Weighty Matters: Earth’s Gravitational Variations

Looking to shed a few pounds quickly? Consider climbing Mount Everest. At the summit of the world’s tallest peak, you’ll weigh approximately half a percentage point less than at sea level (assuming you haven’t lost mass during the ascent!). If mountain climbing isn’t your cup of tea, hop on a scale at the North Pole, then relocate to Kenya or Ecuador. You’ll find yourself weighing slightly less at the equator— about one-fifth of a percentage point less, to be precise.

Depending on your location on Earth, your mass remains constant, but your weight may vary. These minor fluctuations in weight stem from the fact that gravity isn’t uniform everywhere on Earth, owing to various factors.

mass
: a quantity of matter in an object

For instance, as you ascend a tall mountain, gravitational pull weakens slightly due to the increased distance from Earth’s center of gravity. Meanwhile, transitioning from the poles to the equator, gravity weakens due to Earth’s oblate shape and rotation. At the equator, centrifugal force is stronger than at the poles, while gravitational acceleration is weaker, exerting a slight outward push.

weight
: the force with which a body is attracted toward a celestial body by gravitation

The weight of objects on our planet is also impacted by Earth’s irregular gravitational field. Varying surface topography— characterized by bumps, bulges, dips, and depressions— as well as the continuous movement of water, lead to uneven mass distribution across the globe.

Regions like high mountain ranges boast stronger gravitational pull due to their high mass concentration, while ocean trenches exhibit weaker gravity owing to their low mass concentration. Image: “When the sea becomes moutains” by Korf-Adri on Openverse / CC BY 2.0.

While the effects of Earth’s gravitational variations may not be directly perceptible to surface dwellers, they significantly impact objects in space, such as orbiting satellites, which experience slight acceleration when passing over denser regions of Earth and deceleration when moving away. Additionally, understanding our planet’s gravitational field is crucial for climate change research. By measuring and comparing the mass of oceans and seas, scientists can assess the rate of melting of the Arctic sea ice.■

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