Question 1

What is the minimum combined energy of the photons that would produce an electron-positron pair? (Note: me is the rest mass of an electron.)

Accepted Answer

A)  2mec2 
B)  mec2 
C)  1/2mec2 
D)  me2c4 
E)  This cannot happen. 
A)  2mec2 
B)  mec2 
C)  1/2mec2 
D)  me2c4 
E)  This cannot happen.

Question 2

If dark energy is causing the expansion rate of the universe to increase with time, does this mean that you should worry that the Sun, Earth, and your body itself are expanding? Why or why not?

Accepted Answer

Dark energy is indeed causing space to e

Question 3

Describe two different experiments that offer evidence for a flat universe.

Accepted Answer

The observational data obtained from the

Question 4

The figure below shows five graphs of the scale factor of the universe as a function of time.Which of these graphs would occur for a universe with  $\Omega$ m =1 and  $\Omega$ $\bigwedge$  = 0?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
E)  E 
A)  A 
B)  B 
C)  C 
D)  D 
E)  E

Question 5

Which of the following have both been predicted and conclusively confirmed experimentally?

Accepted Answer

A)  the decay of protons 
B)  the inflationary model 
C)  the carrier particles for the force of gravity 
D)  the Higgs boson 
E)  the 10 spatial dimensions in superstring theory 
A)  the decay of protons 
B)  the inflationary model 
C)  the carrier particles for the force of gravity 
D)  the Higgs boson 
E)  the 10 spatial dimensions in superstring theory

Question 6

Which forces would a grand unified theory (GUT) unify?

Accepted Answer

GUT unifies three of the four

Question 7

Explain what the anthropic principle implies for our visible universe, and give a specific example of a small change that would make life impossible.

Accepted Answer

The anthropic principle says that condit

Question 8

The mechanism of ________ can simultaneously solve both the flatness and horizon problems in cosmology.

Accepted Answer

A)  nucleosynthesis 
B)  quantum tunneling 
C)  TOE 
D)  inflation 
E)  dark energy 
A)  nucleosynthesis 
B)  quantum tunneling 
C)  TOE 
D)  inflation 
E)  dark energy

Question 9

Explain why the Higgs boson is important in the context of the standard model.

Accepted Answer

In the standard model,all fundamental pa

Question 10

What would the universe be like if there were complete symmetry between matter and antimatter?

Accepted Answer

A)  It would look similar to our universe, but half of it would be composed of antimatter. 
B)  We would observe two universes, one an antimatter reflection of the other. 
C)  There would be no universe, because all of the matter and antimatter would have been annihilated. 
D)  There would be a universe devoid of matter, entirely composed of photons. 
E)  It would look similar to our universe, but the charges of all of the particles would be reversed. 
A)  It would look similar to our universe, but half of it would be composed of antimatter. 
B)  We would observe two universes, one an antimatter reflection of the other. 
C)  There would be no universe, because all of the matter and antimatter would have been annihilated. 
D)  There would be a universe devoid of matter, entirely composed of photons. 
E)  It would look similar to our universe, but the charges of all of the particles would be reversed.

Question 11

In a closed (spherical) universe, the sum of the angles in a triangle is

Accepted Answer

A)  180$\degree$. 
B)  (  $\lt$ 180$\degree$.) 
C)  120$\degree$. 
D)  ($\gt$ 180$\degree$.) 
E)  240$\degree$. 
A)  180$\degree$. 
B)  (  $\lt$ 180$\degree$.) 
C)  120$\degree$. 
D)  ($\gt$ 180$\degree$.) 
E)  240$\degree$.

Question 12

What was the temperature of the universe when photons were no longer able to spontaneously create proton-antiproton pairs? (Note that a photon's energy is equal to   , the cosmic background at any point in time has a blackbody spectrum that peaks at a wavelength   , and the mass of a single proton is 1.67*10-27 kg.)

Accepted Answer

In order to create a proton and antiprot

Question 13

Summarize the possible shapes of the universe and indicate if the Euclidian geometry is applicable in each case.

Accepted Answer

One important property of the universe i

Question 14

In the 1990s, astronomers studying distant Type Ia supernovae discovered that the

Accepted Answer

A)  universe's expansion rate has been decreasing with time. 
B)  universe is finite in size. 
C)  universe's expansion rate has been increasing with time. 
D)  rate of supernova explosions has been increasing with time. 
E)  universe's expansion rate has stayed constant with time. 
A)  universe's expansion rate has been decreasing with time. 
B)  universe is finite in size. 
C)  universe's expansion rate has been increasing with time. 
D)  rate of supernova explosions has been increasing with time. 
E)  universe's expansion rate has stayed constant with time.

Question 15

If the Hubble constant had a value of 50 km/s/Mpc instead of 70 km/s/Mpc, the value of the critical density $\Omega$0 would be about

Accepted Answer

A)  twice as large. 
B)  half as much. 
C)  the same. 
D)  1.4 times smaller. 
E)  1.4 times larger. 
A)  twice as large. 
B)  half as much. 
C)  the same. 
D)  1.4 times smaller. 
E)  1.4 times larger.

Question 16

The figure below shows a graph of the scale factor, RU, with time, for three different scenarios.The age of the universe is the difference between now and the time at which RU is zero.Which curve illustrates a universe that is expanding at a constant rate?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  All of these curves are valid for constantly-expanding universe. 
E)  None of these curves is valid for constantly-expanding universe. 
A)  A 
B)  B 
C)  C 
D)  All of these curves are valid for constantly-expanding universe. 
E)  None of these curves is valid for constantly-expanding universe.

Question 17

At what temperature would the peak wavelength of blackbody radiation correspond to electron-positron pair production? This would have been the lowest temperature in the early universe at which this effect was common.(Note that a photon's energy is equal to   , the cosmic background at any point in time has a blackbody spectrum that peaks at a wavelength   , and the mass of a single electron or positron is 9.11 *10-31 kg.)

Accepted Answer

A)  2400 K 
B)  420,000 K 
C)  2.4 million K 
D)  42 million K 
E)  2.4 billion K 
A)  2400 K 
B)  420,000 K 
C)  2.4 million K 
D)  42 million K 
E)  2.4 billion K

Question 18

Scientists think that, soon after the Big Bang, the four fundamental forces of nature were united into one "superforce," and ________ was the first to split off from the others.

Accepted Answer

A)  the strong nuclear force 
B)  electromagnetism 
C)  the weak nuclear force 
D)  gravity 
E)  nucleosynthesis 
A)  the strong nuclear force 
B)  electromagnetism 
C)  the weak nuclear force 
D)  gravity 
E)  nucleosynthesis

Question 19

The figure below shows five graphs of the scale factor of the universe as a function of time.Which of these graphs would occur for a universe with  $\Omega$ m = 1 and  $\Omega$  $\bigwedge$  = 0?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
E)  E 
A)  A 
B)  B 
C)  C 
D)  D 
E)  E

Question 20

Even with infinitely powerful telescopes, we can look back in time only until the time when

Accepted Answer

A)  galaxies first formed. 
B)  hydrogen and helium nuclei formed. 
C)  stars first formed. 
D)  gravity split from a superforce. 
E)  recombination happened. 
A)  galaxies first formed. 
B)  hydrogen and helium nuclei formed. 
C)  stars first formed. 
D)  gravity split from a superforce. 
E)  recombination happened.

What is the minimum combined energy of the photons that would produce an electron-positron pair? (Note: m_e is the rest mass of an electron.)

If dark energy is causing the expansion rate of the universe to increase with time, does this mean that you should worry that the Sun, Earth, and your body itself are expanding? Why or why not?

Describe two different experiments that offer evidence for a flat universe.

Which of the following have both been predicted and conclusively confirmed experimentally?

Which forces would a grand unified theory (GUT) unify?

Explain what the anthropic principle implies for our visible universe, and give a specific example of a small change that would make life impossible.

The mechanism of ________ can simultaneously solve both the flatness and horizon problems in cosmology.

Explain why the Higgs boson is important in the context of the standard model.

What would the universe be like if there were complete symmetry between matter and antimatter?

In a closed (spherical) universe, the sum of the angles in a triangle is

Summarize the possible shapes of the universe and indicate if the Euclidian geometry is applicable in each case.

In the 1990s, astronomers studying distant Type Ia supernovae discovered that the

If the Hubble constant had a value of 50 km/s/Mpc instead of 70 km/s/Mpc, the value of the critical density $\Omega$ ₀ would be about

The figure below shows a graph of the scale factor, R_U, with time, for three different scenarios.The age of the universe is the difference between now and the time at which R_U is zero.Which curve illustrates a universe that is expanding at a constant rate?

Scientists think that, soon after the Big Bang, the four fundamental forces of nature were united into one "superforce," and ________ was the first to split off from the others.

Even with infinitely powerful telescopes, we can look back in time only until the time when

Thinking Like an Astronomer

Patterns in the Skymotions of Earth and the Moon

Motion of Astronomical Bodies

Gravity and Orbits

Light

The Tools of the Astronomer

The Formation of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquidthe Giant Planets

Planetary Moons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

Our Starthe Sun

The Interstellar Medium and Star Formation

Evolution of Low-Mass Stars

Evolution of High-Mass Stars

Relativity and Black Holes

Galaxies

The Milky Waya Normal Spiral Galaxy

The Expanding Universe

Large-Scale Structure in the Universe

Life

Filters

Exam 22: Cosmology

What is the minimum combined energy of the photons that would produce an electron-positron pair? (Note: me is the rest mass of an electron.)

If dark energy is causing the expansion rate of the universe to increase with time, does this mean that you should worry that the Sun, Earth, and your body itself are expanding? Why or why not?

Describe two different experiments that offer evidence for a flat universe.

The figure below shows five graphs of the scale factor of the universe as a function of time.Which of these graphs would occur for a universe with Ω\OmegaΩ m =1 and Ω\OmegaΩ ⋀\bigwedge⋀ = 0?

Which of the following have both been predicted and conclusively confirmed experimentally?

Which forces would a grand unified theory (GUT) unify?

Explain what the anthropic principle implies for our visible universe, and give a specific example of a small change that would make life impossible.

The mechanism of ________ can simultaneously solve both the flatness and horizon problems in cosmology.

Explain why the Higgs boson is important in the context of the standard model.

What would the universe be like if there were complete symmetry between matter and antimatter?

In a closed (spherical) universe, the sum of the angles in a triangle is

Summarize the possible shapes of the universe and indicate if the Euclidian geometry is applicable in each case.

In the 1990s, astronomers studying distant Type Ia supernovae discovered that the

If the Hubble constant had a value of 50 km/s/Mpc instead of 70 km/s/Mpc, the value of the critical density Ω\OmegaΩ 0 would be about

The figure below shows a graph of the scale factor, RU, with time, for three different scenarios.The age of the universe is the difference between now and the time at which RU is zero.Which curve illustrates a universe that is expanding at a constant rate?

Scientists think that, soon after the Big Bang, the four fundamental forces of nature were united into one "superforce," and ________ was the first to split off from the others.

The figure below shows five graphs of the scale factor of the universe as a function of time.Which of these graphs would occur for a universe with Ω\OmegaΩ m = 1 and Ω\OmegaΩ ⋀\bigwedge⋀ = 0?

Even with infinitely powerful telescopes, we can look back in time only until the time when

Thinking Like an Astronomer

Patterns in the Skymotions of Earth and the Moon

Motion of Astronomical Bodies

Gravity and Orbits

Light

The Tools of the Astronomer

The Formation of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquidthe Giant Planets

Planetary Moons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

Our Starthe Sun

The Interstellar Medium and Star Formation

Evolution of Low-Mass Stars

Evolution of High-Mass Stars

Relativity and Black Holes

Galaxies

The Milky Waya Normal Spiral Galaxy

The Expanding Universe

Large-Scale Structure in the Universe

Life

Filters

What is the minimum combined energy of the photons that would produce an electron-positron pair? (Note: m_e is the rest mass of an electron.)

If the Hubble constant had a value of 50 km/s/Mpc instead of 70 km/s/Mpc, the value of the critical density $\Omega$ ₀ would be about

The figure below shows a graph of the scale factor, R_U, with time, for three different scenarios.The age of the universe is the difference between now and the time at which R_U is zero.Which curve illustrates a universe that is expanding at a constant rate?