PHYS 1412: Quiz - Cosmology

100% -- finally. Still 92 percentile, now 55.8 mean, 28.5 SD. Flonky numbers.

All quiz attempts concatenated with duplicate questions removed.

Question 1
Which of the following processes slowed the collapse of protogalactic clouds?

1. the formation of the first generation of stars
2. the conversion of gravitational potential energy into kinetic and thermal energy as the cloud collapsed
3. the shock waves from the exploding supemovae of the earliest stars
4. the pull of gravity of the mass of the cloud material
5. the radiating away of thermal energy

Question 2
What evidence suggests that the protogalactic cloud that formed the Milky Way resulted from several collisions among smaller clouds?

1. The stars in the halo of the Milky Way are organized into several dense clusters arranged throughout the halo.
2. The Milky Way resembles an elliptical galaxy more than other spirals do.
3. Halo stars differ in age and heavy-element content, but these variations do not seem to depend on the stars' distance from the galactic center.
4. The bulge of the Milky Way is surrounded by many globular clusters, just as elliptical galaxies are.
5. The Milky Way is the central galaxy of a cluster of galaxies.

Question 3
The most active galactic nuclei are usually found at large distances from us; relatively few nearby galaxies have active galactic nuclei. What does this imply?

1. Massive black holes existed only when the universe was young and no longer exist today.
2. Active galactic nuclei tend to become less active as they age.
3. Active galactic nuclei can form only at large distances from the Milky Way.
4. The jets seen in many active galactic nuclei must cause them to move far away from us.

Question 4
Which of the following types of protogalactic clouds is most likely to form an elliptical galaxy?

1. a very low-density cloud with very little angular momentum
2. a dense cloud with very little angular momentum
3. a low-density cloud with quite a bit of angular momentum
4. a dense cloud with quite a bit of angular momentum
5. a very massive cloud with any density and a lot of angular momentum

Question 5
If we represent the Milky Way galaxy as the size of a baseball (10-cm diameter), the distance to the Andromeda Galaxy would be about

1. 10 cm.
2. 2.5 m.
3. 25 m.
4. 1 km.
5. 100 km.

Question 6
Which of the following is not a piece of evidence supporting the conclusion that active galactic nuclei are powered by accretion disks around massive black holes?

1. Observed radiation from the galactic center varies significantly in brightness in times as short as a few days.
2. Infrared observations show that many stars are forming near the centers of active galaxies.
3. Radio observations sometimes show long jets of material extending millions of light-years out from the galactic center.
4. The total amount of radiation coming from the galactic center is, in some cases, comparable to the amount of radiation put out by 10 billion or more ordinary stars.
5. Spectral lines from the galactic center indicate that clouds of gas are orbiting a central object at very high speed.

Question 7
What is a galactic wind?

1. a jet of ionized particles shot out of a starburst galaxy
2. hot gas erupting into intergalactic space from a large superbubble
3. the heat (infrared radiation) emitted by dust grains in the large molecular clouds of starburst galaxies
4. the cooler gas pushed out of a starburst galaxy by the intense radiation pressure
5. a wind created by the expansion of the universe that can move galaxies around

Question 8
How do we determine the amount of dark matter in elliptical galaxies?

1. We measure the orbital velocities of star-forming gas clouds around the outer portions of the galaxy.
2. We measure the speeds of stars at different radii from the galactic center and determine how much mass is interior to the orbit.
3. We count the number of stars in the galaxy and determine its volume, so that we can calculate the galaxy's density.
4. We search for dark lanes of dust and black holes within the galaxy.
5. We measure how fast the galaxy rotates as a whole.

Question 9
What evidence suggests that the Milky Way contains dark matter?

1. We observe clouds of atomic hydrogen far from the galactic center orbiting the galaxy at unexpectedly high speeds, higher speeds than they would have if they felt only the gravitational attraction from objects that we can see.
2. We see many lanes of dark material blocking out the light of stars behind them along the band of the Milky Way.
3. We see many dark voids between the stars in the halo of the Milky Way.
4. When we observe in different wavelengths, such as infrared or radio, we see objects that don't appear in visible-light observations.
5. When we look at the galactic center, we are able to observe a large black hole that is composed of dark matter.

Question 10
If the universe is open, it will expand forever.

1. True
2. False

Question 11
Although we don't know exactly when clusters, galaxies, or stars began forming, we do know that clusters came first, with galaxies and stars forming later.

1. True
2. False

Question 12
Compared to the central regions of spiral galaxies, we expect elliptical galaxies to have

1. higher mass-to-light ratios because stars in elliptical galaxies are dimmer than those in spirals.
2. lower mass-to-light ratios because stars in elliptical galaxies are dimmer than those in spirals.
3. higher mass-to-light ratios because stars in elliptical galaxies do not have high orbital velocities.
4. lower mass-to-light ratios because elliptical galaxies have less gas and dust than spirals.
5. the same mass-to-light ratio because they are made of the same material, stars and dark matter.

Question 13
Dark matter is purely hypothetical, because we have no way of detecting its presence.

1. True
2. False

Question 14
Why can't current theories describe what happened during the Planck era?

1. We do not yet have a theory that links quantum mechanics and general relativity.
2. We do not understand the properties of antimatter.
3. We do not know how much energy existed during that time.
4. It was a time period from which we cannot receive radiation.
5. The Planck era was the time before the Big Bang, and we cannot describe what happened before that instant.

Question 15
Approximately how long did the era of nucleosynthesis last?

1. 10 ^-10 second
2. 0.001 second
3. 3 seconds
4. 3 minutes
5. 3 years

Question 16
The Planck era is another name for the present period of time in the universe.

1. True
2. False

Question 17
How long after the Big Bang was the Planck time, before which our current theories are completely unable to describe conditions in the universe?

1. 10 ^-10 second
2. 10 ^-35 second
3. 10 ^-43 second
4. 3 minutes
5. 300,000 years

Question 18
Which of the following statements about the cosmic background radiation is not true?

1. It has a temperature of about 3 degrees K above absolute zero.
2. It is the result of a mixture of radiation from many independent sources, such as stars and galaxies.
3. It had a much higher temperature in the past.
4. It was discovered by Penzias and Wilson in the early 1960's.
5. It appears essentially the same in all directions (it is isotropic).

Question 19
You are in a place that is extremely hot and dense, making you feel quite sweaty and claustrophobic. You can't see far because your surroundings are opaque to light. Around you, nuclear fusion is converting carbon into oxygen and other elements. Where are you?

1. You are in the center of a star very much like our Sun.
2. You are in the early universe during the era of nucleosynthesis.
3. You are inside a nuclear power plant on Earth.
4. You are in the center of a massive star near the end of its life.
5. You are in the center of a star much smaller than the Sun.

Question 20
A GUT (grand unified theory) refers to theories that

1. unify all four forces.
2. unify gravity and the electromagnetic and weak forces.
3. unify gravity and the strong and weak forces.
4. unify the strong force and the electromagnetic and weak forces.
5. unify the electromagnetic and weak forces.

Question 21
Why should galaxy collisions have been more common in the past than they are today?

1. Galaxies were more active in the past and therefore would have collided with each other more frequently.
2. Galaxies were much bigger in the past since they had not contracted completely.
3. Galaxies were closer together in the past because the universe was smaller.
4. Galaxies attracted each other more strongly in the past because they were more massive; they had not yet turned most of their mass into stars and light.
5. Galaxy collisions shouldn't have been more common in the past than they are now.

Question 22
What evidence suggests that small galaxies in our Local Group have undergone two or more starbursts in the past?

1. We observe several small galaxies currently undergoing massive star formation.
2. We see small galaxies in which many stars have one age and many others have another age that is billions of years older.
3. We see evidence that small galaxies in our Local Group have experienced several collisions in the past.
4. We see evidence that several small galaxies were shot out of larger galaxies in our Local Group during an age of starburst activity.
5. We do not have any evidence that galaxies in our Local Group were once starburst galaxies.

Question 23
In the 19605, Maarten Schmidt determined that quasars were very distant objects by

1. determining how luminous they were.
2. determining how small the source of light was from its variations in luminosity.
3. discovering that they were embedded in distant galaxies.
4. determining their redshifts.
5. determining their parallax angles.

Question 24
Starburst galaxies produce most of their light in the infrared.

1. True
2. False

Question 25
A protogalactic cloud with slow star formation is more likely to form a spiral galaxy than an elliptical galaxy.

1. True
2. False

Question 26
If a galaxy's overall mass-to-light ratio is 100 solar masses per solar luminosity, and its stars account for only 5 solar masses per solar luminosity, how much of the galaxy's mass must be dark matter?

1. 100%
2. 95%
3. 80%
4. 50%
5. 5%

Question 27
Some MACHOs emit radiation. Why are they considered dark matter?

1. They are not as bright as a normal star and are not visible across great distances of space.
2. They don't emit light in the visible wavelength range.
3. They emit radiation only in the form of particles of dark matter.
4. They are made of particles of dark matter that release some radiation.

Question 28
If they exist, MACHOs are expected to be found only in the disk of the Milky Way, whereas WIMPs would be found only in the halo.

1. True
2. False

Question 29
Which of the following statements about rich clusters of galaxies (those with thousands of galaxies) is not true?

1. They are sources of X-ray emission due to the presence of hot, intergalactic gas.
2. There likely have been numerous collisions among the member galaxies at some time in the past.
3. Galaxies in the central regions are predominantly spirals, while elliptical galaxies roam the outskirts.
4. They often have a very large, central dominant galaxy near their center, perhaps formed by the merger of s.everal individual galaxies.
5. The speeds of the galaxies in the cluster indicate that most of the cluster mass is dark matter.

Question 30
If inflation really occurred, then our observable universe is only a tiny portion of the entire universe born in the Big Bang.

1. True
2. False

Question 31
The Planck era refers to the time period

1. before the Big Bang.
2. before the Planck time.
3. after the Planck time.
4. after inflation.
5. after the GUT era.

Question 32
Olbers' paradox is an apparently simple question, but its resolution suggests that the universe is finite in age. What is the question?

1. What would it be like to ride on a beam of light?
2. Can we measure the position and momentum of an electron at the same time?
3. How does the Sun produce energy?
4. Why is the sky dark at night?
5. How many stars are in the universe?

Question 33
You are in a hot, dense place. You are surrounded by protons and neutrons, some rapidly fusing into helium. You notice that your surroundings are cooling (good, because it's really hot!) and rapidly dropping in density. Within about 3 minutes, the fusion reactions stop. Where are you?

1. You are in the center of a star very much like our Sun.
2. You are in the early universe during the era of nucleosynthesis.
3. You are inside a nuclear power plant on Earth.
4. You are in the center of a star much smaller than the Sun.
5. You are in the center of a massive star near the end of its life.

Question 34
You are in a place where the heat and high density are not bothering you. However, although the density is very low, the gas around you is extremely high in temperature. In fact, the temperature is so high that it is emitting lots of X rays, which are creating cancer-causing mutations in your body at a rapid rate. Well, at least the view is great! There are no stars anywhere within about 10,000 light-years of you, but at slightly greater distances your sky is brightened by many beautiful, star-filled structures, some with majestic spiral shapes. Where are you?

1. You are in the universe when it was about 200 million years old, just before galaxies began forming.
2. You are in the center of the Milky Way Galaxy, looking outward into the Local Group.
3. You are somewhere between the Andromeda and Milky Way galaxies in the Local Group.
4. You are in intergalactic space within a rich cluster of thousands of galaxies.
5. You are in the outskirts of a galaxy whose nucleus is a powerful quasar.

Question 35
Talk about cold, dark, and empty! As far as you look around you, there seems to be nothing at all. Even the nearest electron is light-years away. And, no matter how far you travel, you can find no solid matter, not even a single proton. You do, however, detect a few strong gravitational fields -probably due to black holes -at enormous distances away from you. Where are you?

1. You are in the outskirts of a young cluster of galaxies.
2. You are in the universe when it is over about 10^40 years old.
3. You are in the universe when it is over about 10 ^110 years old.
4. You are in the central regions of a quasar.
5. You are where the Sun should be located, but about 5 billion years from now.

Question 36
What is a central dominant galaxy?

1. a galaxy around which many other smaller galaxies orbit
2. a giant spiral galaxy that exerts large tidal forces on other nearby galaxies
3. a spiral galaxy from which many smaller galaxies formed when it was stripped apart by tidal forces
4. a giant elliptical galaxy at the center of a dense cluster
5. a hypothesized galaxy type that no longer exists but once dominated the structure of the universe

Question 37
What is a quasar?

1. a starlike object that actually represents a bright patch of gas in the Milky Way
2. a very large galaxy thought to be formed by the merger of several smaller galaxies, typically found in the center of a galaxy cluster
3. a specialized astronomical instrument for observing distant stars.
4. the extremely bright center of a distant galaxy, thought to be powered by a massive black hole
5. another name for very bright stars of spectral type O

Question 38
Neutrinos are classified as baryons.

1. True
2. False

Question 39
Why do we expect WIMPs to be distributed throughout galactic halos, rather than settled into a disk?

1. They are light enough that they have expanded out into the halo.
2. WIMPs were produced at the early stages of galaxy evolution, and objects in the halo, such as globular clusters, were formed at the beginning of the galaxy.
3. Since they do not interact with the electromagnetic force, they do not feel friction or drag and hence do not contract with the rest of the protogalactic cloud.
4. Shock waves from supemovae have blown the WIMPs out into the halo.
5. Jets from the early active stage of a galaxy's life shot out most of the WIMPs from the disk.

Question 40
Gravitational lensing occurs when

1. massive objects bend light beams that are passing nearby.
2. massive objects cause more distant objects to appear much larger than they should and we can observe the distant objects with better resolution.
3. dark matter builds up in a particular region of space, leading to a very dense region and an extremely high mass-to-light ratio.
4. telescope lenses are distorted by gravity

Question 41
Which of the following particles are baryons?

1. electrons
2. neutrinos
3. protons
4. quarks
5. photons

Question 42
Observations of the cosmic background radiation from the COBE satellite revealed tiny variations in its temperature from one place to another (corresponding to a few millionths of a degree Kelvin).

1. True
2. False

Question 43
What direct evidence do we have that the weak and electromagnetic forces were once unified as a single electroweak force?

1. The most advanced telescopes are able to see back to this era in the universe.
2. Detectors on Earth have received photons and high-energy particles from this era.
3. Temperatures in the center of the Sun can reproduce the conditions during this era.
4. Particle accelerators on Earth can reach energies equivalent to the high temperatures of this era and have produced particles predicted by the electroweak theory.
5. We have no direct evidence of the electroweak force.

Question 44
Why do we expect the cosmic background radiation to be almost, but not quite, the same in all directions ?

1. The overall structure of the universe is very uniform, but the universe must have contained some regions of higher density in order for galaxies to form.
2. The temperature of the universe can be found by taking an average over the entire sky, but individual stars will create peaks in the spectrum over small angles.
3. Dark matter consisting of WIMPs greatly smooths out the spectrum, but the small patches of "light" matter create peaks in the spectrum.
4. The overall structure of the universe is very uniform, but the synthesis of different elements produces varying signa tures within the background spectrum.
5. The overall structure of the universe is very uniform, but intervening gas between us and the era of nuclei absorbs wavelengths depending on the composition and redshift of the gas.

Question 45
Evidence that the cosmic background radiation really is the remnant of a Big Bang comes from predicting characteristics of remnant radiation from the Big Bang and comparing these predictions with observations. Four of the five statements below are real. Which one is fictitious?

1. The cosmic background radiation is expected to have a temperature just a few degrees above absolute zero, and its actual temperature turns out to be about 3 K (actually 2.7 K).
2. The cosmic background radiation is expected to have a perfect thermal spectrum, and observations from the COBE spacecraft verify this prediction.
3. The cosmic background radiation is expected to contain spectral lines of hydrogen and helium, and it does.
4. The cosmic background radiation is expected to look essentially the same in all directions, and it does.
5. The cosmic background radiation is expected to have tiny temperature fluctuations at the level of about 1 part in 100,000. Such fluctuations were found in the COBE data.

Question 46
What do we mean by inflation?

1. what happened the instant after the Big Bang
2. a sudden expansion of the universe after the strong force froze out from the GUT force
3. the expansion of the universe that we still observe today
4. the sudden release of photons when a particle and antiparticle annihilate each other
5. the separation that occurs after two photons collide and create a particle and an antiparticle

Question 47
Why do we believe that starburst galaxies represent a temporary stage in galaxy evolution?

1. We observe starbursts to last only a few years at a time.
2. Such galaxies produce so much light that they would have consumed all their gas long ago if they had always been forming stars at this high rate.
3. We don't see any nearby starburst galaxies.
4. All starburst galaxies look like normal spiral galaxies, aside from the starbursts.

Question 48
Galaxy collisions were more common in the past.

1. True
2. False

Question 49
Why is a dense cloud more likely to produce an elliptical galaxy than a spiral galaxy?

1. The higher density of gas has a stronger force of gravity, and therefore the cloud collapses more quickly.
2. The force of gravity can pull the material into a more spherical shape.
3. The more frequent collisions between particles randomize the particle orbits.
4. The thickness of the dense cloud prevents a disk from forming.
5. The higher gas density forms stars more efficiently, so all the gas is converted into stars before a disk can form.

Question 50
What evidence supports the idea that a collision between two spiral galaxies might lead to the creation of a single elliptical galaxy?

1. observations of some elliptical galaxies surrounded by shells of stars that probably formed from stars stripped out of smaller galaxies
2. the fact that elliptical galaxies dominate the galaxy populations at the cores of dense clusters of galaxies
3. observations of some elliptical galaxies with stars and gas clouds in their cores that orbit differently from the other stars in the galaxy
4. observations of giant elliptical galaxies at the center of dense clusters that may have grown by consuming other galaxies
5. all of the above

Question 51
If we learn that the universe is closed, it will mean that the universe is presently contracting, rather than expanding as generally believed.

1. True
2. False

Question 52
Which of the following methods used to determine the mass of a cluster does not depend on Newton's laws of gravity?

1. measuring the orbital velocities of galaxies in a cluster
2. measuring the temperature of X-ray gas in the intracluster medium
3. measuring the amount of distortion caused by a gravitational lens
4. none of the above

Question 53
Based on inventoried matter in the universe, including dark matter known to exist in galaxies and clusters, the actual density of the universe is what fraction of the critical density?

1. 1%
2. 10%
3. 25%
4. 100%
5. 200%

Question 54
By definition, our Sun has a mass-to-light ratio of 1 solar mass per solar luminosity.

1. True
2. False

Question 55
Currently, we may understand the behavior of matter and energy well enough to describe generally what was happening in the universe -after the Big Bang.

1. 1 million years
2. 300,000 years
3. 300 years
4. 3 minutes
5. 10 ^-10 second

Question 56
Based on current evidence concerning the amount of deuterium in the universe, we can conclude that

1. ordinary (baryonic) matter makes up most of the mass of the universe.
2. neutrons greatly outnumber protons in the universe.
3. most of the deuterium that was created during the era of nucleosynthesis has since been destroyed.
4. the density of ordinary (baryonic) matter is between 1% and 10% of the critical density.
5. we live in a critical-density universe.

Question 57
GUT theories predict that protons will eventually decay, causing all solid objects in the universe to fall apart if the universe keeps expanding forever.

1. True
2. False

Question 58
Why do we think tiny quantum ripples should have been present in the very early universe?

1. The shock wave of the Big Bang caused ripples that expanded outward with time.
2. The energy released when the strong force froze out of the GUT force caused shock waves that produced ripples in the universe.
3. Matter and antimatter particles that spontaneously formed from high-energy photons caused perturbations in the radiation field.
4. The annihilation of matter and antimatter particles caused tiny explosions that perturbed the radiation field.
5. Quantum mechanics requires that the energy fields at any point in space be continually fluctuating as a result of the uncertainty principle.

Question 59
< Quasars radiate most of their energy as radio emission.

1. True
2. False

Question 60
One possible ingredient of dark matter is known as WIMPs, or weakly interacting massive particles. WIMPs probably are made of protons and neutrons.

1. True
2. False

Question 61
If there is no dark matter in the Milky Way Galaxy, what is the best alternative explanation for the observations?

1. We are not measuring the orbital velocities of atomic clouds and stars properly.
2. We are not measuring the distances to atomic clouds and stars properly.
3. We are not attributing enough mass to the visible or "bright" matter.
4. We are not observing all the visible or "bright" matter in the galaxy.
5. Our understanding of gravity is not correct for galaxy-size scales.

Question 62
What kinds of atomic nuclei formed during the era of nucleosynthesis?

1. only hydrogen
2. only helium
3. hydrogen and helium and trace amounts of lithium, beryllium, and boron
4. roughly equal amounts of each of the following: hydrogen, helium, lithium, beryllium, and boron
5. nuclei of all the chemical elements

Question 63
Why did the era of nuclei end when the universe was about 300,000 years old?

1. All the free particles had combined to form the nuclei of atoms.
2. The universe had expanded and cooled to a temperature of about 3,000 K, cool enough for stable, neutral atoms to form.
3. Neutrinos and electrons were finally able to escape the plasma of the early universe and no longer heated the other particles.
4. Photons were finally able to escape the plasma of the early universe and no longer heated the hydrogen and helium ions.
5. No theory can explain this.

Question 64
Why is the era of nucleosynthesis so important in determining the chemical composition of the universe?

1. All the elements except hydrogen were produced after the era of nucleosynthesis.
2. We can observe spectra from this era to determine what the primordial mix of the elements was at the beginning of the universe.
3. Except for the small amount of matter produced later by stars, the chemical composition of the universe is the same now as at the end of the era of nucleosynthesis.
4. We can study the processes that occurred during the era of nucleosynthesis to determine how most of the elements in the universe were created.
5. By knowing how much matter was created during the era of nucleosynthesis, we can determine whether the universe is open or closed.

Question 65
What evidence supports the theory that elliptical galaxies come from denser clouds?

1. Elliptical galaxies are denser than spiral galaxies.
2. Elliptical galaxies are generally larger than spiral galaxies.
3. Elliptical galaxies are more commonly found in clusters of galaxies.
4. Elliptical galaxies have more gas than spiral galaxies.
5. Elliptical galaxies have denser stars than spiral galaxies.

Question 66
Starburst galaxies produce most of their light in the wavelength range of

1. X rays.
2. the ultraviolet.
3. the visible.
4. the infrared.
5. all wavelengths.

Question 67
individual galaxies generally have higher mass-to-light ratios than clusters of galaxies.

1. True
2. False

Question 68
Which forces have physicists shown to be the same force under conditions of very high temperature or energy, as confirmed by experiments in particle accelerators?

1. gravity and the weak force
2. gravity and the strong force
3. the strong and weak forces
4. the strong and electromagnetic forces
5. the electromagnetic and weak forces