The Earth is always in motion. Although it seems like we are standing still on the Earth's surface, the Earth is spinning on its axis and orbiting the sun.
We can't feel it because it's a constant motion, just like being in an airplane. We are moving at the same rate as the plane, so we don't feel like we're moving at all. The Earth rotates on its axis once each day. Because the circumference of the Earth at the equator is 24, At the North Pole 90 degrees north and South Pole 90 degrees south , the speed is effectively zero because that spot rotates once in 24 hours, at a very, very slow speed.
To determine the speed at any other latitude, simply multiply the cosine of the degree latitude times the speed of 1, Thus, at 45 degrees north, the cosine is. For other latitudes the speed is:.
Everything is cyclical, even the speed of the rotation of the Earth, which geophysicists can measure precisely, in milliseconds. Earth's rotation tends to have a five-year span, where it slows down before speeding back up again, and the final year of the slowdown correlates with an uptick in earthquakes around the world. We can also specify the direction relative to the CBR. It is more fun, though, to look up into the night sky and find the constellation known as Leo the Lion. The earth is moving toward Leo at the dizzying speed of kilometers per second.
It is fortunate that we won't hit anything out there during any of our lifetimes! Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. After all, we don't feel like we're hurtling through space.
Yet we are. So how fast exactly is Earth moving around the sun? Some of the earliest astronomers in recorded history proposed that we live in a geocentric universe in which Earth lies at the center of everything.
According to them, the sun rotated around us, which caused sunrises and sunsets — same for the movements of the moon and the planets. But even then, there were certain things that didn't exactly line up with these theories. For example, sometimes, a planet would back up in the sky before resuming its forward motion. We know now that this back-and-forth — which is called retrograde motion — happens when Earth is "catching up" with another planet in its orbit.
For example, Mars orbits farther from the sun than Earth. So, at one point in the planets' respective orbits, Earth catches up to the Red Planet and passes it by. As we pass Mars by, it moves backward in the sky then forward again after we have passed.
Related: How Big is Earth? Another reason that humans started to realize that we might not be the center of the universe came from looking at parallax , or apparent change in the position of the stars with respect to each other.
For a simple example of parallax, hold up your index finger in front of your face at arm's length. Look at it with your left eye only, closing your right eye. Then close your right eye, and look at the finger with your left. The finger's apparent position changes. That's because your left and right eyes are looking at the finger with slightly different angles.
The same thing happens on Earth when we look at stars. It takes about days for us to orbit the sun. If we look at a star located relatively close to us in the summer and look at it again in the winter, its apparent position in the sky changes because we are at different points in our orbit. At the equator, its circumference is roughly 40, kilometres, so dividing this by the length of day means that, at the equator, Earth spins at about kilometres per hour.
As you move north or south, the circumference of Earth gets smaller, so the speed of spin reduces until it reaches its slowest at both poles. And all of this is nothing compared with the , kilometres per hour at which Earth orbits the sun. Simply put, as Earth is spinning at a constant speed, so does everything on it.
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