Question 1

Refer to this scenario for the following questions:
A multi- dimensional being reaches down to Earth and pulls you out of the universe. You are then thrown back into the universe at a place and time of the being's choosing, and you are permitted to leave only after you have identified your surroundings. This process is repeated several times. Through a scientifically unexplainable miracle, you are able to survive in every one of the places that you find yourself. In each scenario below, identify your surroundings (and potentially your cosmic era) from among the choices given.
-A moment before, you were enveloped in a bright plasma. You could not see very far as free electrons zipped around your head, scattering photons. But now, the universe has suddenly become transparent and you can see clearly. There seem to be no planets or stars, only a gas filled with mostly neutral hydrogen atoms. Where are you?

Accepted Answer

A)  You are in intergalactic space within a rich cluster of galaxies.
B)  You are in a closed universe just as it begins to re- collapse.
C)  You are in the universe about 380,000 year after the Big Bang during the formation of the cosmic background radiation.
D)  You are in the universe when it was about 500 million years old, just before galaxies began to form.
E)  You are in the universe about 5 minutes after the Big Bang just as the nucleosynthesis era is ending.

Question 2

Your friend left your house and has been driving 60 miles per hour the whole time since then, and has gone 30 miles. How long has she been driving?

Accepted Answer

A)  1/2 minute
B)  60 minutes
C)  30 minutes
D)  1800 minutes
E)  2 minutes

Question 3

Gravitational Lensing: Summarize the observational evidence that a gravitational field can deflect the path of light. In figures such as 18.7 on page 467, how would you prove to a skeptic that the distorted images indicated by the arrows are indeed multiple images of a single gravitationally- lensed galaxy? Muster as much observational evidence as you can.

Accepted Answer

Gravitational lensing is the phenomenon ...

Question 4

"Beauty" in Astronomy: In the absence of observational evidence, scientists often rely on other considerations to make decisions. One such consideration that we have met before (Chapter 3)is Occam's razor: the simplest explanation is to be preferred. Another consideration that is often used (and sometimes championed)by astronomers is the perceived "beauty" of the ideas themselves. Imagine you lived at a time before observational tests could be brought to bear on which of the ultimate fates (re- collapsing, critical, coasting, or accelerating)applies to our universe. Which fate would you support based on your own personal idea of "beauty"? Give your arguments, even if you think they are not scientific. Did you choose the observationally supported theory? What do you think of the role such considerations play in science? Are they sometimes necessary?

Accepted Answer

As a non-scientist, my personal idea of ...

Question 5

Which of the following best summarizes what we mean by dark matter?

Accepted Answer

A)  matter that we have identified from its gravitational effects but that we cannot see in any wavelength of light
B)  matter that may inhabit dark areas of the cosmos where we see nothing at all
C)  matter consisting of black holes
D)  matter for which we have theoretical reason to think it exists, but no observational evidence for its existence A

Question 6

Why do we expect WIMPs to be distributed throughout galactic halos, rather than settled into the galaxy's disk?

Accepted Answer

A)  WIMPs annihilate when they come into contact with ordinary matter, such as stars.
B)  WIMPS cannot produce photons, therefore they rarely interact and exchange energy with other particles.
C)  Shock waves from generations of supernovae have blown the WIMPs out into the halo.
D)  WIMPs are light enough that they have expanded out into the halo.
E)  WIMPs were produced in the early stages of galaxy evolution, and objects in the halo, such as globular clusters, were formed first.

Question 7

Which hypothetical universe will eventually contract, if there were no dark energy?

Accepted Answer

A)  the universe with 0.5 times the critical density of matter
B)  the universe with 1.0 times the critical density of matter
C)  the universe with 1.5 times the critical density of matter

Question 8

Explain how observations of white- dwarf supernovae provide information on the expansion of the universe when it was younger.

Accepted Answer

All white- dwarf supernovae attain the s...

Question 9

If the universe is accelerating, it will expand forever.

Accepted Answer

A) True 
 B)False

Question 10

Which of the following is not one of the three main strategies used to measure the mass of a galaxy clusters?

Accepted Answer

A)  observing how the cluster bends light from galaxies located behind it
B)  studying X- ray emission from hot gas inside the cluster
C)  measuring the temperatures of stars in the halos of the galaxies
D)  measuring the speeds of galaxies orbiting the cluster's center

Question 11

What is the primary form of evidence that has led astronomers to conclude that the expansion of the universe is accelerating?

Accepted Answer

A)  measurements of the rotation curve for the universe
B)  measurements of how galaxy speeds away from the Milky Way have increased during the past century
C)  observations of the speeds of individual galaxies in clusters
D)  observations of white dwarf supernovae D

Question 12

Some dark matter may be ordinary matter that orbits in the halo of the galaxy. Which of the following would not be considered a type of ordinary dark matter?

Accepted Answer

A)  globular clusters in the halo of the galaxy
B)  planets in the halo of the galaxy
C)  brown dwarfs in the halo of the galaxy
D)  you, if you happened to be floating in the halo of the galaxy

Question 13

If all the "dark matter" in our universe were to be instantaneously removed, which of the following would not happen?

Accepted Answer

A)  The Solar System would fly apart.
B)  The universe would expand forever.
C)  Clusters of galaxies would fly apart.
D)  The Milky Way would fly apart.
E)  All of the above A

Question 14

Which of the following best describes how galaxies are distributed on large scales in the universe?

Accepted Answer

A)  Galaxies are uniformly distributed.
B)  Galaxies are distributed in a great shell expanding outward from the center of the universe.
C)  Galaxies are distributed in a hierarchy of clusters, superclusters, and hyperclusters.
D)  Galaxies are randomly distributed.
E)  Galaxies appear to be distributed in chains and sheets that surround great voids.

Question 15

Refer to this scenario for the following questions:
A multi- dimensional being reaches down to Earth and pulls you out of the universe. You are then thrown back into the universe at a place and time of the being's choosing, and you are permitted to leave only after you have identified your surroundings. This process is repeated several times. Through a scientifically unexplainable miracle, you are able to survive in every one of the places that you find yourself. In each scenario below, identify your surroundings (and potentially your cosmic era) from among the choices given.
-You are in a hot, dense place. You are surrounded by nuclear reactions that are rapidly fusing hydrogen into helium. You notice that your surroundings are cooling and rapidly dropping in density. Within about 5 minutes, the fusion reactions stop. Where are you?

Accepted Answer

A)  You are inside a nuclear power plant on Earth.
B)  You are in the center of a massive star near the end of its life.
C)  You are in the early universe during the era of nucleosynthesis.
D)  You are in the center of a star much smaller than the Sun.
E)  You are in the center of a star very much like our Sun.

Question 16

The enclosed mass M(<r) represents ALL of the mass inside the radius r. If the enclosed mass M(<r) increases out to larger radii, where is the mass?

Accepted Answer

A)  distributed like a doughnut, with a hole in the center
B)  concentrated in the center
C)  spread out over a large range of radii

Question 17

What might be causing the universe to accelerate?

Accepted Answer

A)  brown dwarfs
B)  WIMPs
C)  gravitation
D)  dark energy
E)  white- dwarf supernovae

Question 18

The idea of inflation makes one clear prediction that, until the discovery of an accelerating expansion, seemed to contradict the available observations. What is this prediction?

Accepted Answer

A)  The universe should be geometrically "flat" (in the four dimensions of spacetime) .
B)  Inflation predicts that the entire universe must be far larger than the observable universe.
C)  Inflation predicts that the temperature of the cosmic microwave background should be almost (but not exactly) the same everywhere.
D)  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.

Question 19

Consider the data points together with the models in the graph of expansion models. Which model is most strongly supported by the data?

Accepted Answer

A)  critical
B)  accelerating
C)  coasting
D)  recollapsing

Question 20

The mass enclosed in any orbit can be estimated from the equation M(<r) = v2r / G. If the quantity v is constant, regardless of radius, where is the mass located?

Accepted Answer

A)  The mass is concentrated in the center.
B)  The mass is spread out over large radius.
C)  The mass is distributed like a doughnut, with a hole in the center.
D)  Cannot be determined from the information given.

Exam 18: Dark Matter, Dark Energy, and the Fate of the Universe

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Your friend left your house and has been driving 60 miles per hour the whole time since then, and has gone 30 miles. How long has she been driving?

Correct Answer
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Correct Answer
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Gravitational lensing is the phenomenon ...
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As a non-scientist, my personal idea of ...
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Which of the following best summarizes what we mean by dark matter?

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A

Why do we expect WIMPs to be distributed throughout galactic halos, rather than settled into the galaxy's disk?

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Which hypothetical universe will eventually contract, if there were no dark energy?

Correct Answer
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Explain how observations of white- dwarf supernovae provide information on the expansion of the universe when it was younger.

Correct Answer
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All white- dwarf supernovae attain the s...
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If the universe is accelerating, it will expand forever.

Correct Answer
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Which of the following is not one of the three main strategies used to measure the mass of a galaxy clusters?

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What is the primary form of evidence that has led astronomers to conclude that the expansion of the universe is accelerating?

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D

Some dark matter may be ordinary matter that orbits in the halo of the galaxy. Which of the following would not be considered a type of ordinary dark matter?

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If all the "dark matter" in our universe were to be instantaneously removed, which of the following would not happen?

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A

Which of the following best describes how galaxies are distributed on large scales in the universe?

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Correct Answer
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The enclosed mass M(<r) represents ALL of the mass inside the radius r. If the enclosed mass M(<r) increases out to larger radii, where is the mass?

Correct Answer
verified

What might be causing the universe to accelerate?

Correct Answer
verified

The idea of inflation makes one clear prediction that, until the discovery of an accelerating expansion, seemed to contradict the available observations. What is this prediction?

Correct Answer
verified

Consider the data points together with the models in the graph of expansion models. Which model is most strongly supported by the data?

Correct Answer
verified

The mass enclosed in any orbit can be estimated from the equation M(<r) = v2r / G. If the quantity v is constant, regardless of radius, where is the mass located?

Correct Answer
verified

Exam 18: Dark Matter, Dark Energy, and the Fate of the Universe

Correct AnswerverifiedShow Answer

Your friend left your house and has been driving 60 miles per hour the whole time since then, and has gone 30 miles. How long has she been driving?

Correct AnswerverifiedShow Answer

Correct AnswerAnswered by ExamLex AIGravitational lensing is the phenomenon ...View AnswerShow Answer

Correct AnswerAnswered by ExamLex AIAs a non-scientist, my personal idea of ...View AnswerShow Answer

Which of the following best summarizes what we mean by dark matter?

Correct AnswerverifiedA

Why do we expect WIMPs to be distributed throughout galactic halos, rather than settled into the galaxy's disk?

Correct AnswerverifiedShow Answer

Which hypothetical universe will eventually contract, if there were no dark energy?

Correct AnswerverifiedShow Answer

Explain how observations of white- dwarf supernovae provide information on the expansion of the universe when it was younger.

Correct AnswerverifiedAll white- dwarf supernovae attain the s...View AnswerShow Answer

If the universe is accelerating, it will expand forever.

Correct AnswerverifiedShow Answer

Which of the following is not one of the three main strategies used to measure the mass of a galaxy clusters?

Correct AnswerverifiedShow Answer

What is the primary form of evidence that has led astronomers to conclude that the expansion of the universe is accelerating?

Correct AnswerverifiedD

Some dark matter may be ordinary matter that orbits in the halo of the galaxy. Which of the following would not be considered a type of ordinary dark matter?

Correct AnswerverifiedShow Answer

If all the "dark matter" in our universe were to be instantaneously removed, which of the following would not happen?

Correct AnswerverifiedA

Which of the following best describes how galaxies are distributed on large scales in the universe?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

The enclosed mass M(<r) represents ALL of the mass inside the radius r. If the enclosed mass M(<r) increases out to larger radii, where is the mass?

Correct AnswerverifiedShow Answer

What might be causing the universe to accelerate?

Correct AnswerverifiedShow Answer

The idea of inflation makes one clear prediction that, until the discovery of an accelerating expansion, seemed to contradict the available observations. What is this prediction?

Correct AnswerverifiedShow Answer

Consider the data points together with the models in the graph of expansion models. Which model is most strongly supported by the data?

Correct AnswerverifiedShow Answer

The mass enclosed in any orbit can be estimated from the equation M(<r) = v2r / G. If the quantity v is constant, regardless of radius, where is the mass located?

Correct AnswerverifiedShow Answer

Correct Answer
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Correct Answer
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Correct Answer
Answered by ExamLex AI
Gravitational lensing is the phenomenon ...
View Answer

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Answered by ExamLex AI
As a non-scientist, my personal idea of ...
View Answer

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A

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Correct Answer
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All white- dwarf supernovae attain the s...
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D

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A

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