This is a 2 hour 47 minute reading of a book, Feynman The Character of Physical Law.
I find it fascinating in general, but also in the specific that at about 1:52:00 he states that conservation of charge in specific and all conservation laws in general, are only local. A person in motion will not see conservation of charge (or other conservation laws). This makes Conservation Of Momentum or Conservation Of Energy depend on your point of view compared to the localization of the event. Something to contemplate.
At 2:0:40 he goes over Conservation Of Energy in some depth. He points out that it is not just a matter of counting, like the conservation of baryons or charge. Overall, it seems that even with conservation of energy, it is terribly hard to account for all of it (and that alone is a potential for usable variation).
I love the point where, after some discussion starting at 2:18:30, he states near 2:20:28 that “If you thought before that science was certain, well, that is just an error on your part”. So much for “The Science is settled”!