Introduction to Cosmology Ingredients of the Primordial Soup

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Introduction to CosmologyIngredients of the
Primordial Soup

• Brian Fields
• Department of Astronomy, UIUC
• Parkland Astronomy Club March 19, 2003

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COSMOLOGY

• Life in an Expanding Universe

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Cosmology

• Structure, Origin, Evolution of the Universe
• stars organized into galaxies
• ex Solar Sytem is part of Milky Way
• Typical galaxy 100 billion stars

Andromeda galaxy
Sombrero galaxy
Think big! galaxies are building
blocks smoothly fill universe (like dust)
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Edwin P. Hubble

• The great observer of galaxies
• Measured galaxy
• Distance
• Speed

Hubble, the man
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Its 1928.Hubble is measuring galaxy
velocities, distances.What will Edwin find?

• More galaxies approaching than receding
• More galaxies receding than approaching
• About equal numbers of each

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Hubbles Law and Its Meaning

• Edwin Hubble (1929)
• galaxies moving away from us
• farther faster
• that is, v D
• v HD

• Interpretation What does it mean?

• Egoist
• view
• We are at
• center of Universe

• Einstein
• view
• Universe is
• expanding!
• No center!

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AGE OF UNIVERSE
Expansion implies finite age
If constant speed, distance speed x time D vt

• Hubble v HD
• D distance between 2 particles (galaxies)

All together v HD H(vt) Htv so Ht
1 expansion age of universe
t1/H
best estimate age t 13 billion years
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A Telescope is a Time Machine
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A Telescope is a Time MachineThe Hubble Deep
Field

• Farther away means
• Takes light longer to get to us
• Light seen now started long ago
• Most distant Universe 10 present age!

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COSMOLOGY

• Looking Back to the Atomic Age
• or
• How the Universe Got Its Spots

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EXPANDING UNIVERSE THE PAST

• U. expanding today
• galaxies closer in past
• more dense

• long ago, very dense
• matter in contact energy, heat flow
• Universe has temperature

• dense compressed heat up
• Expand cool
• Early Universe very dense and very hot

BIG BANG
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INTERLUDE I LIGHT HEAT

• hot objects glow
• light, heat connected
• thermal radiation

Spread out into colors spectrum

• color wavelengths where brightest
• depends on temperature
• color-temperature connection (think flame!)

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TAKING THE TEMPERATURE OF THE UNIVERSE

• Penzias Wilson (1964)
• entire sky bright with microwaves

• spectrum is thermal, with
• the temperature of space"
• ...extremely cold today

Nobel Prize!
the Universe filled with thermal radiation
Cosmic Microwave Background Radiation
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FROM ATOMS TO THE COSMOS

• Microwave background radiation observed
• what does it tell us?
• when was it created?

• To answer follow microscopic behavior
• atoms in expanding Universe

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INTERLUDE II ATOMS IN A NUTSHELL

• Atoms made of
• electrons - charge
• nucleus protons charge, neutrons 0 charge
• neutral equal p and e
• bind" together, stable
• ionized some or all e gone
• not bound, less stable
• To ionize need energy to un-bind
• tear away electron
• Cold gas gentle collisions neutral
• Hot gas violent collisions ionized

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THE COSMIC FLAME

• At present Universe extremely cold neutral
  atoms
• In past Universe hotter
• when T _at_ 3300 K 5500F
• whole universe ionized
• in primeval fireball

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THE COSMIC FOG CLEARS

• When universe ionized opaque
• But universe cooled
• until t _at_ 300, 000 yrs
• collisions gentle neutral
• universe transparent
• atoms formed pe hydrogen
• microwave background is
• faded snapshot of cosmic fireball
• when ionized neutral
• Big bang model works well
• back to t 300 000 yrs !

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Turning Up the Contraston the Cosmic Fireball

• Microwave background temperature almost uniform
  same in all directions
• Cosmic fireball hot but smooth
• but not perfectly smooth
• Tiny temperature differences
• exist (at 0.001 level)
• Why hot spots/cold spots ?
• atoms denser/rarefied
• Compressed by slight irregularities in gravity
  caused by irregularities in matter distribution

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Turning Up the Contraston the Cosmic Fireball

• WMAP The Wilkinson Microwave Anisotropy Probe
• Measuring Ripples in the Microwave Background
• WMAP in the big picture
• Map making

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WMAPs MAPA Cosmological Goldmine
Hot red Cold blue
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WMAP Results Hot off the Presses

• Probing the Universe with unprecedented precision
• Age of the Universe 13.6 billion years
• For comparison age of Earth is 4.55 billion
  years
• First stars born
• within 200 million years
• Crown jewel
• inventory of
• cosmic matter

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THE FUTURE
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EXPANDING UNIVERSE FINAL FATE

• Competition gravity vs inertia
• Compare pop fly!
• quantitative question
• launch speed vs speed to escape Earth
• For Universe
• gravity galaxy mass density
• inertia expansion
• Both are observable!
• Fate quantitative question
• if expand forever
• if expansion halts, collapse

or
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WMAP AND DARK MATTER

• Consequences of WMAP Inventory
• if atoms is all, expand forever
• But they are not
• the universe is exactly (!?) critical, but this
  means
• Can estimate total matter content
• most matter not normal! non-baryonic dark matter
• exotic particles?
• What about the remainder
• dark energy of totally unknown form!

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ORIGIN OF DARK MATTERTHE VERY EARLY UNIVERSE?

• Maybe Dark Matter particles created at times 1 sec !?
• T, energies ultrahigh
• Q how probe such high energies?
• Hint its in the Great State of Illinois
• Fermilab

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INNER SPACE / OUTER SPACE

• Fermilab is a telescope!
• Probes conditions in
• Universe at 10-12 s
• but also
• The Universe is the poor mans accelerator
• Probes conditions inaccesible at laboratories

Russian cosmologist Yakov Zeldovich
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OUTLOOK

• PRESENT
• Big bang theory in great shape
• tested from t 13 billion years 4 x 1017 sec
• down to t 1 sec
• NEAR FUTURE
• New era dawning for Cosmology
• flood of high precision data
• right now Golden Age!
• old questions answered
• new questions emerge
• new tools available
• Exciting, expansive future!
• Stay tuned!