## How fast does the earth spin?

Posted: November 2, 2009 in Astronomy, Science

If it is rotating, how come I don’t feel it?

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?

How fast is it, then?

To figure out the speed of the earth at the equator, we need to know the circumference of the earth at the equator. The circumference of the earth at the equator is 25, 040 miles (40,070 KM). The earth makes a full revolution once a day-about every 24 hours (an exact day is 23 hours 56 minutes 04. 09053 seconds). Once we know the circumference and time required for one revolution, we can simply divide 25040/24. The answer to how fast the earth spins is at the equator is 1,038 miles per hour (1674.66km/hr) or 465 meters/second.

The speed at which the earth spins varies upon your latitudinal location on the planet. If you’re standing at the north pole, the speed is almost zero but at the equator, where the circumference of the earth is greatest, the speed is about 1,038 miles per hour (1,670 kph). The mid-latitudes of the U.S. and Europe speed along at 700 to 900 mph (1125 to 1450 kph).

If the Earth were to stop spinning suddenly, the atmosphere would still be zipping along nicely at around 1,000 miles an hour. As a result, everything not attached to bedrock would pretty much be scoured clean.

How Come at that Speed I am not Spun off into Space?

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.