How Fast Does the Earth Rotate?
Written by Fraser Cain
The ground feels firm and solid beneath your feet. Of course, the Earth is rotating, turning once on its axis every 24 hours. Fortunately gravity keeps you firmly attached to the planet, and because of momentum, you don't feel the movement – the same way you don't feel the speed of a car going down the highway. But how fast does the Earth rotate?
You might be surprised to know that a spot on the surface of the Earth is moving at 1675 km/h or 465 meters/second. That's 1,040 miles/hour. Just think, for every second, you're moving almost half a kilometer through space, and you don't even feel it.
Want to do the calculation for yourself? The circumference of the Earth at the equator is 40,075 km. And the length of time the Earth takes to complete one full turn on its axis is 23.93 hours. So 40,075/23.93 = 1,675 km.
The speed of the Earth's rotation changes as you go North or South away from the equator. Finally, when you reach one of the Earth's poles, you're taking a whole day to just turn once in place – that's not very fast.
Because you're spinning around and around on the Earth, there's a force that wants to spin you off into space; like when you spin a weight on a string. But don't worry, that force isn't very strong, and it's totally overwhelmed by the force of gravity holding you down. The force that wants to throw you into space is only 0.3% the force of gravity. In other words, if the Earth wasn't spinning, you would weigh 0.3% more than you do right now.
Space agencies take advantage of the higher velocities at the Earth's equator to launch their rockets into space. By launching their rockets from the equator, they can use less fuel, or launch more payload with the same amount of fuel. As it launches, the rocket is already going 1,675 km/hour. That makes it easier to reach the 28,000 km/hour orbital velocity; or even faster to reach geosynchronous orbit.
We have written many articles about the Earth for Universe Today. Here's an article about why the Earth rotates.
Want more resources on the Earth? Here's a link to NASA's Human Spaceflight page, and here's NASA's Visible Earth.
We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.
Filed under: Astronomy
