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