I've always loved the time exposure pics of the circumpolar stars. In "Staring at Polaris" there is a short break about half way through the process. It makes for a more interesting picture and I wounder if it was intentional.

I know it's elementary, but for some reason I've always found the relationship between rpm and and speed fascinating. The stars at the outside of the pic travel farther in the same amount of time than stars near the center. Hence they travel faster.

In fact, if you built a wheel in space with a 5000 mile radius and somehow managed to have enough energy to get it spinning at 360 rpm then the outside of the wheel would be traveling faster than the speed of light.

I posted that idea when I first got here. They shot it down because of some nonsense about the contraption approaching infinite mass as it neared "C". ;)