General Knowledge
Why do we not feel the Earth moving at 1,600 kilometres an hour?
- Everything around us moves with it, at a steady speed
- It moves slowly
- Gravity holds us still
The answer is Everything around us moves with it, at a steady speed. Only changes in motion are felt, and the spin is very steady.
Because there is nothing to feel. Bodies detect acceleration, not motion - a change in speed or direction - and the Earth's spin is extraordinarily steady. Everything around you, including the air, is moving with you at the same rate, so there is no wind and no sensation, exactly as in a smooth aircraft at cruising speed.
That is Galileo's point, and he made it with a ship: below decks, with no window, no experiment you can perform will tell you whether the ship is moving steadily or tied up at the dock. Fish swim normally in their bowl, drops fall straight into a jar. Motion at a constant velocity is not a property you can measure from inside.
It becomes the founding idea of relativity - there is no experiment that reveals absolute motion, so there is no such thing as absolutely at rest. There are effects if you look hard: a pendulum's swing rotates through the day, which is what Foucault demonstrated in 1851, and the spin makes the equator bulge and deflects weather systems. But you feel none of it, and the equatorial speed is roughly that of an airliner.