Kim Carl, age 11, of Eugene, Oregon, for her question:
How many miles does the earth go around in a second?
The Spaceship Earth spins like a top and circles the sun while swirling around a great orbit through the Galaxy. What's more, our dizzy old spaceship performs these curly cues at different speeds and with slight variations. For example, it travels around the sun slightly faster in December than in July. And the ground at the equator spins faster than it does at Eugene, Oregon.
Our big round globe spins around its axis, a sort of line straight through the middle from pole to pole. This motion is called rotation and the average length of one rotation is 23 hours, 56 minutes and 4.098 seconds. During this period of time, which is a calendar day, the big ball spins completely around once, like a top. It rotates altogether as a solid unit and, because of its spherical shape, some parts must spin around faster than others.
The axis through the middle stays still while the rest of the earth spins around it. Hence the two poles at the two ends of the axis do not rotate. From these two points, the earth's surface bulges outward to the wide equator. The distance between the bulging equator and the poles is marked off in smaller and smaller circles of latitude. All these circles make one rotation in about 24 hours and the big ones must spin faster than the smaller ones.
If you stand on the equator, the ground beneath your feet spins around at about 1,050 miles per hour. Here the spinning speed is about 50$ yards per second. From the equator, the two hemispheres curve toward the poles, the spinning circles of latitude get smaller and their rotation speed decreases. Latitude 30 degrees runs across southern Texas. There the surface of the earth spins around at about 439 yards per second.
Let's travel farther north to Latitude 60 degrees, which runs along the southern shore of Alaska. There the surface rotation speed is reduced to about 255 yards per second. Farther north, the speed decreases and at Latitude 90 degrees, which is the North Pole, it dwindles to nothing.
As the earth rotates, it also revolves along its orbit around the sun. Its average orbital speed is 66,600 miles per hour which is 1,110 miles per minute or 18k miles per second. This speed is the same at the equator, at the poles, at Eugene, Oregon and everywhere else on earth.
While the Spaceship Earth spins on its axis and orbits the sun, it also travels with the Solar System on an enormous tour through the starry galaxy. The speed of this grand tour, is 43,000 miles per hour which is almost 12 miles per second. At this speed, it takes 200 million years to complete one enormous orbit through the Galaxy.