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Universe 8e Lecture Chapter 26 Cosmology

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Universe Eighth Edition CHAPTER 26 Cosmology * Figure 26-3 The Expanding Universe and the Hubble Law (a) Imagine five galaxies labeled A, B, C, D, and E. – PowerPoint PPT presentation

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Title: 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

Q26.3
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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

A26.3
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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.

Q26.6
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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.

A26.6
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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.
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