The Age of Things: Sticks, Stones and the Universe

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The Age of ThingsSticks, Stones and the Universe
Distances, Redshifts and the Age of the Universe
http//cfcp.uchicago.edu/mmhedman/compton1.html
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WARNING! Cosmologist talking about Cosmology!
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Last Time Globular Clusters
11.5 ? 1.3 billion years 12 ? 1 billion
years 11.8 ? 1.2 billion years 14.0 ? 1.2 billion
years 12 ? 1 billion years 12.2 ? 1.8
billion years
Multiple analyses yield ages of 12-13 billion
years, and an uncertainty of about 1 or 2
billion years
M68
M92
M30
M13
NGC362
NGC6752
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Colors and Spectra
Alberio
1 m
1 km
1 mm
1 ? m
1 nm
1 pm
Visible
600 nm
700 nm
400 nm
500 nm
Wavelength
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Galaxies
M87
Andromeda
Whirlpool
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Galaxy Redshifts
(Coutesy of E. Sheldon)
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The Spectra of different atoms
Sodium
Hydrogen
Calcium
Mercury
Neon
400
500
600
700
Wavelength (nanometers)
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Galaxy Redshifts
Hydrogen
(Coutesy of E. Sheldon)
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Galaxy Redshifts
Hydrogen
Oxygen
(Coutesy of E. Sheldon)
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Galaxy Redshifts
Hydrogen
Oxygen
(Coutesy of E. Sheldon)
Wavelengths measured in Laboratory
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Galaxy Redshifts
Hydrogen
Oxygen
(Coutesy of E. Sheldon)
Wavelengths measured in Laboratory
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The Doppler Effect
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Galaxy Redshifts
Hydrogen
Oxygen
(Coutesy of E. Sheldon)
Wavelengths measured in Laboratory
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Measuring the distance to the stars using Parallax
Background Stars
Nearby Stars
Earth
Earth
Sun
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Estimating distance with brightness
Sirius
Pollux
Castor
Sirius B
Luminosity Total power emitted by star in
the form of light.
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Galaxy Distances Cepheids
Large Magellanic Cloud
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The Period-Luminosity Relation of Cepheids
More Luminous
Less Luminous
Based on Data from Udalski et. al. In Acta
Astronomica Vol 49 (1999) pg 223
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The Period-Luminosity Relation of Cepheids
More Luminous
Less Luminous
Cepheid in Galaxy Period 10 days Magnitude
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Cepheid in LMC Period 10 days Magnitude 14
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The Period-Luminosity Relation of Cepheids
More Luminous
Less Luminous
Cepheid in Galaxy Period 10 days Magnitude
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Cepheid in LMC Period 10 days Magnitude 14
Same Luminosity
10,000 times fainter
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The Period-Luminosity Relation of Cepheids
More Luminous
Less Luminous
Cepheid in Galaxy Period 10 days Magnitude
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Cepheid in LMC Period 10 days Magnitude 14
Same Luminosity
10,000 times fainter
100 times farther away
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The Period-Luminosity Relation of Cepheids
More Luminous
Less Luminous
Cepheid in Galaxy Period 10 days Magnitude
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Cepheid in LMC Period 10 days Magnitude 14
Same Luminosity
10,000 times fainter
100 times farther away
150,000 light years away
15 million light years away
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Galaxy Distances Type Ia Supernova
Luminosity
Supernova 1994D
Days
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The Hubble Diagram
Based on Data from Tonry et. al. astro-ph/0305008
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Now
Then
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Hubble Diagram
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A special point in space implies anisotropies
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Large scale anisotropies are not observed
Distribution of galaxies from the Sloan Digital
Sky Survey
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General Relativity
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Classical Mechanics
An object travels in a straight line at a
constant speed unless acted upon by an outside
force
A force changes the motion of an object by an
amount that depends on its mass
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Objects move differently due to their composition

-

Unless the force is gravity
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Gravity in Classical Mechanics
The more massive object feels a sronger force
The more massive object requires more force to
accelerate it by the same amount
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Gravity in Classical Mechanics
A
A
B
B
The presence of a massive object exerts a force
that causes all objects to deviate from this path
by the same amount
With no outside forces, all particles take the
path with the shortest distance between two points
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Gravity in General Relativity
A
A
B
B
The presence of a massive object changes which
path is the shortest distance between the two
points
With no outside forces, all particles take the
path with the shortest distance between two points
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General Relativity Works
It explains irregularites in Mercurys orbit
It predicted the gravitational lensing of
starlight
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The Expanding Universe
Now
Then
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Re-interpreting the Hubble Diagram
Based on Data from Tonry et. al. astro-ph/0305008
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Redshifts in an Expanding Universe
Time 1
Time 2
Time 3
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Scale Factor
a 1
a 0.5
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Re-interpreting the Hubble Diagram
Based on Data from Tonry et. al. astro-ph/0305008
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Re-interpreting the Hubble Diagram
Based on Data from Tonry et. al. astro-ph/0305008
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Re-interpreting the Hubble Diagram
Based on Data from Riess et. al. astro-ph/0402512
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Based on Data from Riess et. al. astro-ph/0402512
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Re-interpreting the Hubble Diagram
Based on Data from Riess et. al. astro-ph/0402512
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Extraopolating back to the Big Bang
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The Big Bang
a 1
a 0.5
a 0
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Extraopolating back to the Big Bang
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We need more information to do an accurate
extrapolation
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No Talk Next Week
June 5 Parametrizing the Age of the Universe