You already may know this but on 'It Might Get Loud', Page tells the Edge how the song originated. I've known how to play the song for ages but when Page explained how it's almost a circular pattern, I thought, 'holy shit, how come I didn't see this?'. I firmly believe that this is the greatest rock song of all time. There are amazing songs out there but this is incredible. I saw it quoted once, (I'll try to find it later) that this song represents the last dinosaur on Earth walking down the street. Pretty simplistic yet pretty powerful.
Cheers on an interesting topic.