十万个为什么·科学启蒙30篇（4）
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Why Objects Weigh Slightly Less at the Equator
为什么赤道上物体重量略轻
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Earth rotates fastest at the equator, creating a stronger outward centrifugal force there.
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This force slightly opposes gravity, making objects feel lighter than at the poles.
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The equatorial bulge also means you’re farther from Earth’s center, weakening gravitational pull.
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Gravity at the equator is about 0.5% weaker than at the poles due to both effects combined.
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A 100-kg person weighs roughly 0.5 kg less at sea level on the equator than at the North Pole.
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Scientists measure these tiny differences using ultra-precise gravimeters aboard ships and satellites.
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Weight changes don’t affect mass, which stays constant regardless of location.
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Pendulum clocks run slightly slower near the equator because gravity is weaker there.
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GPS systems must account for Earth’s shape and rotation to calculate accurate positions.
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These variations help geophysicists map Earth’s internal density and tectonic movements.