UNIT NINE: Matter and Motion in the Universe

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UNIT NINE Matter and Motionin the Universe

• Chapter 26 The Solar System
• Chapter 27 Stars
• Chapter 28 Exploring the Universe

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Chapter Twenty-EightExploring the Universe

• 28.1 Tools of Astronomers
• 28.2 Galaxies
• 28.3 Theories about the Universe

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Section 28.3 Learning Goals

• Explore theories about the origin of the
  universe.
• Discuss the evidence in support of the Big Bang
  theory.
• Describe planetary systems.

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28.3 Doppler Shift

• In the 1800s, Christian Doppler discovered that
  when the source of a sound wave is moving, its
  frequency changes.
• The change in sound you hear is caused by a
  Doppler shift.
• Doppler shift is related to the net change
  between the source of the waves and the observer.

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28.3 Doppler Shift

• Doppler shift also occurs with electromagnetic
  waves, such as visible light, X-rays, and
  microwaves.
• This phenomenon is an important tool used by
  astronomers to study the motion of objects in
  space.

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28.3 The expanding universe

• The faster the source of light is moving away
  from the observer, the greater the redshift.
• The opposite (blueshift) happens when an object
  is moving toward the observer.

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28.3 The expanding universe

• Edwin Hubble discovered that the farther away a
  galaxy was, the faster it was moving away from
  Earth.
• This concept came to be known as the expanding
  universe.

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28.3 The Big Bang theory

• The theory that the universe was expanding
  implies the universe must have been smaller in
  the past than it is today.
• It implies that the universe must have had a
  beginning.
• Astronomers today believe the universe exploded
  outward from a single point.
• This idea is known as the Big Bang theory.

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28.3 The Big Bang theory

• The Big Bang theory says the universe began as a
  huge explosion between 10 billion and 20 billion
  years ago.
• According to this theory, all matter and energy
  started in a space smaller than the nucleus of an
  atom.

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28.3 Evidence for the Big Bang theory

• In the 1960s, Arno Penzias and Robert Wilson were
  trying to measure electromagnetic waves given off
  by the Milky Way.
• The noise these scientists found was the cosmic
  microwave background radiation predicted by the
  Big Bang theory.

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28.3 Evidence for the Big Bang theory

• The proportion of hydrogen to helium is
  consistent with the physics of the Big Bang.
• If the universe were significantly older, there
  would be more heavy elements present compared
  with hydrogen and helium.

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28.3 Planetary systems

• A star with orbiting planets is called a
  planetary system.
• Scientists now believe that planets are a natural
  by-product of the formation of stars.

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28.3 How the solar system formed

• Scientists think that the solar system was formed
  out of the same nebula that created the Sun.

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28.3 Binary stars

• A binary star is a system with two stars that are
  gravitationally tied and orbit each other.
• About half of the 60 nearest stars are in binary
  (or multiple) star systems.

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Optional Investigation 28C
The Time Machine

• Key Question
• How long does it take for starlight to reach
  Earth?

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Searching the Cosmos

• Astrophysicist Dr. Hakeem Oluseyi (Oh-lu-SHAY-ee)
  is fascinated by stars. A physics and space
  science professor at the Florida Institute of
  Technology, he has invented several new
  instruments to give astronomers a closer look at
  the cosmos.