# Why don't we feel Earth move?

This turns out to be a difficult question to answer concisely and in simple terms. Two of our team members wrote these explanations, and hopefully between them they will answer this question:

Explanation 1: If we are stationary with respect to our surroundings (moving with it), we only feel motion when there is an acceleration involved. As examples of such acceleration are the cases when we hit the brakes in a car, or suddenly swerves to some direction.

Earth is in many kinds of motion, but the accelerations associated with these motions are tiny. The two most familiar motions to us are the spin of Earth itself, and its orbital motion around the Sun. The magnitudes of the accelerations due to these motions are very small, about 0.03 m/s² due to Earth's spin at the Equator, and about 0.006 m/s² due to our orbital motion around the Sun. 0.03 m/s² as the limit of the magnitude of acceleration that humans can sense, and as most things around us move at the same velocities and accelerations with us, we cannot sense these low accelerations.

Of course there is the gravitational force of Earth (and its associated acceleration) as well, but as long as we keep our feet on the ground or on a solid surface under us, we are not moving nor feel any movement toward the center of Earth either.

Explanation 2: In our daily lives, it is usually easy to tell when we are moving due to the many clues our senses relay to us. In a car we feel the vibration of the car or the wind blowing into the window as we hear the noises these things create. But really that less about “feeling the motion” than it is how the car interacts with the road and the air. One kind of motion we can feel directly is when we hit the brakes, or suddenly swerve left or right. In those cases the car experiences a sudden change in its acceleration, and that change in the car’s motion pitches us forward or to the side. So really, it is changes in motion we most directly feel.

The Earth itself is certainly in motion as it orbits around the sun at a speed of about 67,000 miles per hour (107,000 kilometers per hour). But since it is in free-fall in its orbit around the sun, and not suddenly changing its acceleration or direction then we do not feel its motion any more than we would sitting in a quiet car with good suspension driving across a perfectly smooth road. Of course the Earth is under influence of the Sun’s gravity, and this smooth acceleration curves its motion into an elliptical path around the sun. But this places Earth in “free fall” since the Earth doesn’t have brakes or a steering wheel to make sudden changes in its motion. Thus we will not feel the motion of the Earth’s orbit.

Now, the Earth does have a second kind of motion, as it rotates on its axis every 24 hours. This means that at the equator the surface is moving at around 1,000 miles per hour (1,600 kilometers per hour). This speed drops to 0 at the poles, which just rotate slowly. This rotation does create a centrifugal force that is strongest at the equator that makes us feel just a little bit lighter than at the poles. This force is something we can experience if we step on a scale as it will slightly reduce our weight by a fraction of a percent at the equator compared to the weight we would measure at the poles. But again this effect will be constant since the Earth’s rotation is constant, so again there is nothing that we would immediately feel to suggest we are moving.

Other sources: we also found a couple of other explanations which may be helpful: https://physics.stackexchange.com/questions/268062/why-dont-we-feel-the-subtle-speed-change-of-earths-elliptical-orbit and https://astronomy.stackexchange.com/questions/32262/why-cant-we-feel-the-earths-revolution .