Gravity is slightly weaker at Earth’s equator than at the poles because the planet rotates and bulges outward around its middle. The equatorial surface is farther from Earth’s center, and Earth’s rotation partly offsets the downward pull that a stationary observer would feel.
How does Earth’s shape affect gravity?
Earth is an oblate spheroid, slightly wider across the equator than from pole to pole. Because the equator is farther from the center, the gravitational attraction there is a little weaker, although Earth’s actual density varies from place to place as well.
Why does rotation reduce the weight you feel?
As Earth spins, an object on its surface follows a circular path. The necessary centripetal acceleration is largest at the equator and drops to zero at the poles. In Earth’s rotating frame this is often described using a centrifugal effect, which reduces effective weight at the equator.
How large is the difference?
Near sea level, standard gravity is about 9.78 meters per second squared at the equator and about 9.83 meters per second squared near the poles. That’s a difference of roughly half a percent. A person would not ordinarily notice it, but precision instruments can measure it.
Would your mass change if you moved from the equator to a pole?
No. Your mass is the same; a carefully calibrated scale measuring force would register slightly different weight. Elevation, local rock distribution and instrument design also influence a real-world reading.
Frequently asked questions
Does the equator have the lowest gravity everywhere?
Not necessarily for every individual location. Elevation and the distribution of nearby rock and other mass create local gravity anomalies. The equator-to-pole comparison describes a broad average pattern.
Does Earth spin so fast that objects almost float at the equator?
No. The rotational correction is small compared with Earth’s gravitational attraction.
Sources: NOAA: The Downs and Ups of Gravity Surveys, NASA Glenn: Weight and Gravitational Force.
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