We call “gravity” the force causing objects to fall. Newton understands that it is this same gravity that makes the little moon turn around Earth. Without this gravity, it would run away in a straight line. But then also the real moon must orbit Earth because of gravity! And the moons that orbit Jupiter are attracted by Jupiter, and the planets that turn around the sun are attracted by the sun! Without this attraction, every celestial body would move in a straight line. So the universe, then, is a large space where bodies attract one another by means of forces; and there is a universal force,
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