Chapter 18: Cosmology

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Chapter 18 Cosmology
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WHAT DO YOU THINK?

• What does the Universe include?
• Did the Universe have a beginning?
• Is the Universe expanding, fixed in size, or
  contracting?
• Will the Universe last forever?

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You will discover

• Cosmology, which seeks to explain how the
  Universe began, how it evolves, and its fate.
• The best theory we have for the evolution of the
  Universe the Big Bang.
• How astronomers explain the overall structure of
  the Universe.
• Our understanding of the fate of the Universe.

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In the Beginning the Big Bang

• The Universe began 13.7 billion years ago with an
  event called the Big Bang.
• All of space-time, matter, and energy were
  created at the Big Bang.
• The left-over energy from the Big Bang can be
  detected today as the Cosmic Microwave Background
  Radiation.
• The temperature of this radiation is only a few
  degrees above absolute zero.

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The Beginning The Big Bang
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In Search of The Earliest Photons
Wilkinson Microwave Anisotropy Probe (WMAP)
satellite, launched in 2001
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WMAPs Baby Picture of the Universe Cosmic
Microwave Background Radiation
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The Universe is Expanding

• The Redshift of Superclusters shows us that the
  Universe is expanding. This Redshift is called
  the Cosmological Redshift, because it is caused
  by the expansion of space.
• The farther away a galaxy is from us, the faster
  it moves away from us.

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The Expansion of the Universe Cosmological
Redshift
Space itself is expanding.
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Expanding Cake Analogy
Just as all the chocolate chips move apart as the
cake rises, all the superclusters of galaxies
move away from each other as the space of the
Universe expands.
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The Observable Universe
The cosmic light horizon today is about 13.7
billion light-years away in all directions.
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HST Galaxies gt13 Billion LY Away
This HST Ultra Deep Field Telescope image shows
some of the most distant galaxies we have seen.
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Early Universe Temperature Variations
Tiny temperature fluctuations in the Cosmic
Microwave Background Radiation are related to the
large-scale structure of the Universe today,
indicating where Superclusters and voids grew.
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The First Stars much larger than the Sun with
much shorter lives
The burst of star formation that occurred within
a few hundred million years after the Big Bang.
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Proto-Galaxy Formation
Hubble and Keck telescope images of two groups of
stars that are believed to be proto-galaxies,
from which bigger galaxies grew
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Creation of Spiral and Elliptical Galaxies
If the rate of star formation was low, then a
spiral galaxy formed. If the rate of star
formation was high, then an elliptical galaxy
formed.
A galaxy begins as a huge cloud of primordial gas
that collapses gravitationally.
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The Fate of the Universe

• The fate of the Universe depends on the shape of
  space-time.
• The shape of space-time is determined by how much
  total matter and energy there is in the Universe.
• Space-time could have one of three shapes
• Sphere positive curvature closed.
• Our floor no curvature flat.
• Saddle negative curvature open.

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Possible Shapes of Space-time,and the Fate of
the Universe

• Closed Universe would collapse.
• Flat Universe could slowly expand forever.
• Open Universe would expand forever.

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Cosmic Microwave Background indicates that
Space-time is Flat Universe could slowly expand
forever
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BUT dimmer distant Supernovae mean
theexpansion of the Universe is speeding up.
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100 billion years from now the Universe will
appear frozen in time as we look out into space.
Only the light from the Local Group of galaxies
will remain visible, if anyone is still around to
see it.
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Expansion of the Universe is speeding up

• Very distant Type 1a Supernovae are not as bright
  as they should be.
• This means the expansion of the Universe is
  speeding up instead of slowing down or staying
  the same.
• There is something really weird called Dark
  Energy (not the same as Dark Matter) that is
  causing this acceleration.
• Dark Energy acts like anti-gravity, pushing the
  Universe apart.
• We do not know what this Dark Energy is, but it
  makes up 73 of the total energy/matter of the
  Universe.

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Composition of the Universe

• Suppose all the matter and energy in the Universe
  is 100 in your wallet or purse.
• 73 would be Dark Energy the mysterious energy
  thats pushing the Universe apart faster and
  faster.
• 23 would be Dark Matter matter that doesnt
  give off any kind of radiation, so we cant see
  it but it does have gravity.
• So out of your Universe of 100, 96 represents
  Dark Energy and Dark Matter that have yet to be
  identified.
• Only 4 would be visible matter the regular
  stuff we can see, like stars, gas clouds, and
  dust the same stuff were made of.
• Of the visible matter (4), only one-tenth of it
  shines as stars. Thats 40 cents out of your
  total 100. The rest of the visible matter is
  gas clouds and dust.

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Composition of the Universe
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WHAT DID YOU THINK?

• What does the Universe include?
• It is all the matter, energy, and space-time that
  will ever be detectable from the Earth or that
  will ever affect us.
• Did the Universe have a beginning?
• Yes, it occurred about 13.7 billion years ago in
  an event called the Big Bang.
• Is the Universe expanding, fixed in size, or
  contracting?
• The Universe is expanding, faster and faster.
• Will the Universe last forever?
• Current observations support the belief that it
  will last (expand) forever.