1. True or false: The space shuttle orbits at altitudes in excess of 150 kilometers to be above both gravity and Earth’s atmosphere.
2. Satellites in close circular orbit fall about 5 meters during each second of orbit. Why doesn’t this distance accumulate and send satellites crashing into Earth’s surface?
1. False. What satellites are above is the atmosphere and air resistance—not gravity! It’s important to note that Earth’s gravity extends throughout the universe in accord with the inverse-square law.
2. In each second, the satellite falls about 5 m below the straight-line tangent it would have followed if there were no gravity. Earth’s surface also curves 5 m beneath a straight-line 8-km tangent. The process of falling with the curvature of Earth continues from tangent line to tangent line, so the curved path of the satellite and the curve of Earth’s surface “match” all the way around Earth. Satellites do, in fact, crash to Earth’s surface from time to time when they encounter air resistance in the upper atmosphere that decreases their orbital speed.
