- Planes can travel in a relatively straight line for a very long time and not fall off any edges. They can also circle the Earth without stopping.
- If you look out the window on a trans-Atlantic flight, you can, most of the times, see the curvature of the Earth on the horizon. The best view of the curvature used to be on the Concorde, but that plane's long gone. I can't wait to see the pictures from the new plane by Virgin Galactic—the horizon should look absolutely curved, as it actually is from a distance.