How fast of the earth spin

Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Discover World-Changing Science. Get smart. Sign up for our email newsletter. Sign Up. Support science journalism. Knowledge awaits. See Subscription Options Already a subscriber? The solar system, which includes our sun and all of the objects that orbit it, is also moving; it's located within the Milky Way, which orbits around the galaxy's center.

Scientists know that the Milky Way is orbiting a galactic center based on observations of other stars, said Katie Mack, a theoretical astrophysicist at North Carolina State University. If stars very far away seem to be moving, that's because the solar system is moving compared with the relative position of those far away stars.

To bring this concept back down to Earth, "If I start walking, I can tell that I'm moving because the buildings I pass by seem to be moving," from in front to behind me, Mack said. If she looks at something more distant, like a mountain on the horizon, it moves a little slower because it's farther away than the buildings, but it still moves relative to her position.

Then there's the entire Milky Way, which is pulled in different directions by other massive structures, such as other galaxies and galaxy clusters. Just like scientists can tell that the solar system is moving based on the relative movement of other stars, they can use the relative movement of other galaxies to determine how fast the Milky Way is moving through the universe.

Even though everything is moving all the time, living organisms on Earth's surface don't feel it for the same reason passengers on an airplane don't feel themselves zipping through the air at hundreds of miles an hour, Mack said. When the plane lifts off, passengers feel the plane's acceleration as it speeds down the runway and lifts off; that weighted feeling is caused by the plane's quickly changing speed.

But once the plane is flying at cruising altitude, passengers won't feel the speed of hundreds of miles per hour because the speed doesn't change. The passengers won't feel the speed because those passengers are actually moving at the same speed and direction, or velocity, as the airplane. Simply put, as Earth is spinning at a constant speed, so does everything on it. Travelling at the same speed means we cannot feel the spin. It is like driving a car.

Only when you change speeds do you notice you are travelling, like putting your foot on the accelerator or making an emergency stop. A change in speed has been happening here on Earth, but it is far too slow to notice. However, global warming may speed things up again.