Question 1

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

Accepted Answer

The universe can be infinite in size for both an open and flat shaped universe, but not for a closed universe. Therefore, the best choice is E: open and flat.

Question 2

Current observations suggest that the density of luminous matter,all matter,and dark energy are: A)Ω _luminous = 0.1,Ω _mass = 0.3,Ω _Λ = 0.7 B)Ω _luminous = 0.02,Ω _mass = 0.5,Ω _Λ = 0.5 C)Ω _luminous = 0,Ω _mass = 0.1,Ω _Λ = 0.9 D)Ω _luminous = 0.02,Ω _mass = 0.3,Ω _Λ = 0.7 E)Ω _luminous = 0.1,Ω _mass = 0.2,Ω _Λ = 0.7

Accepted Answer

The most widely accepted model of the universe is the Lambda-CDM model, which includes dark energy represented by the Greek letter Lambda (Λ) and different types of matter, including luminous matter (stars, galaxies, etc.) and non-luminous matter (such as dark matter). The overall density of the universe is thought to be equal to the critical density required for the universe to be flat.
The option D has a ratio of luminous matter to total matter consistent with current estimates, and a dark energy component consistent with observations.

Question 3

To determine how the expansion rate of the universe has changed over time,astronomers directly measure the __________ for a sample of Type I supernovae in distant galaxies.
A)redshift and luminosity
B)redshift and brightness
C)redshift and distance
D)distance and luminosity
E)distance and brightness

Accepted Answer

The answer of To determine how the expansion rate of...

Question 4

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

Accepted Answer

The observations suggest there is a force opposing gravity, known as dark energy, that is causing the acceleration in the expansion of the universe.

Question 5

What do astronomers believe is currently having the largest effect on the change in the expansion rate of the present-day universe?
A)dark matter
B)baryonic (normal)matter
C)dark energy
D)radiation pressure
E)gravity

Accepted Answer

Astronomers believe that dark energy is currently having the largest effect on the change in the expansion rate of the present-day universe. This is supported by observations of Type Ia supernovae and the cosmic microwave background radiation.

Question 6

If the fate of the universe were determined SOLELY by what we currently know 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 the universe is ripped apart

Accepted Answer

The answer of If the fate of the universe were...

Question 7

Observations of Type I 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

Accepted Answer

The observations of Type I supernovae have shown that the expansion rate of the universe is increasing, providing evidence for the existence of dark energy. This is known as the accelerating universe. Choices A, C, D, and E are not supported by observations of Type I supernovae.

Question 8

If Ω_mass = 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

Accepted Answer

If Ω_mass = 0.5, it means the density of the universe is less than the critical density needed to stop expansion. Without dark energy, the universe would continue to expand forever, as it is not dense enough to eventually collapse.

Question 9

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

Accepted Answer

In a closed (spherical) universe, the sum of the angles in a triangle is greater than 180 degrees. This is because such a universe has positive curvature, and therefore, the sum of the angles in a triangle would be greater than the 180 degrees found in planar Euclidean geometry. In fact, the sum of the angles in a triangle would be directly proportional to the size of the triangle, and would increase as the size of the triangle increased.

Question 10

Why would it be very improbable for our universe to have Ω _mass+ Ω_Λ =0.9? A)It would quickly evolve to have a much different value of Ω_mass +Ω_Λ. B)In order to exist,every universe must have Ω_mass + Ω_Λ =1. C)We know Ω_mass = 1,based on the average density of galaxies. D)The fluctuation in the CMB tell us that Ω_mass + Ω_Λ = 0.7. E)Dark energy studies tell us Ω_Λ = 0.9.

Accepted Answer

The universe is observed to be flat, meaning Ω_mass + Ω_Λ is very close to 1. If it were 0.9, it would not be stable and would evolve to a different value.

Question 11

If gravity were slowing down the expansion of the universe,how would very distant galaxies differ from nearby galaxies? A)Distant galaxies would have a larger value for H₀ than nearby galaxies. B)Distant galaxies would have a smaller value for H₀ than nearby galaxies. C)Distant galaxies would contain more dark energy than nearby galaxies. D)Distant galaxies would contain less dark energy than nearby galaxies. E)Distant and nearby galaxies would be the same.

Accepted Answer

The answer of If gravity were slowing down the expansion...

Question 12

The flatness problem arises because only a universe with __________ can have that value forever. A)Ω_mass +Ω_Λ= 0 B)Ω_mass +Ω_Λ =1 C)Ω_mass +Ω_luminous =1 D)Ω_luminous +Ω_Λ =1 E)Ω_luminous+ Ω_Λ =0

Accepted Answer

The flatness problem is concerned with the value of Ω (omega), the density parameter. The question is why is Ω so close to 1 today and what was its value in the past? The answer is that only a universe with Ω = 1 can have that value forever, meaning that the universe will neither expand nor contract but will maintain its current size. Therefore, the correct choice is B, Ωmass + ΩΛ = 1, which implies a flat universe.

Question 13

If there were no dark energy in the universe,the value of __________ would determine the evolution and fate of the universe. A)H₀ B)1/H₀ C)Ω_luminous D)Ω_mass E)Ω_Λ

Accepted Answer

The value of Ωmass (the ratio of the mass density of the universe to the critical density) would determine the evolution and fate of the universe if there were no dark energy. A value of Ωmass greater than 1 would lead to a closed universe, where the expansion of the universe stops and begins to contract. A value of Ωmass less than 1 would lead to an open universe, where the expansion continues indefinitely. A value of Ωmass equal to 1 would lead to a flat universe, where the expansion continues indefinitely at a decreasing rate.

Question 14

In the 1990s,astronomers found that distant Type I supernova 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

Accepted Answer

The fact that the distant Type I supernova were fainter than expected led astronomers to conclude that the universe's expansion rate has been increasing with time, which is known as the accelerating expansion of the universe. This theory was further supported by the discovery of dark energy.

Question 15

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

Accepted Answer

The Big Rip is a hypothetical cosmological model that suggests the universe could end in a catastrophic way if the effect of dark energy, which is thought to be responsible for the accelerating expansion of the universe, continues to increase with time. This would cause the expansion to accelerate so fast that it would tear apart everything, including atoms and subatomic particles, in what is known as the Big Rip. The effects of other choices such as quantum mechanics, gravity, luminous matter, and dark matter are not expected to cause such a phenomenon.

Question 16

From the analysis of distant Type I supernovae and the Cosmic Microwave Background,we know that the Universe is approximately
A)4.6 million years old
B)4.6 billion years old
C)6.5 thousand years old
D)13.7 million years old
E)13.7 billion years old

Accepted Answer

The analysis of Type I supernovae and the Cosmic Microwave Background have provided strong evidence suggesting that the universe is 13.7 billion years old. This estimate is widely accepted in the scientific community and is based on multiple lines of evidence from different sources.

Question 17

What two properties of the universe are determined by the values of Ω _mass and Ω _Λ? A)size and temperature B)expansion rate and size C)size and age D)age and expansion rate E)age and temperature

Accepted Answer

The values of Ωmass and ΩΛ determine the age and expansion rate of the universe. Ωmass is the density parameter for matter in the universe and sets the rate of deceleration of the expansion, while ΩΛ is the density parameter for dark energy which sets the rate of acceleration of the expansion. The age of the universe is determined by the expansion rate, and so both of these properties are affected by the values of Ωmass and ΩΛ.

Question 18

In a universe with an accelerating expansion rate,the actual age of the universe is __________ the Hubble time.
A)larger than
B)smaller than
C)negligible compared to
D)the same as
E)independent of

Accepted Answer

The Hubble time, which is the inverse of the Hubble constant, is an estimate of the age of the universe based on its current rate of expansion. However, in a universe with an accelerating expansion rate, the actual age of the universe would be larger than the Hubble time because the expansion rate has been increasing over time, meaning the universe has been expanding faster in the past than it is currently.

Question 19

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.

Accepted Answer

Dark energy produces a repulsive force that counteracts gravity, leading to an acceleration in the expansion of the universe. This means that even if the mass density of the universe is below the critical density, the universe can still continue to expand forever due to the presence of dark energy. This is known as the "Big Rip" scenario. Option A, C, D and E are incorrect based on current understanding of the role of dark energy in the universe.

Question 20

If Ω _mass + Ω _Λ = 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

Accepted Answer

If the equation Ω _mass + Ω _Λ = 1 holds and dark energy were a cosmological constant, then the universe would continue to expand at an accelerating rate due to the repulsive effect of dark energy. This means that the expansion would go on forever without slowing down or reversing. Therefore, the correct answer is A) expand forever.

Quiz 22: Modern Cosmology

The universe can be infinite in size for which shapes of the universe?

Current observations suggest that the density of luminous matter,all matter,and dark energy are:

To determine how the expansion rate of the universe has changed over time,astronomers directly measure the __________ for a sample of Type I supernovae in distant galaxies.

The observations that show that the expansion of the universe is speeding up tell us the universe must contain:

What do astronomers believe is currently having the largest effect on the change in the expansion rate of the present-day universe?

If the fate of the universe were determined SOLELY by what we currently know 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:

Observations of Type I supernovae in distant galaxies have shown that:

If Ω_mass = 0.5 today and there were no dark energy,the universe would:

In a closed (spherical) universe,the sum of the angles in a triangle is:

Why would it be very improbable for our universe to have Ω _mass+ Ω_Λ =0.9?

If gravity were slowing down the expansion of the universe,how would very distant galaxies differ from nearby galaxies?

The flatness problem arises because only a universe with __________ can have that value forever.

If there were no dark energy in the universe,the value of __________ would determine the evolution and fate of the universe.

In the 1990s,astronomers found that distant Type I supernova were than they expected,leading them to conclude that .

The Big Rip could occur in a universe where the effect of __________ increases with time.

From the analysis of distant Type I supernovae and the Cosmic Microwave Background,we know that the Universe is approximately

What two properties of the universe are determined by the values of Ω _mass and Ω _Λ?

In a universe with an accelerating expansion rate,the actual age of the universe is __________ the Hubble time.

How does the existence of dark energy affect the expansion of the universe?

If Ω _mass + Ω _Λ = 1 today and dark energy were a cosmological constant,the universe would: