ANNOUNCER: Richard Maxwell from Salmon Arm, British Columbia would like to know:</s>RICHARD MAXWELL: Does a spacecraft choose its own speed once it's in orbit? And if, on a spacewalk, an instrument is dropped, would it travel in the same orbit and speed as the space station?</s>MILES O'BRIEN, CNN ANCHOR: Richard, the speed of an orbiting object relative to the earth is dictated by its altitude. Objects in low earth orbit -- the space shuttle, the international space station -- rotate around the globe about every 90 minutes, about 17,500 miles an hour. The lower you go, the faster you move relative to the surface to the earth. The best analogy is, think of a yo-yo at the end of your finger. As you spin that yo-yo and the string becomes shorter that yo-yo, relative to your finger, starts moving more quickly.
Ask CNN: What Determines a Spacecraft's Speed?