Cosmology

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Cosmology

• Tim Arlen
• UCLA Physics Department
• Fall 2006

Image Credit NASA, ESA, and The Hubble Heritage
Team (STScI/AURA)
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Cosmology- study of the overall structure and
properties of the universe as a whole.
Pleiades Star Cluster. Image Credit Robert
Gendler.
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Topics to Explore

• Highlight history of human thought
• Overview of our current theory
• Do we believe our theory is correct?

Image Credit NASA, ESA, and Martino Romaniello
(European Southern Observatory, Germany)
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Greek Cosmology

• 400 B.C. Plato and Aristotle
• 5 Elements of the universe Earth, Air, Fire,
  Water, and Quintessence.
• Earth-stationary, everything revolved around it
  in circles.

Image Credit NASA, ESA, HEIC, and The Hubble
Heritage Team (STScI/AURA)
Cats Eye Nebula
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Greek Cosmology
Image Credit NASA,ESA, M. Robberto (Space
Telescope Science Institute/ESA) and the Hubble
Space Telescope Orion Treasury Project Team
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More Greek Cosmology

• Ptolemy 200 A.D, geocentric model, Earth is
  very small compared to heavens
• Based on mathematics planets move in Epicycles
• Taught throughout Middle Ages.

Image Credit NASA, NOAO, ESA, the Hubble Helix
Nebula Team, M. Meixner (STScI), and T.A. Rector
(NRAO)
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Pre-20th Century Cosmology

• Copernicus, Kepler, and Galileo
• Heliocentric Model
• Advancement of telescope, galaxies discovered
• By end of 19th Century belief in infinite,
  static, homogeneous universe.

Image Credit Credit NASA, ESA, S. Beckwith
(STScI) and the HUDF Team
Hubble Ultra Deep Field
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Birth of Modern Cosmology

• Einstein bursts onto the scene!
• Formulated General Relativity by 1915
• Equations showed that the universe is expanding.
• He didnt like this!

Image Credit NASA, ESA, and The Hubble Heritage
Team (STScI/AURA)
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Some Gravity Concepts

• Mass affects space by bending it.
• Imagine space in 2D, like a trampoline.

Pleiades Star Cluster. Image Credit Robert
Gendler.
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Dramatic Comfirmation of GR

• Bending of starlight.
• Confirmed with eclipse in 1916.

Image http//astro.physics.sc.edu
/selfpacedunits/Unit57.html
Image Credit (Cover) Spacetime and Geometry An
Introduction to General Relativity by Sean
Carroll, published by Addison-Wesley.
Image Credit NASA, ESA, HEIC, and The Hubble
Heritage Team (STScI/AURA)
Cats Eye Nebula
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Expansion of Space
Some Time T
Some Time Later T ?T
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Hubble and Expansion

• 1929-Hubble demonstrated his famous resultThe
  farther away an object is from us, the faster it
  moves away from us.

Image Credit NASA,ESA, M. Robberto (Space
Telescope Science Institute/ESA) and the Hubble
Space Telescope Orion Treasury Project Team
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Modern Cosmology

• Theory of universes origins developed
• Expansion and GR equations imply a beginning,
  called singularity
• Came to be called Big Bang Theory
• Explosion of space, matter, energy
• Use known laws of physics to reconstruct history
  of Universe, predict new phenomena.

Image Credit NASA, NOAO, ESA, the Hubble Helix
Nebula Team, M. Meixner (STScI), and T.A. Rector
(NRAO)
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Image Credit Credit NASA, ESA, S. Beckwith
(STScI) and the HUDF Team
Hubble Ultra Deep Field
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Cosmic Microwave Background

• About 300,000 yrs ATB, era of recombination
• Photons can pass through universe unimpeded
• Before this time, universe was a plasma

Image Credit NASA, ESA, and Martino Romaniello
(European Southern Observatory, Germany)
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Observational Consequences

• Universe itself (space) emits radiation, because
  its hot
• After Era of Recombination universe is
  transparent to photons
• Blackbody Radiation predicted- Cosmic Microwave
  Background (CMB) in 1960s.

Image Credit NASA, ESA, and The Hubble Heritage
Team (STScI/AURA)
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Major Discovery

• ATT Bell Laboratory, Penzias Wilson
  inadvertently discover background noise in the
  microwave region.
• Awarded Nobel Prize in 1978

Pleiades Star Cluster. Image Credit Robert
Gendler.
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Cosmic Microwave Background

• COBE (Cosmic Background Explorer) found that CMB
  is uniform (isotropic) to 1 part in 10,000

Image Credit NASA, ESA, HEIC, and The Hubble
Heritage Team (STScI/AURA)
Cats Eye Nebula
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Problem-Galaxy Formation

• If all matter is spread out uniformly, how could
  matter clump together and form galaxies and star
  clusters?

Image Credit NASA,ESA, M. Robberto (Space
Telescope Science Institute/ESA) and the Hubble
Space Telescope Orion Treasury Project Team
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Anisotropy Discovered

• CMB is nonuniform to 1 part in 100,000.
• Slightly denser region of space implies slightly
  hotter region of space

Image Credit NASA, NOAO, ESA, the Hubble Helix
Nebula Team, M. Meixner (STScI), and T.A. Rector
(NRAO)
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Major Discovery

• Slightly hotter (more dense) regions are the
  seeds of galaxy formation
• Further evidence for dark matter?
• John Mather and George Smoot Awarded 2006 Nobel
  Prize in Physics for this work

Image Credit NASA, ESA, and Martino Romaniello
(European Southern Observatory, Germany)
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Brief Recap
Image Credit Credit NASA, ESA, S. Beckwith
(STScI) and the HUDF Team
Hubble Ultra Deep Field
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Olbers Paradox

• If the universe was infinite static, then along
  any line of sight, you will eventually hit a
  star.
• Then the night sky should be as bright as an
  average star!

Image Credit NASA, ESA, and Martino Romaniello
(European Southern Observatory, Germany)