Spinning Faster Than You Think
As most of us learned in grammar school, the earth spins or rotates on a modestly tipped axis once every 24 hours (every 23.93 hours to be exact). So how fast does that mean the earth, and you, are moving? Well, it depends on where you are.
Let’s start at the middle. The earth is a slightly oblong sphere divided into equal halves or hemispheres by the equator line. The circumference of the planet is at its widest at the equator – 24,902 miles. Dividing that distance by the time it takes for an object on the equator to make a complete turn, 23.93 hours, gives you an impressive rotation speed of 1,041 miles per hour. In fact, space agencies sometimes use that intrinsic speed to help with rocket launches. Think of the money saved on rocket fuel when you’re already moving at over 1,000 mph!
As you progress away from the equator and towards the poles, the circumference of the planet decreases, decreasing the rotational speed of a given point on the surface. To calculate earth’s spin at any location, multiply the speed at the equator, given above, by the cosine of that location’s latitude (the north/south position on earth relative to the equator). You can find the degree of latitude on globes and maps, by using GPS or via the web. The simplest way to get a cosine is to use the cosine button on a scientific calculator. More exacting latitude figures include minutes and seconds; these can be ignored or converted to decimal points for your calculation.
So why don’t we feel this movement? Because the spin rate of the earth is constant…mostly. It can fluctuate due to winds, currents and plate tectonics but only by miniscule amounts. The 2011 Japanese earthquake, for example, subtly shifted the mass of earth thereby increasing its rotation and shortening our day by 1.8 millionths of a second.
Rocket Ship Earth
Need more speed? Not only does our planet turn on its axis, but we’re also rotating around the sun at the approximate rate of 67,000 miles per hour. On top of that, our solar system is taking a whirlwind tour through the Milky Way galaxy while the entire galaxy is hurtling through space. Yes, it’s enough to make your head spin.