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Olber's Paradox and the Distant Universe

Olber's Paradox and the Distant Universe. Robert Nemiroff Michigan Tech U. Physics X: About This Course. Officially "Extraordinary Concepts in Physics" Being taught for credit at Michigan Tech Light on math, heavy on concepts Anyone anywhere is welcome No textbook required

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Olber's Paradox and the Distant Universe

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  1. Olber's Paradox and the Distant Universe Robert Nemiroff Michigan Tech U.

  2. Physics X: About This Course • Officially "Extraordinary Concepts in Physics" • Being taught for credit at Michigan Tech • Light on math, heavy on concepts • Anyone anywhere is welcome • No textbook required • Wikipedia, web links, and lectures only • Find all the lectures with Google at: • "Starship Asterisk" then "Physics X"  • http://bb.nightskylive.net/asterisk/viewforum.php?f=39

  3. Considering Our Universe as a Whole The Cosmological Principle Universe Homogeneous & Isotropic Homogeneous Smooth when averaged out Example: jello, even fruity jello Isotropic Same in every direction Example: room with the lights out 

  4. Olber’s Paradox Why is the sky dark at night? Why is it bright during the day? Assume the universe is infinite Assume stars all have the same surface brightness Surface brightness does not depend on distance

  5. Olber’s Paradox Point in any direction That direction goes through empty space but ends on a star Every direction should be as bright as the surface of a star The sky should be bright at night What’s wrong with this picture?

  6. http://hyperphysics.phy-astr.gsu.edu/Hbase/astro/imgast/olbers.gifhttp://hyperphysics.phy-astr.gsu.edu/Hbase/astro/imgast/olbers.gif

  7. Dense Forest Analogy Picture you are in a dense forest Trees are found in every direction Every direction you point ends on a tree  Therefore, every direction is tree-bark brown

  8. Olber’s Paradox: Possible Solutions Universe is finite in size Universe is finite in age Dust blocks out most light Light gets too redshifted to see Which do you think is correct? Take a minute to think about it!

  9. Olber’s Paradox: Solution All of those have some affect BUT The finite age of the universe is the most important factor Light just can’t get to us from distant stars

  10. The Sky IS bright at night Background radiations in all energy bands The sky is never completely dark at any wavelength Olber was correct after all!

  11. COBE All-Sky Map Credit: COBE Project, DMR, NASA APOD: 2006 October 7

  12. Our Dusty Universe Credit: DIRBE Team, COBE, NASA APOD: 2000 November 19

  13. The Cosmic Infrared Background Credit: A. Kashlinsky (SSAI) & S. Odenwald (Raytheon),  2MASS, NSF, NASA APOD: 2002 February 6

  14. ROSAT Explores The X-Ray Sky Credit: S. Digel and S. Snowden (USRA/ LHEA/ GSFC),  ROSAT Project, MPE, NASA APOD: 2000 August 19

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