On Day 18, we returned to the spacetime symmetries we discussed last time, but treated them with a bit more rigor and tighter notation. In the context of the Newton’s 2nd law, we worked out the math for
- Translation group as applied to three-dimensional space and to time.
- Rotations in space and their matrix representation in 2D.
- We formally defined the orthogonal group O(2) and the special orthogonal group SO(2).