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171 pages, Paperback
First published January 1, 1956
Newton, according to legend, had this epiphany while sitting in his garden noticing apples falling from a tree as he contemplated the motion of the moon. To complete the thought, he asked another crucial question: How does that force decrease with the distance between the objects? For decrease it must, otherwise we would be pulled upward to the sun rather than downward to Earth.Now I’m not questioning the obvious fact that the force of gravity decreases with distance, but is Smolin’s argument valid? My reasoning was that we're in orbit around the Sun, so it shouldn't matter very much if the Sun's gravitational pull is stronger. I even remembered Jupiter Five, an SF short story in this collection by Arthur C. Clarke, which hinged on that exact question. They are on Jupiter V, a small satellite near Jupiter. The gravitational attraction of Jupiter is much stronger than the gravitational attraction of the satellite. Yet even when they push themselves gently away from the satellite and drift into nearby space, they are in no danger of falling into the nearby planet.