The Origin

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The Origin Age of our Universe

• By Christos N. Hadjichristidis

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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. So the furthest we look in the Universe the
  deepest we look at its past. 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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Determining Universe age by looking for old stars
in globular clusters

• A globular cluster is a dense collection of close
  to a million stars, all of which formed at
  roughly the same time so they can serve as cosmic
  clocks
• The fate of every star depends solely on its
  initial mass. So what should we look for
  (Corpses of massive or light stars)?
• The brightest of white dwarfs is no more luminous
  than a 100 watt light bulb seen at the moon's
  distance so their detection is very hard
• Result The oldest white dwarf observed is about
  13 billions years old but big uncertainties due
  both to the difficulty of accurately determining
  distances and our incomplete knowledge of
  stellar evolution.

http//imgsrc.hubblesite.org/hu/db/2002/10/videos/
b/formats/low_mpeg.mpg
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A method based upon the idea of an expanding
Universe (but we need to learn some tools in
order to firstly accept the idea .. )

• Something you have observed http//faraday.physic
  s.utoronto.ca/PVB/Harrison/Flash/ClassMechanics/Do
  ppler/DopplerEffect.html
• Understanding the Doppler Effect
• http//www.fearofphysics.com/Sound/dopwhy2.html
• Seeing the star light

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..Tools Continued..

• Objects moving away from us emit light that is
  "redshifted," meaning its wavelengths are shifted
  from higher energy to lower energy
• http//www.wwnorton.com/earth/egeo/flash/1_2.swf
• Determining large distances The Cepheid stars
  yardstick
• http//imgsrc.hubblesite.org/hu/db/1999/19/videos/
  c/formats/low_quicktime.mov

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Hubbles Discovery
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Hubbles discovery continued

• The red shift of galaxies increases roughly in
  proportion to the distance from us
• In other words, the more distant the galaxy, the
  faster it is moving away, and most importantly
  this is true no matter where exactly in the
  Universe you are! Thus, despite long-lived
  beliefs (Aristotelian/Ptolemaic theory) there is
  nothing special about our place in the Universe.
• http//observe.phy.sfasu.edu/courses/ast105/lectu
  res105/chapter01/raisin_cake.htm

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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 does that sound like?

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Determining the Bing Bang time by using Hubbles
law

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"Let there be light"

• The early Universe was so hot and dense that
  atoms were dissociated into their nuclei and
  electrons. The light was scattered by the free
  electrons and was not allowed to escape. As
  universe expanded and cooled, nuclei and
  electrons combined to form the first atoms and
  THERE WAS LIGHT.

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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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Using the CMB to determine the Age of our
Universe ?

• 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
  seconds ago.
• Redshift-Distance Ruler Visible light appears
  reddish . The most distant the object the largest
  the redshift. But, there is no exact relationship
  between redshift-distance (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. And the distance (since we know the
  speed of light) yields the age

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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 reign over 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 -- the force that acts like anti-gravity
  -- then the Universe will continue to expand
  until every 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 amount of matter and
  dark energy to keep it from flying apart or
  crashing in.
• http//www.astro.ubc.ca/scharein/a311/Sim/bang/Bi
  gBang.html

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In Conclusion

• Our Universe has probably originated from a Big
  Bang as supported by both Hubbles and Cosmic
  Microwave Radiation Background (first light to
  break free after the Big Bang) discoveries
• We found that the age of our Universe is about
  12-13 billion years by
• Looking for the oldest stars, and
• Measuring the rate of the expansion of the
  Universe and extrapolating back to the Big Bang
• And because a (Greek Orthodox) priest blesses
  his own beard first, as the saying goes, there is
  no escape from watching this ..

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Carlos Frenk's Model Universes
Frenks work is being supported by The Ogden
Trust
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Indicative Reading List

• Books
• Hawking, S.W. A Brief History of Time (Bantam
  Press, Great Britain 1997)
• Weinberg, S. The First Three Minutes (Basic
  Books, New York,1993)
• Filkin, D. Stephen Hawkings Universe (BBC Books,
  London 1997)
• Barrow, J.D. The Origin Of The Universe (Clays
  Ltd, St Ives plc, London 1994)
• and links to the educational resources included
  in this presentation