Universe 8e Lecture Chapter 26 Cosmology

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Roger A. Freedman William J. Kaufmann III
Universe Eighth Edition
CHAPTER 26 Cosmology
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Last HW!

• Chapter 24 and 26 online quizzes due Thursday
  12/9
• Skip Chapter 27
• Final Exam Monday 12/13, 530-730 PM
• The final will cover chapters 23, 24 and 26 only,
  same format as Exams 1-3

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What does it mean to say the universe is
expanding?

1. Galaxies are moving through space away from each
   other.
2. Space is expanding, carrying galaxies along with
   it.
3. All galaxies are moving away from a point at the
   center of the universe.
4. Space is expanding but the galaxies are not
   carried along with it, so the separation of
   galaxies does not change.
5. The galaxies are all getting larger.

Q26.2
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What does it mean to say the universe is
expanding?

1. Galaxies are moving through space away from each
   other.
2. Space is expanding, carrying galaxies along with
   it.
3. All galaxies are moving away from a point at the
   center of the universe.
4. Space is expanding but the galaxies are not
   carried along with it, so the separation of
   galaxies does not change.
5. The galaxies are all getting larger.

A26.2
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Galaxies further away from us have larger
cosmological redshifts than those closer to us.
What is the cosmological redshift?

1. A Doppler shift in which the wavelength of
   photons is increased due to the motion of the
   galaxies away from us
2. A Doppler shift in which the wavelength of
   photons is decreased due to the motion of the
   galaxies away from us
3. Photons traveling through space have their
   wavelength increased because the space through
   which they are traveling is expanding
4. Photons traveling through space have their
   wavelength decreased because the space through
   which they are traveling is expanding

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Galaxies further away from us have larger
cosmological redshifts than those closer to us.
What is the cosmological redshift?

1. A Doppler shift in which the wavelength of
   photons is increased due to the motion of the
   galaxies away from us
2. A Doppler shift in which the wavelength of
   photons is decreased due to the motion of the
   galaxies away from us
3. Photons traveling through space have their
   wavelength increased because the space through
   which they are traveling is expanding
4. Photons traveling through space have their
   wavelength decreased because the space through
   which they are traveling is expanding

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Which of the following statements about the Big
Bang model of cosmology are correct?

1. The universe began as an infinitely dense cosmic
   singularity.
2. The Big Bang can be described as the beginning of
   time.
3. The size of the observable universe is related to
   the age of the universe.
4. During the first 10-43 second after the Big Bang,
   the universe was too dense to be described by the
   known laws of physics.
5. All of these statements are correct.

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Which of the following statements about the Big
Bang model of cosmology are correct?

1. The universe began as an infinitely dense cosmic
   singularity.
2. The Big Bang can be described as the beginning of
   time.
3. The size of the observable universe is related to
   the age of the universe.
4. During the first 10-43 second after the Big Bang,
   the universe was too dense to be described by the
   known laws of physics.
5. All of these statements are correct.

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Key Ideas

• The Expansion of the Universe The Hubble law
  describes the continuing expansion of space. The
  redshifts that we see from distant galaxies are
  caused by this expansion, not by the motions of
  galaxies through space.
• The redshift of a distant galaxy is a measure of
  the scale of the universe at the time the galaxy
  emitted its light.
• It is meaningless to speak of an edge or center
  to the universe or of what lies beyond the
  universe.
• The Cosmological Principle Cosmological theories
  are based on the idea that on large scales, the
  universe looks the same at all locations and in
  every direction.

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Key Ideas

• The Big Bang The universe began as an infinitely
  dense cosmic singularity that began its expansion
  in the event called the Big Bang, which can be
  described as the beginning of time.
• The observable universe extends about 14 billion
  light-years in every direction from the Earth. We
  cannot see objects beyond this distance because
  light from these objects has not had enough time
  to reach us.
• During the first 10-43 second after the Big Bang,
  the universe was too dense to be described by the
  known laws of physics.

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Key Ideas

• Cosmic Background Radiation and the Evolution of
  the Universe The cosmic microwave background
  radiation, corresponding to radiation from a
  blackbody at a temperature of nearly 3 K, is the
  greatly redshifted remnant of the hot universe as
  it existed about 380,000 years after the Big
  Bang.
• The background radiation was hotter and more
  intense in the past. During the first 380,000
  years of the universe, radiation and matter
  formed an opaque plasma called the primordial
  fireball. When the temperature of the radiation
  fell below 3000 K, protons and electrons could
  combine to form hydrogen atoms and the universe
  became transparent.
• The abundance of helium in the universe is
  explained by the high temperatures in its early
  history.

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Key Ideas

• The Geometry of the Universe The curvature of
  the universe as a whole depends on how the
  combined average mass density ?0 compares to a
  critical density ?c.
• If ?0 is greater than ?c, the density parameter
  ?0 has a value greater than 1, the universe is
  closed, and space is spherical (with positive
  curvature).
• If ?0 is less than ?c, the density parameter ?0
  has a value less than 1, the universe is open,
  and space is hyperbolic (with negative
  curvature).
• If ?0 is equal to ?c, the density parameter ?0 is
  equal to 1 and space is flat (with zero
  curvature).

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Key Ideas

• Cosmological Parameters and Dark Energy
  Observations of temperature variations in the
  cosmic microwave background indicate that the
  universe is flat or nearly so, with a combined
  average mass density equal to the critical
  density. Observations of galaxy clusters suggest
  that the average density of matter in the
  universe is about 0.24 of the critical density.
  The remaining contribution to the average density
  is called dark energy.
• Measurements of Type Ia supernovae in distant
  galaxies show that the expansion of the universe
  is speeding up. This may be due to the presence
  of dark energy in the form of a cosmological
  constant, which provides a pressure that pushes
  the universe outward.

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Key Ideas

• Cosmological Parameters and Primordial Sound
  Waves Temperature variations in the cosmic
  background radiation are a record of sound waves
  in the early universe. Studying the character of
  these sound waves, and the polarization of the
  background radiation that they produce, helps
  constrain models of the universe.