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Parameterizing the Age of the Universe The Age of Things: Sticks, Stones and the Universe http://cfcp.uchicago.edu/~mmhedman/compton1.html
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Parameterizing the Age of the Universe
The Age of Things:Sticks, Stones and the Universe
http://cfcp.uchicago.edu/~mmhedman/compton1.html
WARNING!
Cosmologist talking about Cosmology!
Today
Past
Last Time: The Expanding Universe
Today
Past
The Scale Factor
a = 1
a = 0.5
Scale Factor from Redshifts
Time 1
Time 2
Time 3
Based on Data from Riess et. al. astro-ph/0402512
The Scale Factor Over Time
Supernova 1994D
PastPresent
The Expansion History and Material Content of the Universe
General Relativity
Distribution of Matter and Energy
Geometry of Space and Time
Energy Density(Amount of Energy contained in
a unit volume)
Expansion Rate(How fast the Scale Factor
changes with Time)
The Expansion History and Material Content of the Universe
General Relativity
Distribution of Matter and Energy
Geometry of Space and Time
Energy Density(Amount of Energy contained in
a unit volume)
Expansion Rate(How fast the Scale Factor
changes with Time)
Higher Energy Density Faster Expansion Rate
Slower Expansion RateLower Energy Density
The Expansion History and Material Content of the Universe
General Relativity
Distribution of Matter and Energy
Geometry of Space and Time
Scale Factor(Average Distance between
particles)
Energy Density(Amount of Energy contained in
a unit volume)
Expansion Rate(How fast the Scale Factor
changes with Time)
Equation of State(How Energy Density changes
with Scale factor)
A closer look at the expanding universe
PastPresent
Types of Energy
Scale Factor IncreasesEnergy Density FallsExpansion Rate Slows
Matter
Matter Only
PastPresent
Predictions for a Universe with only Matter
Scale Factor SmallerExpansion Rate Faster
Scale Factor LargerExpansion Rate Slower
Types of Energy
Scale Factor IncreasesEnergy Density FallsExpansion Rate Slows
Matter
Dark Energy
Scale Factor IncreasesEnergy Density Stays ConstantExpansion Rate Grows
Dark Energy Only
Matter Only
PastPresent
Predictions for a Universe with only Dark Energy
Scale Factor SmallerExpansion Rate Faster
Scale Factor LargerExpansion Rate Slower Scale Factor Smaller
Expansion Rate Slower
Scale Factor LargerExpansion Rate Faster
Dark Energy Only
Matter Only
25% Matter,75% Dark Energy
75% Matter,25% Dark Energy
PastPresent
50% Matter,50% Dark Energy
Predictions for a Universe with mixtures of matter and D.E.
Best Fit is about 3 Parts Dark Energy for every 1 part Matter
Note Fractions only valid today
The Expansion History and Material Content of the Universe
General Relativity
Distribution of Matter and Energy
Geometry of Space and Time
Scale Factor(Average Distance between
particles)
Energy Density(Amount of Energy contained in
a unit volume)
Expansion Rate(How fast the Scale Factor
changes with Time)
Equation of State(How Energy Density changes
with Scale factor)
Predictions for Universes with different total Energy Densities
Energy Density Today=
Critical Density
Energy Density Today=
1.5 x Critical Density
Dark Energy Only
Matter Only
Dark Energy Only
Matter Only
25% Matter,75% Dark Energy
75% Matter,25% Dark Energy
50% Matter,50% Dark Energy
400 nm 500 nm 600 nm 700 nm
Visible
What is the Cosmic Microwave Background?
Wavelength1 m 1 km1 mm1 m1 nm1 pm
Microwaves are Electromagnetic Radiation with Wavelengths between 1 mm and 10 cm
What is the Cosmic Microwave Background ?
Penzias and Wilson, discoverers of the CMB
Telescopes sensitive to microwaves detect a signal from space
This signal is nearly the same from every point on the sky (it is nearly isotropic)
This radiation has a spectrum characteristic of heavily redshifted thermal radiation
What is the Cosmic Microwave Background?
Decoupling
Wavelength1 m 1 km1 mm1 m1 nm1 pm
Brightness Variations in the Cosmic Microwave Background
Data from the WMAP Satellite, processed by Tegmark et. al.
The Size of features in the CMB
Angular Size of Features ~ 1/2o
Decoupling
The Size of features in the CMB
Angular Size of Features ~ 1/2o
Actual Size of Features ~ 400,000 Light Years
Decoupling
Curvature
Energy Density
Critical DensityLower Density Higher Density
Zero Curvature Positive CurvatureNegative Curvature
Curvature and the Apparent Size of Objects
Energy Density
Critical DensityLower Density Higher Density
Zero Curvature Positive CurvatureNegative Curvature
Object Appears LargerObject Appears SmallerFrom Observer’s Viewpoint
Curvature and the Apparent Distance to Objects
Energy Density
Critical DensityLower Density Higher Density
Zero Curvature Positive CurvatureNegative Curvature
Object is Farther AwayObject is Closer
Object appears to be the same size
The CMB and the total energy density of the Universe
Angular Size of Features ~ 1/2o
Actual Size of Features ~ 400,000 Light Years
The distance the light has to travel depends on the curvature
The CMB and the total energy density of the Universe
Angular Size of Features ~ 1/2o
Actual Size of Features ~ 400,000 Light Years
The Scale Factor increases by a factor of 1000 between decoupling and Today
The distance the light has to travel depends on the curvature
The amount of time this takes depends on the total energy density
Decoupling, radiation mostly in visible: wavelength ~ 500 nm
Today, radiation mostly in microwaves wavelength ~ 1 mm
Distance and Time
Energy Density
Critical DensityLower Density Higher Density
Zero Curvature Positive CurvatureNegative Curvature
Object is Farther AwayObject is Closer
Expansion Rate Slower Expansion Rate Faster
Longer Time Shorter Time
The CMB and the total energy density of the Universe
Angular Size of Features ~ 1/2o
Actual Size of Features ~ 400,000 Light Years
The Scale Factor increases by a factor of 1000 between decoupling and Today
The distance the light has to travel depends on the curvature
The amount of time this takes depends on the total energy density
Decoupling, radiation mostly in visible: wavelength ~ 500 nm
Today, radiation mostly in microwaves wavelength ~ 1 mm
Apparent Size of CMB Features is only consistent with Zero Curvature
Energy Density
Critical DensityLower Density Higher Density
Zero Curvature Positive CurvatureNegative Curvature
Object is Farther AwayObject is Closer
Expansion Rate Slower Expansion Rate Faster
Longer Time Shorter Time
Only in this case can light travel the required distance in the allowed time
The Expansion History and Material Content of the Universe
General Relativity
Distribution of Matter and Energy
Geometry of Space and Time
Scale Factor(Average Distance between
particles)
Energy Density(Amount of Energy contained in
a unit volume)
Expansion Rate(How fast the Scale Factor
changes with Time)
Equation of State(How Energy Density changes
with Scale factor)
Matter Density
Dar
k E
ner
gy
Den
sity
Cosmological Consistency
The Age of the Universe is
13.6 billion years,
Give or take a few hundred million years
The Concordance Model
Thanks to:
James PilcherBruce Winstein, Dorothea Samtleben and the whole CAPMAP groupNanci Carrothers, Charlene Neal, and Dennis Gordon
The Chicago Maya Society, K.E. Spence, John C. Whittaker, Wen-Hsiung Li, Robert Clayton, Stephen Simon, Andrey Kravstov, James Truran, Stephan Meyer, Erin Sheldon, Wayne Hu
And all the people who attend and support these lectures!
So Long, Enjoy the Luncheon!
Next Lecture Series:
Origin of Mass: A Challenge for Experimental Particle Physics
By
Ambreesh Gupta
