The BIG BANG

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The BIG BANG

• If the universe is expanding, it must have been
  smaller in the past
• If it was smaller in the past, then at some point
  the expansion must have started
• The start of the expansion is thought to have
  been an explosion called the BIG BANG
• The age of the universe is can be found by
  distance of the most distant galaxies and their
  recessional velocities
• Current figures place the age about about 13.7
  billion years

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The cosmic microwave background radiation that
fills all space is evidence for the BIG BANG
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COBE background
Dipole radiation (our motion)
Milky Way radio waves
Lumpiness of cosmic background
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Aquarius (redshifted)
Leo (blueshifted)
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Wilkinson Microwave Anisotropy Probe (WMAP)

• Mapped cosmic background radiation
• Measured age of universe at 13.7 billion years

• Supports open universe (will expand forever)
• Universe is 4 normal matter, 23 dark matter,
  73 dark energy

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The Cosmic Calendar

• What if the age of the universe was compressed to
  one year?

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Life in the Universe
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Requirements for life

• Solvent (water)
• Atom for bonding (carbon)
• Complex molecules
• The right temperature (liquid water)
• Time...

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The Drake equation predicts how many
civilizations are in the Milky Way
Ex 200 billion 50 1 50 20 20 1/1,000,000
(10,000y)

• N RfpneflfifcfL
• N Number of solar-type stars in the galaxy
• fp fraction of stars that have planets
• ne number of planets per stay system suitable
  for life
• fl fraction of those habitable planets on
  which life actually arises
• fi fraction of those life forms that evolve
  into intelligent species
• fc fraction of those species that develop
  adequate technology and then choose to send
  messages out into space
• fL fraction of stars lifetime of that
  technologically advanced civilization survives

2000
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Life on Mars?
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Arecibo message sent from Earth in 1974
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Voyager carries a message to the stars
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Search for Extra-Terrestrial Intelligence (SETI)
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Suggested Summer Reading

• A Short History of the Universe by Joseph Silk
  (Cosmology)
• The First Three Minutes by Steven Weinberg (The
  Big Bang)
• The Elegant Universe by Brian Greene (String
  Theory)
• Understanding Relativity by Leo Sartori
• Cosmos by Carl Sagan (Life, the universe and
  everything)
• Sky Telescope magazine (observational
  astronomy)
• Red Mars Green Mars Blue Mars by Kim Stanley
  Robinson (Science Fiction)