While riding a carnival attraction, you can feel the pull outward caused by the circular motion. Our planet’s rotation is much faster, so why don’t we experience this force? There are two main reasons for this. First, Earth’s rotation is steady. Astronomer and content strategist Stephanie Deppe explains that if you were in a car traveling at a constant speed on the highway and tuned out the road noise, you would feel as though you were stationary. This is because constant speed creates a sense of motionlessness. In the words of Greg Gbur, a professor of physics and optical science, “we know there’s no such thing as absolute motion. The only thing that matters is relative motion.” He referenced Galileo’s thought experiment on a ship to emphasize that according to the laws of physics, being in motion is relative. Just like being in a moving car or ship, everything on Earth is also in motion with us. The planet’s atmosphere, for example, moves at the same speed as us and therefore feels stationary relative to us. Furthermore, the force of gravity holds us to the Earth much more strongly than the force that would pull us outward due to centripetal acceleration. Although Earth’s spin pulls everything outward, gravity keeps everything firmly grounded, overpowering the outward pull. The acceleration of gravity on the Earth’s surface is about 9.8 m/s^2, while the reduction of that due to the Earth’s rotation at the equator is about 0.03 m/s^2, which is detectable but significantly smaller compared to the force of gravity itself, so it goes unnoticed.
