Realizing that space-time symmetries provide more intuitive introduction to the abstract notion of a symmetry used in physics, on day 17 we switched gears by discussing Richard Feynman’s lecture “Symmetry in Physical Law,” which students watched outside the class.
Feynman introduces the notion of a symmetry of a physical law, which we disected in the context of Coulomb’s law.
- We defined a coordinate system and discussed the difference between passive and active transformations.
- We worked out the translational and rotational spatial symmetries in 2D and showed that translations form a group.
- We also introduced translations in time and showed how they leave the kinematic equations unchanged.
As a transition to the discussion of moving observers, we watched the first half of a wonderful video from the 60’s titled Frames of Reference.