Deck 14: Modern Cosmology

Question 1

When a proton and an antiproton collide

A) they destroy each other and produce energy in the form of gamma rays.
B) one of the protons is converted to a neutron and they form a nucleus consisting of one proton and one neutron.
C) one of the protons is converted to an electron and they form a hydrogen atom.
D) one proton is converted to a neutron and the other is converted to an electron.
E) A proton and an antiproton cannot collide because the Coulomb barrier is too great.

Answer 1

A

Question 2

The cosmological principle states that the Universe is
I) expanding.
II) accelerating.
III) homogeneous.
IV) isotropic.

A) I and II
B) III and IV
C) I and III
D) II and IV
E) I, II, III, and IV

Answer 2

B

Question 3

Measured ages of globular clusters suggests that the Universe is about

A) 1.4 billion years old.
B) 14 billion years old.
C) 140 billion years old.

Answer 3

B

Question 4

Space-time will be flat if

A) the Universe is expanding.
B) the Universe is accelerating.
C) the average density of the Universe is equal to the critical density.
D) the Universe is finite.
E) the Universe is homogeneous and isotropic.

Question 5

The cosmic background radiation comes from a time

A) when protons and neutrons were first formed.
B) when the big bang first began to expand.
C) during the inflationary period.
D) when gamma rays had enough energy to destroy nuclei.
E) when electrons began to recombine with nuclei to form atoms.

Question 6

The Hubble time is

A) the time it takes a galaxy moving at 1000 km/s to move 1 Mpc.
B) the time it takes the galaxy to double its size.
C) the time since recombination occurred.
D) the time remaining before the Universe stops expanding and begins to contract.
E) an estimate of the age of the Universe based on the Hubble constant.

Question 7

If gravity alone acts to retard the expansion and nothing acts to accelerate it, the Universe is said to be closed if
I) gravity is strong enough to stop the expansion in a finite time.
II) the density of the Universe is less than the critical density.
III) the Universe is finite.

A) I & II
B) I & III
C) II & III
D) I, I, & III
E) None of the other choices are correct.

Question 8

If the Universe is closed, then its age will be

A) less than two-thirds of 1/ H .
B) more than two-thirds of 1/ H .
C) equal to 1/ H .
D) equal to H squared.
E) equal to the square-root of H .

Question 9

During the first moments of the big bang when elements could be created, nuclear fusion reactions made few heavy elements because

A) all heavy nuclei are unstable.
B) no stable nuclei exist with masses of 5 or 8 hydrogen masses.
C) the helium nucleus is unstable.
D) the temperature and density were too low.
E) no nuclei heavier than helium could form since there weren't any electrons formed.

Question 10

If the Universe is closed and finite, then

A) the Universe will expand forever.
B) the Universe has a center.
C) the Universe has an edge.
D) None of the other choices are correct.

Question 11

In the late 1990's, it was announced that the expansion of the Universe is accelerating. What does this imply from the perspective of the big bang?

A) A force exists that we knew nothing about that causes the acceleration.
B) The Universe must be closed.
C) The Universe is finite.
D) The amount of dark matter must be greatly less than the amount of normal matter.
E) The Universe must be infinitely old.

Question 12

In the late 1990's, it was discovered from distances of ___________ in distant galaxies that the expansion of the Universe is ___________.

A) Cepheid variables; accelerating
B) Cepheid variables; decelerating
C) supernovae; accelerating
D) supernovae; decelerating

Question 13

Current observations indicate that the amount of baryonic matter and dark matter in the Universe

A) is sufficient great enough to overcome the expansion of the Universe.
B) implies that the Universe is closed.
C) is mostly in the form of black holes and quasars.
D) are roughly equal.
E) implies that the Universe is open.

Question 14

The assumption of homogeneity states that

A) the Universe looks the same at all epochs.
B) the Universe looks the same from all locations over sufficiently great distances.
C) the Universe looks the same in all directions over sufficiently great distances.
D) the Universe looks the same at all epochs, the Universe looks the same from all locations over sufficiently great distances, and the Universe looks the same in all directions over sufficiently great distances.
E) None of the other choices are correct.

Question 15

The assumption of isotropy states that

A) the Universe looks the same at all epochs.
B) the Universe looks the same from all locations over sufficiently great distances.
C) the Universe looks the same in all directions over sufficiently great distances.
D) the Universe looks the same at all epochs, the Universe looks the same from all locations over sufficiently great distances, and the Universe looks the same in all directions over sufficiently great distances.
E) None of the other choices are correct.

Question 16

What was the temperature of the Universe when the recombination took place that produced the cosmic background radiation we observe today?

A) about 2.7 K
B) about 300 K
C) about 3000 K
D) about 3 million K
E) about 3 billion K

Question 17

Dark energy is the name of the

A) force that lead to the inflationary period of the Universe.
B) five-dimensional space of the Universe.
C) force suspected to cause the current acceleration in the rate of expansion of the Universe.
D) one of the particles of dark matter related to WIMPs.
E) the force that holds the proton together.

Question 18

The resolution of Olbers's paradox suggests that it gets dark at night because

A) the Universe is not infinite in age.
B) the Universe is static.
C) the Universe is closed.
D) the Universe is not infinite in age and the Universe is static.
E) All of the other choices are correct.

Question 19

The ___________ view of the Universe is that it is eternal and unchanging.

A) inflationary
B) accelerating
C) static
D) big bang

Question 20

As the Universe cooled, it eventually reached a temperature of 3,000 K and protons were able to capture and hold electrons to form neutral hydrogen. This process is known as

A) ionization.
B) isotropy.
C) annihilation.
D) recombination.
E) hydration.

Question 21

Which of the following types of Universe has no center and no edge?

A) closed
B) flat
C) open
D) All of the other choices are correct.

Question 22

Evidence for a very early "super rapid" inflation of the universe is that the 3-K radiation from opposite sides of the sky (i.e., 180 degrees or about 28 billion light years apart) is of nearly ___________ intensity. Time for light to travel this distance is ___________ the age of the universe in years.

A) equal; greater than
B) unequal; greater than
C) equal; less than
D) unequal; less than

Question 23

What observation has prompted astronomers to ponder the possible existence of dark energy?

A) discovery of quasars
B) discovery of superclusters
C) supernovae appear fainter than expected at large redshifts
D) uniform nature of the cosmic microwave background (CMB)

Question 24

Which of the following agrees with a no-center, no-edge Universe?

A) a flat geometry
B) a positive-curved geometry
C) a negative-curved geometry
D) All of the other choices are correct.

Question 25

Current evidence suggests that the Universe is

A) flat, infinite, and neither expanding nor contracting.
B) closed, finite, and slowing its expansion.
C) open, infinite, and slowing in its expansion.
D) static with no expansion.
E) flat, infinite, and accelerating in its expansion.

Question 26

The flatness problem and horizon problem

A) are solved if there was a sudden inflation of the Universe at time before recombination occurred.
B) show that the Universe can be described as static and unchanging.
C) show that dark matter must be a small fraction of the total mass of the Universe.
D) imply that the Universe was once much colder than it is now.
E) imply that the inflationary theory is incorrect.

Question 27

Possible equations (choose the correct one): τ =10¹²/ H ; H = v / d . If gravity is unimportant and H equals 75 km/s/Mpc, then the age of the universe is about

A) 8.9 billion years.
B) 13 billion years.
C) 16.6 billion years.
D) 26 billion years.
E) 74 billion years.

Question 28

Astronomers believe that the hydrogen atoms in your body were created

A) in the planets.
B) inside the stars.
C) in the Sun.
D) in the big bang.
E) in neutron stars.

Question 29

The density of the Universe is

A) equal to the critical density if the Universe is closed.
B) equal to the critical density if the Universe is flat.
C) greater than the critical density if the Universe is flat.
D) greater than the critical density if the Universe is open.
E) None of the other choices are correct.

Question 30

Where did the cosmic microwave background (CMB) come from?

A) photons emitted from the first stars
B) photons released from hydrogen in our galaxy
C) light scattered by dust in our Solar System
D) photons released when electrons and nuclei combined for the first time

Question 31

Why is the cosmic microwave background (CMB) so cold if the early Universe was so hot?

A) Enough time has passed for matter in the universe to release enough heat to cool down.
B) The CMB constantly interacts with atoms, which effectively cool down the photons.
C) The expansion of the Universe has redshifted those photons to an effectively cooler temperature.
D) Misleading; The big bang was initially hot but the CMB was released from cold material much later on.

Question 32

Whether the Universe is open, closed or flat depends, on the ___________ of the Universe.

A) luminosity
B) density
C) temperature
D) radius
E) rotation rate

Question 33

Astronomers have found the center of the Universe to be located in

A) Earth
B) the Sun
C) Sagittarius A
D) the Virgo Cluster of galaxies
E) no center is thought to exist.

Question 34

How old is the Universe since the big bang? Pick the best answer according to radioactive dating in the solar system, light travel times to most distant galaxies, time reversal of the big bang, and observations of the 3-K radiation.

A) 1400 years
B) 14,000 years
C) 14,000,000 years
D) 14,000,000,000 years

Question 35

The flatness problem states that

A) the density of the Universe is very close to the critical density.
B) the density of the Universe is much larger than the critical density.
C) the density of the Universe is much less than the critical density.
D) the Universe is two-dimensional.
E) the Universe is one-dimensional.

Question 36

"Seeds" around which galaxies, clusters and walls grew may have been ___________ before inflation and recombination.

A) caused by hot dark matter
B) caused by baryons
C) the result of the separation of the electromagnetic and weak forces
D) the result of freezing water molecules shortly after the Universe became transparent to photons
E) caused by initially tiny quantum mechanical fluctuations in space-time

Question 37

If a galaxy is located at a distance of 18 Mpc and is found to have recessional velocity of 1170 km/s, what is Hubble's constant based only on this galaxy?

A) 65 km/s
B) 75 km/s
C) 55 km/s
D) 85 km/s
E) 95 km/s

Question 38

One explanation of the dark sky Olbers's Paradox is that light can reach us only from objects in space out to a distance in light years _______ the age of the universe in years.

A) less than
B) greater than
C) equal to
D) less than or equal to
E) greater than or equal to

Question 39

If galaxy A is four times more distant than galaxy B, then according to the Hubble law, galaxy A will recede ___________ than galaxy B.

A) 16 times faster
B) 4 times faster
C) 2 times faster
D) 1.2 times faster
E) 0.25 times faster

Question 40

What observational evidence supports the fact that our universe is static and unchanging?

A) detection of the cosmic microwave background (CMB)
B) dark sky at night
C) redshift of galaxies
D) evolution of galaxies with distance
E) None of the other choices are correct.

Question 41

Which of the following is NOT true about the above graph?

A) Helium was formed early in the universe but the universe became too cool for the fusion to continue.
B) Recombination occurs at a lower temperature than electron-positron annihilation.
C) A time existed where neither radiation nor matter dominated in the universe.
D) Temperature increases with time.

Question 42

Large scale structures of the Universe include ___________.

A) filaments
B) voids
C) walls
D) All of the other choices are correct.

Question 43

Which event occurred at a redshift around 1100?

A) big bang
B) inflation
C) CMB
D) first stars formed

Question 44

If a region of the universe during the big bang is the pink/black colors and a region of the universe today shows the sky-blue galaxies and stars, what are the yellow squiggly lines and when did they occur?

A) photons, matter-antimatter annihilation
B) photons, CMB
C) hydrogen fusion to helium, era when neither matter nor radiation dominates
D) gamma rays, dark age

Question 45

As shown in the above graph, neither radiation nor matter dominated for __________.

A) ˜10⁴ years
B) ˜10⁵ years
C) ˜10⁶ years
D) ˜1 second

Question 46

The ___________ is that the Universe is both isotropic and homogeneous.

Question 47

How long is one Hubble time?

A) 1/4 the age of the Universe
B) 1/2 the age of the Universe
C) the age of the Universe
D) double the age of the Universe

Question 48

The Universe contains _____________________.

A) 22.7% baryonic, 4.5% WIMPs, 72.8% dark energy
B) 22.7% normal, 4.5% non-Baryonic, 72.8% dark energy
C) 22.7% non-Baryonic, 4.5% normal, 72.8% dark energy
D) 22.7% dark energy, 4.5% baryonic, 72.8% non-baryonic

Question 49

After recombination occurred, the Universe was plunged into a period of time known as the ___________, which lasted hundreds of millions of years until the first stars were born.

Question 50

In the above observations of the CMB, the mottled (i.e., non-uniform) appearance is due to ___________ in a/an ____________ Universe.

A) irregularities, open
B) hotter temperatures, flat
C) irregularities, flat
D) hotter temperatures, open

Question 51

Which of the above galaxy spectra has the highest blueshift as indicated by velocity value?

A) 1,200 km/s
B) 15,000 km/s
C) 61,000 km/s
D) None of the other choices are correct.

Question 52

Which of the following is a force of nature?

A) gravity
B) weak
C) strong
D) All of the other choices are correct.

Question 53

The ___________ are theories that unify the electromagnetic, weak, and strong forces at extremely high energies.

Question 54

Observations of type Ia supernovae reveal that the expansion of the universe is speeding up because of the presence of ___________ in empty space.

Question 55

If the galaxy shown above has a 6.964 redshift, the galaxy is __________ and __________.

A) young, nearby
B) old, nearby
C) young, far away
D) old, far away

Question 56

The initial high-temperature, high-density state from which time starts is known as the ___________.

Question 57

If the Universe is truly flat, then what is the curvature and type of Universe?

A) positive, open
B) zero, flat
C) negative, closed
D) None of the other choices are correct.

Question 58

If in every direction we point to a star, then the conundrum that the sky is dark is known as ___________.

Question 59

A(n) ___________ Universe is infinite and would have a density equal to the critical density.

Question 60

Which of the following simulated curvatures best matches the above observations of non-uniformity (i.e., irregularities) in the CMB?

A)
B)
C)
D) All of the other choices are correct.

Question 61

The inflationary theory of the Universe may explain why the background radiation is so isotropic.

Question 62

The elements hydrogen and helium were made during the first few minutes after the big bang.

Question 63

The cosmological principle states that any observer in any galaxy will see the same general features of the Universe.

Question 64

Even if the Universe has no edge, it has a center.

Question 65

If the average density of the universe is less than the critical density, the Universe is open.

Question 66

Antiprotons and positrons are examples of ______________, which are not ordinary matter.

Question 67

If the density of the universe is equal to the critical density, and H equals 50 km/s/Mpc, then the true age of the Universe is 13.3 billion years.

Question 68

The deuterium and lithium-7 in distant quasars and in the interstellar medium suggests that the Universe is open.

Question 69

The rate of expansion of the Universe is currently increasing.

Question 70

The redshifts of the galaxies imply that the Universe is expanding and that we are at the center.

Question 71

We are among the products of nuclear fusion and gravitational contraction.

Question 72

If the density of the universe equals the critical density, then the Universe must be ___________ (i.e., having zero curvature).

Question 73

Cosmetologists are the astronomers and physicists who do research in cosmology.

Question 74

Most of the elements heavier than helium were made during the first few minutes after the big bang.

Question 75

The night sky is dark because the Universe is not infinitely old.

Question 76

Cosmology is the study of the structure, history, and evolution of the observable Universe.

Question 77

A center or an edge of the Universe would be a special place, contradicting the cosmological principle.

Question 78

During its early history, matter dominated the Universe.

Question 79

The cosmic microwave background radiation was released shortly after the formation of the first stars.

Question 80

By adding the cosmological constant, Einstein made the universe steady in that the Universe neither expanded nor contracted.