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By Don Lincoln, Ph.D., University of Notre DameEarths rotation is realized in movements if they are large enough. (Image: 3d_and_photo/Shutterstock)

The Coriolis effect is realized in how Earths rotation affects the direction of objects flying long distances. An example can help us understand the Coriolis effect best. If there existed a bow and arrow big enough to shoot across the globe, one could stand around the equator and shoot it northward, aiming to hit the north pole. If the arrow was shot from Texas and traveled in a line of constant longitude, youd imagine that it would fly over Oklahoma, Nebraska, South Dakota, North Dakota, and on into Canada. However, in reality, this does not happen.

In reality, the arrow would probably fly over New York State and eventually land somewhere in the Atlantic Ocean. The arrow is deflected rightward to the east due to the earths Coriolis effect the force that does not obey falling and throwing rules in physics.

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In 1651, the Italian scientist Giovanni Battista Riccioli realized that the Earths rotation would make a cannonball shot northward deflect towards the east. However, the final name of the effect came from the French physicist Gaspard-Gustave de Coriolis. He published a paper in 1835 about the forces on the rotating parts of industrial machines, particularly water wheels. It took until 1920 for the modern name to become common, but it did. Now it is called the Coriolis effect.

This is a transcript from the video series Understanding the Misconceptions of Science. Watch it now, on The Great Courses Plus.

By using some simple physicsequations, the rotation speed of the Earth can be calculated. The circumferenceof the Earth at the equator is about 25,000 miles. Besides, the Earth rotatesonce every 24 hours to make a full rotation. Consequently, the Earth at theequator is moving at around 1042 miles per hour.

An object four feet away from theNorth Pole travels only a circle of around 24 feet in circumference. The speedin the middle of the northern hemisphere, i.e., around Minneapolis andMinnesota, is a little more than 700 miles per hour. The same speeds apply forthe southern hemisphere. Due to the rotation direction, everything moving fromthe equator to the poles moves eastward: rightward in the northern hemisphereand leftward in the southern one. The air is also something flowing around theEarth.

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Hurricanes are a result of theCoriolis effect. Thus, they rotate counterclockwise in the Northern Hemisphereand clockwise in the Southern Hemisphere. Regardless of the air pressure indifferent areas, air flows into the center and is deflected rightward. Withinthe hurricane, the rotating air also wants to deflect to the right. Hence, thehurricane finds a size limit due to air resistance to new incoming air.

There is a constant tensionbetween the pressure differential, making the air flow inward. The outwardpressure is also due to the Coriolis effect. The air pressure difference regulatesthe velocity of the winds. Further, the strength of the Coriolis force isproportional to wind speed, and this interplay sets a limit on the size of thehurricane. As the Coriolis effect is very weak at the equator, no hurricaneshappen there. What else realizes the effect?

Even though some people believethe water in the toilet rotates proportionate to the Coriolis effect, it is toosmall a movement to show it. The water does rotate different directions in thenorthern and southern hemispheres, but that is due to the different directionsof the jets. What can show the effect is the Foucault pendulum, invented in 1851by the French physicist Lon Foucault.

It is made of a very heavy weighthanging from a long cable, moving back and forth like other pendulums. Thedifference is that due to its size, the change in its oscillation direction canalso be seen.

Conclusively, the Earths rotationis the reason hurricanes happen, and it can deviate other flying objects fromtheir path as well.

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Earths rotation is the main reason for the Coriolis effect. The effect deflects anything that flies or flows over a long distance above the ground, proportionate to Earths spin direction. Even storms can be a result of the rotation; hence, they do not form similarly everywhere on Earth.

The Coriolis effect refers to how a moving object shifts direction rightward in the Northern hemisphere and leftward in the Southern hemisphere. This is the reason hurricane winds turn left in the Northern hemisphere. The effect can be seen in large-scale movements.

The Coriolis effect is the result of Earths counterclockwise spin around its axis. Thus, it is strongest at the Earths poles. The further one moves away from the poles; the lower becomes the Coriolis effect. The effect pushes flying or flowing objects eastward in both hemispheres, but the direction is different in each, depending on the objects destination location.

Even though the water in toilets spins different directions in the northern and southern hemispheres, it is not a result of the Coriolis effect. To see the effect, one needs a much bigger scale, such as hurricanes. The reason water rotates different directions in northern and southern hemispheres when flushing, is the different direction of the jets. The Coriolis effect does exist, but it is too small to see on such a small scale.

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The Coriolis Effect, Earth's Spin, and Its Consequences - The Great Courses Daily News