Fact Check: Video Does NOT Prove Earth Is Flat -- Coriolis Effect DOES Affect Planes, Weather

Fact Check

  • by: Madison Dapcevich
Fact Check: Video Does NOT Prove Earth Is Flat -- Coriolis Effect DOES Affect Planes, Weather Well-Studied

Does the Coriolis effect fail to affect aircraft trajectory, which proves that the Earth is flat, as is implied in a video shared on social media? No, that's not true: A professor emeritus of physics and astronomy told Lead Stories that "the Coriolis effect is, of course, well known and thoroughly analyzed." Though airplanes experience Coriolis force, it is "pretty small and varies only slowly with the speed, latitude, and direction of the plane," he added. The phenomenon is described by the National Oceanic and Atmospheric Administration as a force that affects weather patterns, ocean currents and air travel. The Federal Aviation Administration includes the study of the Coriolis effect in some of its curricula.

A version of the claim appeared in a video on Facebook on May 10, 2024, with a caption that read:

Flat earth 👁️💯

Here is how the post appeared at the time of writing:

image (2).png

(Source: Facebook screenshot taken Mon May 13 07:45:00 UTC 2024)

The post above is a video showing two people sitting opposite one another while throwing a ball. Later, the clip shows what appears to be flight radar systems, but the post does not elaborate or explain what the video shows. Some flat Earth conspiracy theorists claim the Coriolis effect does not affect airplanes, which they offer as false proof that our planet is flat and stationary.

Lawrence Lerner (archived here), a professor emeritus of physics and astronomy at California State University, Long Beach, told Lead Stories in an email received on May 28, 2024, that "the Coriolis effect is, of course, well known and thoroughly analyzed." He added:

The fact is that airplanes do experience a Coriolis force, It is pretty small, and varies only slowly with the speed, latitude, and direction of the plane.

The National Oceanic and Atmospheric Administration (NOAA) (archived here), which works to understand and predict changes in climate, weather, oceans and coasts, describes the Coriolis effect (archived here) as a force that affects weather patterns, ocean currents and air travel. It "makes things (like planes or currents of air) traveling long distances around Earth appear to move at a curve as opposed to a straight line."

Because of the shape of the Earth, different parts of our planet move at different speeds. The equator, for example, is the widest part of our planet. Compared to the North or South Pole, objects along the equator require more time to travel the same distance.

Lerner described this phenomenon by using the example of a submarine just below the ocean's surface as it travels eastward along the equator. He wrote:

[The submarine] will not experience any Coriolis force. From the point of view of an observer situated at a fixed point in space. it is moving eastward with both its own speed with respect to the Earth, and the Earth's surface speed at the Equator. Now let it turn northward. As it moves northward, it is also getting closer and closer to the Earth's axis.

At this point, the rotational surface speed of the earth is less that it is at the Equator. So the submarine, which by the law of inertia still has that equatorial speed, is moving not only northward, but a bit eastward with respect to the ocean surface. That eastward motion can be attributed to a 'fictitious' force called the Coriolis force (after the French physicist who first studied it.) As you can see, this force comes into being by virtue of the shift of the observer's point of view from a fixed point outside the Earth to the surface of the rotating Earth.

NOAA elaborates:

Think about this: It takes the Earth 24 hours to rotate one time. If you are standing a foot to the right of the North or South Pole, that means it would take 24 hours to move in a circle that is about six feet in circumference. That's about 0.00005 miles per hour.


(Source: NOAA)

Hop on down to the equator, though, and things are different. It still takes the Earth the same 24 hours to make a rotation, but this time we are traveling the entire circumference of the planet, which is about 25,000 miles long. That means you are traveling almost 1040 miles per hour just by standing there.

So even though we are all on Earth, how far we are from the equator determines our forward speed. The farther we are from the equator, the slower we move.

Though limited, the Coriolis effect does impact aircraft, according to the education portal National Geographic Education (archived here):

The weather impacting fast-moving objects, such as airplanes and rockets, is influenced by the Coriolis effect. The directions of prevailing winds are largely determined by the Coriolis effect, and pilots must take that into account when charting flight paths over long distances.

The Federal Aviation Administration (FAA) includes (archived here) information about the Coriolis effect in some of its curricula, noting that the force "affects the paths of aircraft; missiles; flying birds; ocean currents; and, most importantly to the study of weather, air currents." The regulatory agency further notes (archived here):

Air flows from areas of high pressure into areas of low pressure because air always seeks out lower pressure. The combination of atmospheric pressure differences, Coriolis force, friction, and temperature differences of the air near the earth cause two kinds of atmospheric motion: convective currents (upward and downward motion) and wind (horizontal motion). Currents and winds are important as they affect takeoff, landing, and cruise flight operations. Most importantly, currents and winds or atmospheric circulation cause weather changes.

Aside from flight planning, studies indicate that the Coriolis effect can cause disorientation (archived here) in pilots and astronauts as a pilot turns the aircraft while also turning their head, notes author Thomas Brandt in the 2003 book "Vertigo: Its Multisensory Syndromes" (archived here). Coriolis forces can affect "not only whole-body movements, but also the vestibular system," according to the book "Fundamentals of Space Medicine" (archived here).

Other Lead Stories fact checks related to flat Earth conspiracies can be read here.

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  Madison Dapcevich

Raised on an island in southeast Alaska, Madison grew up a perpetually curious tidepooler and has used that love of science and innovation in her now full-time role as a science reporter for the fact-checking publication Lead Stories.

Read more about or contact Madison Dapcevich

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