Chapter 23 Quiz Questions              

KEY

* marks correct answer

1.  Based on our current understanding of physics, it would seem that we can understand the conditions that prevailed in the early universe as far back in time as ______.
 

*a    one ten-billionth of a second after the Big Bang.
b
10 billion years ago.
c
3 minutes after the Big Bang.
d
380,000 years after the Big Bang.



2 .       What happens when a particle of matter meets its corresponding antiparticle of antimatter?

a    They fuse to make a heavier particle.
*b
The combined mass-energy of the two particles is completely transformed into radiation-energy (two photons).
c
They can form a complete atom.
d
The question makes no sense, since antimatter does not really exist.

3 .       What is the significance of the Planck time

*a    Before it, conditions were so extreme that our current understanding of physics is insufficient to predict what might have occurred.
b
It is the time when the cosmic microwave background was released.
c
It is the amount of time required for two protons to fuse to make deuterium.
d
It is the time at which inflation is thought to have occurred.

4 .       The four fundamental forces that operate in the universe today are: 

a    nuclear force, electromagnetic force, gravity, tidal force.
*b
strong force, weak force, electromagnetic force, gravity.
c
nuclear force, gravity, electric force, magnetic force.
d
strong force, weak force, electric force, magnetic force.

5 .       A "GUT" (grand unified theory) refers to theories that ______. 

*a    unify the strong force with the electromagnetic and weak forces.
b
unify the electromagnetic and weak forces.
c
unify all four forces together.
d
unify gravity with the strong and weak forces.


6.       Based on our current understanding of physics, it would seem that we can understand the conditions that prevailed in the early universe as far back in time as ______. 

*a    one ten-billionth of a second after the Big Bang.
b
10 billion years ago.
c
3 minutes after the Big Bang.
d
380,000 years after the Big Bang.

7 .       What happens when a particle of matter meets its corresponding antiparticle of antimatter?

a    They fuse to make a heavier particle.
*b
The combined mass-energy of the two particles is completely transformed into radiation-energy (two photons).
c
They can form a complete atom.
d
The question makes no sense, since antimatter does not really exist.

8 .       What is the significance of the Planck time

*a    Before it, conditions were so extreme that our current understanding of physics is insufficient to predict what might have occurred.
b
It is the time when the cosmic microwave background was released.
c
It is the amount of time required for two protons to fuse to make deuterium.
d
It is the time at which inflation is thought to have occurred.

9.       The four fundamental forces that operate in the universe today are: 

a.
nuclear force, electromagnetic force, gravity, tidal force.
*b.
strong force, weak force, electromagnetic force, gravity.
c.
nuclear force, gravity, electric force, magnetic force.
d.
strong force, weak force, electric force, magnetic force.

10 .       A "GUT" (grand unified theory) refers to theories that ______.

*a.    unify the strong force with the electromagnetic and weak forces.
b.    unify the electromagnetic and weak forces.
c.    unify all four forces together.
d.    unify gravity with the strong and weak forces.

11 .       What do we mean by inflation?

*a.    We mean a sudden and rapid acceleration of the universe that went on for a tiny fraction of a second at the time the strong force froze out from the GUT force.
b.
We mean the sudden release of photons when a particle and antiparticle annihilate one another
c.
We mean quantum fluctuations by high speed, relativistic particles in a state of false vacuum cause disturbances in the space-time continuum leading to the process described in the question to which this answer refers.
d.
We mean the expansion of the universe that we still observe today.


12 .       Which statement about the cosmic microwave background is NOT true? 

a.
It is thought to be radiation that began its journey to our telescopes when the universe was about 380,000 years old.
b.
With the exception of very small variations, it appears essentially the same in all directions in which we look into space.
c.
Its spectrum corresponds to a temperature of just under 3 degrees above absolute zero.
*d.
It is the result of a mixture of radiation from many independent sources, such as stars and galaxies.


13 .       Based on the Big Bang theory, what do observations of the cosmic microwave background and of chemical abundances in the universe suggest about dark matter?

a.
Dark matter probably does not really exist.
b.
Dark matter was produced during the era of nuclei.
*c.
Much of the dark matter must be made of non-ordinary (nonbaryonic) matter, such as WIMPs.
d.
Dark matter must be made of MACHOs.

14 .       Which of the following observations cannot be explained by the Big Bang theory UNLESS we assume that an episode of inflation occurred?

*a.  The fact that the temperature of the cosmic microwave background is almost the same everywhere.
b.
The existence of the cosmic microwave background.
c.
The fact that the universe is expanding.
d.
The fact that about 25% of the ordinary matter in the universe consists of helium.

15 .       The idea of inflation makes one clear prediction that, until quite recently, seemed to contradict the available observations. What is this prediction?

a.
Inflation predicts that the temperature of the cosmic microwave background should be almost (but not exactly) the same everywhere.
b.
Inflation predicts that the early universe should have regions of enhanced density that could have acted as "seeds" for the formation of galaxies and large structures.
c.
Inflation predicts that the entire universe must be far larger than the observable universe.
*d.
The universe should be geometrically "flat" (in the four dimensions of spacetime).


16 .       Olber's Paradox is an apparently simple question, but its resolution suggests that the universe is finite in age. What is the question? 

*a.
Why is the sky dark at night?
b.
What would it be like to ride on a beam of light?
c.
Can we measure the position and momentum of an electron at the same time?
d.
How many stars are in the universe?

17 .       Why can't current theories describe what happened during the Planck era?

a.
We do not know how hot or dense the universe was during that time.
*b.
We do not yet have a theory that links quantum mechanics and general relativity.
c.
We do not understand the properties of antimatter.
d.
The Planck era was the time before the Big Bang, and we cannot describe what happened before that instant.

18 .       When we say that the electroweak and strong forces "freeze out" at 10--35 seconds after the Big Bang, we mean that ______.

a.
these forces are only important at temperatures below the freezing point of water --- a temperature that the universe reached at an age of about 10--35 seconds.
b.
following this time, neither the strong nor electroweak forces are ever important in the universe again.
c.
"freezing out" was a term coined by particle physicists who think that the Big Bang theory is really cool.
*d.
prior to this time, the electroweak and strong forces maintained a single identity, but they possessed separate identities following this time.

19.       According to the Big Bang theory, how many forces -- and which ones --- operated in the universe during the GUT era?

a.
3: gravity, the strong force, and the electroweak force
*b.
2: gravity and a single force that later became the strong, weak, and electromagnetic forces.
c.
1 force that represented the unification of all four forces that operate today.
d.
2: the strong force and the electroweak force


20 .       How do we determine the conditions that existed in the very early universe?

*a.
From the current expansion rate we can work backward to estimate temperature and densities at various times in the early universe.
b.
The conditions in the very early universe must have been much like those found in stars today, so we learn about them by studying stars.
c.
We can only guess at the conditions, since we have no way to calculate or observe what they were.
d.
By looking all the way to the cosmological horizon, we can see the actual conditions that prevailed all the way back to the first instant of the Big Bang.

2 1.       Why can't current theories describe what happened during the Planck era?

a.
We do not know how hot or dense the universe was during that time.
*b.
We do not yet have a theory that links quantum mechanics and general relativity.
c.
We do not understand the properties of antimatter.
d.
The Planck era was the time before the Big Bang, and we cannot describe what happened before that instant.

22.       When we say that the electroweak and strong forces "freeze out" at 10--35 seconds after the Big Bang, we mean that ______.

a.
these forces are only important at temperatures below the freezing point of water --- a temperature that the universe reached at an age of about 10--35 seconds.
b.
following this time, neither the strong nor electroweak forces are ever important in the universe again.
c.
"freezing out" was a term coined by particle physicists who think that the Big Bang theory is really cool.
*d.
prior to this time, the electroweak and strong forces maintained a single identity, but they possessed separate identities following this time.

23 .       According to the Big Bang theory, how many forces -- and which ones --- operated in the universe during the GUT era? 

a.
3: gravity, the strong force, and the electroweak force
*b.
2: gravity and a single force that later became the strong, weak, and electromagnetic forces.
c.
1 force that represented the unification of all four forces that operate today.
d.
2: the strong force and the electroweak force

24 .       Laboratory experiments conducted with particle accelerators confirm predictions made by the theory that unifies ______. 

a.
the strong and weak forces into the combined nuclear force.
b.
the strong, weak, and electromagnetic forces into the GUT force.
c.
the unification of all four forces into a single "superforce."
*d.
the electromagnetic and weak forces into the electroweak force.

25 .       What was the significance of the end of the era of nucleosynthesis, when the universe was about 3 minutes old? 

a.
It marks the time at which the expansion of the universe had settled down to its current rate.
b.
The proportions of dark matter and luminous matter had been determined.
*c.
The basic chemical composition of the universe had been determined.
d.
It marks the time at which the first stars formed.

26.       Which of the following is NOT a characteristic of the cosmic microwave background?

a.
Its temperature is the same everywhere, except for small variations at the level of 1 part in 100,000.
*b.
It contains prominent spectral lines of hydrogen, the primary chemical ingredient of the universe.
c.
Its temperature is a little less than 3 Kelvin (3 degrees above absolute zero).
d.    It has a perfect thermal radiation spectrum,

27.       In principle, if we could see all the way to the cosmological horizon we could see the Big Bang taking place. However, our view is blocked for times prior to about 380,000 years after the Big Bang. Why? 

a,    380,000 years after the Big Bang marks the time when stars were first born, and thus began to shine the light by which we can see the universe.
b.    Before that time, the universe was too crowded with stars.
c.    Before that time, the universe was dark so there was no light to illuminate anything.
*d.    Before that time, the gas in the universe was dense and ionized and thus did not allow light to travel freely.

28 .       If astronomers had discovered that the cosmic microwave background was precisely the same everywhere, rather than having very slight variations in temperature, then we would have no way to account for: 

a.    the relationship between the strong and the weak force.
b.    the existence of helium in the universe.
*c.    how galaxies came to exist.
d.    the fact that our universe is expanding.

29 .       Which of the following is NOT consistent with recent observations of the cosmic microwave background by the WMAP satellite?

a.    The majority of the energy in the universe is NOT in the form of mass-energy.
b.    The universe is geometrically "flat" (in the four dimensions of spacetime).
*c.    The universe is at least 20 billion years old
d.    The matter density (both luminous and dark matter combined) in the universe is only about one-fourth of the critical density.

30.       Based on the results from the WMAP satellite, the overall composition of the energy of the universe is ______. 

a.    100% ordinary (baryonic) matter
b.    15% ordinary (baryonic) matter, 85% non-baryonic dark matter
c.    1% ordinary (baryonic) matter, 99% non-baryonic dark matter
*d.    4% ordinary (baryonic) matter, 23% non-baryonic dark matter, 73% dark energy