The Origin of the Universe

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The Origin of the Universe

• By Christos

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How old is our Universe?

• We can roughly tell that our planet is about 4
  1/2 billion years old by radiometric dating of
  rocks. (QUIZ the oldest earthly rock so far
  found is 3.8 billion years old, could you explain
  why one can be sure that the Earth is older?)
• But how on Earth can we determine how old is our
  Universe?

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Looking at distant objects in the Universe means
looking at the PAST

• We get an idea about how old objects are in the
  Universe when we see their light. The speed of
  light is constant, and distance is a measure of
  time. When we see a distant star explosion that
  occurs billions of light years away, we know that
  that star exploded billions of years ago.

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OK, but HOW do we measure the distance(time) ?

• Understanding the Doppler Effect
• http//www.fearofphysics.com/Sound/dopwhy2.html
• Objects moving away from us emit light that is
  "redshifted," meaning its wavelengths are shifted
  from higher energy to lower energy.

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Hubble discovery

• The red shift of galaxies increase roughly in
  proportion to the distance from us
• In other words, the more distant the galaxy, the
  faster it is moving away. Thus if the exact
  relation between redshift and distant was known,
  one could see an object of known redshift, and
  determine exactly how far it is and (because we
  know the speed of light) figure out a minimum age
  for that object

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The Big Bang

• But, if the galaxies are rushing apart, then they
  must once have been closer together
• http//www.schoolscience.co.uk/flash/bang.htm
• http//map.gsfc.nasa.gov/m_or/mr_media2.html
• Ok, but how that must have sound like?

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The first Light

• Imagine the Universe as a loaf of rising raisin
  bread, in which the nearly formed galaxies are
  the raisins. The region in space that ultimately
  became home to the Milky Way galaxy is moving
  away from all the other regions... or all the
  other raisins in the bread. Now imagine that
  first light that was released simultaneously
  everywhere in the Universe. Light released within
  our own region has long since passed us. Light
  released in regions very far from us, however, is
  just reaching us now.
• http//www.gsfc.nasa.gov/gsfc/spacesci/pictures/20
  03/0206mapresults/COBE-MAP_HDfast.mov

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The Fate of the Universe

• The fate of the Universe depends on its contents
  (i.e. how much matter and energy there is
• If there is a lot of matter, then gravity will
  dominate, slowly reigning in the expansion and
  pulling all matter together back to one point.
  Some call this the Big Crunch.
• If there is not so much matter but rather dark
  energy -- that force that acts like anti-gravity
  -- then the Universe will continue to expand
  until ever single speck of matter is pulled
  infinitely apart from each other.
• A more pleasant notion is the situation where
  the Universe has just the right about of matter
  and dark energy to keep it from flying apart or
  crashing in.

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In Conclusion

• Our Universe is about 13-14 billion years old. In
  order to estimate that two rulers are needed
• Distance-Age The light travels (in vacuum) with
  a constant velocity of . Thus,
  when we observe (collect visible light from) a
  distant object we see it as it was
  s ago.
• Redshift-Distance Ruler If a source (of waves)
  moves away from a receiver, the frequency with
  which waves are received falls. Sound waves The
  difference in the pitch of a police car as it
  passes you.
• Light waves Visible light appears reddish . The
  most distant the object the largest the redshift.
  But, there is no exact relationship between
  redshif-distant (current research).
• Thus, once we have a firm redshift ruler,
  we can see the CMB
• ( the first light to escape after the
  Big Bang) as a redshift. The redshift yields the
  distance. The distance (knowing the speed of
  light) yields the age