Question 1

What does the theory of quantum electrodynamics describe?

Accepted Answer

A) the change of one type of quark into another type of quark into another type of quark by the weak force 
B) the interactions of charged particles by the exchange of virtual photons 
C) the bonding between quarks by the exchange of gluons 
D) the interactions of nuclear particles by the strong force 
A) the change of one type of quark into another type of quark into another type of quark by the weak force 
B) the interactions of charged particles by the exchange of virtual photons 
C) the bonding between quarks by the exchange of gluons 
D) the interactions of nuclear particles by the strong force

Question 2

The first 380,000 years of our universe, before matter and radiation decoupled, were dominated by the primordial fireball filled with an immense quantity of radiant energy. What was the source of these photons?

Accepted Answer

A) They were created during the cosmic singularity and bounced around until the universe became transparent to radiation. 
B) They were given off when the free electrons were captured by protons to form the first hydrogen atoms. 
C) As the universe expanded and the radiation cooled, photons no longer had enough energy to create particles by pair production. But particles continued to annihilate and produce additional photons. 
D) The "fireball" that we see in the distant past is really a reflection of all the radiation produced before that time bouncing back from the universe in its early opaque state. 
A) They were created during the cosmic singularity and bounced around until the universe became transparent to radiation. 
B) They were given off when the free electrons were captured by protons to form the first hydrogen atoms. 
C) As the universe expanded and the radiation cooled, photons no longer had enough energy to create particles by pair production. But particles continued to annihilate and produce additional photons. 
D) The "fireball" that we see in the distant past is really a reflection of all the radiation produced before that time bouncing back from the universe in its early opaque state.

Question 3

The early universe was characterized by a much lower metal content than the present universe. What difference did that make to the process of star formation?

Accepted Answer

A) The first generation of stars had lower metallicity than the present generation, but in each era the formation of large stars and small stars was equally likely. 
B) It is easier to make a gas and dust cloud collapse when the metal content is low. Thus, even small stars could be formed in the early universe, but large stars were a rarity. 
C) It is harder to make a gas and dust cloud collapse when the metal content is low. Thus, even small stars could be formed in the early universe, but large stars were a rarity. 
D) It is harder to make a gas and dust cloud collapse when the metal content is low. Thus, large stars were more likely to be formed in the early universe, but small stars were a rarity. 
A) The first generation of stars had lower metallicity than the present generation, but in each era the formation of large stars and small stars was equally likely. 
B) It is easier to make a gas and dust cloud collapse when the metal content is low. Thus, even small stars could be formed in the early universe, but large stars were a rarity. 
C) It is harder to make a gas and dust cloud collapse when the metal content is low. Thus, even small stars could be formed in the early universe, but large stars were a rarity. 
D) It is harder to make a gas and dust cloud collapse when the metal content is low. Thus, large stars were more likely to be formed in the early universe, but small stars were a rarity.

Question 4

Why might it be impossible for us to observe the very massive particles predicted by string theory?

Accepted Answer

A) They are not actually particles, but just points in space. 
B) Extremely high energies are needed to create these particles. 
C) The fundamental strings that make up these particles vibrate at frequencies we cannot detect. 
D) The particles do not exist in three-dimensional space. 
A) They are not actually particles, but just points in space. 
B) Extremely high energies are needed to create these particles. 
C) The fundamental strings that make up these particles vibrate at frequencies we cannot detect. 
D) The particles do not exist in three-dimensional space.

Question 5

The universe began in the Big Bang. When did the first stars and galaxies begin to appear?

Accepted Answer

A) immediately, as they were a direct product of the Big Bang 
B) about 380,000 years later 
C) about 400 million years later 
D) not until about 3.2 billion years later 
A) immediately, as they were a direct product of the Big Bang 
B) about 380,000 years later 
C) about 400 million years later 
D) not until about 3.2 billion years later

Question 6

During what time was helium created in the Big Bang?

Accepted Answer

A) during the first 300,000 years 
B) during the first 10-43 second 
C) during the first 10-6 second 
D) during the first 15 minutes 
A) during the first 300,000 years 
B) during the first 10-43 second 
C) during the first 10-6 second 
D) during the first 15 minutes

Question 7

What is the deuterium bottleneck?

Accepted Answer

A) Deuterium had to form before helium could form, but deuterium is easily destroyed, thus preventing the formation of helium. 
B) Deuterium absorbs neutrons efficiently, thus producing heavier and heavier isotopes of hydrogen instead of heavier elements such as helium. 
C) Deuterium had to form before helium could form, but deuterium is almost impossible to create, thus preventing the formation of helium. 
D) Helium is used up in the formation of deuterium. However, deuterium is difficult to create, thus leaving us with large amounts of helium. 
A) Deuterium had to form before helium could form, but deuterium is easily destroyed, thus preventing the formation of helium. 
B) Deuterium absorbs neutrons efficiently, thus producing heavier and heavier isotopes of hydrogen instead of heavier elements such as helium. 
C) Deuterium had to form before helium could form, but deuterium is almost impossible to create, thus preventing the formation of helium. 
D) Helium is used up in the formation of deuterium. However, deuterium is difficult to create, thus leaving us with large amounts of helium.

Question 8

Suppose the inflationary epoch lasted 10-32 seconds. How much mass could have been created in a virtual pair during this time without violating the law of conservation of energy?

Accepted Answer

A) 2 × 10-27 kg, about the mass of one hydrogen atom 
B) 10-19 kg 
C) about 1 kg 
D) 2 × 1030 kg, about the mass of the Sun 
A) 2 × 10-27 kg, about the mass of one hydrogen atom 
B) 10-19 kg 
C) about 1 kg 
D) 2 × 1030 kg, about the mass of the Sun

Question 9

Detailed examination of the cosmic microwave background suggests that the material from which it scattered had been re-ionized. What do we believe to be the source of this reionization?

Accepted Answer

A) The cosmic microwave background itself caused the reionization of hydrogen and helium. 
B) Large, hot Population III stars emitted enough high-energy radiation during their lifetimes to cause reionization. 
C) The intense background of neutrinos and antineutrinos released much earlier than the cosmic microwave background radiation had enough energy to cause reionization. 
D) The explosions of giant Population III stars would cause a shower of high-speed particles that could result in reionization. 
A) The cosmic microwave background itself caused the reionization of hydrogen and helium. 
B) Large, hot Population III stars emitted enough high-energy radiation during their lifetimes to cause reionization. 
C) The intense background of neutrinos and antineutrinos released much earlier than the cosmic microwave background radiation had enough energy to cause reionization. 
D) The explosions of giant Population III stars would cause a shower of high-speed particles that could result in reionization.

Question 10

The Higgs particle is particularly important because other particles, through their interaction with the Higgs field, gain:

Accepted Answer

A) energy. 
B) mass. 
C) charge. 
D) strangeness. 
A) energy. 
B) mass. 
C) charge. 
D) strangeness.

Question 11

In 1919, Theodor Kaluza introduced a five-dimensional spacetime. In 1995 Edward Witten extended this to 11 dimensions. Was this necessary? Why?

Accepted Answer

A) No, this was not really necessary. Witten was attempting to recast the theory to make its connections with general relativity more apparent. 
B) Yes, this was necessary. Mistakes had been found in the earlier theory, and additional dimensions seemed the easiest way to fix these. 
C) Yes, this was necessary. Between Kaluza and Witten, two additional forces had been discovered, and the natural solution was to add more dimensions to the theory. 
D) Yes, this was necessary. Witten's extra dimensions were specifically an attempt to account for dark matter. 
A) No, this was not really necessary. Witten was attempting to recast the theory to make its connections with general relativity more apparent. 
B) Yes, this was necessary. Mistakes had been found in the earlier theory, and additional dimensions seemed the easiest way to fix these. 
C) Yes, this was necessary. Between Kaluza and Witten, two additional forces had been discovered, and the natural solution was to add more dimensions to the theory. 
D) Yes, this was necessary. Witten's extra dimensions were specifically an attempt to account for dark matter.

Question 12

What is the range of the strong nuclear force compared to the size of the nucleus, 10-14 m?

Accepted Answer

A) The range of the strong nuclear force is 10 times smaller than the size of an atomic nucleus. 
B) The range of the strong nuclear force is infinite; it has no limit. 
C) The range of the strong nuclear force is the same as the size of the nucleus. 
D) The range of the strong nuclear force is 10 times larger than the size of an atomic nucleus. 
A) The range of the strong nuclear force is 10 times smaller than the size of an atomic nucleus. 
B) The range of the strong nuclear force is infinite; it has no limit. 
C) The range of the strong nuclear force is the same as the size of the nucleus. 
D) The range of the strong nuclear force is 10 times larger than the size of an atomic nucleus.

Question 13

The neutrino has been shown to have a small mass. What difference does that make in determining its speed?

Accepted Answer

A)  Because it is a particle with mass, its speed is governed by the temperature of its surroundings because it will always be in thermal equilibrium. 
B)  Because it is a particle with mass, its speed must be less than the speed of light, c. 
C)  Its speed must be faster than the speed of light, because this is the only way that a lepton can have mass. 
D)  Because of its nature, a neutrino can only exist when it is traveling at the speed of light, just like photons of electromagnetic radiation. 
A)  Because it is a particle with mass, its speed is governed by the temperature of its surroundings because it will always be in thermal equilibrium. 
B)  Because it is a particle with mass, its speed must be less than the speed of light, c. 
C)  Its speed must be faster than the speed of light, because this is the only way that a lepton can have mass. 
D)  Because of its nature, a neutrino can only exist when it is traveling at the speed of light, just like photons of electromagnetic radiation.

Question 14

In the present-day universe there are about 10 hydrogen atoms (1H) to each helium atom (4He). Considering just hydrogen and helium (the vast majority of matter), what is the ratio of neutrons to protons?

Accepted Answer

A) 1:10 
B) 1:6 
C) 1:4 
D) 1:1 
A) 1:10 
B) 1:6 
C) 1:4 
D) 1:1

Question 15

The mass of a proton is 1.67 × 10-27 kg. For what maximum length of time could a proton-antiproton pair spontaneously come into existence, without violating any laws of physics such as conservation of energy?

Accepted Answer

A) 3.5 × 10-25 s 
B) 1.1 × 10-16 s 
C) 2.2 × 10-16 s 
D) 7.0 × 10-27 s 
A) 3.5 × 10-25 s 
B) 1.1 × 10-16 s 
C) 2.2 × 10-16 s 
D) 7.0 × 10-27 s

Question 16

The inflationary epoch accomplished all of the following EXCEPT one. Which is the EXCEPTION?

Accepted Answer

A) It took whatever curvature the early universe had and flattened it. 
B) The epoch allowed the early, preinflationary universe to be very small and thus capable of thermal equalization. 
C) It permitted matter to move faster than the speed of light for a brief period. 
D) It forced the observed density of the universe to be equal to the critical density to great precision. 
A) It took whatever curvature the early universe had and flattened it. 
B) The epoch allowed the early, preinflationary universe to be very small and thus capable of thermal equalization. 
C) It permitted matter to move faster than the speed of light for a brief period. 
D) It forced the observed density of the universe to be equal to the critical density to great precision.

Question 17

Where and how was most of the helium in the universe created?

Accepted Answer

A) by nuclear reactions in the cores of stars, and was then thrown out into space by supernovae 
B) by the collision of cosmic rays with hydrogen nuclei in interstellar gas clouds 
C) by high-energy processes during the collapse of protogalactic clouds during the formation of galaxies 
D) by nuclear reactions during the Big Bang 
A) by nuclear reactions in the cores of stars, and was then thrown out into space by supernovae 
B) by the collision of cosmic rays with hydrogen nuclei in interstellar gas clouds 
C) by high-energy processes during the collapse of protogalactic clouds during the formation of galaxies 
D) by nuclear reactions during the Big Bang

Question 18

Models of the evolution of structure in the early universe fall into the categories of "bottom-up" formation (stars $ \rightarrow $ superclusters) or "top-down" formation (large sheets $ \rightarrow $ galaxies and stars). What parameter in the assumptions for the model is most important in determining which one of these scenarios results?

Accepted Answer

A) whether dark matter is hot or cold, cold dark matter resulting in the top-down scenario 
B) whether dark matter is hot or cold, hot dark matter resulting in the top-down scenario 
C) whether neutrinos have mass, massless neutrinos resulting in the top-down scenario 
D) whether the early universe had an abundance or a scarcity of metals, an abundance resulting in the bottom-up scenario 
A) whether dark matter is hot or cold, cold dark matter resulting in the top-down scenario 
B) whether dark matter is hot or cold, hot dark matter resulting in the top-down scenario 
C) whether neutrinos have mass, massless neutrinos resulting in the top-down scenario 
D) whether the early universe had an abundance or a scarcity of metals, an abundance resulting in the bottom-up scenario

Question 19

During the epoch of cosmic inflation, the universe expanded very rapidly. What was the effect on the temperature of the universe?

Accepted Answer

A) As the universe expanded rapidly, it cooled rapidly. Thereafter it expanded and cooled at a more moderate rate. 
B) Because of the incredible speed of the expansion, there was no time for particles to exchange energy. Thus, the temperature remained constant during the expansion. 
C) Because of the tremendous amount of energy available, the temperature actually rose during the expansion. 
D) The temperature decreased during the expansion and then rose again to essentially the value it had initially. 
A) As the universe expanded rapidly, it cooled rapidly. Thereafter it expanded and cooled at a more moderate rate. 
B) Because of the incredible speed of the expansion, there was no time for particles to exchange energy. Thus, the temperature remained constant during the expansion. 
C) Because of the tremendous amount of energy available, the temperature actually rose during the expansion. 
D) The temperature decreased during the expansion and then rose again to essentially the value it had initially.

Question 20

According to the Heisenberg uncertainly principle, can matter spontaneously come into existence without having been created from energy?

Accepted Answer

A) No, never. Matter is a form of energy, and the spontaneous creation of matter would violate conservation of energy. 
B) Yes, but only for extremely short times. 
C) Yes, but only if the particles created are electrically neutral. 
D) Yes, but only if an equal amount of matter disappears from some other part of the universe. 
A) No, never. Matter is a form of energy, and the spontaneous creation of matter would violate conservation of energy. 
B) Yes, but only for extremely short times. 
C) Yes, but only if the particles created are electrically neutral. 
D) Yes, but only if an equal amount of matter disappears from some other part of the universe.

Exam 26: Exploring the Early Universe

What does the theory of quantum electrodynamics describe?

The first 380,000 years of our universe, before matter and radiation decoupled, were dominated by the primordial fireball filled with an immense quantity of radiant energy. What was the source of these photons?

The early universe was characterized by a much lower metal content than the present universe. What difference did that make to the process of star formation?

Why might it be impossible for us to observe the very massive particles predicted by string theory?

The universe began in the Big Bang. When did the first stars and galaxies begin to appear?

During what time was helium created in the Big Bang?

What is the deuterium bottleneck?

Suppose the inflationary epoch lasted 10-32 seconds. How much mass could have been created in a virtual pair during this time without violating the law of conservation of energy?

Detailed examination of the cosmic microwave background suggests that the material from which it scattered had been re-ionized. What do we believe to be the source of this reionization?

The Higgs particle is particularly important because other particles, through their interaction with the Higgs field, gain:

In 1919, Theodor Kaluza introduced a five-dimensional spacetime. In 1995 Edward Witten extended this to 11 dimensions. Was this necessary? Why?

What is the range of the strong nuclear force compared to the size of the nucleus, 10-14 m?

The neutrino has been shown to have a small mass. What difference does that make in determining its speed?

In the present-day universe there are about 10 hydrogen atoms (1H) to each helium atom (4He). Considering just hydrogen and helium (the vast majority of matter), what is the ratio of neutrons to protons?

The mass of a proton is 1.67 × 10-27 kg. For what maximum length of time could a proton-antiproton pair spontaneously come into existence, without violating any laws of physics such as conservation of energy?

The inflationary epoch accomplished all of the following EXCEPT one. Which is the EXCEPTION?

Where and how was most of the helium in the universe created?

During the epoch of cosmic inflation, the universe expanded very rapidly. What was the effect on the temperature of the universe?

According to the Heisenberg uncertainly principle, can matter spontaneously come into existence without having been created from energy?

Astronomy and the Universe

Knowing the Heavens

Eclipses and the Motion of the Moon

Gravitation and the Waltz of the Planets

The Nature of Light

Optics and Telescopes

Comparative Planetology I: Our Solar System

Comparative Planetology II: the Origin of Our Solar System

The Living Earth

Our Barren Moon

Mercury, Venus, and Mars: Terrestrial, yet Unique

Jupiter and Saturn: Lords of the Planets

Jupiter and Saturns Satellites of Fire and Ice

Uranus, Neptune, Pluto, and the Kuiper Belt: Remote Worlds

Asteroids, Comets, and Impacts

Our Star, the Sun

The Nature of the Stars

The Birth of Stars

Stellar Evolution: on and After the Main Sequence

Stellar Evolution: The Death of Stars

Stellar Remnants: Neutron Stars and Black Holes

Our Galaxy

Galaxies

Quasars and Active Galaxies

Cosmology: The Origin and Evolution of the Universe

The Search for Extraterrestrial Life

Filters

Suppose the inflationary epoch lasted 10^-32 seconds. How much mass could have been created in a virtual pair during this time without violating the law of conservation of energy?

What is the range of the strong nuclear force compared to the size of the nucleus, 10^-14 m?

In the present-day universe there are about 10 hydrogen atoms (¹H) to each helium atom (⁴He). Considering just hydrogen and helium (the vast majority of matter), what is the ratio of neutrons to protons?

The mass of a proton is 1.67 × 10^-27 kg. For what maximum length of time could a proton-antiproton pair spontaneously come into existence, without violating any laws of physics such as conservation of energy?