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## Parameterizing the Age of the Universe

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The Age of Things:Sticks, Stones and the Universe

Parameterizing the Age of the Universe

http://cfcp.uchicago.edu/~mmhedman/compton1.html

Cosmologist talking about Cosmology!

Supernova 1994D

Present

Past

Based on Data from Riess et. al. astro-ph/0402512

The Expansion History and Material Content of the Universe

Distribution of Matter and Energy

Geometry of Space and Time

General Relativity

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

Distribution of Matter and Energy

Geometry of Space and Time

General Relativity

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

Lower Energy Density

Slower Expansion Rate

The Expansion History and Material Content of the Universe

Distribution of Matter and Energy

Geometry of Space and Time

General Relativity

Energy Density

(Amount of Energy contained in a unit volume)

Expansion Rate

(How fast the Scale Factor changes with Time)

Scale Factor

(Average Distance between particles)

Equation of State

(How Energy Density changes with Scale factor)

Predictions for a Universe with only Matter

Scale Factor Larger

Expansion Rate Slower

Matter Only

Scale Factor Smaller

Expansion Rate Faster

Present

Past

Matter

Scale Factor Increases

Energy Density Falls

Expansion Rate Slows

Dark Energy

Scale Factor Increases

Energy Density Stays Constant

Expansion Rate Grows

Predictions for a Universe with only Dark Energy

Scale Factor Larger

Expansion Rate Faster

Scale Factor Larger

Expansion Rate Slower

Scale Factor Smaller

Expansion Rate Slower

Dark Energy Only

Matter Only

Scale Factor Smaller

Expansion Rate Faster

Present

Past

Predictions for a Universe with mixtures of matter and D.E.

Best Fit is about 3 Parts Dark Energy for every 1 part Matter

25% Matter,

75% Dark Energy

Dark Energy Only

Matter Only

50% Matter,

50% Dark Energy

75% Matter,

25% Dark Energy

Present

Past

Note Fractions only valid today

The Expansion History and Material Content of the Universe

Distribution of Matter and Energy

Geometry of Space and Time

General Relativity

Energy Density

(Amount of Energy contained in a unit volume)

Expansion Rate

(How fast the Scale Factor changes with Time)

Scale Factor

(Average Distance between particles)

Equation of State

(How Energy Density changes with Scale factor)

Predictions for Universes with different total Energy Densities

Energy Density Today

=

Critical Density

Dark Energy Only

Matter Only

25% Matter,

75% Dark Energy

50% Matter,

50% Dark Energy

75% Matter,

25% Dark Energy

Dark Energy Only

Energy Density Today

=

1.5 x Critical Density

Matter Only

What is the Cosmic Microwave Background?

Microwaves are Electromagnetic Radiation

with Wavelengths between 1 mm and 10 cm

Wavelength

1 pm

1 nm

1 m

1 mm

1 m

1 km

Visible

600 nm

700 nm

400 nm

500 nm

What is the CosmicMicrowave Background ?

Telescopes sensitive to microwaves detect a signal from space

Penzias and Wilson, discoverers of the CMB

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

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

Actual Size of Features ~ 400,000 Light Years

Decoupling

Energy Density

Lower Density

Higher Density

Critical Density

Negative Curvature

Positive Curvature

Zero Curvature

Curvature and the Apparent Size of Objects

Energy Density

Lower Density

Higher Density

Critical Density

Negative Curvature

Positive Curvature

Zero Curvature

From Observer’s Viewpoint

Object Appears Smaller

Object Appears Larger

Curvature and the Apparent Distance to Objects

Energy Density

Lower Density

Higher Density

Critical Density

Negative Curvature

Positive Curvature

Zero Curvature

Object is Closer

Object is Farther Away

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 distance the light has to travel depends on the curvature

Decoupling, radiation mostly in visible: wavelength ~ 500 nm

Today, radiation mostly in microwaves wavelength ~ 1 mm

The Scale Factor increases by a factor of 1000 between decoupling and Today

The amount of time this takes depends on the total energy density

Energy Density

Lower Density

Higher Density

Critical Density

Negative Curvature

Positive Curvature

Zero Curvature

Object is Closer

Object is Farther Away

Expansion Rate Faster

Expansion Rate Slower

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 distance the light has to travel depends on the curvature

Decoupling, radiation mostly in visible: wavelength ~ 500 nm

Today, radiation mostly in microwaves wavelength ~ 1 mm

The Scale Factor increases by a factor of 1000 between decoupling and Today

The amount of time this takes depends on the total energy density

Apparent Size of CMB Features is only consistent with Zero Curvature

Only in this case can light travel the required distance in the allowed time

Energy Density

Lower Density

Higher Density

Critical Density

Negative Curvature

Positive Curvature

Zero Curvature

Object is Closer

Object is Farther Away

Expansion Rate Faster

Expansion Rate Slower

Longer Time

Shorter Time

The Expansion History and Material Content of the Universe

Distribution of Matter and Energy

Geometry of Space and Time

General Relativity

Energy Density

(Amount of Energy contained in a unit volume)

Expansion Rate

(How fast the Scale Factor changes with Time)

Scale Factor

(Average Distance between particles)

Equation of State

(How Energy Density changes with Scale factor)

The Concordance Model

Dark Energy Density

The Age of the Universe is 13.6 billion years,

Give or take a few hundred million years

Matter Density

James Pilcher

Bruce Winstein, Dorothea Samtleben and the whole CAPMAP group

Nanci 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!

Next Lecture Series:

Origin of Mass: A Challenge for Experimental Particle Physics

By

Ambreesh Gupta

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