We spent three days discussing the conceptual framework of **special relativity**.

We reviewed the expressions for **time dilation** and **length contraction** (we didn’t derive the latter) and discussed what they tell us about the nature of space and time. We introduced the **Lorentz boosts** as a replacement for the **Galilean boosts, **and formally introduced the Lorentz group, SO(1,3). New concepts and ideas included

**Spacetime events****Spacetime diagrams and****null cones****Causally connected events****Relativity of simultaneity**

The key takeaway was that Lorentz transformations leave **the causal structure of spacetime **the same, just like rotations of a polygon leave the shape and the orientation of the polygon the same.