Question 1

The Planck era refers to the time period

Accepted Answer

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

Question 2

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

Accepted Answer

The era of nucleosynthesis is important because during this time, all the primordial hydrogen and helium was created by nuclear fusion. Except for the few percent of matter that stars later fused into heavier elements, the chemical composition set in the nucleosynthesis era remains unchanged today.

Question 3

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

Accepted Answer

COBE found that the cosmic background radiation has a perfect thermal radiation spectrum, with a peak corresponding to a temperature of 2.73 K. However, it also found slight fluctuations in the radiation. The temperature varies very slightly from one place to another by a few parts in 100,000.

Question 4

The observed composition of ordinary matter in the universe-roughly 75 percent hydrogen and 25 percent helium by mass-closely matches theoretical predictions based on the Big Bang model.

Accepted Answer

A) True 
 B)False

Question 5

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

Accepted Answer

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. 
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 6

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

Accepted Answer

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. 
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 7

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?

Accepted Answer

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). 
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 8

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

Accepted Answer

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 
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 9

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

Accepted Answer

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. 
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 10

In the cosmic timeline for the universe starting at the Big Bang, we live in the Planck era.

Accepted Answer

A) True 
 B)False

Question 11

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

Accepted Answer

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. 
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 12

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

Accepted Answer

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. 
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 13

Falsifying a theory: The steady state universe was an alternate hypothesis to the Big Bang. Summarize this hypothesis, and explain the two observations which disproved it.

Accepted Answer

In the steady state universe hypothesis,

Question 14

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

Accepted Answer

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 
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 15

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

Accepted Answer

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 
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 16

Helium originates from

Accepted Answer

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. 
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 17

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)

Accepted Answer

Hubble's discovery showed that the unive

Question 18

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?

Accepted Answer

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. 
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 19

The Big Bang produced no elements heavier than helium because it was never hot enough for helium to undergo fusion.

Accepted Answer

A) True 
 B)False

Question 20

In the particle era, particles of matter outnumbered particles of antimatter by about 1 particle in one billion.

Accepted Answer

A) True 
 B)False

The Planck era refers to the time period

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

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

The observed composition of ordinary matter in the universe-roughly 75 percent hydrogen and 25 percent helium by mass-closely matches theoretical predictions based on the Big Bang model.

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

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

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?

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

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

In the cosmic timeline for the universe starting at the Big Bang, we live in the Planck era.

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

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

Falsifying a theory: The steady state universe was an alternate hypothesis to the Big Bang. Summarize this hypothesis, and explain the two observations which disproved it.

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

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

Helium originates from

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)

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?

The Big Bang produced no elements heavier than helium because it was never hot enough for helium to undergo fusion.

In the particle era, particles of matter outnumbered particles of antimatter by about 1 particle in one billion.

A Modern View of the Universe

Discovering the Universe for Yourself

The Science of Astronomy

Making Sense of the Universe: Understanding Motion, Energy, and Gravity

Light: the Cosmic Messenger

Formation of the Solar System

Earth and the Terrestrial Worlds

Jovian Planet System

Asteroids, Comets, and Dwarf Planets: Their Nature, Orbits, and Impacts

Other Planetary Systems: the New Science of Distant Worlds

Our Star

Surveying the Stars

Star Stuff

The Bizarre Stellar Graveyard

Our Galaxy

A Universe of Galaxies

Dark Matter, Dark Energy, and the Fate of the Universe

Life in the Universe

Filters

Exam 17: The Birth of the Universe

The Planck era refers to the time period

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

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

The observed composition of ordinary matter in the universe-roughly 75 percent hydrogen and 25 percent helium by mass-closely matches theoretical predictions based on the Big Bang model.

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

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

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?

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

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

In the cosmic timeline for the universe starting at the Big Bang, we live in the Planck era.

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

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

Falsifying a theory: The steady state universe was an alternate hypothesis to the Big Bang. Summarize this hypothesis, and explain the two observations which disproved it.

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

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

Helium originates from

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)

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?

The Big Bang produced no elements heavier than helium because it was never hot enough for helium to undergo fusion.

In the particle era, particles of matter outnumbered particles of antimatter by about 1 particle in one billion.

A Modern View of the Universe

Discovering the Universe for Yourself

The Science of Astronomy

Making Sense of the Universe: Understanding Motion, Energy, and Gravity

Light: the Cosmic Messenger

Formation of the Solar System

Earth and the Terrestrial Worlds

Jovian Planet System

Asteroids, Comets, and Dwarf Planets: Their Nature, Orbits, and Impacts

Other Planetary Systems: the New Science of Distant Worlds

Our Star

Surveying the Stars

Star Stuff

The Bizarre Stellar Graveyard

Our Galaxy

A Universe of Galaxies

Dark Matter, Dark Energy, and the Fate of the Universe

Life in the Universe

Filters