Deck 18: Cosmology

Question 1

The Universe's geometry is determined by its:

A) size.
B) age.
C) density of matter-energy.
D) homogeneity.

Answer 1

density of matter-energy.

Question 2

Arrange the following events in order,from soonest after the Big Bang to most recent:

A) recombination, Dark Ages, nucleosynthesis, inflation.
B) inflation, nucleosynthesis, recombination, Dark Ages.
C) inflation, Dark Ages, nucleosynthesis, recombination.
D) Dark Ages, inflation, recombination, nucleosynthesis.

Answer 2

inflation, nucleosynthesis, recombination, Dark Ages.

Question 3

The figure below shows a phase transition in the early Universe.What kinds of particles were created during this transition?

A) inflatons
B) baryons
C) nuclei
D) atoms

Answer 3

baryons

Question 4

By approximately what factor did the Universe expand between 10⁻⁴³ and 10⁻³³ seconds after the Big Bang,according to present models?

A) 10
B) 10¹⁰
C) 10⁵⁰
D) The Universe did not expand during that interval.

Question 5

Which of the following pieces of evidence favor the Big Bang model over the steady-state model?

A) the cosmological constant does not change with time
B) the quasar population changes with redshift
C) the ongoing creation of matter in the spaces between galaxies
D) the average density of dark matter in the Universe

Question 6

The standard model of particle physics:

A) explains the masses of each subatomic particle.
B) classifies all subatomic particles into quarks and leptons.
C) predicts the forces that affect each subatomic particle.
D) all of the above.

Question 7

Cosmic inflation was driven by:

A) curvature.
B) quantum fields.
C) baryons.
D) leptons.

Question 8

Which of the following questions can the Big Bang model answer?

A) Will the expansion of the Universe stop?
B) What caused the Universe to expand?
C) What is the source of the mass-energy in our Universe?
D) What existed before the Big Bang?

Question 9

Of the following,who is responsible for creating the Big Bang model?

A) Robert Wilson
B) Fred Hoyle
C) Edwin Hubble
D) George Gamow

Question 10

What is the major difference between quarks and leptons?

A) Quarks occur in three "generations," unlike leptons.
B) Leptons are always electrically charged.
C) Leptons are more massive.
D) Quarks interact with gluons.

Question 11

Which of the following statements is true in both the steady-state and Big Bang models of cosmology?

A) The cosmic microwave background was only generated at a particular time period in the past.
B) The curvature of the Universe evolves over time as matter spreads out due to expansion.
C) The Universe is homogeneous and isotropic.
D) The density of galaxies never changes.

Question 12

Suppose that an exotic quantum process keeps the Universe's temperature elevated during the first several years after the Big Bang.Which of the following would occur?

A) Nucleosynthesis would persist for longer.
B) Structure formation would be delayed.
C) Decoupling would occur sooner.
D) The Dark Ages would not occur.

Question 13

Which of the following factors prevents protons and electrons from recombining in the early phases of the Universe's history?

A) Photons have too much energy.
B) Protons and electrons do not have enough energy.
C) Protons and electrons are too far apart to collide.
D) Protons and electrons have too high of a temperature for gravity to attract them.

Question 14

Which of the following is NOT an example of a cosmological investigation?

A) using supernovas to understand the stellar population
B) using Cepheid variables to measure the Hubble constant
C) using the cosmic microwave background to measure the geometry of the Universe
D) characterizing the average abundance of different elements in the Universe

Question 15

Which of the following were necessary for Einstein to formulate equations describing the Universe as a whole?

A) homogeneity
B) isotropy
C) general relativity
D) all of the above

Question 16

Leptons:

A) are susceptible to the strong nuclear force.
B) are susceptible to the weak nuclear force.
C) carry the electromagnetic force.
D) carry the gravitational force.

Question 17

The cosmic singularity describes:

A) the initial conditions of the Big Bang model.
B) the equilibrium state toward which the Big Bang model approaches.
C) the opacity of the Universe in the first few minutes after the Big Bang.
D) our Universe's place within the multiverse.

Question 18

Which of the following describes the study of the Universe as a whole?

A) inflationary theory
B) astronomy
C) cosmology
D) astrophysics

Question 19

A photon is produced 300,000 years after the Big Bang,eventually reaching a telescope on Earth.How did it travel to get there?

A) It traveled in a straight line.
B) It scattered off matter until it hit the telescope.
C) It traveled in a straight line for 100,000 years and then scattered off matter until it hit the telescope.
D) It scattered off matter for 100,000 years and then traveled in a straight line.

Question 20

Which of the following events occurred just before normal matter began assembling structure through gravity?

A) inflation
B) baryogenesis
C) recombination
D) nucleosynthesis

Question 21

Which of the following provides the strongest evidence for the classic Big Bang model?

A) the age of the Solar System
B) the cosmic microwave background
C) the abundance of galaxies
D) none of the above

Question 22

When the cosmic microwave background was produced,it was a blackbody with a temperature of 4,000 K.Today,we observe it to have a temperature of 2.7 K.By approximately what factor has the Universe expanded between those two time periods?

A) 300
B) 1,000
C) 3,000
D) 7,000

Question 23

According to our present understanding,in the distant future the Universe will:

A) expand at an accelerating rate.
B) expand at a decelerating rate.
C) expand and then recollapse.
D) recollapse.

Question 24

Which of the following astronomers helped discover the cosmic microwave background?

A) Edwin Hubble
B) Vera Rubin
C) Arno Penzias
D) George Gamow

Question 25

To what accuracy are the relative densities of dark energy and dark matter known,according to current cosmological measurements?

A) to 1 part in 10,000
B) to 1 part in 100
C) within a factor of 2
D) to an order of magnitude

Question 26

Radiation from the first 400,000 years of the Universe's history can be observed as:

A) optical line radiation.
B) microwaves.
C) X-rays.
D) gamma rays.

Question 27

A photon is emitted from a galaxy with a wavelength of 100 nm.By the time it reaches a telescope on Earth,the photon has a wavelength of 800 nm.By what factor has the Universe expanded between the photon's emission and detection?

A) 2
B) 4
C) 8
D) 16

Question 28

An alternate universe is filled with normal matter and dark matter,but not dark energy.If its density is twice the critical value,which curve on the figure below might represent its size?

A) A
B) B
C) C
D) D

Question 29

An astronomer discovers that the abundance of helium in the first galaxies to form in our Universe is only half that of small galaxies near the Milky Way.This would provide evidence:

A) against the Big Bang model.
B) in support of the Big Bang model.
C) in support of the fusion model for main sequence stars.
D) against the fusion model for main sequence stars.

Question 30

Which of the following correctly characterizes the composition of our Universe?

A) 5 percent normal matter, 68 percent dark matter, 27 percent dark energy
B) 27 percent normal matter, 5 percent dark matter, 68 percent dark energy
C) 5 percent normal matter, 27 percent dark matter, 68 percent dark energy
D) 27 percent normal matter, 68 percent dark matter, 5 percent dark energy

Question 31

The figure below shows a map of the temperature of the cosmic microwave background.The features shown here are instrumental in forming:

A) black holes.
B) baryons.
C) nuclei.
D) the cosmic web.

Question 32

Which of the following isotopes is NOT a potential probe of the first three minutes of the Universe's history?

A) deuterium
B) helium-3
C) lithium-7
D) carbon-13

Question 33

Why is baryogenesis NOT a key observational pillar of the classic Big Bang model?

A) Baryogenesis occurred too early to be directly observable.
B) Baryogenesis would have occurred in the same way in a steady-state universe.
C) Baryogenesis occurs too rapidly to depend upon the expansion of the Universe.
D) Cosmologists do not fully understand baryogenesis.

Question 34

Why is the cosmic microwave background a blackbody?

A) because it was in equilibrium with matter in the early Universe
B) because it no longer interacts with matter
C) because it has redshifted so much
D) because of inflation

Question 35

What process explains why the cosmic microwave background has nearly the same temperature in every direction on the sky?

A) recombination
B) inflation
C) decoupling
D) redshifting

Question 36

What process produced the initial density perturbations that would later grow into galaxies and galaxy clusters?

A) inflation
B) recombination
C) fragmentation
D) phase transitions

Question 37

Which of the following elements has an observed abundance that supports the Big Bang model?

A) iron
B) helium
C) oxygen
D) nitrogen

Question 38

Which of the following provides the best test of inflation?

A) the geometry of the Universe
B) the temperature fluctuations in the cosmic microwave background
C) nucleosynthesis
D) the size of the observable Universe

Question 39

What is the total density parameter of our Universe?

A) W = 0.1
B) W = 0.3
C) W = 1
D) W = 2

Question 40

Which of the following types of universes has the LOWEST density?

A) positive curvature
B) flat curvature
C) negative curvature
D) fluctuating curvature

Question 41

Consider two universes with identical Hubble constants.Universe A has a higher density than universe B.If neither universe has dark energy,this implies that:

A) universe A is older than universe B.
B) universe A is the same age as universe B.
C) universe A is younger than universe B.
D) This situation is not possible according to the Big Bang model.

Question 42

How does the Universe's expansion during the inflationary era differ from that in the classic Big Bang model?

A) During inflation, the curvature of the Universe changes.
B) During inflation, regions initially outside of causal contact are allowed to interact with each other.
C) During inflation, Hubble's law is violated.
D) During inflation, expansion makes the density closer to the critical value.

Question 43

Which of the following presents the best motivation for inflation?

A) the density of the Universe today
B) the formation of baryons in the Universe
C) the size of the observable Universe
D) the apparent recession velocity at large distances, which exceeds the speed of light

Question 44

An astronomer wishes to test the Big Bang model by studying helium-4.In which environment should he or she look in order to test the Big Bang model?

Question 45

The classic Big Bang model attributes the initial moment of creation to:

A) high energy density.
B) baryogenesis.
C) quantum fluctuations.
D) nothing; it is not part of the theory.

Question 46

What were the two most common nuclei in the Universe ten minutes after the Big Bang,and what were their relative abundances?

Question 47

Arrange the following events in chronological order,from earliest to latest after the cosmic singularity: baryogenesis,inflation,nucleosynthesis,recombination.

Question 48

How does inflation solve the paradox of universal uniformity?

A) It separates nearby parts of the Universe very rapidly.
B) It allows electromagnetic waves to travel faster than the speed of light.
C) It removes any fluctuations from the Universe.
D) It forces special relativity to be true.

Question 49

The figure below shows how two electrons,traveling from left to right on the diagram,repel each other.What quantum particle causes the electrons to change direction?

Question 50

In the early history of the Universe,an unstable quantum field decayed to its ground state.How did this affect the Universe?

Question 51

How does cosmological recombination affect the interaction of photons and matter?

Question 52

Why is the size distribution of temperature fluctuations on the cosmic microwave background useful to astronomers?

A) It shows that the Universe is mostly opaque at the present day.
B) It shows that the cosmological principle is not accurate.
C) It shows how recombination occurred differently in different parts of the Universe.
D) It allows precise measurements of the density of dark energy.

Question 53

Why does measuring the matter and energy content of the Universe tell astronomers how the curvature of space is changing?

Question 54

How did astronomers rule out the steady-state model of the Universe in the 1960s?

Question 55

What are the three most important observational pillars for the Big Bang model?

Question 56

The figure below shows a portion of the Universe's expansion history.What problem with the classic Big Bang model is solved by the highlighted portion?

A) the observed geometry of the Universe
B) the observed acceleration of the Universe's expansion
C) the observed size of the Universe
D) the observed dominance of dark energy at the present day

Question 57

Which curve on the figure below corresponds to the Universe undergoing the most deceleration?

A) the middle (light gray) curve
B) the lower (medium gray) curve
C) the upper (black) curve
D) It is impossible to determine.

Question 58

What is goal of cosmology?

Question 59

If dark energy continues to dominate the expansion of the Universe,it will:

A) recollapse.
B) decelerate until it stops expanding.
C) accelerate for a time and then recollapse.
D) enter another inflationary era.

Question 60

A theory of quantum gravity is necessary to describe:

A) baryogenesis.
B) the cosmic singularity.
C) observations of distant supernovas.
D) all of the above.

Question 61

How do scientists characterize the Universe before the Big Bang?

Question 62

An astronomer discovers that brightnesses of distant supernovas do not precisely obey Hubble's law (shown by the middle curve in the figure below)but instead follow the uppermost curve.What should he or she infer?

Question 63

A particular region in space has a galaxy cluster today.How would the density and temperature of that same region have compared to an average region of the Universe at the time of cosmological recombination?

Question 64

The figure below shows two spectra of the relic radiation from the recombination era.By how much has the Universe expanded between the times these spectra would have been taken?

Question 65

An astronomer discovers that all galaxies with a particular characteristic have a radius precisely equal to 10 kpc.He or she measures the angular sizes of a large set of these galaxies.How can he or she use his or her measurements to deduce the overall density of the Universe?

Question 66

What process is thought by most astronomers to be responsible for making the Universe flat?

Question 67

An astronomer images the most distant source of light observable in the Big Bang model.What kind of telescope did he or she use?

Question 68

An astronomer measures the properties of an alternate universe.He or she discovers that the angles of a triangle in this universe add up to more than 180 degrees.What can he or she deduce about the universe's density?

Question 69

In the context of the classic Big Bang model,why is the uniformity of the cosmic microwave background's temperature puzzling?

Question 70

To what precision have astronomers measured the dark matter density of the Universe?