The term "gravity" implies to many the notion of weight. Since antiquity, objects have been observed to "fall down" to the ground, and it therefore seemed obvious to associate gravity with Earth itself. Earth pulls all material bodies downward, but some appear to fall faster. For example, a rock and a feather fall to the ground at appreciably differing rates, and the logical conclusion of such great intellects as Greek philosopher Aristotle (384-322 B.C.E.) was that heavier objects fall faster than lighter ones. In fact, many erroneously believe this today, but it is found not to be true when tested in a controlled experimental manner. Air resistance is the confusing culprit and, when removed or minimized, all bodies are observed to hit the ground in the same amount of time when dropped from the same height.

Newton's Law of Universal Gravitation

In 1687, English physicist and mathematician...