Thank you very much for providing this resource. I have only got as far as lecture 3 of classical mechanics but I have already learned some important principles and terminology.
Some time ago, years (I think), I was trying to describe continual movement of everything and described it as moving along a dimension of Universal potential energy. I can see now that it was the idea of minimizing potential energy which is incorporated into the Lagrangian that I needed but did not know about. Being ignorant of a lot of physics I am reinventing the wheel some of the time and though it seems a revelation to me it is just common knowledge that I am not describing as well as I might.
Lecture 3 introduced translation and rotation symmetry. I did not know symmetry had that meaning in physics. I had only known about the mathematical kind of symmetry. So may well have been misunderstanding some of the posts where symmetry has been discussed. Now it makes sense that the object just keeps on going as the potential energy is not depleted just shifted to a different location in space.That makes sense to me like the continual falling of something in orbit.