Fifty-three years ago, Armstrong, Aldrin and Collins were on their way to the Moon, an occasion to recall each July, not only for those who remember, but also those who do not. Not long ago, I happened across this remarkable video about a very specific, and well known interval of only a few minutes in that mission: the Eagle’s final approach to the lunar surface.

More specifically, the video is a lecture about what the guidance computer was doing and why during those fraught minutes, including a lot of detail that isn’t that well known. Posted by the National Museum of Computing, I was skeptical I would make it all the way through. I was wrong.

One Robert Wills, a software engineer with a clear enthusiasm for the computing that made the Apollo missions possible, tells the tale in simple enough terms — but not too simple — that a non-specialist like me can understand much of it, if not everything. No mean feat, as attested by the non-trivial number of teachers and professors who cannot do so.

I knew a fair amount of the story, but hardly all of it, and the video filled in a lot that I didn’t know. That should be the goal of any video with any claims to being educational, I believe.