Question 1

A particle and an antiparticle have:

Accepted Answer

A) the same mass and the same electric charge. 
B) the same mass and equal electric charges of opposite sign. 
C) equal masses of opposite sign and the same electric charge. 
D) equal masses of opposite sign and equal charges of opposite sign. 
A) the same mass and the same electric charge. 
B) the same mass and equal electric charges of opposite sign. 
C) equal masses of opposite sign and the same electric charge. 
D) equal masses of opposite sign and equal charges of opposite sign.

Question 2

Particle-antiparticle pairs are coming into existence all the time in the space around (and inside!) us. According to the Heisenberg uncertainty principle, the more massive the particles, the:

Accepted Answer

A) shorter the time that they can exist. 
B) less precisely we know their position. 
C) longer the time that they can exist. 
D) more precisely we know their position. 
A) shorter the time that they can exist. 
B) less precisely we know their position. 
C) longer the time that they can exist. 
D) more precisely we know their position.

Question 3

The formula for the Jeans length is   , where m is the single particle mass and ρm is the density. Population III stars formed in the early universe where the material consisted almost entirely of hydrogen and helium rather than material enriched by heavy elements. Thus, for the formation of Population III stars, LJ was:

Accepted Answer

A) small because ρm was large. 
B) small because m was large. 
C) large because m was small. 
D) unaffected by the composition of the material. 
A) small because ρm was large. 
B) small because m was large. 
C) large because m was small. 
D) unaffected by the composition of the material.

Question 4

All of the following are attributes of string theory EXCEPT one. Which is the EXCEPTION?

Accepted Answer

A) Some of the dimensions of spacetime are hidden. 
B) Massive particles are predicted-perhaps giving a clue to dark matter. 
C) String theories can include quantum gravity. 
D) String theory has been discredited in favor of M-theory. 
A) Some of the dimensions of spacetime are hidden. 
B) Massive particles are predicted-perhaps giving a clue to dark matter. 
C) String theories can include quantum gravity. 
D) String theory has been discredited in favor of M-theory.

Question 5

The early universe had a large flux of neutrinos and antineutrinos. What happened to them?

Accepted Answer

A) They annihilated to produce protons and antiprotons. 
B) They are still present as a cosmic background. 
C) They were absorbed by matter, giving it some of the additional energy required for inflationary expansion. 
D) They were absorbed by neutrons to form protons and electrons. 
A) They annihilated to produce protons and antiprotons. 
B) They are still present as a cosmic background. 
C) They were absorbed by matter, giving it some of the additional energy required for inflationary expansion. 
D) They were absorbed by neutrons to form protons and electrons.

Question 6

How was the "deuterium bottleneck" removed so that helium could form?

Accepted Answer

A) With the formation of the first stars, nucleosynthesis had a confined, uninterrupted space in which to produce both deuterium and hydrogen. 
B) The formation of deuterium requires the strong force, and this did not separate out from the other forces until sometime after the cosmic singularity. When it did, the deuterium bottleneck ended. 
C) As the universe expanded, its photons cooled, lost energy, and eventually became unable to disrupt deuterium. 
D) As the universe expanded, the protons and neutrons cooled, lost energy, and were eventually able to stick together without bouncing apart. 
A) With the formation of the first stars, nucleosynthesis had a confined, uninterrupted space in which to produce both deuterium and hydrogen. 
B) The formation of deuterium requires the strong force, and this did not separate out from the other forces until sometime after the cosmic singularity. When it did, the deuterium bottleneck ended. 
C) As the universe expanded, its photons cooled, lost energy, and eventually became unable to disrupt deuterium. 
D) As the universe expanded, the protons and neutrons cooled, lost energy, and were eventually able to stick together without bouncing apart.

Question 7

Why is it that we find no free (unbound) neutrons floating around in the universe today, whereas free protons and electrons exist in profusion?

Accepted Answer

A) Free neutrons decay spontaneously to produce protons, electrons, and neutrinos. 
B) The free neutrons interact quickly with the free electrons to produce antiprotons, so there are few neutrons left. 
C) The original Big Bang produced only charged particles; hence neutrons were not produced, and those that now exist in the nuclei of atoms have come from proton decay. 
D) Free neutrons react readily with free protons to produce high-energy photons, or γ radiation. 
A) Free neutrons decay spontaneously to produce protons, electrons, and neutrinos. 
B) The free neutrons interact quickly with the free electrons to produce antiprotons, so there are few neutrons left. 
C) The original Big Bang produced only charged particles; hence neutrons were not produced, and those that now exist in the nuclei of atoms have come from proton decay. 
D) Free neutrons react readily with free protons to produce high-energy photons, or γ radiation.

Question 8

Suppose the Jeans length in a large interstellar cloud at a temperature of 20 K is 0.8 ly. If the cloud gradually heats up to 40 K while its density remains constant, what would happen to the Jeans length?

Accepted Answer

A) The Jeans length would decrease to 0.4 ly. 
B) The Jeans length would increase to 1.6 ly. 
C) The Jeans length would increase to 1.1 ly. 
D) The Jeans length would decrease to 0.6 ly. 
A) The Jeans length would decrease to 0.4 ly. 
B) The Jeans length would increase to 1.6 ly. 
C) The Jeans length would increase to 1.1 ly. 
D) The Jeans length would decrease to 0.6 ly.

Question 9

The universe began in the Big Bang. When did were the first atoms formed?

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 10

The era of recombination saw the formation of the first permanent atoms, paving the way for the formation of larger structures. At this time the mass contained in a volume 1 Jeans length on a side was about 500,000 M. ${\odot}$ This suggests the mass of a typical structure formed early in the universe. What familiar object has this mass?

Accepted Answer

A) a spiral galaxy 
B) a Population III star 
C) an open cluster 
D) a globular cluster 
A) a spiral galaxy 
B) a Population III star 
C) an open cluster 
D) a globular cluster

Question 11

Tritium (3H) is a heavy isotope of hydrogen, composed of one proton and two neutrons. Tritium decays into 3He, a light isotope of helium, composed of two protons and one neutron, through the reaction . ${ }^{3} H \rightarrow{ }^{3} H e+\bar{e}+\bar{v}$ The production of an electron and an antineutrino in this decay shows that the reaction was governed by the:

Accepted Answer

A) electromagnetic force. 
B) gravitational force. 
C) strong force. 
D) weak force. 
A) electromagnetic force. 
B) gravitational force. 
C) strong force. 
D) weak force.

Question 12

When did the inflationary epoch occur?

Accepted Answer

A) during the Planck time-that is, during the first 10-43 seconds after the cosmological singularity 
B) immediately after the Planck time 
C) throughout the first 3 minutes 
D) throughout the first 380,000 years 
A) during the Planck time-that is, during the first 10-43 seconds after the cosmological singularity 
B) immediately after the Planck time 
C) throughout the first 3 minutes 
D) throughout the first 380,000 years

A particle and an antiparticle have:

Particle-antiparticle pairs are coming into existence all the time in the space around (and inside!) us. According to the Heisenberg uncertainty principle, the more massive the particles, the:

All of the following are attributes of string theory EXCEPT one. Which is the EXCEPTION?

The early universe had a large flux of neutrinos and antineutrinos. What happened to them?

How was the "deuterium bottleneck" removed so that helium could form?

Why is it that we find no free (unbound) neutrons floating around in the universe today, whereas free protons and electrons exist in profusion?

Suppose the Jeans length in a large interstellar cloud at a temperature of 20 K is 0.8 ly. If the cloud gradually heats up to 40 K while its density remains constant, what would happen to the Jeans length?

The universe began in the Big Bang. When did were the first atoms formed?

When did the inflationary epoch occur?

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

Exam 26: Exploring the Early Universe

A particle and an antiparticle have:

Particle-antiparticle pairs are coming into existence all the time in the space around (and inside!) us. According to the Heisenberg uncertainty principle, the more massive the particles, the:

All of the following are attributes of string theory EXCEPT one. Which is the EXCEPTION?

The early universe had a large flux of neutrinos and antineutrinos. What happened to them?

How was the "deuterium bottleneck" removed so that helium could form?

Why is it that we find no free (unbound) neutrons floating around in the universe today, whereas free protons and electrons exist in profusion?

Suppose the Jeans length in a large interstellar cloud at a temperature of 20 K is 0.8 ly. If the cloud gradually heats up to 40 K while its density remains constant, what would happen to the Jeans length?

The universe began in the Big Bang. When did were the first atoms formed?

When did the inflationary epoch occur?

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