How Fast is the Earth Rotation Speed?
At the equator, the Earth rotation speed is at about 1670 km/hour (1037 mph). It takes 23 hours and 56 minutes (almost a full day) for the Earth to make one rotation. Even if you don’t feel the Earth is always spinning!
Why can’t we feel the rotation of the Earth?
The answer lies in the nature of the Earth’s motion. Think about if you were on an airplane while traveling smoothly at a constant speed and constant altitude. You have unbuckled your seat belt to walk down the aisle, but you can’t feel the movement of the plane. The reason is simple: you, the plane and everything else on it are moving at the same speed. To feel the movement of the plane, you have to look at the clouds outside.
1. Earth’s rotation, uniform motion
The rotational speed of the Earth is certainly relatively high. What is important, however, is that this speed is constant. The rotational motion of the Earth is uniform, which does not cause any particular sensation. Sit on the train. When traveling at its cruising speed, you feel nothing, even if it’s a high-speed train. Only acceleration and braking can be felt physically. Indeed, at these moments, the force of acceleration can pull us to our seat or vice versa, i.e. throw us off the chair.
2. Effect of centrifugal force
To follow the circular motion of the Earth, a force must be applied to the body. Otherwise, the principle of inertia will keep us moving in a straight line. The force in question is the gravitational force, which is divided into two terms:
- the gravitational force (responsible for the 9.8 m/s² acceleration) that results from the mass of the Earth and which pulls us to its center;
- the centrifugal force (responsible for the acceleration of about 0.02 m/s²) that results from the Earth’s rotation and which tends to pull us out of it.
To feel the Earth’s rotation, the centrifugal effect must be stronger than gravity.
Photo credit: Public Domain Pictures