormous quantities of microwaves similar to those that existed in the early universe, thus allowing the study of the interaction of microwaves with matter. 
C)  Motions of particles in circular orbits around the original black hole produced by the Big Bang were similar to the particle motions in an accelerator. 
D)  Collisions in nuclear accelerator laboratories produce large numbers of neutrinos and hence mimic the conditions that were thought to exist in the early universe, where neutrinos occupied most of the space. 
A)  The temperature of the early universe was so high that mutual collisions of particles occurred at energies equivalent to those in nuclear particle accelerators. 
B)  Nuclear accelerators generate enormous quantities of microwaves similar to those that existed in the early universe, thus allowing the study of the interaction of microwaves with matter. 
C)  Motions of particles in circular orbits around the original black hole produced by the Big Bang were similar to the particle motions in an accelerator. 
D)  Collisions in nuclear accelerator laboratories produce large numbers of neutrinos and hence mimic the conditions that were thought to exist in the early universe, where neutrinos occupied most of the space.

Question 18

The cosmological redshift in the light from distant galaxies is explained by which of these effects?

Accepted Answer

A)  A photon's wavelength is a distance and is therefore lengthened by the general expansion of the universe, making the light appear reddened. 
B)  The light observed on Earth was Doppler-shifted to longer wavelengths by the motion of the objects (e.g., galaxies) away from Earth. 
C)  The light spreads out over larger areas as distance increases according to 1/(distance)2, which causes the wavelength to increase in proportion to distance. 
D)  The light from more distant galaxies has traveled through the gravitational fields of more galaxies in getting to Earth and is therefore more gravitationally redshifted. 
A)  A photon's wavelength is a distance and is therefore lengthened by the general expansion of the universe, making the light appear reddened. 
B)  The light observed on Earth was Doppler-shifted to longer wavelengths by the motion of the objects (e.g., galaxies) away from Earth. 
C)  The light spreads out over larger areas as distance increases according to 1/(distance)2, which causes the wavelength to increase in proportion to distance. 
D)  The light from more distant galaxies has traveled through the gravitational fields of more galaxies in getting to Earth and is therefore more gravitationally redshifted.

Question 19

A star with no elements heavier than lithium is referred to as

Accepted Answer

A)  Population 0. 
B)  Population I. 
C)  Population II. 
D)  Population III. 
A)  Population 0. 
B)  Population I. 
C)  Population II. 
D)  Population III.

Question 20

The first 10-43 seconds of the universe's existence are called the Planck era. The kind of physics needed to describe that era is

Accepted Answer

A)  Newtonian physics. 
B)  general relativity. 
C)  quantum physics. 
D)  presently unknown. 
A)  Newtonian physics. 
B)  general relativity. 
C)  quantum physics. 
D)  presently unknown.

In the present universe, the "mass density" of radiation, using Einstein's equation E = mc² for the photons, is

Physicists speculate that, early in its history, the universe shifted from a "false vacuum" state to a "true vacuum" state. What is the significance of this transition?

Suppose new experimental evidence were to point to a Hubble constant value of H₀ = 50 km/s/Mpc. A calculation of the age of the universe using this value would give

Suppose an object is at rest and that it is emitting radiation. An observer at rest with respect to the object observes the radiation to be blueshifted from its original frequency. This blueshift can be caused by

Astronomers detect the slight anisotropy in the cosmic microwave background by making redshift measurements: wavelengths coming from the direction of Aquarius are slightly longer and those from the direction of Leo are slightly shorter. This redshift is a

Which of these statements correctly describes the universe for the entire first 380,000 years of its life?

When the isotropy of the cosmic microwave radiation was first realized, what effect did this discovery have on the contemporary theories of cosmology?

Cosmologists presently consider the universe to be matter dominated. In this stage the number of photons

Within which time frame from the initial Big Bang do cosmologists believe all four fundamental forces of nature were united into a single force?

The physical force that controls the structure of the nucleus and binds together protons and neutrons is the

Astronomers can determine the amount of mass in a cluster of galaxies by observing its gravitational interactions. How much of this mass is luminous matter?

Because of the general expansion of space, all distant galaxies appear to be moving away from Earth, with speeds that increase with distance from the Milky Way Galaxy. What would an observer in one of these distant galaxies see?

At an age of 380,000 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?

What do superstring theories try to explain?

How does the universe behave, according to the steady-state theory?

In what way does the study of the collisions of very high-speed nuclear particles with other matter at particle accelerator laboratories help in the understanding of the early universe?

The cosmological redshift in the light from distant galaxies is explained by which of these effects?

A star with no elements heavier than lithium is referred to as

The first 10^-43 seconds of the universe's existence are called the Planck era. The kind of physics needed to describe that era is

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

In the present universe, the "mass density" of radiation, using Einstein's equation E = mc2 for the photons, is

Physicists speculate that, early in its history, the universe shifted from a "false vacuum" state to a "true vacuum" state. What is the significance of this transition?

Suppose new experimental evidence were to point to a Hubble constant value of H0 = 50 km/s/Mpc. A calculation of the age of the universe using this value would give

Suppose an object is at rest and that it is emitting radiation. An observer at rest with respect to the object observes the radiation to be blueshifted from its original frequency. This blueshift can be caused by

Astronomers detect the slight anisotropy in the cosmic microwave background by making redshift measurements: wavelengths coming from the direction of Aquarius are slightly longer and those from the direction of Leo are slightly shorter. This redshift is a

Which of these statements correctly describes the universe for the entire first 380,000 years of its life?

When the isotropy of the cosmic microwave radiation was first realized, what effect did this discovery have on the contemporary theories of cosmology?

Cosmologists presently consider the universe to be matter dominated. In this stage the number of photons

Within which time frame from the initial Big Bang do cosmologists believe all four fundamental forces of nature were united into a single force?

The physical force that controls the structure of the nucleus and binds together protons and neutrons is the

Astronomers can determine the amount of mass in a cluster of galaxies by observing its gravitational interactions. How much of this mass is luminous matter?

Because of the general expansion of space, all distant galaxies appear to be moving away from Earth, with speeds that increase with distance from the Milky Way Galaxy. What would an observer in one of these distant galaxies see?

At an age of 380,000 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?

What do superstring theories try to explain?

How does the universe behave, according to the steady-state theory?

In what way does the study of the collisions of very high-speed nuclear particles with other matter at particle accelerator laboratories help in the understanding of the early universe?

The cosmological redshift in the light from distant galaxies is explained by which of these effects?

A star with no elements heavier than lithium is referred to as

The first 10-43 seconds of the universe's existence are called the Planck era. The kind of physics needed to describe that era is

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

In the present universe, the "mass density" of radiation, using Einstein's equation E = mc² for the photons, is

Suppose new experimental evidence were to point to a Hubble constant value of H₀ = 50 km/s/Mpc. A calculation of the age of the universe using this value would give

The first 10^-43 seconds of the universe's existence are called the Planck era. The kind of physics needed to describe that era is