Deck 17: The Birth of the Universe

Question 1

This figure shows the relative strength of the four basic forces as a function of temperature. At what temperature does the strong force become distinct from the electroweak force?

A)about 1032 K
B)about 1027 K
C)about 1015 K
D)These forces were never unified.

Answer 1

B

Question 2

What kinds of atomic nuclei formed during the nucleosynthesis era?

A)essentially all of the chemical elements, except for those heavier than uranium
B)hydrogen, helium and trace amounts of lithium, beryllium, and boron
C)only helium
D)only hydrogen
E)roughly equal amounts of hydrogen, helium, lithium, beryllium, and boron

Answer 2

B

Question 3

How long after the Big Bang was the Planck time, the time at which our current theories become completely unable to describe conditions any earlier in the universe?

A)3 minutes
B)10- 10 seconds
C)380,000 years
D)10- 35 seconds
E)10- 43 seconds

Answer 3

E

Question 4

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

A)The energy released when the strong force froze out of the GUT force caused shock waves that produced ripples in the universe.
B)The shock wave of the Big Bang caused ripples that expanded outward with time.
C)The principles of quantum mechanics require that the energy fields at any point in space be continually fluctuating.
D)The annihilation of matter and antimatter particles caused tiny explosions that produced ripples in the radiation field.
E)The principles of quantum mechanics require that matter and antimatter particles formed from high- energy photons continuously eject energy into the universe causing the ripples.

Question 5

What are the two key observational facts that led to widespread acceptance of the Big Bang model?

A)the predominance of matter over antimatter and the near- critical density of the universe
B)the cosmic background radiation and the near- critical density of the universe
C)the cosmic background radiation and the expansion of the universe
D)the cosmic background radiation and the helium content of the universe
E)the predominance of matter over antimatter and the large scale structure of the universe

Question 6

Laboratory experiments conducted with particle accelerators confirm predictions made by the theory that unifies .

A)the unification of all four forces into a single "superforce"
B)the strong, weak, and electromagnetic forces into the GUT force
C)the strong and weak forces into the combined nuclear force
D)the electromagnetic and weak forces into the electroweak force

Question 7

The electromagnetic force is stronger than gravity. Why is it over- powered by gravity on large scales?

A)The electromagnetic force only works on scales of about an atomic nucleus.
B)Most objects are electrically neutral.
C)Electrical charge is canceled out by mass.
D)The electromagnetic force follows an inverse cube law with distance, rather than an inverse square law.

Question 8

How does the theory of inflation explain the near- uniformity of the cosmic microwave background?

A)The expanding universe would have cooled.
B)Matter was near the critical- density for a universal collapse, which smoothed out the differences in temperatures.
C)Prior to rapid inflation, all regions of space were close enough to bounce radiation back- and- forth and reach the same temperature.
D)Matter expanded into regions of space that had no matter, and thus ended up at the same temperature.

Question 9

Approximately how long did the nucleosynthesis era last?

A)5 years
B)0)001 seconds
C)10- 10 seconds
D)5 seconds
E)5 minutes

Question 10

We have direct experimental evidence (from large particle accelerators)for the physical conditions in the universe back to about after the Big Bang.

A)380,000 years
B)300 years
C)3 minutes
D)10- 10 seconds
E)1 million years

Question 11

Why is the night sky dark?

A)The universe is finite in age.
B)The universe has a physical edge, beyond which there is nothing.
C)The dust clouds in interstellar space block the light.
D)Dark matter obscures light from distant objects.

Question 12

What happens when matter collides with anti- matter?

A)The two particles repel each other, and they fly apart.
B)The two particles destroy each other, and create photons.
C)The two particles attract each other, and form a neutral atom.

Question 13

Which of the following histories are in the correct order of occurrence?

A)The Big Bang happens simultaneously with the start of the expansion of the universe, then stars make the first elements heavier than helium, then the Sun forms.
B)The Big Bang happens simultaneously with the start of the expansion of the universe, then the Sun and stars make the first elements heavier than helium.
C)The Big Bang, then the expansion starts, then the Sun and stars make the first elements heavier than helium.
D)The Big Bang, then the expansion starts, then stars make the first elements heavier than helium, then the Sun forms.

Question 14

A GUT (grand unified theory)refers to theories that

A)unify gravity and the electromagnetic and weak forces.
B)unify the strong force and the electromagnetic and weak forces.
C)unify gravity and the strong and weak forces.
D)unify all four forces.
E)unify the electromagnetic and weak forces.

Question 15

What do we mean by inflation?

A)the photons released when electrons and protons first combined, forming the Cosmic Microwave Background Radiation
B)the sudden release of photons when particles and antiparticles annihilate each other
C)the expansion of universe starting with the instant after the Big Bang
D)a sudden expansion of the universe driven by the energy released when the strong and electroweak forces froze out from the GUT force
E)the rapid expansion of the universe, driven by white dwarf supernova, that we still observe today

Question 16

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

A)We do not yet have a theory that links quantum mechanics and general relativity.
B)We do not yet have a theory that explains how the universe underwent a rapid period of inflationary expansion.
C)We do not yet have a theory that links the weak and electromagnetic forces.
D)The Planck era was the time before the Big Bang, and we cannot describe what happened before the beginning of the universe.
E)We do not understand the properties of the antimatter that would have been produced at this time.

Question 17

From what cosmic epoch do the photons in the cosmic background radiation originate?

A)the end of the Planck era
B)during the era of nucleosynthesis
C)during the era of galaxy formation
D)the end of the era of nuclei
E)the moment of the Big Bang

Question 18

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

A)How many stars are in the universe?
B)What would it be like to ride on a beam of light?
C)Why is the sky dark at night?
D)Can we measure the position and momentum of an electron at the same time?
E)How does the Sun produce energy?

Question 19

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

A)Particle accelerators on Earth can reach energies equivalent to the high temperatures of the Electroweak era and have produced particles predicted by the unified theory.
B)Temperatures in the center of the Sun can reproduce the conditions during the Electroweak era.
C)The most advanced telescopes are able to see back to the GUT era in the universe.
D)Detectors on Earth have received photons and high- energy particles from the GUT era.
E)We have no direct evidence of such a unified force.

Question 20

Helium originates from

A)mostly from stellar nucleosynthesis with a small contribution from the Big Bang.
B)radioactive decay of elements heavier than carbon.
C)stellar nucleosynthesis only.
D)mostly from the Big Bang with a small contribution from stellar nucleosynthesis.
E)the Big Bang only.

Question 21

Which of the following is not consistent with observations of the cosmic microwave background?

A)The universe is at least 20 billion years old.
B)The universe is geometrically "flat" (in the four dimensions of spacetime).
C)The matter density (both luminous and dark matter combined)in the universe is only about one- fourth of the critical density.
D)Dark energy, whatever it is, represents the majority of the energy content of the universe.

Question 22

Which of the following claims cannot be proved or disproved by science?

A)The universe was created by God.
B)The universe is about 14 billion years old.
C)The universe started out very hot.
D)The universe is about 2000 years old.

Question 23

If observations had shown that the cosmic microwave background was perfectly smooth (rather than having very slight variations in temperature), then we would have no way to account for .

A)the relationship between the strong and the weak force
B)how galaxies came to exist
C)the fact that our universe is expanding
D)the existence of helium in the universe

Question 24

Why did the Big Bang not produce heavier elements?

A)By the time helium could survive, the temperature had become too low for heavier elements to form.
B)They did, but radioactive decay caused these elements to disappear again.
C)Too many high energy photons were present during the era of nucleosynthesis for heavy elements to form.

Question 25

Why does the Big Bang theory predict that the cosmic background radiation should have a perfect thermal radiation spectrum?

A)The spectrum of pure hydrogen gas must be a perfect thermal radiation spectrum.
B)The background radiation came from the heat of the universe, with a peak corresponding to the temperature of the universe.
C)The spectrum of 75 percent hydrogen and 25 percent helium must be a perfect thermal radiation spectrum.
D)The light from all the stars and gas in the sky averaged over the entire universe will be a perfect thermal radiation spectrum.
E)It doesn't predict that the cosmic background radiation should have a perfect thermal radiation spectrum.

Question 26

According to the Big Bang theory, why do we live in a universe that is made of almost entirely of matter rather than antimatter?

A)The fact that we live in a universe made of matter is not surprising, because antimatter has never been shown to exist for real.
B)GUT theories predict that under the conditions that prevailed in the early universe, the normal laws of physics would have been suspended so that only matter particles were created, and no particles of antimatter.
C)During the first 0.001 second after the Big Bang, particles and antiparticles were made in almost but not perfectly equal numbers. Everything annihilated except the very slight excess of matter particles.
D)Einstein's famous equation E = mc2 tells us that energy can turn into matter, but does not tell us that it can turn into antimatter.

Question 27

Which of the following statements cannot be tested by science today?

A)The universe is 14 billion years old.
B)The expansion of the universe is now accelerating.
C)Our universe is flat.
D)Prior to the Planck time, our universe sprouted from another universe.

Question 28

The Big Bang theory seems to explain how elements were formed during the first few minutes after the Big Bang. Which hypothetical observation below (these are not real observations)would call our current theory into question?

A)the discovery of a galaxy with a helium abundance of only 10% by mass
B)the discovery of a galaxy with 27% helium rather than the 25% that theory tells us was produced in the Big Bang
C)the discovery of a star- like object made entirely of carbon and oxygen
D)the discovery of a planet that with no helium in its atmosphere

Question 29

Which of the following statements correctly summarizes the events in the early universe according to the Big Bang theory?

A)The Big Bang began with the initiation of what we call inflation, which gradually slowed to the current expansion rate of the universe. Forces came to exist for a different reason, having to do with quantum fluctuations in the space- time continuum. Particles came to exist as a result of cracks made when forces froze. Once there were particles, gravity brought them together to make stars, and the stars then turned the particles into hydrogen, helium, and other elements.
B)An episode of what we call inflation initiated the event of the Big Bang. Once the Big Bang got underway, particles and forces began to appear one by one. The forces produced protons, which fused to make hydrogen and helium until the universe was about 380,000 years old. Then gravity began to act, turning the hydrogen and helium into galaxies.
C)Forces and various subatomic particles began to appear during the first second after the Big Bang. For reasons not understood, the particles were all made of ordinary matter and none were made of antimatter, thus explaining why we live in a universe made of matter. The particles underwent some fusion for the first 380,000 years after the Big Bang, at which time the first stars were born.
D)The universe began with the forces unified. During the first fraction of a second, the forces separated and there was a brief but important episode of inflation. Subatomic particles of both matter and antimatter then began to appear from the energy present in the universe. Most of the particles annihilated to make photons, but some became protons, neutrons, electrons, and neutrinos. The protons and neutrons underwent some fusion during the first five minutes, thereby determining the basic chemical composition of the universe.

Question 30

According to the Big Bang theory, how many forces-and which ones-operated in the universe during the GUT era?

A)1 force that represented the unification of all four forces that operate today
B)2 forces: the strong force and the electroweak force
C)3 forces: gravity, the strong force, and the electroweak force
D)2 forces: gravity and a single force that later became the strong, weak, and electromagnetic forces

Question 31

What is the temperature of the universe (as a whole)today?

A)3000 K
B)3 K
C)300 K
D)The universe cannot be said to have a single temperature.

Question 32

What is postulated to have caused a sudden inflation of the early universe?

A)the energy released from the "freezing out" of the strong force from the GUT force
B)the energy released from the annihilation of matter and antimatter
C)the energy absorbed by giant quantum fluctuations
D)the energy absorbed by the separation of the electromagnetic and weak forces
E)the energy released in the fusion of protons and neutrons to produce helium

Question 33

Why might inflation have occurred at the end of the GUT era?

A)An enormous amount of energy was released when the strong and electroweak forces froze out from the GUT force.
B)Large amounts of matter and antimatter annihilated at this time.
C)Gravity was an extremely weak force at this period in time.
D)The universe was too small and needed to grow quickly.
E)There wasn't enough matter present to slow down the expansion at that time.

Question 34

In principle, if we could see all the way to the cosmological horizon we could see the Big Bang taking place. However, our view is blocked for times prior to about 380,000 years after the Big Bang. Why?

A)Before that time, the gas in the universe was dense and ionized and therefore did not allow light to travel freely.
B)Before that time, the universe was dark so there was no light to illuminate anything.
C)Before that time, the universe was too crowded with stars.
D)380,000 years after the Big Bang marks the time when stars were first born, and thus began to shine the light by which we can see the universe.

Question 35

The four fundamental forces that operate in the universe today are _ .

A)strong force, weak force, electric force, magnetic force
B)nuclear force, gravity, electric force, magnetic force
C)nuclear force, electromagnetic force, gravity, tidal force
D)strong force, weak force, electromagnetic force, gravity

Question 36

The cosmic microwave background gives us a view of the universe when it was

A)14 billion years old.
B)about 1 million years old.
C)380,000 years old.
D)3- 5 minutes old.

Question 37

What happened to all of the quarks that existed freely during the particle era?

A)They combined in groups to make protons, neutrons, and their antiparticles.
B)They evaporated.
C)They froze out of the soup of particles at the end of the era.
D)They combined in groups to make electrons and neutrinos.

Question 38

What are the two possible explanations for not seeing something glowing brightly along every line- of- sight? I)The universe is infinite in size and infinitely old, but dust absorbs starlight from far away stars.
II)The universe has a finite number of stars.
III)The universe is changing in some way as to prevent us from seeing an infinite number of stars.

A)I and II
B)II and III
C)I and III

Question 39

Which event in the history of the universe happened last?

A)Stable helium nuclei formed.
B)The GUT force separated into the electroweak force and strong force.
C)Neutral atoms formed.
D)The electroweak force separated into electromagnetic and weak nuclear forces.

Question 40

What was the significance of the end of the era of nucleosynthesis, when the universe was about 5 minutes old?

A)It marks the time at which the first stars formed.
B)The basic chemical composition of the universe had been determined.
C)The proportions of dark matter and luminous matter had been determined.
D)It marks the time at which the expansion of the universe had settled down to its current rate.

Question 41

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

A)Can we measure the position and momentum of an electron at the same time?
B)Why is the sky dark at night?
C)How many stars are in the universe?
D)What would it be like to ride on a beam of light?

Question 42

What do we mean by inflation?

A)the sudden release of photons when a particle and antiparticle annihilate one another
B)quantum fluctuations by high speed, relativistic particles in a state of false vacuum that caused disturbances in the space- time continuum leading to the process described in the question to which this answer refers
C)the expansion of the universe that we still observe today
D)a sudden and extremely rapid expansion of the universe that occurred in a tiny fraction of a second during the universe's first second of existence

Question 43

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

A)The temperature of the universe can be found by taking an average over the entire sky, but individual stars will create peaks in the temperature over small angles.
B)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.
C)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.
D)Dark matter will smooth out the spectrum, but the small patches of "light" matter create fluctuations in the temperature.
E)The overall structure of the universe is very uniform, but the synthesis of different elements produces varying signatures within the background radiation.

Question 44

Which statement about the cosmic microwave background is not true?

A)With the exception of very small variations, it appears essentially the same in all directions in which we look into space.
B)Its spectrum corresponds to a temperature of just under 3 degrees above absolute zero.
C)It is thought to be radiation that began its journey to our telescopes when the universe was about 380,000 years old.
D)It is the result of a mixture of radiation from many independent sources, such as stars and galaxies.

Question 45

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

A)the electromagnetic and weak forces
B)the strong and electromagnetic forces
C)the strong and weak forces
D)gravity and the strong force
E)gravity and the weak force

Question 46

A "GUT" (grand unified theory)refers to theories that .

A)unify gravity with the strong and weak forces
B)unify the strong force with the electromagnetic and weak forces
C)unify the electromagnetic and weak forces
D)unify all four forces together

Question 47

Which of the following hypothetical observations, if true, would disprove a prediction of the Big Bang theory?

A)the discovery of two galaxies at the same distance, moving away with slightly different speeds
B)the discovery of a galaxy moving toward us
C)the discovery that the temperature of the universe is only 2.73 K
D)the discovery of a galaxy with 10% helium abundance
E)the discovery of a galaxy with 30% helium abundance

Question 48

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

A)It had a much higher temperature in the past.
B)It was discovered by Penzias and Wilson in the mid- 1960s.
C)It has a temperature of about 3 degrees K above absolute zero.
D)It appears essentially the same in all directions (it is isotropic).
E)It is the result of a mixture of radiation from many independent sources, such as stars and galaxies that formed within the first billion years of the Big Bang.

Question 49

Why did the era of nuclei end when the universe was about 380,000 years old?

A)The universe had expanded and cooled enough for stable, neutral atoms to form.
B)The nucleosynthesis era that produced the nuclei heavier than helium ended.
C)All the free particles had combined to form the nuclei of atoms.
D)Atomic nuclei were finally able to escape the plasma of the early universe.
E)Photons were finally able to escape the plasma of the early universe and were no longer available to produce hydrogen and helium nuclei.

Question 50

What is the significance of the Planck time?

A)It is the amount of time required for two protons to fuse to make deuterium.
B)It is the time at which inflation is thought to have occurred.
C)Before it, conditions were so extreme that our current understanding of physics is insufficient to predict what might have occurred.
D)It is the time when the cosmic microwave background was released.

Question 51

How does the idea of inflation account for the existence of the "seeds" of density from which galaxies and other large structures formed?

A)Inflation would have caused random, microscopic quantum fluctuations to grow so large in size that they became the seeds of structure.
B)Inflation predicts that temperatures and densities should have become nearly equal throughout the universe.
C)Inflation predicts that gravity would have been very strong and thereby would have concentrated mass into seeds.
D)Inflation tells us that the universe should have a "flat" overall geometry, and this led to the flat disks of galaxies.

Question 52

The Planck era refers to the time period

A)before the Planck time.
B)after the GUT era.
C)before the Big Bang.
D)after inflation.
E)after the Planck time.

Question 53

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

A)We do not yet have a theory that links quantum mechanics and general relativity.
B)The Planck era was the time before the Big Bang, and we cannot describe what happened before that instant.
C)We do not know how hot or dense the universe was during that time.
D)We do not understand the properties of antimatter.

Question 54

How many forces operated in the universe during the GUT era?

A)One: a single, symmetric "super force"
B)Two: gravity and the GUT force
C)Two: gravity and the electroweak force
D)Three: gravity, the strong force, and the electroweak force
E)All four of the known forces

Question 55

The cosmic microwave background peaks at a wavelength of about 1 mm, and the universe has a temperature of about 3 K. If the microwave background peaked at a wavelength of 10 micrometers, what would its temperature be? (Hint: see Cosmic Calculations 5.1 and 17.1)

A)about 300 K
B)about 0.03 K
C)about 0.3 K
D)about 30 K

Question 56

Based on our current understanding of physics, we can understand the conditions that prevailed in the early universe as far back in time as about .

A)10 billion years ago
B)one ten- billionth of a second after the Big Bang
C)380,000 years after the Big Bang
D)10- 45 seconds after the Big Bang

Question 57

Which adjective does not necessarily describe a known feature of the early universe? (Be sure to consider the universe as a whole, not just the observable universe.)

A)small
B)filled with intense radiation
C)dense
D)hot

Question 58

Early in the history of the universe, the universe was

A)the same temperature it is now.
B)colder.
C)hotter.

Question 59

How do we determine the conditions that existed in the very early universe?

A)The conditions in the very early universe must have been much like those found in stars today, so we learn about them by studying stars.
B)We work backward from current conditions to calculate what temperatures and densities must have been when the observable universe was much smaller in size.
C)We look all the way to the cosmological horizon, where we can see the actual conditions that prevailed all the way back to the first instant of the Big Bang.
D)We can only guess at the conditions, since we have no way to calculate or observe what they were.

Question 60

Creation science claims that scientific evidence can and does prove God made the universe. Select the statement which does not identify a legitimate objection to this claim. (Recall the hallmarks of science.)

A)If "God did it" is the explanation for everything, then final exams in astronomy would be very simple (all answers would be the same!), and science experiments would be very easy to explain, but we wouldn't learn much about the natural world.
B)Scientists are not allowed to believe in God.
C)Science cannot prove (or disprove)the existence of a superpowerful, supernatural deity.
D)The statement that "God did it" cannot be falsified by science, and therefore it is not a statement that science can test.

Question 61

Briefly explain how Hubble's discovery of a relationship between galactic distance and redshift led to the idea of the Big Bang. (Hint: review chapter 16)

Question 62

Rank these times based on the wavelength of the peak intensity of the cosmic background radiation at those times, from shortest to longest. (Hint: consider how the temperature of the universe or the cosmic background radiation changed with time.)

A)100 million years after the Big Bang, 1 million years after the Big Bang, today
B)today, 100 million years after the Big Bang, 1 million years after the Big Bang
C)1 million years after the Big Bang, 100 million years after the Big Bang, today
D)today, 1 million years after the Big Bang, 100 million years after the Big Bang

Question 63

Which of the following is not an observed characteristic of the cosmic microwave background?

A)It has a perfect thermal radiation spectrum.
B)It contains prominent spectral lines of hydrogen, the primary chemical ingredient of the universe.
C)Its temperature is a little less than 3 Kelvin (3 degrees above absolute zero).
D)Its temperature is the same everywhere, except for small variations at the level of 1 part in 100,000.

Question 64

Why did the era of nucleosynthesis end?

A)Too many heavy elements were produced.
B)The temperature of the universe became too low.
C)Neutrinos carried off too much energy.
D)The density of the universe became too low.

Question 65

Which of the following observations cannot be explained by the Big Bang theory unless we assume that an episode of inflation occurred?

A)the fact that the universe is expanding
B)the fact that the temperature of the cosmic microwave background is almost the same everywhere
C)the existence of the cosmic microwave background
D)the fact that about 25% of the ordinary matter in the universe consists of helium

Question 66

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

Question 67

In stars, helium can sometimes be fused into carbon and heavier elements (in their final stages of life). Why didn't the same fusion processes produce carbon and heavier elements in the early universe?

A)Temperatures in the early universe were never above the roughly 100 million Kelvin required for helium fusion.
B)Helium fusion occurred, but the carbon nuclei that were made were later destroyed by the intense radiation in the early universe.
C)By the time stable helium nuclei had formed, the temperature and density had already dropped too low for helium fusion to occur.
D)No one knows-this is one of the major mysteries in astronomy.

Question 68

What happens when a particle of matter meets its corresponding antiparticle of antimatter?

A)They fuse to make a heavier particle.
B)They can form a complete atom.
C)The question makes no sense, since antimatter does not really exist.
D)The combined mass of the two particles is completely transformed into energy (photons).

Question 69

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

A)The cosmic background radiation is expected to have a perfect thermal spectrum, and observations from the COBE spacecraft verify this prediction.
B)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 2.73 K.
C)The cosmic background radiation is expected to look essentially the same in all directions, and it does.
D)The cosmic background radiation is expected to contain redshifted emission lines from hydrogen and helium, and it does.
E)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 70

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

A)All the elements except hydrogen were produced in the nucleosynthesis era.
B)We can study the processes that occurred during the nucleosynthesis era to determine how most of the elements in the universe were created.
C)We can observe spectra from this era to determine what the primordial mix of the elements was at the beginning of the universe.
D)Except for a small amount of elements heavier than helium produced later by stars, the chemical composition of the universe is the same now as at the end of the nucleosynthesis era.
E)By knowing how much matter was created during the nucleosynthesis era, we can determine whether the universe is open or closed.

Question 71

(From a science quiz that appeared in the weekly magazine The Economist.)Economic history is easier to write than the history of the universe. Nevertheless, most cosmologists now think that when the universe was formed,

A)first there was inflation, which caused the Big Bang, then recession.
B)first there was a Big Bang and then inflation (of space)which caused recession (of all matter, away from the Big Bang).
C)first there was a Big Bang. There has not been any inflation yet, but if it comes it will cause recession.

Question 72

In order for the cosmic microwave background to show hydrogen absorption lines at the redshift corresponding to the universe's age of 380,000 years, what condition would have been necessary?

A)There would have needed to be ionized hydrogen (which would contradict the idea that the CMB originates at the time the universe cooled enough for protons and electrons to combine, making neutral atoms).
B)There would have needed to be cooler hydrogen clouds (which would contradict the observation of a uniform temperature in all directions).
C)There would have needed to be even warmer hydrogen clouds (which would contradict the observation of a uniform temperature in all directions).

Question 73

Which of the following statements best explains what we mean when we say that the electroweak and strong forces "froze out" at 10- 38 second after the Big Bang?

A)Following this time, neither the strong nor electroweak forces were ever important in the universe again.
B)These forces are important only at temperatures below the freezing point of water-a temperature that the universe reached at an age of about at 10- 38 second.
C)Freezing out was a term coined by particle physicists who think that the Big Bang theory is really cool.
D)These two forces first became distinct at this time.

Question 74

Briefly explain why radiation was trapped for 380,000 years during the era of nuclei, and why the cosmic background radiation was formed at the end of this era.

Question 75

The Big Bang theory is supported by two major lines of evidence that alternative models have not successfully explained. What are they?

A)(1)The theory predicts the existence of and the specific characteristics of the observed cosmic microwave background; (2)the theory correctly predicts the observed overall chemical composition of the universe.
B)(1)The theory correctly predicts that the universe should be expanding; (2)the theory predicts the existence of and the specific characteristics of the observed cosmic microwave background.
C)(1)The theory predicts the episode of inflation that we think occurred in the early universe; (2)the theory predicts the existence of large quantities of dark matter.
D)(1)The theory correctly predicts that the universe should be expanding; (2)the theory correctly predicts the observed ratio of spiral to elliptical galaxies in the universe.

Question 76

Briefly describe one of the three questions left unanswered by the standard Big Bang theory which are solved by inflation. That is, describe either the structure problem, the uniformity (or smoothness)problem, or the density (or flatness)problem.

Question 77

What is the Big Bang theory?

A)the idea that the universe as we see it formed when two massive galaxies collided together
B)the idea that the galaxy formed from the supernova explosion of a massive star
C)the idea that all matter and energy in the universe began in an unimaginably dense state, and then space itself began expanding

Question 78

Briefly describe the two key pieces of evidence that support the Big Bang theory.

Question 79

This figure shows the temperature of the universe over time, according to models of the Big Bang. At what age did the universe cool to 1 million degrees?

A)about 1 second after the Big Bang
B)about 1015 seconds after the Big Bang
C)about 10- 3 seconds after the Big Bang
D)about 107 seconds after the Big Bang

Question 80

What did the COBE satellite find regarding the smoothness of the cosmic background radiation?