Our Ability to Perceive Speed and Acceleration

When we are aboard a plane flying at cruising speed, we will not be able to feel that the plane is in fact moving at speed of more than 900 km/h. But if the plane changes speed, turns or changes its altitude, we can easily feel it.

Same thing happens with the motion of the Earth. Because of the Earth’s rotation, the surface of the Earths moves at a speed of 1656 km/h near the equator. It also travels around the Sun at a speed of about 107000 km/h. We never feel any of these because the speed is constant, or in other words, the acceleration is zero.

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Eötvös Effect: Evidence of Spherical, Rotating Earth

Eötvös effect is the change in perceived gravitational acceleration when moving eastward vs westward. An object will weigh more when moving eastward than when it is stationary or moving westward.

The effect was discovered by Loránd Eötvös in the 1900s after noticing the difference in gravity measurement on moving ships. He noticed that the readings were lower when the boat moved eastwards, higher when it moved westward. He identified this as primarily a consequence of the rotation of the Earth.

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