Carl Sagan's 1977 Royal Institution Christmas Lecture. The Royal Institution Christmas Lectures have been held in London annually since 1825. They serve as a forum for presenting complex scientific issues to a general audience in an informative and entertaining manner.

Part 1: The Earth as a Planet
http://www.videosift.com/video/Carl-Sagan-The-Planets-1-The-Earth-as-a-Planet
Part 3: The History of Mars
http://www.videosift.com/video/Carl-Sagan-The-Planets-3-The-History-of-Mars
Part 4: Mars Before Viking
http://www.videosift.com/video/Carl-Sagan-The-Planets-4-Mars-Before-Viking
Part 5: Mars After Viking
http://www.videosift.com/video/Carl-Sagan-The-Planets-5-Mars-After-Viking
Part 6: Planetary Systems Beyond the Sun
http://www.videosift.com/video/Carl-Sagan-The-Planets-6-Planetary-Systems-Beyond-The-Sun