The final episode of Crash Course Astronomy went up last week, but if you miss it already, we have one final video for you: the fifth outtakes reel, which basically features me trying to pronounce ...

Today on Crash Course Astronomy, Phil dives into some very dark matters. The stuff we can actually observe in the universe isn’t all there is.

It’s an example of an astronomical cycle visible to the naked eye, and the first of three subjects in Episode 3 of Crash Course Astronomy, a new series by Bad Astronomy’s Phil Plait.