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The Universe - 2
Inflation
• When the strong force began separating from the
electroweak force at the end of the GUT era, theorists
hypothize that a major release of energy caused the
Universe to expand at an exponential rate (at every step
in time, the size of the Universe doubled). This is the
Inflation.
• For instance, a region the size of a proton at 10-35 sec
would have grown to the size of a basketball by 10-33 sec.
• Although nothing can travel faster than light in space,
space itself can expand faster than light; this is what
happened during Inflation.
• The tremendous expansion `flattened’ the Universe and
created, possibly, parallel Universes.
Why do we need Inflation?
The light from the CMB has
the same temperature
everywhere and in every
direction.
However, the causally
connected space had the
size of a small dot: .
Thus, the CMB should
appear with small
temperature variations,
but it does not: Inflation!
The Geometry of the Universe
• The Big Bang and early evolution of the Universe does
not tell us anything about its geometry
• This is determined by how much mass there is in the
Universe
• For all practical purposes, the mass in the Universe
bends the space-time, pretty much like a Black Hole bends
the space around itself.
• The geometry of the Universe determines its fate:
• a closed Universe will at some point reverse its
expansion into a contraction, and proceed towards a
Big Crunch
• a flat or open Universe will expand forever.
Whether the universe is open, close,
or flat depends on how much matter
(and energy) it contains
For a flat Universe, the mean density (matter in
a unit of volume) of the Universe at the
present time must be about 10-26 kg/m3
It is determined by fundamental quantities, like the
Hubble constant and the Gravitational constant:
c = 3 H2 / (8  G)
TheThree
geometry
of the Universe
possibilities:
Flat Universe, real and apparent
sizes are the same - (critical case,
stops at infinite times)
Closed Universe, objects appear
larger than they are
(expands and re-collapses)
Open Universe, objects appear
smaller than they are
(expands forever)
The Universe as viewed in the Microwave by the WMAP satellite
Contrast x 30,000
1 degree = Universe Horizon
The angular sizes of the structure tells us about the geometry of the
Universe, because the real sizes are known.
The most prominent structures
are about 1 degree, meaning the
Universe is flat
Why is the Universe flat: because
of Inflation
Formation of structures
• By `structures’ we mean: stellar
clusters, galaxies and clusters of
galaxies;
• They were formed out of the fluctuations
formed gravitationally by Dark Matter
while the baryonic matter was still
interacting with the light before the last
recombination surface (z=1100)
The Universe as viewed in the Microwave by the WMAP satellite
This small anisotropy (~ 1/106) in the CMB, emitted 300,000 years after
the Big Bang, represents the small fluctuationContrast
in the matter
distribution
x 30,000
which provides the seed for the structure formation in the universe.
Structure Formation in the Universe
Cosmological Simulations
Observational Cosmology
Formation of the Large-Scale
Structure
Due to gravity,
acting on Dark
Matter
Big Questions
• What will be the fate of the universe?
• What are the dark matter and dark energy?
• What causes the big bang (inflation)?
• What, if any, of this should we believe?
A summary of this course
How do we combine geology
and astronomy?
1. Astrobiology is one of the most recent fields of Astronomy,
and is still under development; it combines the strengths of
astronomy, biology, geology, climate science to investigate
the possibility of life outside Earth;
2. The investigation of Solar System objects requires geologists
to be involved in the quest; for instance, Prof. Hanner’s
presentation talked about analyzing samples of comets.
Geologists are the experts who know how best to perform
such analyses. Not to forget: Lunar and Mars explorations!
What telescopes does NASA use to get
the colorful pictures of nearby and distant
galaxies?
Chandra:
X-ray
Hubble:
UV and Optical
Spitzer:
Infrared
What is the evidence for the
existence of anti-matter?
• Antimatter has been created in particle accelerators
around the world; its existence is well established.
• What we do not not is the origin of the slight
primordial imbalance that produced the current `matter’
Universe.
What is the farthest thing/object we have
identified from Earth?
It really depends on what you mean by `object’. The
farthest we think we will ever be able to `see’ is the
Cosmic Microwave Background.
The farthest galaxy, so far, is at redshift z=7, equivalent to
an age of the Universe of less than 1 Gyr.
The M.A.G.I.C. Gamma-ray Telescope team just
released the discovery that high-energy gamma-rays
from Mrk501 arrived with 4 minutes delay relative to
lower-energy radiation. What does it mean?
The authors suggest that this is an effect of quantum
gravity (the high energy photons travel more slowly
through the `quantum foam’).
However, energy scales are much below the `Planck
energy scale’, which is needed to test effects that
happen at the level of individual protons.
And uncertainties in our knowledge of gamma-ray-burst
sources compounds to raise some questions about the
result.
What is in the center of the
Milky Way?
A black holes, plus a large number of stellar clusters.
Is the presence of a white dwarf in a
binary system shorten the life of the
companion star?
No. Because the mass loss from the companion star would
happen anyway; the difference is that instead of being lost
in space, it is accreted onto the white dwarf.
What is the chemical that makes the
Neptune’s atmosphere appear blue?
Largely due to the methane
in the atmosphere, which
absorbs the red light
(but there could be some
yet unknown component in
addition)
If a comet collided into
Jupiter’s Red Spot, would it
stop the storm?
It would really depend on
the size (mass) and speed
of the comet, I.e., on the
total energy that an impact
would impart to Jupiter.