Special Relativity and Local Inertial Frame

In special relativity, we can only make measurements of things that are nearby. If you go far enough away, those velocities start to get greater than the speed of light. That's when you need to apply general relativity for things that are not in your local inertial frame. We're going to drive this huge, expanding universe throughlocal inertial frame,. What that means is: I'm here at this core of my XYZ, and I'm making a bunch of measurements.