Formation of the Universe

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Formation of the Universe
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Formation of the Universe

• Cosmology is the study of the origin,
  properties, processes, and evolution of the
  universe.
• Universal Expansion
• Galaxy Movement To understand how the universe
  formed, scientists study the movement of
  galaxies.
• A Raisin-Bread Model The universe, like the
  rising raisin bread dough, is expanding. Think of
  the raisins in the dough as galaxies. As the
  universe expands, the galaxies move farther apart.

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Formation of the Universe
The Big Bang Theory

• A Tremendous Explosion The theory that the
  universe began with a tremendous explosion is
  called the big bang theory.
• Cosmic Background Radiation In 1964, two
  scientists using a huge antenna accidentally
  found radiation coming from all directions in
  space. One explanation for this radiation is that
  it is cosmic background radiation left over from
  the big bang.

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Formation of the Universe
The BIG BANG
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The Structure of the Universe
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Formation of the Universe
How Old Is the Universe?

• Age of the Universe Scientist use to methods
  to study the age of the universe.
• By measuring the distance between Earth and
  various galaxies, scientists can predict the rate
  of expansion and calculate the age of the
  universe at about 13.77 billion years.
• Because the universe must at least be as old as
  the oldest stars it contains, the ages of the
  stars provide a clue to the age of the universe.

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Formation of the Universe
A Forever Expanding Universe

• The expansion of the universe depends on the
  amount of matter it contains. A large enough
  quantity of matter would cause gravity to stop
  the expansion. The universe could start
  collapsing.
• Scientist now think that there may not be enough
  matter in the universe, so the universe would
  continue to expand forever and become cold and
  dark as all the stars die.

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Galaxies
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Galaxies

• A galaxy is a collection of stars, dust, and gas
  held together by gravity.
• Types of Galaxies
• Spiral Galaxies make up 75 of all galaxies and
  have a bulge at the center with spiral arms.
• The Milky Way Astronomers think that our solar
  system is in a spiral galaxy.

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Galaxies
Types of Galaxies, continued

• Elliptical Galaxies About one-third or 20 of
  all galaxies are simply massive blobs of stars.
  These are called elliptical galaxies.
• Irregular Galaxies Galaxies, about 5 of all
  galaxies that do not fit into any other class are
  called irregular galaxies.

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Galaxies
Contents of Galaxies

• Gas Clouds A large clouds of gas and dust in
  interstellar space is called a nebula.
• Star Clusters A globular cluster is a tight
  group of stars that looks like a ball and
  contains up to 1 million stars.
• An open cluster is a group of stars that are
  close together relative to surrounding stars.

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Galaxies
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Galaxies
Origin of the Galaxies

• Because if takes light time to travel through
  space, looking at distant galaxies reveals what
  early galaxies looked like.
• Quasars A very luminous, starlike object that
  generates energy at a high rate is called a
  quasar. Some scientists think that quasars may
  be the core of young galaxies that are in the
  process of forming.

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Heliocentric vs. GeocentricThe structure of the
Universe
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Astronomy The Original Science
Whos Who of Early Astronomy

• Ptolemy An Earth-Centered Universe Ptolemy
  thought that the Earth was at the center of the
  universe and that the other planets and the sun
  revolved around the Earth.
• Geocentric Model

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Astronomy The Original Science
Whos Who of Early Astronomy

• Copernicus A Sun-Centered Universe Copernicus
  thought the sun is at the center of the universe,
  and all of the planetsincluding the Earthorbit
  the sun.
• Heliocentric Model