This blew my mind when I was a kid, and influenced my thought process ever since then. This is totally worth 7 minutes 16 seconds of your time. You don't even have to be technical as long as you know what a "right angle" is.
And now I feel the need to remind everyone of the comedic take on All This, thanks to ellielabelle: A Brief Brief History of Time (links to a page of links to all 10 chapters)
Ah... Carl Sagan, the thinking woman's pinup. My astronomy teacher in Hugh school had us watch parts of the Cosmos series, and even the "Git 'Er Done" guys in the class thought he was a cool guy. Aside from the obvious reference to a tesseract, I couldn't help but be reminded of "A Wrinkle in Time" while watching the clip. His description of the apple trying to talk to the square reminded me of Mrs. Which.