Cycles in the Sky: Crash Course Astronomy #3

In this episode of Crash Course Astronomy, Phil Plait builds on our naked eye observations from the last episode and takes a look at the cyclical phenomena that we can see at work in the universe.

PBS Digital Studios: http://youtube.com/pbsdigitalstudios

Follow Phil on Twitter: https://twitter.com/badastronomer

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PHOTOS
http://en.wikipedia.org/wiki/Right_ascension#mediaviewer/File:Stars_and_ra.png
http://en.wikipedia.org/wiki/File:Ecliptic_path.jpg
http://commons.wikimedia.org/wiki/File:Sagittarius_Hevelius.jpg
http://en.wikipedia.org/wiki/Scorpius#mediaviewer/File:Sidney_Hall_-_Urania%27s_Mirror_-_Scorpio.jpg
http://en.wikipedia.org/wiki/Libra_(constellation)#mediaviewer/File:Sidney_Hall_-_Urania%27s_Mirror_-_Libra.jpg
http://en.wikipedia.org/wiki/Virgo_(constellation)#mediaviewer/File:Sidney_Hall_-_Urania%27s_Mirror_-_Virgo.jpg
http://commons.wikimedia.org/wiki/File:Leo_Hevelius.jpg
http://en.wikipedia.org/wiki/Cancer_(constellation)#mediaviewer/File:Sidney_Hall_-_Urania%27s_Mirror_-_Cancer.jpg
http://en.wikipedia.org/wiki/Globe#mediaviewer/File:GEO_Globe.jpg
http://sailornanny.weebly.com/uploads/1/0/5/0/10509307/4835516_orig.gif
http://www.slate.com/content/dam/slate/blogs/bad_astronomy/2013/04/28/earth_elliptical_orbit.jpg.CROP.original-original.jpg
http://en.wikipedia.org/wiki/Pole_star#mediaviewer/File:Precession_