Atoms in Motion, The Feynman Lectures on Physics, Vol. I, Ch. 1

This was Feynman's first undergraduate lecture, given on Sept. 26, 1961 at The California Institute of Technology. At https://www.feynmanlectures.caltech.edu/I_01.html you can read the edited version of this lecture in the online edition of The Feynman Lectures on Physics, which includes the original lecture recording as well as the "reconstructed" version used in this video. At https://www.feynmanlectures.caltech.edu/flpphotos.html#1 the lecture photos shown in this video can be viewed in deep-zoomable format.