The spacecraft in the movie 2001: A Space Odyssey has a rotating cylinder to create the illusion of gravity, inside of which the crew walks and exercises. While watching this old movie, you realize that the radius of the cylinder is roughly three times a crew member's height. You imagine this cylinder rotating sufficiently rapidly to replicate Earth's gravity, but you worry about the difference between the acceleration at the top of the astronaut's head and the acceleration at her feet. Not wanting lightheaded astronauts, you phone NASA with your new design.