# Scientists Say: Coriolis Effect

Earth’s rotation causes this deflection in airborne objects’ motion

#### Coriolis Effect (noun, “Kor-ee-OHL-iss Eh-FEKT”)

The Coriolis Effect causes airborne objects moving across Earth to travel along curved paths rather than straight lines. It mostly affects objects that are traveling long distances very quickly, such as air currents and airplanes. The paths of these objects through the air bend through due to Earth’s rotation.

As Earth spins, the ground near the planet’s equator moves faster than the ground near its poles. Why? Think of it like this. Every place on Earth must complete one full circle around the planet each day. Ground that is 1 meter (3.3 feet) from the North or South Poles must complete a circle just 6.3 meters (20.6 feet) around every 24 hours. Meanwhile, the ground near Earth’s equator has to whip around the planet’s whole circumference each day. That’s a distance of about 40,000 kilometers (25,000 miles) to be completed in 24 hours. So the ground near Earth’s equator is moving much, much faster than the ground near the poles. So are the objects on the ground — including us.

If an airplane takes off from the equator and heads to the North Pole, the plane has the same velocity — or speed in one direction — as the ground at the equator. As the plane flies north, it continues to have that velocity in the direction of Earth’s rotation. This causes the plane’s path through the sky to curve — even though the plane is flying straight.

This type of curvature is the Coriolis Effect. It was named after Gaspard Gustave de Coriolis. He’s the French mathematician who first described the effect in 1835.

The Coriolis Effect doesn’t just affect how airplanes fly. It also influences weather patterns. One cool consequence of the Coriolis Effect is the spinning of tropical storms, such as hurricanes. These storms suck air toward them. But, due to the Coriolis Effect, that air does not move straight toward the center of the storm. It curves around the storm, giving tropical cyclones their signature spirals.

#### In a sentence

The Coriolis Effect doesn’t just happen on Earth — it also affects winds on other planets, such as Jupiter.