The background music here is really annoying, but he does make quick work of the basic definitions.
http://www.youtube.com/watch?v=Iimklyw9T3U&feature=related
If your math skills are good (think sin, cos, tan…) you may be interested in this definition of what a parsec is…
Cosmic Distances & Light Speed
The Scale of the Universe
The Scale of the Universe Interactive Applet
Howdy! Would you mind if I share your blog with my twitter group?
There’s a lot of folks that I think would really enjoy your content. Please let me know. Thank you
Sure…