Crash Course Astronomy - a series of short instructional videos by Phil Plait

In January Phil Plait began delivering a series of ten to twelve minute long introductory lectures about astronomy that were recorded by PBS Digital Studios and released as YouTube videos. They just released a humorous video of outtakes. Watch at the one-minute mark, as Phil tries different hand gestures for showing the orientation of the Earth’s axis.    

Topics so far in this series are:

#1    Introduction to Astronomy

#2    Naked Eye Observations

#3    Cycles in the Sky

#4    Moon Phases

#5    Eclipses

#6    Telescopes

#7    The Gravity of the Situation

#8    Tides

#9    Introduction to the Solar System

#10  The Sun

Back in 2011 Phil also gave a TED talk on How to defend Earth from Asteroids.