Dark Energy and the Accelerating Universe

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Dark Energy and the Accelerating Universe

• Beyond Einstein and the Big Bang

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Time Magazine Person of the Century
There are critical questions in cosmology whose
answers eluded Einstein
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The Standard Hot Big Bang Model

• Expansion of the Universe is a result of the Big
  Bang
• The Universe is about 15 billion years old
• After the Big Bang
• Inflation occurred between 10-35- 10-32 second
• The Particle Zoo emerged within 1 millisecond
• Baryogenesis era began after 1 millisecond
• Light elements synthesized within first 3 minutes
• Galaxies formed by 1 billion years

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Matter dominated universe
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Old Matter Dominated Universe

• Matter Composition
• Light elements created in Big Bang heavy
  elements in stars
• 13 baryons
• (1 stars, 12 molecular clouds, planets and
  stellar remnants)
• 0.8 neutrinos
• 86 dark matter (non-baryonic)
• 100 Total Mass-Energy Budget

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Energy dominated universe
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Now Energy Dominated Universe

• Matter Composition
• 35 Baryons Neutrinos Dark Matter
• Energy Composition
• 65 Vacuum (Dark) Energy
• 100 Total Mass-Energy Budget

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The New Standard Hot Big Bang Model

• The Universe is
• Flat no spacetime curvature
• Accelerating the expansion rate in the present
  epoch is increasing

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Dark energy
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Dark Energy The Fundamental Nature of Matter

• Unexpected Discovery of Dark Energy leads us to
  ask
• What is it?
• Why is it there?
• Do we need new theories of space and time?
• Are there Mysterious Particles Permeating Space?

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Solving the Mystery of Dark Energy

• What is the connection between dark energy,
  gravity and the fate of the universe?
• Is general relativity the ultimate theory of
  gravity for the universe?

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The Accelerating Universe
by Anne Field, STSCI
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Recent Discoveries

• Recent discoveries have revealed the fundamental
  connections between the forces of nature and the
  structure of universe
• Distant Type Ia Supernovae
• Cosmic Microwave Background
• Galaxy Cluster Counting
• Theoretical Developments

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Supernovae
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Type Ia Supernovae

• SN Ia
• Are very bright light sources visible across the
  Cosmos
• Show that expansion of the universe is
  accelerating through distance-redshift relation
• Reveal evidence for a mysterious dark energy in
  the universe
• Will provide the first measurements of equation
  of state of universe

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Cosmic Microwave Background
Cosmic microwave background
Dense quark-gluon plasma
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Cosmic Microwave Background

• Measures the geometry of spacetime
• Spacetime geometry depends on the mass-energy
  density of the universe
• Observation of a flat universe confirms some of
  the predictions of inflation
• a revolutionary theory with roots in particle
  physics

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Large Scale Structure
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Large Scale Structure

• Measures the mass density in the universe
• Reveals matter density is less than half the
  mass-energy density of a flat universe
• SNe Ia CMB Large Scale Structure show that
  dark energy and dark matter are more than 90 of
  the mass-energy budget of the universe.

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Theoretical questions
"Nature is a perpetual circulatory worker,
generating fluids out of solids, and solids out
of fluids, fixed things out of volatile,
volatile out of fixed. Isaac Newton
"Once you eliminate the impossible, whatever
remains, no matter how improbable, must be the
truth." - Sherlock Holmes (by Sir Arthur
Conan Doyle)
Facts that at first seem improbable will, even
on scant explanation, drop the cloak that has
hidden them and stand forth in naked and simple
beauty. -- Galileo Galilei
"If we knew what it was we were doing, it would
not be called research, would it?" "The most
incomprehensible thing about the universe is that
it is comprehensible. - Albert Einstein
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Theoretical Questions

• Why is the energy density so small?
• 120 orders of magnitude too small and yet not
  zero fine tuning?
• Why now?
• the energy density is about equal to the energy
  density coincidence?
• Will these be answered by new theories beyond
  Einstein?

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Unveiling the Dark Energy

• Precision Cosmology
• Measuring the equation of state
• is it constant in time and space?
• Supernovae Are the Most Powerful Tools to
  Discover the Nature of the Dark Energy

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Next Steps SNAP
magnitude - redshift

• SNAP is better than anything else for acquiring
  images and spectra of thousands of SNe

w(z)
w0
equation of state
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Supernova Acceleration Probe

• Space observations of thousands of supernovae
  will provide the vital breakthrough in precision
  cosmology to characterize the dark energy
• SNAP will measure the matter and energy
  densities, WM WDE , with exquisite precision
• SNAP will precisely determine the equation of
  state of the universe as a function of time and
  space

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Roadmap toward Dark Energy
Lightcurve Peak Brightness
Images
?M and ?DE Equation of State Dark Energy
Properties
Redshift SN Properties
Spectra
data
analysis
physics
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SNAP Timeline
Launch
Construction
Science
RD
2001
2004
2008
2009
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Bold Ideas, Innovative Tools
A Billion Pixel Imager
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Students Today -Leaders Tomorrow

• Undergraduates work with scientists and engineers
  at collaborating institutions.
• Graduate Students gain immediate research
  experience on the most exciting current science!

First class students become first class
scientists and engineers by using first class
instruments and techniques
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Education and Public Outreach
... if we do discover a complete theory, it
should in time be understandable in broad
principle by everyone, not just a few scientists.
- Stephen Hawking
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Education and Public Outreach
Scientists Engineers
Undergraduates Graduate students
SNAP / EPO Operations
Science Centers Classrooms Students Teachers
Partnerships
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• We Are on the Cusp of Major Advances That
  Connect Particle Physics, Astrophysics and
  Cosmology Which Are Leading to Breakthroughs in
  Fundamental Physics.