Deck 15: Observing the Evolution of the Universe

Question 1

The universe is expanding in such a way suggesting that we live in a matter-dominated universe.

Answer 1

False

Question 2

After carefully removing all potential sources of electronic "noise," including bird droppings inside the microwave horn antenna,Penzias and Wilson realized that they were actually detecting radiation from space.

Answer 2

True

Question 3

If the universe were found to have a positive curvature,than space would be open rather than closed or flat.

Answer 3

False

Question 4

The era of combination occurred about 3 minutes after the Big Bang,and the era of recombination occurred about 3000 years after the Big Bang.

Question 5

There is far more helium in the universe than could have been created by hydrogen fusion in stars alone.

Question 6

Olbers's paradox asks the question,"Is there life elsewhere in the universe?"

Question 7

Temperature variations in the early universe appear as "hot spots" in the cosmic microwave background.The apparent size of these spots depends on the curvature of space.

Question 8

The Andromeda Galaxy has an overall blue shift meaning that it is moving toward the Milky Way Galaxy.

Question 9

The universe has been expanding for billions of years.

Question 10

The strong force is one of the four fundamental forces of the universe and it holds protons and neutrons in the nuclei of atoms.

Question 11

The Hubble law states that the more distant a galaxy,the less its redshift and the slower it is receding from us.

Question 12

The value of the accepted Hubble constant is about 73 km s^-1 Mpc^-1.

Question 13

The question,"If the universe is expanding,what is it expanding into?" can easily be answered with observations.

Question 14

Two prominent research groups came to the same surprising conclusion after taking measurements of the luminosity of Type Ia supernovae at great distances,this being that the universe is accelerating while it expands.

Question 15

Recent satellite missions have confirmed the lumpiness of the cosmic microwave background,which helps explain the current structure of the universe.

Question 16

The strongest of the fundamental forces of the universe is gravity.

Question 17

The theory of everything (TOE)would provide one equation to describe all of the processes in the universe,and there would be no differences among the gravitational,electromagnetic,and strong and weak nuclear forces.

Question 18

Because the universe has continued to expand over the past 13.7 billion years,the radius of our cosmic light horizon is greater than 13.7 billion light-years;the present radius is about 47 billion light-years.

Question 19

The Big Bang explains why so much helium exists in the universe when it could not have been created by hydrogen fusion in stars alone.

Question 20

The wavelengths of light from very distant galaxies are shifted to the blue part of the spectrum,indicating that the universe is contracting.

Question 21

Is the universe really expanding? If so,how do we describe the expansion?

A) It is not expanding-it is our local space that is getting smaller as we fall into a supermassive black hole,making the universe seem bigger and bigger.
B) Space itself is expanding,carrying the galaxies (or superclusters of galaxies)with it.
C) An infinitely small but infinitely dense clump of matter exploded,sending the galaxies (or superclusters of galaxies)hurtling out through space.
D) The energy from all the stars is heating the universe,making it expand like a gas that is heated.

Question 22

What causes cosmological redshift of photons that reach us from distant galaxies?

A) The photons have moved from high gravitational field regions toward lower fields,thereby becoming reddened.
B) The photons were emitted from the galaxies much earlier in time when the overall temperature of matter was much lower.Hence,the observed photons are redder,the farther away from Earth that they were produced.
C) The photons have traveled across space that has been expanding and their wavelengths have expanded with it,becoming redder.
D) The photons were emitted by objects that were moving rapidly away from us,and thereby have been reddened by the Doppler effect.

Question 23

The cosmological redshift of the light from very distant galaxies is caused by

A) the expansion of space,stretching the photon's wavelength while the photon is traveling toward us.
B) absorption of blue light by interstellar dust between us and the galaxy so that only the red wavelengths reach us.
C) the rotation of the universe around its center (faster at greater distances from us).
D) the Doppler shift,in which the photon's wavelength is stretched as the photon is being emitted by the galaxy's motion away from us through space.

Question 24

Because of the general expansion of space,all distant galaxies appear to be moving away from us,with speeds that increase with distance from our Galaxy.Observers in one of these distant galaxies would apparently see all galaxies

A) on one side of the observers moving toward them and all galaxies on the other side moving away from them;the more distant the galaxy,the faster its motion.
B) moving away from them,with the more distant galaxies moving faster.
C) moving away from them,with the closer galaxies moving faster.
D) moving toward them,with the more distant galaxies moving faster.

Question 25

What does Hubble's law give for the age of the universe? (H₀ = Hubble's constant,v is the recessional velocity of objects in the universe,and d = distance to objects in Mpc. )

A) Age = v/H₀
B) Age = H₀
C) Age = d/H₀
D) Age = 1/H₀

Question 26

The farther away a galaxy is,the more its light is redshifted,as seen by us on Earth.This redshift-distance law is caused by

A) energy losses.The universe does not really expand,but photons lose energy as they travel,hence their wavelength lengthens.Photons from more distant galaxies have traveled farther,are more "tired," and so are more redshifted.
B) the expansion of space itself,which stretches the wavelength of the photon.The longer the photon travels,the more space expands and the more the photon is redshifted during the time it is traveling.
C) the gravitational redshift.Photons leaving a more distant galaxy have traveled farther through the galaxy's gravitational field,so they have lost more energy and are more redshifted.
D) the Doppler shift of light leaving a moving object.More distant galaxies are moving faster through space,so their light is more strongly Doppler-shifted toward the red wavelengths.

Question 27

What is the general meaning of the cosmological principle?

A) There is no unique time in our universe;it has always looked the way it is now and will always do so.
B) We do not occupy a special location in space because the universe is the same everywhere,on average.
C) The universe appears to be expanding outward,but this is because of our motion as we descend into a supermassive black hole that has distorted space to produce the illusion of general "expansion."
D) We occupy a very special location near the original location of the Big Bang because everything appears to be moving away from this location as the universe expands.

Question 28

In cosmology,the constant that is intimately related to the present "age" of the universe is

A) 1/G,the inverse of the universal gravitational constant.
B) 1/H₀,the inverse of the constant in Hubble's universal expansion law.
C) The constant in Wien's law of radiation,representing the redness of a spectrum for a certain temperature.
D) The inverse of 10^-43 s,the Planck time at which space and time came into existence

Question 29

Which of the following does NOT describe the universe as envisioned by Isaac Newton?

A) Infinite
B) Static
C) Having existed forever
D) Expanding slowly

Question 30

Which two parameters representing observations of distant objects in the universe are related in the Hubble law?

A) The luminosity of a star and its distance from the center of the galaxy
B) The distance to the object and the redshift of its light
C) The mass of a distant object and its velocity away from our Galaxy
D) The mass of an object and its luminosity

Question 31

For which objects in the universe has the Hubble relation been shown to hold experimentally?

A) Only stars in the near neighborhood of the Sun,in our Galaxy
B) Distant galaxies only
C) Galaxies in the Local Group,in the near vicinity of the Milky Way
D) All objects in the universe,from planets and stars out to the farthest galaxies

Question 32

Where are we?

A) Near the edge of an expanding universe,as shown by the Great Wall of Galaxies
B) Somewhere in an expanding universe,but not in any special part of it
C) At the exact center of an expanding universe,as shown by the universal expansion away from us in all directions
D) Off-center in an expanding universe,as shown by the fact that the microwave background radiation is at a different temperature in one direction than in the opposite direction

Question 33

The resolution of Olber's paradox (i.e. ,the reason why the sky is dark at night)is that

A) we cannot see those stars that are farther away from us than the distance that light has traveled since the beginning of the universe.
B) matter cannot have traveled farther than light has traveled during the age of the universe,so there are no stars beyond a certain distance from us.
C) the light from very distant stars is bent out of our line of sight by the gravitational fields of nearby galaxies.
D) the light from stars beyond a certain,very large distance is completely absorbed by matter between us and the star.

Question 34

In stating his paradox,Olber expected the night sky to be bright and not dark as we see it because he thought that

A) the space between the stars would be filled with gas (such as the Orion Nebula),which would emit light.
B) airglow and auroral light excited by solar particles,by his calculations,would produce significant illumination in our atmosphere.
C) Earth's atmosphere should refract (bend)the sunlight around Earth to illuminate the night sky.
D) every line of sight should eventually intersect a star in an infinite universe randomly scattered with stars.

Question 35

What do cosmologists study?

A) The origin,structure,and evolution of the solar system
B) The formation,structure,and evolution of galaxies
C) The formation,structure,and evolution of stars
D) The origin,structure,and evolution of the universe

Question 36

In our description of the universe,what does the word "isotropic" mean?

A) The expansion is the same in all directions.
B) The speed of expansion is the same at all distances.
C) The speed of expansion at any given distance is the same at all times.
D) The universe is the same everywhere,neither expanding nor contracting.

Question 37

What is the "cosmological redshift"?

A) The stretching of wavelengths of photons by the Doppler shift,because they are emitted by galaxies that are moving away from us
B) The loss of energy of photons as they interact with virtual particles in the vacuum,so that their wavelengths gradually increase as they travel toward us through space
C) The stretching of the wavelengths of photons as they travel through expanding space
D) The stretching of the wavelengths of photons as they pass through absorbing matter in galaxies between us and the emitting galaxy

Question 38

Why does the observable universe have an "edge"?

A) Because there are so many galaxies in the universe that every line of sight eventually hits a galaxy,preventing us from seeing any farther
B) Because the density of neutrinos at the "edge" is so large that photons cannot pass through,preventing us from seeing beyond that point
C) Because absorbing matter prevents us from seeing past a certain distance
D) Because we cannot see any farther than the distance that light has traveled over the lifetime of the universe

Question 39

Calculate the age of the universe if Hubble's constant,H₀,is 73 km/s/Mpc,and the expansion is assumed to be uniform.

A) 2.27 million years
B) 1.43 billion years
C) 13.4 billion years
D) 1340 billion years

Question 40

The Hubble distance-velocity relationship states that

A) all galaxies are being pulled toward a central gravitational attractor in the universe,with the galaxies closest to the center traveling the fastest.
B) the farther away a galaxy is from the Local Group of galaxies,the faster it is traveling toward this group.
C) the farther away a galaxy is from our Galaxy,the faster it appears to be traveling away from it.
D) all galaxies are being repelled by the pressure from the hot central "engine" of the universe,with the ones closest to the center traveling the fastest.

Question 41

Strong evidence for an original Big Bang,which "created" our universe,comes from

A) the very high flux of 21-cm radio energy,coming from the atomic hydrogen atoms produced in the explosion.
B) the rapid motions of some nearby stars,such as Barnard's star.
C) the amount of gas and dust in the solar neighborhood.
D) a background "glow" of microwaves,with blackbody temperature of about 3 K.

Question 42

What is the cosmic microwave background radiation?

A) An almost-uniform background radiation from distant,unresolved,overlapping galaxies
B) Radiation left over from the Big Bang,after the universe expanded and cooled
C) A uniform background of radiation from electrons spiraling in weak intergalactic magnetic fields
D) Radiation from a very tenuous,ionized gas that fills the universe equally in all directions

Question 43

When the intensity of the cosmic microwave background radiation is plotted against wavelength,what is the shape of the resulting curve?

A) Emission lines from hydrogen gas,strongest and most densely concentrated in the microwave region
B) A blackbody curve modified by many deep,overlapping absorption lines and several emission lines
C) A composite of many overlapping blackbody curves from gas clouds of different temperatures,peaking in the microwave region
D) An almost perfect blackbody spectrum peaking in the microwave region

Question 44

Which of the following statements does NOT correctly describe the universe at the era of recombination?

A) The universe was about 380,000 years old.
B) Electrons and protons combined to form neutral hydrogen atoms.
C) The temperature of the universe was about 3 K.
D) The universe became transparent to radiation.

Question 45

The formation of the solar system occurred at what point in the history of the universe?

A) Right at the beginning
B) During the first third
C) About halfway through
D) About two-thirds of the way through

Question 46

If the density of matter in the universe turned out to be greater than the critical density,it would imply that the universe is

A) closed.
B) open.
C) oscillating.
D) contracting.

Question 47

The cosmic microwave background radiation is not uniform over the sky: It is slightly hotter toward the constellation Leo and slightly cooler in the opposite direction toward Aquarius.Why?

A) The background radiation really is uniform;the observed difference is due to Earth's motion through the universe.
B) That is the way the universe began: hotter in one direction and cooler in the other.
C) The difference is probably a statistical fluctuation,and therefore not real.
D) Earth is slightly off-center in the universe,so one side of the universe is a bit closer and the other side is a bit farther away.

Question 48

The cosmic background radiation is

A) the flux of visible radiation contributed to empty space by all visible stars in the universe.
B) the beam of atomic nuclei,also known as cosmic rays,which rain down continuously on Earth from all directions in space.
C) the radio noise generated by Earth-bound transmitters,spreading out into space since about 1920.
D) low-intensity radio noise,with a 3 K blackbody temperature,almost uniform in intensity in all directions.

Question 49

Which of the following sources contributes the greatest number of photons to the general radiation background in our universe?

A) The cosmic microwave background,the remnant of the Big Bang
B) The very large number of average solar-type cool stars,contributing vast numbers of visible and infrared photons
C) Atomic hydrogen,which is very abundant throughout the universe,contributing mainly 21-cm radio photons.
D) Extremely hot intergalactic gas in clusters of galaxies,producing copious numbers of X-ray photons

Question 50

What was the approximate temperature of the universe at the time when the universe became transparent to radiation?

A) 30 billion K
B) 3000 K
C) 3 K
D) 300,000 K

Question 51

The effect that makes the cosmic microwave background appear slightly warmer in one direction and cooler in the opposite direction is

A) the focusing effect of the gravitational field of the local galaxy on the radiation.
B) the presence of many extra sources of the radiation in one direction.
C) a basic asymmetry in the background radiation,related to its origin.
D) the Doppler shift,caused by motion of our Galaxy through space toward the constellation Leo.

Question 52

What is the temperature of the cosmic microwave background radiation we detect as a blackbody curve that originated in the Big Bang?

A) 3 K
B) 3000 K
C) 30 billion K
D) 30 K

Question 53

Who discovered the radiation left over from the Big Bang,the so-called "cosmic microwave background"?

A) Anthony Hewish and Jocelyn Bell
B) Robert Dicke and P.J.E.Peebles
C) Arno Penzias and Robert Wilson
D) Ralph Alpher and George Gamow

Question 54

At an age of 380,000 years,the temperature of the universe had fallen to 3000 K,and electrons could then combine with protons to produce hydrogen gas instead of roaming freely through space.What major transition occurred as a consequence of this change in the universe at this time?

A) The universe would have lost its electrical charge suddenly to become electrically neutral.
B) The present laws of physics were applicable to the properties of the universe for the first time.
C) The universe became transparent to light for the first time.
D) Nuclear fusion no longer occurred below this temperature,so general fusion throughout the universe would have ceased.

Question 55

Which of the following statements correctly describes the universe for the entire first 380,000 years of its life?

A) All of the fundamental forces were united into one force.
B) It was filled with free quarks (not confined inside neutrons or protons).
C) It was a sea of nuclear reactions occurring at a gradually decreasing rate.
D) It was opaque.

Question 56

What significant event occurred about 380,000 years after the Big Bang started?

A) The universe became transparent to radiation.
B) All of the present galaxies in the universe were formed within a short time span.
C) The temperature of the radiation decreased to 2.76 K.
D) The solar system was formed.

Question 57

Why does the cosmic microwave background appear to be slightly warmer in one direction in the sky and slightly cooler in the opposite direction?

A) Because this is the direction in which the Big Bang occurred,hence we are seeing the remnant of the explosion in this direction
B) Because the center of the Local Group of galaxies is in this direction and this is a bright source of microwaves
C) Because the radiation in one direction is Doppler-shifted to shorter wavelengths by Earth's motion in space and to longer wavelengths in the other direction
D) Because the amount of dark matter in that direction in space has focused the radiation slightly by gravitational lensing,making this direction appear hotter

Question 58

The very small detected irregularities in the uniformity of the cosmic microwave background are considered to be important in the study of the evolution of our universe because they

A) were the seeds of supermassive black holes around which all galaxies then formed.
B) are thought to have led to the development of the present concentrations of matter and energy in superclusters of galaxies.
C) are thought to contain most of the elusive "missing matter" in the form of energy concentration in the universe.
D) show us how non-uniform the Big Bang explosion was.

Question 59

The cosmic microwave background was discovered by

A) rocket-borne telescopes while they were searching for X-ray sources in space.
B) the Voyager 2 spacecraft during one of its "coasting" periods between planetary encounters.
C) the IRAS satellite,which produced an all-sky infrared survey.
D) scientists testing a new antenna and receiver for satellite communications.

Question 60

What was the COBE satellite designed to measure?

A) 21-cm radio radiation from intergalactic hydrogen
B) Redshifts of objects at cosmological distances,to obtain an accurate measurement of Hubble's constant
C) X-rays from quasars and other objects at cosmological distances
D) The cosmic microwave background radiation

Question 61

Astrophysicists believe the dominant hot spots in the cosmic background radiation should be about 1° in angular size if the universe is flat.What do experimental measurements of this angular size tell us?

A) The measurements show angular sizes of less than 1°,which suggests that the universe is spherical.
B) The measurements show angular separations of about 1°,which suggests that the universe is flat.
C) The measurements show angular sizes larger than 1°,which suggests that the universe is hyperbolic.
D) The measurements thus far are inconclusive.

Question 62

What method is being used to discover whether we live in an unbounded universe,in which expansion will continue forever,or a bounded universe,in which expansion will eventually turn into contraction and lead us to recollapse?

A) Careful monitoring of the Moon-Earth distance to detect the slowdown of the expansion of the universe
B) Measurement of the deviation from uniformity of the cosmic background radiation
C) Measurement of the curvature of the Hubble relationship,v = H₀d,at large distances
D) Measurement of the bending of light by distant galaxies as it follows the curvature of space

Question 63

The weak force

A) acted only during the Big Bang and has no known role in the universe at the present time.
B) holds the quarks together inside a proton or neutron.
C) acts during certain kinds of radioactive decay.
D) attracts the electrons to the nucleus,holding the atom together.

Question 64

What kind of curvature (geometry of space)does the universe have if the universe is unbounded (density < critical density)?

A) Flat
B) Closed
C) Open
D) Curvature does not depend on density.

Question 65

In cosmology,the phrase "critical density" refers to the

A) smallest density that will produce inflation of the universe.
B) density below which stars will never form.
C) density above which the universe is opaque to radiation.
D) density needed to produce precisely flat space,on average,throughout the universe.

Question 66

Which parameter of the present universe,more than any other,is considered to be critical in determining the ultimate fate of the universe?

A) The average density of neutrinos
B) The average density of matter
C) The average density of black holes throughout the universe
D) The average density of photons of radiation

Question 67

If space has a flat geometry,what will happen to two initially parallel flashlight beams as they traverse billions of light-years of space?

A) They will remain parallel.
B) They will gradually diverge (move apart)to a maximum separation,and then gradually converge and cross.
C) They will gradually converge (move together)and eventually cross.
D) They will gradually diverge (move apart).

Question 68

The degree of "flatness" of the universe,which determines whether we live in an open or a closed universe,has been determined recently by measuring the

A) average density of matter compared to the average density of radiation energy.
B) typical size of the "hot spots" in the structure of the cosmic microwave background.
C) hemispheric asymmetry in the temperature of the cosmic microwave background radiation.
D) extent of the bending of light from distant galaxies,the so-called "lensing."

Question 69

The present universe seems to require a "cosmological constant" equivalent to that introduced into general relativity by Einstein when his theory would not explain the expected static universe.What is the effect on the evolution of the present universe of the "new" cosmological constant?

A) It produces a pressure to oppose the mutual gravitational pull of all the matter in the universe,accelerating its expansion.
B) It is a term that accounts for the negative gravity generated by antimatter in the universe,the presence of which will produce an accelerated expansion.
C) It just balances gravity to allow the universe to remain static,as Einstein predicted.
D) It produces an extra attractive force in addition to gravity,slowing down the expansion of the universe.

Question 70

What kind of curvature (geometry of space)does the universe have if the universe is bounded (density > critical density)?

A) Flat
B) Closed
C) Open
D) Curvature does not depend on density.

Question 71

What is "dark energy"?

A) The energy associated with the matter that has fallen into a black hole
B) The matter-energy needed to bridge the gap between the energy we see or infer and the energy needed to make the universe flat
C) The energy associated with "dark matter"
D) The unseen matter-energy needed to make the observed curvature of space spherical (as we believe it should be),whereas the observed matter-energy only makes it hyperbolic

Question 72

Recent results from very bright supernovae in very distant galaxies seem to indicate that the expansion of the universe

A) is continuing at a constant rate and has done so since just after the Big Bang.
B) has now stopped and the universe will shortly begin to contract again toward a recollapse.
C) is accelerating (speeding up).
D) is decelerating (slowing down).

Question 73

Opposite sides of the universe have the same temperature,yet according to the standard Big Bang theory,these points are too far apart for light to have traveled from one side to the other in the age of the universe;that is,they cannot have exchanged heat to even out their temperature.Why,then,do they have the same temperature?

A) Light (and heat)could travel much faster in the early universe,allowing them to exchange heat while the universe was young.
B) The expansion of the universe has always been the same everywhere;therefore,all parts of the universe have the same temperature,regardless of whether they have ever exchanged heat or not.
C) Pure coincidence
D) They were originally close together and evened out their temperature,then a rapid inflation of the universe carried them far apart.

Question 74

What kind of curvature (geometry of space)does the universe have if the universe is just bounded (density = critical density)?

A) Flat
B) Closed
C) Open
D) Curvature does not depend on density.

Question 75

How many fundamental forces are known in science?

A) Five
B) Three
C) Four
D) Six

Question 76

The isotropy of the cosmic microwave background radiation (same temperature in all directions)indicates that

A) the universe has always been dominated by matter.
B) the universe had an early period of inflation in which regions initially in contact were carried out of contact with each other.
C) the universe did not begin to expand significantly until after the era of recombination.
D) regions that appear to us to be on opposite sides of the visible universe are in fact in close contact with each other.

Question 77

How many fundamental forces are there in nature?

A) Three: strong,electromagnetic,and gravitational
B) Six: color,strong,weak,magnetic,electric,and gravitational
C) Five: strong,weak,magnetic,electric,and gravitational
D) Four: strong,weak,electromagnetic,and gravitational

Question 78

Which of the four fundamental forces holds the electrons in the atom?

A) Gravitational force
B) Weak nuclear force
C) Electromagnetic force
D) Strong nuclear force

Question 79

What is the range of the gravitational force (the maximum distance over which it acts)?

A) 1026 m,or roughly the distance to the farthest quasars
B) Infinity
C) 1013 m,or roughly the size of the solar system
D) 1021 m,or roughly the size of the Milky Way Galaxy

Question 80

Immediately after the cosmological singularity,the four forces were indistinguishable.Then they began to "branch off" and become separate.Which was the first of the four to branch off?

A) Gravitation
B) The weak force
C) The strong force
D) Electromagnetism