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Section 4: The Big Bang Theory

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Title: Section 4: The Big Bang Theory


1
Section 4 The Big Bang Theory
  • Preview
  • Key Ideas
  • Hubbles Observations
  • A Theory Emerges
  • Big Bang Theory
  • Universal Expansion
  • A Universe of Surprises
  • Maps In Action

2
Key Ideas
  • Explain how Hubbles discoveries lead to an
    understanding that the universe is expanding.
  • Summarize the big bang theory.
  • List evidence for the big bang theory.

3
Hubbles Observations
  • cosmology the study of the origin, properties,
    processes, and evolution of the universe
  • Cosmologists and astronomers can use the light
    given off by an entire galaxy to create the
    spectrum for that galaxy.
  • Edwin Hubble used galactic spectra to uncover new
    information about our universe.

4
Hubbles Observations, continued
  • Measuring Red Shifts
  • Hubble found that the spectra of galaxies, except
    for the few closest to Earth, were shifted toward
    the red end of the spectrum.
  • Hubble determined the speed at which the galaxies
    were moving away from Earth.
  • Hubble found that the most distant galaxies
    showed the greatest red shift and thus were
    moving away from Earth the fastest.

5
Hubbles Observations, continued
  • The Expanding Universe
  • Using Hubbles observations, astronomers have
    been able to determine that the universe is
    expanding.
  • The expanding universe can be thought of as a
    raisin cake rising in the oven. If you were able
    to sit on one raisin, you would see all the other
    raisins moving away from you.
  • Similarly, galaxies in the universe are moving
    farther away from each other due to the expansion
    of the universe.

6
A Theory Emerges
  • Although cosmologists have proposed several
    different theories to explain the expansion of
    the universe, the current and most widely
    accepted is the big bang theory.
  • big bang theory the theory that all matter and
    energy in the universe was compressed into an
    extremely small volume that 3 to 15 billion years
    ago exploded and began expanding in all
    directions
  • By the mid-20th century, almost all astronomers
    and cosmologists accepted the big bang theory.

7
A Theory Emerges, continued
  • Reading Check
  • What does the big bang theory tell us about the
    early universe?
  • All matter and energy in the early universe were
    compressed into a small volume at an extremely
    high temperature until the temperature cooled and
    all of the matter and energy were forced outward
    in all directions.

8
A Theory Emerges, continued
  • Cosmic Background Radiation
  • cosmic background radiation radiation uniformly
    detected from every direction in space
    considered a remnant of the big bang
  • Astronomers believe that cosmic background
    radiation formed shortly after the big bang.
  • The background radiation has cooled after the big
    bang, and is now about 270 C below zero.

9
A Theory Emerges, continued
  • Ripples in Space
  • Maps of cosmic background radiation over the
    whole sky look very smooth. But on satellite maps
    that show where temperatures differ from the
    average background temperature, ripples become
    apparent.
  • These ripples are irregularities caused by small
    fluctuations in the distribution of matter in the
    early universe.
  • The ripples are thought to indicate the first
    stages in the formation of the universes first
    galaxies.

10
A Theory Emerges, continued
  • Timeline of the Big Bang

11
Big Bang Theory
Click below to watch the Visual Concept.
12
Universal Expansion
Click below to watch the Visual Concept.
13
A Universe of Surprises
  • Dark Matter
  • Analysis of the ripples in the cosmic background
    radiation suggests that the matter that humans,
    the planets, the stars and the matter between the
    stars makes up only 4 of the universe.
  • About 23 of the universe is made up of a type of
    matter that does not give off light but that has
    gravity. This type of matter is called dark
    matter.

14
A Universe of Surprises, continued
  • Dark Energy
  • Most of the universe is made up of an unknown
    material called dark energy.
  • Scientists think that dark energy acts as a force
    that opposes gravity. Many scientists think that
    some form of undetectable dark energy is pushing
    galaxies apart.
  • Because of dark energy, the universe is not only
    expanding, but the rate of expansion also seems
    to be accelerating.

15
Maps In Action
  • The Milky Way
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