Actually I was looking for Day the Universe Changed a couple of weeks ago. I found that it IS available on DVD and video tape. But it is priced for educational use at $750 for the set. Ouch!
Oh, and the publisher changed the name of all of the episodes of The Day The Universe Changed. For example: The first episode was called (in the companion book and TWICE in the show itself) “The Way We Are”. But “Churchill Pictures” shows on the packaging and in the title splash screen of the video the title “It Started With the Greeks”. Because this is being sold for educational use each video is split into two parts (rather harshly at times, with the show stopped at a minor break in the action) to allow easier viewing in the time available in a classroom. A short summary is given by James Burke as an ending to the first half, there is a quick pause and then a short introduction for the second half. If they would get it down to $99 I would buy a copy for myself.