Conservation of momentum
To Sean Carroll the conservation of momentum represents the transition from premodern to modern physics. It’s an amazing idea that took a while to formulate, seen here in the first of a series of the best ideas in the universe. Donate on patron as Sean sends all the money to help solve corona virus and help its victims.
Khan Academy also cover it. So fundamental, its easy to miss completely before getting into more complex physical ideas
Here is the Q and A Carroll published a few days later. Goes into more detail on some points. He is a great explainer – just what we need right now – especially in confused qm physics.
Great video, explains a lot and I didn’t realise it but yeah, conservation of momentum and energy are great ideas it would take a while to fully getting to grips with.