Download The Origin of the Universe - Christos N. Hadjichristidis

The Origin & Age
of our Universe
By Christos N. Hadjichristidis
How old is our Universe?
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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?
Looking at distant objects in the
Universe means looking at the PAST
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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.
Determining Universe age by looking
for old stars in globular clusters
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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
A method based upon the idea of an expanding
Universe (but we need to learn some tools in
order to firstly accept the idea ….. )
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Something you have observed:
http://faraday.physics.utoronto.ca/PVB/Harrison/Flash/ClassMechanics
/Doppler/DopplerEffect.html
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Understanding the Doppler Effect
http://www.fearofphysics.com/Sound/dopwhy2.html
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Seeing the star light:
…..Tools Continued…..
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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
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Determining large distances: The Cepheid
stars yardstick
http://imgsrc.hubblesite.org/hu/db/1999/19/videos/c/format
s/low_quicktime.mov
Hubble’s Discovery
…Hubble’s discovery continued
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“The red shift of galaxies increases roughly in
proportion to the distance from us”
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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/lectures105/chapter
01/raisin_cake.htm
The Big Bang
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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?
Determining the Bing Bang time by
using Hubble’s law
"Let there be light";
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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.
The first Light
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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/space
sci/pictures/2003/0206mapresults/C
OBE-MAP_HDfast.mov
Using the CMB to determine the
Age of our Universe ?
1.
Distance-Age: The light travels (in vacuum) with a
constant velocity of 3  10 m s . Thus, when we
observe (collect visible light from) a distant object we
see it as it was t  dis tan ce / 3  10 8 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).
8
2.
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
The Fate of the Universe
1.
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3.
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/BigBang.html
In Conclusion
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Our Universe has probably originated from a Big Bang
as supported by both Hubble’s 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:
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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 …..
Carlos Frenk's Model Universes
Frenk’s work is being supported by The Ogden Trust
Indicative Reading List
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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 Hawking’s 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
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