# Speed of the Earth

## Did you know that Earth wobbles as well as speeds up and slows down?

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.

### How Fast Is the Earth Rotating on Its Axis?

The Earth rotates on its axis once each day. Because the circumference of the Earth at the equator is 24,901.55 miles, a spot on the equator rotates at approximately 1,037.5646 miles per hour (1,037.5646 times 24 equals 24,901.55), or 1,669.8 km/h.

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 1,037.5646.

Thus, at 45 degrees north, the cosine is .7071068, so multiply .7071068 times 1,037.5464, and the speed of the rotation is 733.65611 miles per hour (1,180.7 km/h).

For other latitudes the speed is:

• 10 degrees: 1,021.7837 mph (1,644.4 km/h)
• 20 degrees: 974.9747 mph (1,569.1 km/h)
• 30 degrees: 898.54154 mph (1,446.1 km/h)
• 40 degrees: 794.80665 mph (1,279.1 km/h)
• 50 degrees: 666.92197 mph (1,073.3 km/h)
• 60 degrees: 518.7732 mph (834.9 km/h)
• 70 degrees: 354.86177 mph (571.1 km/h)
• 80 degrees: 180.16804 mph (289.95 km/h)

### Cyclical Slowdown

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. Scientists predicted that due to being the last year in this five-year slowing cycle, 2018 would be a big year for earthquakes. Correlation is not causation, of course, but geologists are always looking for tools to try and predict when an earthquake is coming.

### Doing the Wobble

Earth's spin has a bit of a wobble to it, as the axis drifts at the poles. The spin has been drifting faster than normal since 2000, NASA has measured, moving 7 inches (17 cm) per year to the east. Scientists determined that it continued east instead of going back and forth because of the combined effects of the melting of Greenland and Antarctica and a loss of water in Eurasia; the axis drift appears to be especially sensitive to changes happening at 45 degrees north and south. That discovery led scientists to finally be able to answer the long-held question of why there was drift in the first place. Having dry or wet years in Eurasia has caused the wobble to the east or west.

### How Fast Does the Earth Travel While Orbiting the Sun?

In addition to the rotational speed of the Earth spinning on its axis, the planet is also speeding at about 66,660 miles per hour (107,278.87 km/h) in its revolution around the sun once every 365.2425 days.

### Historical Thought

It took until the 16th century before people understood that the sun was the center of our section of the universe and that Earth moved around it, instead of Earth being stationary and the center of our solar system.