The earth's gravitational pull radiates from its core much like the ripples of a stone thrown in a pond. The closer you are to the earth's cote, the stronger its pull. Because the earth is not perfectly round, an athlete is farther from the core standing at the equator than standing at the North or South pole. As a result an athlete, or an implement like a javelin, will weigh a little less at the equator than at either Pole. If the athlete climbed to the top of a mountain at the equator, she would be farther from the earth's core, and her weight would be reduced even more. We must also consider two additional items: the earth's daily rotation around its axis and the fact that the earth's spin causes it to bulge outward at the equator and flatten our at the poles. This means that the closer you are to the equator, the larger the rotary pathway you travel around as the earth turns on its axis. As a result, an athlete or an object at the equator travels more than 1,000 miles an hour faster than at the North or South Pole! The faster you travel during the earth's daily rotation, the more your body mass tries to fly out and away from the earth's surface. You don't take off into space of course, but the body's increased outward pull fights against gravity's inward attraction. This characteristic also causes you to weigh a little less than you would at the Poles. Consider the result of all these factors: An athlete who weighs 200 Ib at the poles will weigh about 198.94 Ib at sea level at the equator, and an athlete who weighs 200 Ib at sea level will weigh approximately 199.77 Ib at an altitude of 12,000 ft. These small changes in poundage tell us that an athlete's body weight is a function of variations in the earth's gravitational pull on the athlete's mass. An athlete's body mass can remain constant, yet the same person's body weight can fluctuate, depending on where the athlete is on the earth. The same principle applies to the weight of a shot, a javelin, or any kind of equipment used in a sporting contest.