十万个为什么·科学启蒙30篇（4）

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为什么赤道上物体重量略轻

Earth rotates fastest at the equator, creating a stronger outward centrifugal force there.
This force slightly opposes gravity, making objects feel lighter than at the poles.
The equatorial bulge also means you’re farther from Earth’s center, weakening gravitational pull.
Gravity at the equator is about 0.5% weaker than at the poles due to both effects combined.
A 100-kg person weighs roughly 0.5 kg less at sea level on the equator than at the North Pole.
Scientists measure these tiny differences using ultra-precise gravimeters aboard ships and satellites.
Weight changes don’t affect mass, which stays constant regardless of location.
Pendulum clocks run slightly slower near the equator because gravity is weaker there.
GPS systems must account for Earth’s shape and rotation to calculate accurate positions.
These variations help geophysicists map Earth’s internal density and tectonic movements.