Question 1

What is the temperature of the blackbody radiation that Earth receives from the Big Bang (the cosmic microwave background radiation)?

Accepted Answer

A)  30 K 
B)  30 billion K 
C)  3 K 
D)  3000 K 
A)  30 K 
B)  30 billion K 
C)  3 K 
D)  3000 K

Question 2

The 2003 observation of a very distant galaxy, the light from which passed through a less distant galaxy cluster on its way to Earth, showed an overall blueshift. What is the significance?

Accepted Answer

A)  The observation shows that the most distant galaxies have already started to fall back to the center of the universe (the Big Crunch), and their light experiences a Doppler blueshift. 
B)  The mass density at Earth's location is larger than the mass density in the vicinity of the very distant galaxy, so light experiences a gravitational blueshift as it moves toward Earth. 
C)  The apparent blueshift is not unusual. Most distant galaxies look blue because of the predominance of blue stars in the early universe. 
D)  The gravitational blueshift experienced by the light approaching the cluster (at an earlier time) outweighed the gravitational redshift it experienced (at a later time) while moving away from the cluster. This suggests an outward cosmological acceleration. 
A)  The observation shows that the most distant galaxies have already started to fall back to the center of the universe (the Big Crunch), and their light experiences a Doppler blueshift. 
B)  The mass density at Earth's location is larger than the mass density in the vicinity of the very distant galaxy, so light experiences a gravitational blueshift as it moves toward Earth. 
C)  The apparent blueshift is not unusual. Most distant galaxies look blue because of the predominance of blue stars in the early universe. 
D)  The gravitational blueshift experienced by the light approaching the cluster (at an earlier time) outweighed the gravitational redshift it experienced (at a later time) while moving away from the cluster. This suggests an outward cosmological acceleration.

Question 3

When Hubble first calculated the recessional speeds of galaxies in the 1920s, he used

Accepted Answer

A)  the Doppler shift relationship. This was an error, and the calculations had to be repeated using the cosmological redshift relationship. 
B)  the Doppler shift relationship. This was an error, and the calculations had to be repeated using the gravitational redshift relationship. 
C)  the Doppler shift relationship. This was correct because the nonrelativistic cosmological redshift relationship gives the same result. 
D)  the cosmological redshift relationship. This was an error, and the calculations had to be repeated using the Doppler shift relationship. 
A)  the Doppler shift relationship. This was an error, and the calculations had to be repeated using the cosmological redshift relationship. 
B)  the Doppler shift relationship. This was an error, and the calculations had to be repeated using the gravitational redshift relationship. 
C)  the Doppler shift relationship. This was correct because the nonrelativistic cosmological redshift relationship gives the same result. 
D)  the cosmological redshift relationship. This was an error, and the calculations had to be repeated using the Doppler shift relationship.

Question 4

The four physical forces at work in the universe are gravitational, electromagnetic, strong nuclear, and weak nuclear forces. Which two of these are very short-ranged, extending over distances of only about 10-15 m?

Accepted Answer

A)  strong nuclear and electromagnetic forces 
B)  electromagnetic and weak nuclear forces 
C)  strong and weak nuclear forces 
D)  gravitational and electromagnetic forces 
A)  strong nuclear and electromagnetic forces 
B)  electromagnetic and weak nuclear forces 
C)  strong and weak nuclear forces 
D)  gravitational and electromagnetic forces

Question 5

If space were flat and there were no "dark energy," what would be the future of the universe?

Accepted Answer

A)  The universe would expand forever, but only barely; if it had any more matter in it than it does, it would eventually stop expanding and start to collapse. 
B)  The universe would expand to a maximum size and then collapse into a Big Crunch. 
C)  The future of the universe is not related to the geometry of space. 
D)  The universe would have more than enough energy to expand forever, not stopping even when infinite time has elapsed. 
A)  The universe would expand forever, but only barely; if it had any more matter in it than it does, it would eventually stop expanding and start to collapse. 
B)  The universe would expand to a maximum size and then collapse into a Big Crunch. 
C)  The future of the universe is not related to the geometry of space. 
D)  The universe would have more than enough energy to expand forever, not stopping even when infinite time has elapsed.

Question 6

Which of these accurately characterizes the current understanding of the expansion of the universe?

Accepted Answer

A)  The universe is expanding too slowly to overcome its mutual gravitational attraction, and thus it will eventually stop expanding and eventually collapse. 
B)  The universe is expanding at exactly its escape speed. Thus it will continue to slow forever and stop at an infinite time in the future. 
C)  The universe is expanding at a rate greater than its escape speed. Although the expansion is slowing down, it will continue to expand forever without ever stopping. 
D)  None of these are correct. 
A)  The universe is expanding too slowly to overcome its mutual gravitational attraction, and thus it will eventually stop expanding and eventually collapse. 
B)  The universe is expanding at exactly its escape speed. Thus it will continue to slow forever and stop at an infinite time in the future. 
C)  The universe is expanding at a rate greater than its escape speed. Although the expansion is slowing down, it will continue to expand forever without ever stopping. 
D)  None of these are correct.

Question 7

The fact that matter exists today is evidence that matter particles outnumber antimatter particles in the universe. This imbalance was caused by

Accepted Answer

A)  matter inflation. 
B)  symmetry breaking. 
C)  chirality. 
D)  the cosmic overshift. 
A)  matter inflation. 
B)  symmetry breaking. 
C)  chirality. 
D)  the cosmic overshift.

Question 8

What would the age of the universe be if the Hubble constant, H0, is 90 km/s/Mpc?

Accepted Answer

A)  17 billion years 
B)  11 billion years 
C)  15 billion years 
D)  9 billion years 
A)  17 billion years 
B)  11 billion years 
C)  15 billion years 
D)  9 billion years

Question 9

How many fundamental forces are there in nature at the present time under normal conditions?

Accepted Answer

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 
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

Question 10

What method is being used to discover whether this is an unbounded universe, in which expansion will continue forever, or a bounded universe, in which expansion will eventually turn into contraction and lead to recollapse?

Accepted Answer

A)  careful monitoring of the Moon-Earth distance to detect the slowdown of the expansion of the universe 
B)  measurement of the deviation from uniformity of the cosmic background radiation 
C)  measurement of the brightnesses of distant supernovae 
D)  measurement of the bending of light by distant galaxies as it follows the curvature of space 
A)  careful monitoring of the Moon-Earth distance to detect the slowdown of the expansion of the universe 
B)  measurement of the deviation from uniformity of the cosmic background radiation 
C)  measurement of the brightnesses of distant supernovae 
D)  measurement of the bending of light by distant galaxies as it follows the curvature of space

Question 11

What was the temperature of the universe at the time the universe became transparent to radiation?

Accepted Answer

A)  300,000 K 
B)  30 billion K 
C)  3 K 
D)  3000 K 
A)  300,000 K 
B)  30 billion K 
C)  3 K 
D)  3000 K

Question 12

When did the universe cool to a temperature of 3 K?

Accepted Answer

A)  1 second after the start of the Big Bang, when pair production ceased 
B)  380,000 years after the Big Bang, when the universe became transparent to radiation 
C)  3 minutes after the start of the Big Bang, when primordial nuclear reactions ceased 
D)  very recently 
A)  1 second after the start of the Big Bang, when pair production ceased 
B)  380,000 years after the Big Bang, when the universe became transparent to radiation 
C)  3 minutes after the start of the Big Bang, when primordial nuclear reactions ceased 
D)  very recently

Question 13

Two light beams that are initially parallel to each other will eventually converge in what kind of universe?

Accepted Answer

A)  flat only 
B)  hyperbolic only 
C)  either flat or hyperbolic 
D)  closed 
A)  flat only 
B)  hyperbolic only 
C)  either flat or hyperbolic 
D)  closed

Question 14

How do physicists know that the fundamental forces become unified as the energy of particle interactions increases?

Accepted Answer

A)  The theory that says that they do is a very elegant one, and it would be nice if it were right. 
B)  Experiments have actually been done with high-energy particle accelerators where all four forces have been unified. 
C)  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)  Physicists have actually seen the start of the unification in high-energy particle accelerators, where the electromagnetic and weak forces become unified. 
A)  The theory that says that they do is a very elegant one, and it would be nice if it were right. 
B)  Experiments have actually been done with high-energy particle accelerators where all four forces have been unified. 
C)  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)  Physicists have actually seen the start of the unification in high-energy particle accelerators, where the electromagnetic and weak forces become unified.

Question 15

Which of these is NOT predicted by superstring theories?

Accepted Answer

A)  The universe cannot have a negative curvature. 
B)  Spacetime may not be entirely smooth. 
C)  Dark matter may include particles predicted by string theory. 
D)  The basic theory of the universe, of which string theories are a modification, is general relativity. 
A)  The universe cannot have a negative curvature. 
B)  Spacetime may not be entirely smooth. 
C)  Dark matter may include particles predicted by string theory. 
D)  The basic theory of the universe, of which string theories are a modification, is general relativity.

Question 16

How did cosmic inflation affect the geometry of the universe?

Accepted Answer

A)  Inflation made the expansion rate so large that the gravity of normal matter was not enough to slow it down, even today. Thus the universe still has a hyperbolic geometry. 
B)  By expanding it so much, inflation spread out the matter so much that the geometry became hyperbolic. 
C)  By expanding it so much, inflation forced the universe to be flat. 
D)  Inflation did not affect the geometry of the universe. 
A)  Inflation made the expansion rate so large that the gravity of normal matter was not enough to slow it down, even today. Thus the universe still has a hyperbolic geometry. 
B)  By expanding it so much, inflation spread out the matter so much that the geometry became hyperbolic. 
C)  By expanding it so much, inflation forced the universe to be flat. 
D)  Inflation did not affect the geometry of the universe.

Question 17

Does the initial rate of star formation have any effect on the type of galaxy that is formed from a pregalactic gas cloud?

Accepted Answer

A)  No. The initial rate of star formation determines the size of the galaxy. A high initial rate of star formation means that many stars have formed a large galaxy before the remaining gas and dust dissipate and star formation ceases. But a galaxy of any type is equally likely to form. 
B)  Yes. A high initial rate of star formation uses up the gas and dust before it has a chance to settle into a disk. This results in an elliptical galaxy. 
C)  Yes. A high initial rate of star formation produces an early generation of stars that evolve and send out more gas and dust to form a disk and to perpetuate star formation. So, this results in a spiral galaxy. 
D)  Yes. An initially high rate of star formation produces many high-mass stars that explode and send out shock waves to trigger the formation of other stars. This chaotic situation results in an irregular galaxy. 
A)  No. The initial rate of star formation determines the size of the galaxy. A high initial rate of star formation means that many stars have formed a large galaxy before the remaining gas and dust dissipate and star formation ceases. But a galaxy of any type is equally likely to form. 
B)  Yes. A high initial rate of star formation uses up the gas and dust before it has a chance to settle into a disk. This results in an elliptical galaxy. 
C)  Yes. A high initial rate of star formation produces an early generation of stars that evolve and send out more gas and dust to form a disk and to perpetuate star formation. So, this results in a spiral galaxy. 
D)  Yes. An initially high rate of star formation produces many high-mass stars that explode and send out shock waves to trigger the formation of other stars. This chaotic situation results in an irregular galaxy.

Question 18

Who first proposed that the observed motion of galaxies away from Earth originated as an expansion outward from an extremely dense state of matter at the beginning of the universe?

Accepted Answer

A)  Edwin Hubble 
B)  George Gamow 
C)  Fred Hoyle 
D)  Georges Lemaître 
A)  Edwin Hubble 
B)  George Gamow 
C)  Fred Hoyle 
D)  Georges Lemaître

Question 19

What do astronomers mean when they say that the universe is homogeneous?

Accepted Answer

A)  The number of galaxies, averaged over large scales, is the same at any distance from Earth. 
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. 
A)  The number of galaxies, averaged over large scales, is the same at any distance from Earth. 
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.

Question 20

If the geometry of space is hyperbolic, what is the future of the universe?

Accepted Answer

A)  The universe will expand to a maximum size and then collapse into a Big Crunch. 
B)  The universe will expand forever, but only barely; if it has any more matter in it than it does, it will eventually stop expanding and start to collapse. 
C)  The future of the universe is not related to the geometry of space. 
D)  The universe will expand forever. 
A)  The universe will expand to a maximum size and then collapse into a Big Crunch. 
B)  The universe will expand forever, but only barely; if it has any more matter in it than it does, it will eventually stop expanding and start to collapse. 
C)  The future of the universe is not related to the geometry of space. 
D)  The universe will expand forever.

What is the temperature of the blackbody radiation that Earth receives from the Big Bang (the cosmic microwave background radiation)?

The 2003 observation of a very distant galaxy, the light from which passed through a less distant galaxy cluster on its way to Earth, showed an overall blueshift. What is the significance?

When Hubble first calculated the recessional speeds of galaxies in the 1920s, he used

The four physical forces at work in the universe are gravitational, electromagnetic, strong nuclear, and weak nuclear forces. Which two of these are very short-ranged, extending over distances of only about 10^-15 m?

If space were flat and there were no "dark energy," what would be the future of the universe?

Which of these accurately characterizes the current understanding of the expansion of the universe?

The fact that matter exists today is evidence that matter particles outnumber antimatter particles in the universe. This imbalance was caused by

What would the age of the universe be if the Hubble constant, H₀, is 90 km/s/Mpc?

How many fundamental forces are there in nature at the present time under normal conditions?

What method is being used to discover whether this is an unbounded universe, in which expansion will continue forever, or a bounded universe, in which expansion will eventually turn into contraction and lead to recollapse?

What was the temperature of the universe at the time the universe became transparent to radiation?

When did the universe cool to a temperature of 3 K?

Two light beams that are initially parallel to each other will eventually converge in what kind of universe?

How do physicists know that the fundamental forces become unified as the energy of particle interactions increases?

Which of these is NOT predicted by superstring theories?

How did cosmic inflation affect the geometry of the universe?

Does the initial rate of star formation have any effect on the type of galaxy that is formed from a pregalactic gas cloud?

Who first proposed that the observed motion of galaxies away from Earth originated as an expansion outward from an extremely dense state of matter at the beginning of the universe?

What do astronomers mean when they say that the universe is homogeneous?

If the geometry of space is hyperbolic, what is the future 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 temperature of the blackbody radiation that Earth receives from the Big Bang (the cosmic microwave background radiation)?

The 2003 observation of a very distant galaxy, the light from which passed through a less distant galaxy cluster on its way to Earth, showed an overall blueshift. What is the significance?

When Hubble first calculated the recessional speeds of galaxies in the 1920s, he used

The four physical forces at work in the universe are gravitational, electromagnetic, strong nuclear, and weak nuclear forces. Which two of these are very short-ranged, extending over distances of only about 10-15 m?

If space were flat and there were no "dark energy," what would be the future of the universe?

Which of these accurately characterizes the current understanding of the expansion of the universe?

The fact that matter exists today is evidence that matter particles outnumber antimatter particles in the universe. This imbalance was caused by

What would the age of the universe be if the Hubble constant, H0, is 90 km/s/Mpc?

How many fundamental forces are there in nature at the present time under normal conditions?

What method is being used to discover whether this is an unbounded universe, in which expansion will continue forever, or a bounded universe, in which expansion will eventually turn into contraction and lead to recollapse?

What was the temperature of the universe at the time the universe became transparent to radiation?

When did the universe cool to a temperature of 3 K?

Two light beams that are initially parallel to each other will eventually converge in what kind of universe?

How do physicists know that the fundamental forces become unified as the energy of particle interactions increases?

Which of these is NOT predicted by superstring theories?

How did cosmic inflation affect the geometry of the universe?

Does the initial rate of star formation have any effect on the type of galaxy that is formed from a pregalactic gas cloud?

Who first proposed that the observed motion of galaxies away from Earth originated as an expansion outward from an extremely dense state of matter at the beginning of the universe?

What do astronomers mean when they say that the universe is homogeneous?

If the geometry of space is hyperbolic, what is the future 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

The four physical forces at work in the universe are gravitational, electromagnetic, strong nuclear, and weak nuclear forces. Which two of these are very short-ranged, extending over distances of only about 10^-15 m?

What would the age of the universe be if the Hubble constant, H₀, is 90 km/s/Mpc?