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by Rick Groleau Ask someone why astronauts in the Space Shuttle or the MIR space station float in their cabins, and quite often you'll hear that it's because there's zero gravity in space. This kinda makes sense, doesn't it? After all, the space travelers are about hundred miles above the Earth's surface, right? Actually, that answer is completely wrong. It is true that the pull of gravity is less on the astronauts and their craft, but the pull is only slightly less. With the center of the Earth 3,960 miles away from someone standing on the surface and 4,060 miles away from someone orbiting 100 miles above, the difference in the pull of gravity is only about 5 percent. That means if you weigh 100 pounds on Earth, you would weigh 95 when 100 miles high. No, the real reason that astronauts float around is that they're in a continuous free fall. To find out exactly how this works, check out "the full explanation" below, starting with Part 1. If you want more of a challenge, skip right to "just the activities" and see if you can figure it out yourself. The full explanation Part 1: Free-falling and weightlessness Part 2: Falling Far requires the Shockwave plug-in Part 3: Speed is key requires the Shockwave plug-in Summary Just the Activities Clear the Edge (from Part 2) requires the Shockwave plug-in Into Orbit (from Part 3) requires the Shockwave plug-in Blueprint for a Space Station | Astronauts in Hard Hats Inspired by Science Fiction | Free-Falling | Resources Transcript | Site Map | Stationed in the Stars Home Editor's Picks | Previous Sites | Join Us/E-mail | TV/Web Schedule About NOVA | Teachers | Site Map | Shop | Jobs | Search | To print PBS Online | NOVA Online | WGBH © | Updated November 2000 |
Go to part 1 of Free-Falling