Cosmology Tim Arlen UCLA Physics Department Fall 2006 Image Credit: NASA, ESA, and The Hubble...
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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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Transcript of Cosmology Tim Arlen UCLA Physics Department Fall 2006 Image Credit: NASA, ESA, and The Hubble...
Cosmology
Tim Arlen
UCLA Physics Department
Fall 2006
Image Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)
Pleiades Star Cluster. Image Credit: Robert Gendler.
Cosmology- study of the overall structure and
properties of the universe as a whole.
Image Credit: NASA, ESA, and Martino Romaniello (European Southern Observatory, Germany)
Topics to Explore
• Highlight history of human thought
• Overview of our current theory
• Do we believe our theory is correct?
Image Credit: NASA, ESA, HEIC, and The Hubble Heritage Team (STScI/AURA)
Cat’s Eye Nebula
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.
Greek Cosmology
Image Credit: NASA,ESA, M. Robberto (Space Telescope Science Institute/ESA) and the Hubble
Space Telescope Orion Treasury Project Team
Image Credit: NASA, NOAO, ESA, the Hubble Helix Nebula Team, M. Meixner (STScI), and T.A. Rector (NRAO)
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: http://math-ed.com /Resources/GIS/Geometry_In_Space/
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
Image Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)
• Einstein bursts onto the scene!
• Formulated General Relativity by 1915
• Equations showed that the universe is expanding.
• He didn’t like this!
Birth of Modern Cosmology
Pleiades Star Cluster. Image Credit: Robert Gendler.
Some Gravity Concepts
• Mass affects space by bending it.
• Imagine space in 2D, like a trampoline.
Image Credit: NASA, ESA, HEIC, and The Hubble Heritage Team (STScI/AURA)
Cat’s Eye Nebula
Dramatic Comfirmation of GR• Bending of starlight.• Confirmed with eclipse in 1916.
Image: http://astro.physics.sc.edu /selfpacedunits/Unit57.htmlImage Credit: (Cover) Spacetime
and Geometry: An Introduction to General Relativity by Sean Carroll, published by Addison-Wesley.
Expansion of Space
Some Time T
Some Time Later T + T
Image Credit: NASA,ESA, M. Robberto (Space Telescope Science Institute/ESA) and the Hubble
Space Telescope Orion Treasury Project Team
Hubble and Expansion
• 1929-Hubble demonstrated his famous result:The farther away an object is from us, the faster it moves away from us.
Courtesy of the Archives, California Institute of Technology
Image Credit: NASA, NOAO, ESA, the Hubble Helix Nebula Team, M. Meixner (STScI), and T.A. Rector (NRAO)
Modern Cosmology
• Theory of universe’s 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: Credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team Hubble Ultra Deep Field
Source: The Birth of the Universe: The Kingfisher Young People’s Book of Space
Image Credit: NASA, ESA, and Martino Romaniello (European Southern Observatory, Germany)
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 The Hubble Heritage Team (STScI/AURA)
Observational Consequences
• Universe itself (space) emits radiation, because it’s hot
• After “Era of Recombination” universe is transparent to photons
• Blackbody Radiation predicted- “Cosmic Microwave Background” (CMB) in 1960’s.
Pleiades Star Cluster. Image Credit: Robert Gendler.
Major Discovery
• AT&T Bell Laboratory, Penzias & Wilson inadvertently discover “background noise” in the microwave region.
• Awarded Nobel Prize in 1978
Image Credit: NASA, ESA, HEIC, and The Hubble Heritage Team (STScI/AURA)
Cat’s Eye Nebula
Cosmic Microwave Background
• COBE (Cosmic Background Explorer) found that CMB is uniform (isotropic) to 1 part in 10,000
Source: Ned Wright’s Cosmology Tutorialhttp://www.astro.ucla.edu/~wright/cosmolog.htm
Image Credit: NASA,ESA, M. Robberto (Space Telescope Science Institute/ESA) and the Hubble
Space Telescope Orion Treasury Project Team
Problem-Galaxy Formation
• If all matter is spread out uniformly, how could matter clump together and form galaxies and star clusters?
Image Credit: NASA, NOAO, ESA, the Hubble Helix Nebula Team, M. Meixner (STScI), and T.A. Rector (NRAO)
Source: Ned Wright’s Cosmology Tutorialhttp://www.astro.ucla.edu/~wright/cosmolog.htm
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, ESA, and Martino Romaniello (European Southern Observatory, Germany)
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: Credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team Hubble Ultra Deep Field
Brief Recap
Source: The Birth of the Universe: The Kingfisher Young People’s Book of Space
Image Credit: NASA, ESA, and Martino Romaniello (European Southern Observatory, Germany)
Olber’s 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!
