Question 1

Why does Olbers's paradox suggest that the night sky should be light instead of dark?

Accepted Answer

The answer of Why does Olbers's paradox suggest that the...

Question 2

The era of combination occurred about 3 minutes after the Big Bang,and the era of recombination occurred about 3000 years after the Big Bang.

Accepted Answer

A) True 
 B)False

Question 3

How do we know that matter in the early universe was extremely smooth (i.e. ,not really lumpy)?

Accepted Answer

A)  Because the cosmic background radiation is almost completely isotropic 
B)  Because,at the present time,galaxies are spread almost completely uniformly through the universe 
C)  Because quasars are spread almost completely uniformly around the sky 
D)  Because the expansion of the universe is almost completely isotropic

Question 4

Strong evidence for an original Big Bang,which "created" our universe,comes from

Accepted Answer

A)  the very high flux of 21-cm radio energy,coming from the atomic hydrogen atoms produced in the explosion. 
B)  the rapid motions of some nearby stars,such as Barnard's star. 
C)  the amount of gas and dust in the solar neighborhood. 
D)  a background "glow" of microwaves,with blackbody temperature of about 3 K.

Question 5

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 hydrogen gas instead of roaming freely through space.What major transition occurred as a consequence of this change in the universe at this time?

Accepted Answer

A)  The universe would have lost its electrical charge suddenly to become electrically neutral. 
B)  The present laws of physics were applicable to the properties of the universe for the first time. 
C)  The universe became transparent to light for the first time. 
D)  Nuclear fusion no longer occurred below this temperature,so general fusion throughout the universe would have ceased.

Question 6

The four physical forces at work in the universe are gravitation,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)  Strong and weak nuclear forces 
C)  Gravitation and electromagnetic forces 
D)  Electromagnetic and weak nuclear forces

Question 7

After carefully removing all potential sources of electronic "noise," including bird droppings inside the microwave horn antenna,Penzias and Wilson realized that they were actually detecting radiation from space.

Accepted Answer

A) True 
 B)False

Question 8

The wavelengths of light from very distant galaxies are shifted to the blue part of the spectrum,indicating that the universe is contracting.

Accepted Answer

A) True 
 B)False

Question 9

Opposite sides of the universe have the same temperature,yet according to the standard Big Bang theory,these points are too far apart for light to have traveled from one side to the other in the age of the universe;that is,they cannot have exchanged heat to even out their temperature.Why,then,do they have the same temperature?

Accepted Answer

A)  Light (and heat)could travel much faster in the early universe,allowing them to exchange heat while the universe was young. 
B)  The expansion of the universe has always been the same everywhere;therefore,all parts of the universe have the same temperature,regardless of whether they have ever exchanged heat or not. 
C)  Pure coincidence 
D)  They were originally close together and evened out their temperature,then a rapid inflation of the universe carried them far apart.

Question 10

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

Accepted Answer

A)  All of the fundamental forces of nature were unified into one force. 
B)  It was a sea of gradually decreasing nuclear reactions. 
C)  It was filled with free quarks (not confined inside neutrons or protons). 
D)  It was opaque to radiation.

Question 11

Immediately after the cosmological singularity,the four forces were indistinguishable.Then they began to "branch off" and become separate.Which was the first of the four to branch off?

Accepted Answer

A)  Gravitation 
B)  The weak force 
C)  The strong force 
D)  Electromagnetism

Question 12

How is the Hubble constant measured?

Accepted Answer

The answer of How is the Hubble constant measured?...

Question 13

Describe how the universe changed in the first second after the Big Bang.

Accepted Answer

The answer of Describe how the universe changed in the...

Question 14

The two fundamental forces that act over infinite distances are

Accepted Answer

A)  gravity and the electromagnetic force. 
B)  the weak and strong nuclear forces. 
C)  the electromagnetic force and the weak nuclear force. 
D)  the strong nuclear force and gravity.

Question 15

If space has an open geometry what will happen to two initially parallel flashlight beams as they traverse billions of light-years of space?

Accepted Answer

A)  They will remain parallel. 
B)  They will gradually diverge (move apart)to a maximum separation,and then gradually converge and cross. 
C)  They will gradually converge (move together)and eventually cross. 
D)  They will gradually diverge (move apart).

Question 16

In which order did the fundamental forces of nature "freeze out" of the initial phase of the Big Bang at the beginning of the universe?

Accepted Answer

A)  Weak,strong,gravity 
B)  Gravity,weak,strong 
C)  Gravity,strong,weak 
D)  Strong,gravity,weak

Question 17

The resolution of Olber's paradox (i.e. ,the reason why the sky is dark at night)is that

Accepted Answer

A)  we cannot see those stars that are farther away from us than the distance that light has traveled since the beginning of the universe. 
B)  matter cannot have traveled farther than light has traveled during the age of the universe,so there are no stars beyond a certain distance from us. 
C)  the light from very distant stars is bent out of our line of sight by the gravitational fields of nearby galaxies. 
D)  the light from stars beyond a certain,very large distance is completely absorbed by matter between us and the star.

Question 18

The theory of everything (TOE)would provide one equation to describe all of the processes in the universe,and there would be no differences among the gravitational,electromagnetic,and strong and weak nuclear forces.

Accepted Answer

A) True 
 B)False

Question 19

In our description of the universe,what does the word "isotropic" mean?

Accepted Answer

A)  The expansion is the same in all directions. 
B)  The speed of expansion is the same at all distances. 
C)  The speed of expansion at any given distance is the same at all times. 
D)  The universe is the same everywhere,neither expanding nor contracting.

Question 20

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

Accepted Answer

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

Exam 15: Observing the Evolution of the Universe

Why does Olbers's paradox suggest that the night sky should be light instead of dark?

The era of combination occurred about 3 minutes after the Big Bang,and the era of recombination occurred about 3000 years after the Big Bang.

How do we know that matter in the early universe was extremely smooth (i.e. ,not really lumpy) ?

Strong evidence for an original Big Bang,which "created" our universe,comes from

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 hydrogen gas instead of roaming freely through space.What major transition occurred as a consequence of this change in the universe at this time?

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

After carefully removing all potential sources of electronic "noise," including bird droppings inside the microwave horn antenna,Penzias and Wilson realized that they were actually detecting radiation from space.

The wavelengths of light from very distant galaxies are shifted to the blue part of the spectrum,indicating that the universe is contracting.

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

Immediately after the cosmological singularity,the four forces were indistinguishable.Then they began to "branch off" and become separate.Which was the first of the four to branch off?

How is the Hubble constant measured?

Describe how the universe changed in the first second after the Big Bang.

The two fundamental forces that act over infinite distances are

If space has an open geometry what will happen to two initially parallel flashlight beams as they traverse billions of light-years of space?

In which order did the fundamental forces of nature "freeze out" of the initial phase of the Big Bang at the beginning of the universe?

The resolution of Olber's paradox (i.e. ,the reason why the sky is dark at night) is that

The theory of everything (TOE)would provide one equation to describe all of the processes in the universe,and there would be no differences among the gravitational,electromagnetic,and strong and weak nuclear forces.

In our description of the universe,what does the word "isotropic" mean?

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