![]() ![]() Since the strength of gravity weakens as you get farther away from a gravitational body, the points on the equator are farther and have weaker gravity than the poles. In contrast, at each pole, you are only 6357 km from the center of the earth. If you stand at sea level on the equator, you are 6378 km from the center of the earth. As a result, the earth is an oblate spheroid and not a perfect sphere. The earth is spinning, causing it to slightly flatten like a pizza crust thrown and spun in the air. There are three major complications to earth's gravitational field. If the earth were perfectly spherical and if its density were perfectly uniform, then the strength of earth's gravity would be exactly constant at all points on its surface. This leaves only earth's gravity and earth's centrifugal force as the two forces that contribute to your weight differing at the equator versus the poles.Īs we learned in high school, earth's gravity is approximately constant all over the surface of the earth. As a result, averaged over a few days, the gravitational force of the sun on a spot on the equator is the same as the gravitational force of the sun on a spot on the poles. While the sun's gravity is strong enough to keep us and the earth in orbit, the sun's position relative to a spot on the equator versus the poles is constantly changing. Finally, electromagnetic and nuclear forces are either too small-scale, or too short-term to contribute to your overall weight.įor our purposes, we want to consider the forces that differ significantly at the equator versus the poles. Also, additional forces appear when you ride a roller-coaster, an elevator, a swing, or another vehicle, but these forces are transient, so they do not contribute to your overall, long-term weight. Note that although earth's Coriolis force plays a major role in shaping hurricanes and ocean currents, since it is not a static force, it does not contribute to your overall weight. The four dominant large-scale, long-term forces are: What you experience as "something pulling you down" is actually the total of all the forces and not just gravity. While the earth's gravity is by far the strongest large-scale force, it is not the only one. Your weight is the combination of all the large-scale, long-term forces on your body. In short, a trip to the equator is not a viable long-term weight-loss program. These forces change right back when you return to your original latitude. Rather it is the force of gravity and other forces that change as you approach the poles. Note that your body itself does not change. Yes, you weigh less on the equator than at the North or South Pole, but the difference is small. Public Domain Image, source: Christopher S. As a result, people at sea level at the equator are farther from earth's center and experience less gravity than people at sea level at the poles. This exaggerated illustration shows how the earth bulges at the equator. ![]()
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