We just learned about this great web site,Universe Scale done by Nikon from a visit to The Smug Baldy Speaks (Thanks, Smuggie)
It uses excellent, advanced graphics to explain about distance and size is a very unique way.
SI units are used and illustrated in this presentation that can become almost hypnotic, if you focus on the calming sound track too much.
A great way to get to understand and remember the various terms used in measurement of length.
