TEST BANK 21ST CENTURY ASTRONOMY THE SOLAR SYSTEM 5TH EDITION BY KAY
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Chapter 22: Cosmology
Learning
Objectives
Define the boldfaced vocabulary terms within the chapter.
22.1 Gravity and the Expansion of the
Universe
Illustrate why gravity determines the fate of the universe.
Multiple Choice: 1
Explain why density, rather than mass, determines the
evolution of the universe (i.e., expansion, contraction, acceleration,
deceleration).
Short Answer: 2
Relate the value of
the density parameter Ω to the evolution of the universe (i.e., expansion,
contraction, acceleration, deceleration).
Multiple Choice: 2, 3
Short Answer: 1
22.2 The Accelerating Universe
Summarize the evidence that there is a nonzero cosmological
constant.
Multiple Choice: 7, 8, 11, 13, 18, 19
Explain the effects of dark energy.
Multiple Choice: 6, 17
Short Answer: 4, 8, 12
Characterize how the amounts of matter and
dark energy in the universe determine its evolution and fate.
Multiple Choice: 12, 22, 23, 24, 27, 28, 30, 31, 32
Differentiate between the Big Crunch, Big Rip, and Big Chill.
Multiple Choice: 14, 15, 16, 20, 21
Short Answer: 11
Identify how gravity and dark energy influence the age of the
universe.
Multiple Choice: 9, 25
Short Answer: 5, 7
Illustrate the causes and behavior of different shapes
(geometries) of the universe.
Multiple Choice: 10, 26, 29
Short Answer: 6, 9, 10
22.3 Inflation Solves Several Problems in
Cosmology
Explain how inflation solves the horizon and flatness
problems.
Multiple Choice: 34, 35, 37, 38, 39
Short Answer: 16, 17, 18
Illustrate the effects of inflation on the early universe.
Multiple Choice: 36
Short Answer: 15
22.4 The Earliest Moments of the Universe
Connect the Very Largest Size Scales to the Very Smallest
List the four forces of nature.
Multiple Choice: 40, 46, 47, 48, 49, 50, 54, 64
Short Answer: 19, 21, 24
Illustrate the relationship between temperature of the
universe and unification of forces.
Multiple Choice: 44, 53, 61, 65, 66
Short Answer: 20
Explain how the events that occurred in the early universe
are related to the forces that operate in the universe today.
Multiple Choice: 43, 45, 51, 52, 57, 58, 59, 60, 62, 63, 67,
68
Short Answer: 22, 23, 25, 26
Illustrate the processes of pair production and annihilation.
Multiple Choice: 41, 42, 55, 56
Short Answer: 27
22.5 String Theory and Multiverses
Describe the motivation for string theory.
Short Answer: 29, 30
Assess whether string theory is a scientific theory.
Multiple Choice: 69, 70
Short Answer: 28
Assess whether multiverses are a scientific theory.
Multiple Choice: 71
Working It Out 22.1
Calculate the critical density of the Universe.
Multiple Choice: 4, 5
Short Answer: 3
Working It Out 22.2
Calculate the temperature and energy above which pair
production of different particles can occur.
Multiple Choice: 33
Short Answer: 13, 14
MULTIPLE CHOICE
1.
If there were no dark
energy in the universe, the value of __________ would solely determine the
evolution and fate of the universe.
a.
H0
b.
1/H0
c.
G
d.
Ωm
e.
ΩΛ
2.
If Ωm = 0.5 today and there were no dark energy, the universe would
a.
expand forever.
b.
slow its expansion but
never reverse it.
c.
stop expanding and
eventually collapse.
d.
oscillate between
expansion and collapse.
e.
expand so quickly that
the universe is ripped apart.
3.
If the fate of the
universe were determined solely by what is currently known to be
the total mass of the universe in luminous and dark matter (excluding dark
energy), astronomers would predict that we live in a universe that will
a.
expand forever.
b.
slow its expansion but
never reverse it.
c.
stop expanding and
eventually collapse.
d.
oscillate between
expansion and collapse.
e.
expand so quickly that
it will rip apart.
4.
If the Hubble constant
had a value of 50 km/s/Mpc, the value of the critical density ρc would be about
a.
twice larger.
b.
twice smaller.
c.
the same.
d.
1.4 times smaller.
e.
1.4 times larger.
5.
The critical density of
the universe is closest to
a.
6 protons/m3.
b.
5 g/m3.
c.
1 kg/m3.
d.
1 MEarth/m3.
e.
1 M⊙/m3.
6.
Gravity acts to
_________ the expansion of the universe, and dark energy acts to __________ the
expansion.
a.
slow down; slow down
b.
slow down ; speed up
c.
speed up; slow down
d.
speed up; speed up
7.
To determine how the
expansion rate of the universe has changed over time, astronomers directly
measure the _____________________ for a sample of Type Ia supernovae in distant
galaxies.
a.
redshift and luminosity
b.
redshift and brightness
c.
redshift and distance
d.
distance and luminosity
e.
distance and brightness
8.
The observations that
show that the expansion of the universe is speeding up tell us the universe
must contain
a.
gravity.
b.
dark matter.
c.
a force opposing
gravity.
d.
black holes.
e.
cosmic microwave
background radiation.
.
9.
What two properties of
the universe are determined by the values of Ωm and ΩΛ?
a.
size and temperature
b.
expansion rate and size
c.
size and age
d.
age and expansion rate
e.
age and temperature
10.
In a closed (spherical)
universe, the sum of the angles in a triangle is
a.
180 degrees.
b.
< 180 degrees.
c.
120 degrees.
d.
> 180 degrees.
e.
240 degrees.
11.
The accelerated
expansion of the universe was observationally discovered using
a.
Type Ia supernovae.
b.
Cepheid variables.
c.
RR Lyrae.
d.
stellar parallax.
e.
colors of galaxies.
12.
In a universe
undergoing an accelerated expansion,
a.
ΩΛ must be exactly zero.
b.
the fate of the
universe is exclusively dictated by Ωm.
c.
the mass density must
be larger than the critical density.
d.
the only possible
outcome is the Big Crunch.
e.
the age of the universe
is greater than the Hubble time.
13.
In modern cosmology,
Einstein’s cosmological constant is
a.
an example of dark
energy that causes an accelerated expansion of the universe.
b.
vanishingly zero.
c.
another name for the
critical density of the universe.
d.
the only explanation
for an infinite universe.
e.
of no use, as it
predicts a static universe.
14.
Which of the curves in
the figure shown below would best describe the scenario of a Big Rip for the
universe?
a.
A
b.
B
c.
C
d.
All three of them
e.
None of them
15.
Which of the curves in
the figure shown below would best describe the scenario of a Big Crunch for the
universe?
a.
A
b.
B
c.
C
d.
All three of them
e.
None of them
16.
In a scenario in which
dark energy is changing significantly over time, which of the following
outcomes are possible?
a.
Big Crunch and Big Rip
b.
Big Crunch and Big
Chill
c.
Big Rip and Big Freeze
d.
Big Crunch and Big
Freeze
e.
Big Chill and Big
Freeze
17.
Which of the following
is false?
a.
When the universe was
young, matter worked to slow the expansion rate of the universe.
b.
The Big Bang occurred
approximately 13.8 billion years ago.
c.
Only in the last 5 billion
to 6 billion years has dark energy caused the universe’s expansion rate to
increase over time.
d.
Throughout the age of
the universe, dark energy has caused its expansion rate to increase over time.
e.
Astrophysicists are
unsure whether or not dark energy always will continue to increase the
expansion rate of the universe.
18.
In the 1990s,
astronomers found that distant Type Ia supernovae were __________ than they
expected, leading them to conclude that ___________________.
a.
brighter; the
universe’s expansion rate was decreasing with time
b.
brighter; the universe
was finite in size
c.
fainter; the universe’s
expansion rate has been increasing with time
d.
fainter; the universe
was infinite in size
e.
fainter; the universe
was finite in size
19.
Observations of Type Ia
supernovae in distant galaxies have shown that
a.
the star formation rate
in galaxies decreases with increasing redshift.
b.
the expansion rate of
the universe is increasing.
c.
the cosmological
constant is zero.
d.
dark energy is
negligible at the present time.
e.
there were more stars
in the past than at the present time.
20.
The Big Rip could occur
in a universe where the effect of _____________ increases with time.
a.
quantum mechanics
b.
luminous matter
c.
dark energy
d.
gravity
e.
dark matter
21.
Current observations
suggest that the density of all matter and the density of dark energy are
a.
Ωm = 0.3; ΩΛ = 0.7
b.
Ωm = 0.02; ΩΛ = 0.5
c.
Ωm = 0.0; ΩΛ = 0.9
d.
Ωm = 0.7; ΩΛ = 0.3
e.
Ωm = 0.02; ΩΛ = 0.0
22.
What has had the
largest effect on the change in the expansion rate of the present-day universe?
a.
dark matter
b.
luminous matter
c.
dark energy
d.
radiation pressure
e.
gravity
23.
If Ωm + ΩΛ = 1 today and dark energy were a cosmological constant, the
universe would
a.
expand forever.
b.
slow its expansion but
never reverse it.
c.
stop expanding and
eventually collapse.
d.
oscillate between
expansion and collapse.
e.
expand so quickly that
the universe is ripped apart.
24.
How does the existence
of dark energy affect the expansion of the universe?
a.
It is possible for the
mass density of the universe to be below the critical density and still
collapse.
b.
It is possible for the
mass density of the universe to be below the critical density and still expand
forever.
c.
It is impossible to
have a collapsing universe, regardless of its density.
d.
It is impossible to
have an expanding universe, regardless of its density.
e.
It is impossible for
the mass density of the universe to be above the critical density and still
expand forever.
25.
In a universe
undergoing an accelerated expansion rate, the actual age of the universe is
__________ the Hubble time.
a.
older than
b.
younger than
c.
negligible compared
with
d.
the same as
e.
independent of
26.
The universe can be
infinite in size for which shapes of the universe?
a.
open
b.
closed
c.
flat
d.
closed and flat
e.
open and flat
27.
The figure below shows
a graph of the value of Ωm as a function of time
in a universe with no dark energy. The five different curves correspond to
universes with slightly different values for Ωm one second after the
Big Bang.
Which line corresponds to a universe with the largest value
of Ωm one second after the Big Bang?
a.
A
b.
B
c.
C
d.
D
e.
E
28.
The figure below shows
a graph of the value of Ωm as a function of time
in a universe with no dark energy. The five different curves correspond to
universes with slightly different values for Ωm one second after the
Big Bang.
Which line corresponds to a universe with the smallest value
of Ωm one second after the Big Bang?
a.
A
b.
B
c.
C
d.
D
e.
E
29.
Which of the following
statements is not valid?
a.
ΩΛ + Ωm = 1 indicates a flat universe.
b.
ΩΛ + Ωm = 1 ties into the flatness problem.
c.
ΩΛ and Ωm both affect the predictions about the fate and age of the
universe.
d.
In an open or closed
universe, Euclidian geometry is still applicable.
e.
Current observational
data seem to suggest that the universe is quite flat.
30.
The figure below shows
five graphs of the scale factor of the universe as a function of time. Which of
these graphs would occur for a universe with Ωm > 1 and ΩΛ = 0?
a.
A
b.
B
c.
C
d.
D
e.
E
31.
The figure below shows
five graphs of the scale factor of the universe as a function of time. Which of
these graphs would occur for a universe with Ωm < 1 and ΩΛ = 0?
a.
A
b.
B
c.
C
d.
D
e.
E
32.
The figure below shows
five possible graphs of the scale factor of the universe as a function of time.
Which of these graphs represent our universe where Ωm = 0.3 and ΩΛ = 0.7?
a.
A
b.
B
c.
C
d.
D
e.
E
33.
What was the
temperature of the universe when photons were no longer able to spontaneously
create electron and positron pairs? (Note that a photon’s energy is equal to 
, the cosmic background at any point in time
has a blackbody spectrum that peaks at a wavelength 
, and the mass of a single electron is 9.11 × 10-31
kg.)
, the cosmic background at any point in time
has a blackbody spectrum that peaks at a wavelength , and the mass of a single electron is 9.11 × 10-31
kg.)
a.
2,000 K
b.
400,000 K
c.
2 million K
d.
40 million K
e.
8 billion K
34.
The flatness problem
arises because only a universe with a value of __________ can have that value
forever.
a.
Ωm + ΩΛ = 0
b.
Ωm + ΩΛ = 1
c.
Ωm + ΩΛ = 0.7
d.
Ωm + ΩΛ = 0.02
e.
Ωm = ΩΛ = 0
35.
What can simultaneously
solve both the flatness and horizon problems in cosmology?
a.
GUT
b.
quantum mechanics
c.
TOE
d.
inflation
e.
dark energy
36.
Which of the following
is a false statement about inflation?
a.
Inflation occurred when
the universe was < 10−33 seconds old.
b.
Inflation occurred when
the universe expanded by a factor of approximately 1030.
c.
Inflation solves the
horizon problem.
d.
Inflation is currently
driving the expansion of the universe.
e.
Inflation solves the
flatness problem.
37.
Choose the correct
statement about inflation.
a.
It helps solve both the
problems of the flatness of the universe and the smoothness of the cosmic
background radiation.
b.
It assumes that at some
point in the future dark energy will decay and the universe will expand rapidly
by a factor of 1030.
c.
When the universe was
approximately 1 second old, its size grew by a factor of 1030.
d.
It is the best version
for a TOE.
e.
Scientists have
obtained direct and undisputable observational evidence that inflation did
occur.
38.
Why would it be very
improbable for our universe to have Ωm + ΩΛ = 0.9?
a.
It would quickly evolve
to have a much different value of Ωm + ΩΛ.
b.
In order to exist,
every universe must have Ωm + ΩΛ = 1.
c.
We know Ωm = 1, based on the average density of galaxies.
d.
The CMB fluctuations
tell us that Ωm+ ΩΛ = 0.7.
e.
Dark energy studies
tell us ΩΛ = 0.9.
39.
Why is the smoothness
of the cosmic microwave background radiation (CMB) considered a problem?
a.
A universe as smooth as
predicted by the CMB should not have formed as many galaxies as have been
observed.
b.
A universe as smooth as
predicted by the CMB should have collapsed by now.
c.
A universe as smooth as
predicted by the CMB should be expanding much faster than we are now.
d.
A universe as smooth as
predicted by the CMB should never occur, because quantum mechanical
fluctuations would have been imprinted on it.
e.
A universe as smooth as
predicted by the CMB should never have formed any stars or galaxies.
40.
Quantum chromodynamics
(QCD) describes how __________ works.
a.
gravity
b.
the strong nuclear
force
c.
electricity
d.
magnetism
e.
light
41.
The figure below
illustrates pair production in the early universe, with one particle labeled
with a question mark.
What type of particle must this be?
a.
proton
b.
electron
c.
Antiproton
d.
positron
e.
neutron
42.
What is the minimum
combined energy of the photons that would produce a pair of massive particles
electron-positron? (Note: me is the rest mass of an electron.)
a.
2mec2
b.
mec2
c.
1/2mec2
d.
E = mec2
e.
This cannot happen.
43.
A grand unified theory
(GUT) unites which forces?
a.
only electromagnetism,
weak nuclear forces, and strong nuclear forces
b.
only gravity and strong
nuclear forces
c.
only electromagnetism,
gravity, and weak nuclear forces
d.
only gravity and
electromagnetism forces
e.
all four known forces
44.
Scientists think that,
soon after the Big Bang, the four fundamental forces of nature were united into
one superforce, and __________ was the first to split off from the others.
a.
the strong force
b.
electromagnetism
c.
the weak force
d.
gravity
e.
nucleosynthesis
45.
Which list correctly
orders objects from the first one to form after the Big Bang to the last one to
form.
a.
neutral atoms, protons,
nuclei
b.
protons, nuclei,
neutral atoms
c.
nuclei, neutral atoms,
protons
d.
protons, neutral atoms,
nuclei
e.
nuclei, protons,
neutral atoms
46.
Which of the
fundamental forces in nature have an infinite range of action?
a.
electromagnetic and
gravity
b.
strong nuclear and
gravity
c.
strong and weak nuclear
d.
electromagnetic and
strong nuclear
e.
all four fundamental
forces have an infinite range of action
47.
What particles are the
carriers of the electromagnetic force?
a.
electrons
b.
magnetic monopoles
c.
gluons
d.
photons
e.
W+
48.
Which of the four
fundamental forces is the weakest of all?
a.
electromagnetic
b.
gravity
c.
weak nuclear
d.
magnetic
e.
strong nuclear
49.
Which of the four
fundamental forces governs the nuclear fusion inside stars?
a.
electromagnetic
b.
gravity
c.
weak nuclear
d.
magnetic
e.
strong nuclear
50.
What fundamental force
is responsible for holding the nucleons together inside atomic nuclei?
a.
electromagnetic
b.
gravity
c.
weak nuclear
d.
gluons
e.
strong nuclear
51.
Which of the following
is not true about the standard model?
a.
All particles are
created without mass.
b.
It is a complete
description of nature.
c.
Forces between
particles are mediated by carrier particles.
d.
Particles acquire mass
as they interact with the Higgs boson.
e.
Every particle in
nature has a corresponding antiparticle.
52.
Which of the following
would represent the unification of all fundamental forces?
a.
the electroweak theory
b.
quantum chromodynamics
(QCD)
c.
quantum electrodynamics
(QED)
d.
grand unified theories
(GUT)
e.
the Theory of
Everything (TOE)
53.
The TOE breaks within
___________ of the Big Bang.
a.
10-43 s
b.
10-35 s
c.
10-13 s
d.
15 s
e.
3 min
54.
Which of the following
are not considered carrier particles used to mediate forces
between other particles?
a.
photons
b.
gluons
c.
Zo particles
d.
quarks
e.
W+ particles
55.
How would scientists
describe the antiparticle of an electron?
a.
It would have the same
charge but opposite spin.
b.
It would have the same
mass but opposite charge.
c.
It would have the
opposite charge and higher mass.
d.
It would have the
opposite spin and higher mass.
e.
It would have the
opposite charge but same spin.
56.
In the very early
universe, which type of particles and antiparticles first stopped being
spontaneously formed out of photons any why?
a.
protons and neutrons,
because their formation requires a larger number of photons
b.
electrons and
positrons, because their formation requires a smaller number of photons
c.
protons and
antiprotons, because their formation requires higher energy photons
d.
electrons and
neutrinos, because their formation requires lower energy photons
e.
protons, antiprotons,
electrons, and neutrinos stopped forming at the same time.
57.
What would the universe
be like if there were complete symmetry between matter and antimatter?
a.
It would look similar
to our universe, but half of it would be composed of antimatter.
b.
We would observe two
universes, one an antimatter reflection of the other.
c.
There would be no
universe, because all of the matter and antimatter would have been annihilated.
d.
There would be a
universe devoid of matter, entirely composed of photons.
e.
It would look similar
to our universe, but the charges of all of the particles would be reversed.
58.
To verify whether or
not some grand unified theories are correct, physicists are searching for
a.
the Big Rip.
b.
mini−black holes.
c.
antimatter.
d.
protons that decay.
e.
dark matter that
decays.
59.
Grand unified theories
are very attractive because they can explain
a.
why we have five
fundamental forces in the universe today.
b.
why the Big Bang never
made any antimatter.
c.
why the universe
consists mostly of matter.
d.
why the CMB is very
smooth.
e.
what happens inside a
black hole.
60.
What is the Planck era?
a.
the earliest moments
after the Big Bang
b.
a period when quantum
mechanics is needed to describe both spacetime and particles
c.
the time period when a
theory of everything (TOE) is needed to understand the universe
d.
when spacetime can be
described as a quantum mechanical “foam” rather than a smooth sheet
e.
all of the above
61.
As the universe cooled
shortly after the Big Bang, which was the first fundamental force to separate
itself out from the others?
a.
electromagnetism
b.
gravity
c.
the nuclear force
d.
the strong force
e.
the weak force
62.
Which of the following
is an invalid statement?
a.
The inflation epoch
must have occurred before all four forces broke apart.
b.
Scientists have
confirmed the Grand Unified Theory by observing the decay of protons in
laboratory experiments.
c.
In the superstring
theory that successfully unites gravity and quantum mechanics, the universe
must have 11 dimensions (10 spatial and 1 temporal).
d.
The weak force mediates
the beta decay of neutrons into protons, electrons, and antineutrinos.
e.
The four fundamental
forces of nature are gravity, electromagnetism, the weak and the strong nuclear
forces.
63.
At what stage in the
universe’s history do we think the asymmetry between matter and antimatter was
created?
a.
at the very moment the
Big Bang occurred
b.
around the time gravity
separated out of the single superforce
c.
around the time the
strong force separated out of the grand unified theory
d.
around the time the
weak force and electromagnetism separated
e.
around the time the
electric and magnetic forces separated
64.
Which was a triumph of
quantum electrodynamics (QED)?
a.
QED predicted the
existence of three carrier particles before they were discovered in laboratory
experiments.
b.
QED unites the strong
and weak nuclear forces.
c.
QED is an example of a
theory of everything.
d.
QED successfully
explains the origin of quantum mechanical fluctuations in the CMB.
e.
QED combined the
electric and magnetic forces.
65.
The standard model of
particle physics is incomplete because it leaves which question(s) unanswered?
a.
Do neutrinos have mass?
b.
Why is the strong
nuclear force so much stronger than the weak nuclear force?
c.
Why was there an
imbalance between matter and antimatter?
d.
Does gravity have a
corresponding charge carrier?
e.
all of the above
66.
Why does a unified
force split to become two separate forces?
a.
The universe expands so
much that carrier particles become too dense.
b.
The average energy of
photons was not enough to produce particles mediating the interactions
c.
Dark energy becomes
significant at later times and forces the two to split.
d.
The spatial dimensions
split and so must the forces.
e.
Too many particles are
created for the unified force to manage.
67.
Even with infinitely
powerful telescopes, we can look back in time only until the time when
a.
galaxies first formed.
b.
hydrogen and helium
formed.
c.
stars first formed.
d.
gravity split off from
a superforce.
e.
recombination happened.
68.
Which of the following
have both been predicted and conclusively confirmed experimentally?
a.
the decay of proton
b.
the inflationary model
c.
the carrier particles
for the force of gravity
d.
the Higgs boson
e.
the 10 spatial
dimensions in superstring theory
69.
In the superstring
theory that successfully unites gravity and quantum mechanics, the universe
must have
a.
four dimensions (three
spatial and one temporal).
b.
six dimensions (three
spatial and three temporal).
c.
seven dimensions (six
spatial and one temporal).
d.
nine dimensions (eight
spatial and one temporal).
e.
eleven dimensions (10
spatial and 1 temporal).
70.
In some particle
physics theories, the universe must have more than three spatial dimensions,
but we experience only three. Why would we not see the other spatial
dimensions?
a.
The other nine spatial
dimensions are too small to be noticeable.
b.
The other seven spatial
dimensions are tightly wrapped around each other and have not expanded.
c.
The other seven spatial
dimensions undergo inflation and flatten themselves out.
d.
The other nine spatial
dimensions wrap around each another and form the temporal dimension.
e.
The other seven spatial
dimensions are completely full of dark matter.
71.
Which of these are
possible types of multiple universes that could exist?
a.
parallel universes with
different physics and different mathematical explanations
b.
other parts of an
infinite universe that are so far away that we cannot observe them
c.
quantum mechanical
parallel universes, which are created each time something happens that has a
probability of occurring in a different way, such as a roll of dice
d.
a multiverse with
constant inflation, where each universe forms due to quantum fluctuations
stopping that inflation
e.
all of the above
SHORT ANSWER
1.
In a universe with no
dark energy, what will happen to the expansion of the universe in the future if
(a) Ωm > 1, (b) Ωm = 1, and (c) Ωm < 1?
2.
Why does the critical
mass density of the universe depend on the value of Hubble’s constant, H0?
3.
The critical mass
density of the universe today is 9.5 × 10−27 kg/m3.
Using (only) the currently observed amount of luminous matter, what would be
the average mass density in the universe? If protons were spread evenly
throughout the universe, what would be their typical separation? (Note that the
typical separation between protons would be roughly equal to the cubic root of
the average volume occupied by one proton, and the mass of a proton is 1.67 × 10−27 kg.)
4.
If dark energy is
currently causing the expansion rate of the universe to increase with time,
does this mean that you should worry that the Sun, the Earth, and your body
itself are expanding? Why or why not?
5.
If you found a globular
cluster that had an age of 20 billion years, what cosmological observations
would conflict with this observation?
6.
Why does the sum of Ωm and ΩΛ determine the shape of our universe?
7.
If the Hubble constant
were larger than it is, how would that change the measured age of the universe?
Explain your answer.
8.
Outline the essential
difference between the view of the empty space employed by Friedmann and the
properties of the empty space in modern cosmology.
9.
Indicate two different
experiments that offer evidence for a flat universe.
10.
Summarize the possible
shapes of the universe and indicate if the Euclidian geometry is applicable in
each case.
.
11.
Briefly explain the
possible scenarios for the fate of the universe assuming that: (i) dark energy
decreases in time, (ii) it increases in time, and (iii) it is a constant.
12.
If there were enough
mass to slow down the expansion rate of the universe, how would the Hubble
constant measured using very distant galaxies be different from what is
observed in galaxies that are closer to us? Explain your answer. Is this what
we observe in our universe?
13.
Explain why the
production of electron-positron pairs requires less energetic photons than the
production of proton-antiproton pairs?
14.
What was the
temperature of the universe when photons were no longer able to spontaneously
create proton-antiproton pairs? (Note that a photon’s energy is equal to 
, the cosmic background at any point in time
has a blackbody spectrum that peaks at a wavelength 
, and the mass of a single proton is 1.67 × 10−27 kg.)
, the cosmic background at any point in time
has a blackbody spectrum that peaks at a wavelength , and the mass of a single proton is 1.67 × 10−27 kg.)
15.
Why does inflation not
violate the fundamental rule that nothing can travel through space faster than
the speed of light?
16.
What is the “flatness
problem” in cosmology?
17.
What can solve the
flatness and horizon problem in cosmology, and why?
18.
Explain what the
uncertainty principle means and how it relates to the horizon problem.
19.
What are the names of
the two particles that mediate the electromagnetic force in quantum
electrodynamics (QED) and the strong force in quantum chromodynamics (QCD)?
20.
What is the difference
between a grand unified theory (GUT) and a theory of everything (TOE)?
21.
Indicate the four
fundamental forces of nature by listing their names and describing what effect
each force has on objects in the universe.
22.
What is the main reason
that GUT theories are being pursued?
23.
Explain why the Higgs
bosons are important in the context of the standard model.
24.
In quantum
electrodynamics (QED), what mediates the electromagnetic force between particles?
25.
Explain why astronomers
cannot accurately model the exact history of the universe in the first few
fractions of a second after the Big Bang.
26.
Outline two essential
problems/questions to which the standard model doesn’t offer an answer.
27.
How would the
antiparticle of the neutron be different from the neutron itself?
28.
Explain why the
superstring theory is considered more like a speculative idea or hypothesis
rather than a scientific theory.
29.
According to
superstring theory, how are different varieties of elementary particles
similar? How do they differ?
30.
Explain why inflation
could lead to an infinite number of multiverses inside our own universe. Are
they likely to be similar or different than our own universe?
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