Antipodal Flight: Shanghai–Buenos Aires

Shanghai, China and Buenos Aires, Argentina are a near antipodal pair. Both are located at the diametrically opposite points to each other on Earth’s surface. Therefore, we can fly from Buenos Aires in any direction and arrive in Shanghai after traveling a roughly similar distance, regardless of the course taken.

Any flight between an antipodal pair has a similar duration even though the different flights have different directions. This fact is only consistent with spherical Earth and cannot possibly be explained if Earth is flat.

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Geoid and Altitude Above Sea Level

The geoid is the shape that the ocean would take under the influence of the gravity and rotation of Earth alone. The geoid is smooth but irregular because Earth’s density and surface are uneven. ‘Height above sea level’ is measured relative to the geoid.

Some flat-Earthers claim that measuring height above sea level is not possible if the Earth is spherical. They are wrong. Height/altitude/elevation is usually measured relative to the geoid, which is approximately a sphere. The geoid is a more accurate model depicting the shape of the Earth, compared to the spherical & ellipsoid model.

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Leveling

Leveling is the process of determining the elevation of a point relative to another point. The curvature of the Earth and atmospheric refraction affect the result of leveling. There are techniques and formulas to correct the effect of Earth’s curvature and atmospheric refraction.

Flat-Earthers assume that construction works like roads, bridges, railways, etc. are built without accounting for Earth’s curvature. They are wrong. The leveling in such works are done in such a way it minimizes the errors due to Earth’s curvature and atmospheric refraction.

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Earth Globe

An Earth globe is a spherical model of Earth with similar purposes to maps, but unlike maps, do not distort the surface that they portray except to scale it down. The Greeks from the 3rd century BC knew Earth is a sphere, and the earliest globe appeared from that period.

Flat-Earthers take the appearance of a globe before NASA existed as a sign of misconduct, like Universal Studios logo from the 20s. They incorrectly claim that it should not be possible to know Earth is a sphere before the first spaceflight. In reality, we knew spherical Earth since 3rd century BC and globes were already commonplace far before the first spaceflight. In fact, the success of spaceflight depends on our understanding of the spherical shape of the Earth.

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The Ball and Water ‘Experiment’

Gravity is the attraction between objects with mass. The higher the mass, the greater is the gravitational attraction. Gravity is not the result of the shapes of the objects.

Flat-Earthers like to perform the ball-and-water ‘experiment.’ They spray water to a ball, then observe the water does not stick to the ball the same way the ocean water curves over the surface of the Earth. They would wrongly conclude that “gravity does not exist.” Gravity does not come from the spherical shape of objects, Continue reading “The Ball and Water ‘Experiment’”

Geocentrism: Incompatible with the Flat Earth Model

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Geocentrism is a superseded description of the universe with Earth at the center. Under geocentrism, celestial bodies all orbited Earth. Geocentrism was the accepted model of the Universe for approximately 18 centuries; before we knew that Earth orbits the Sun —or what we call as heliocentrism.

We often observe flat-Earthers using the arguments for geocentrism as if it supports the flat Earth model. They are wrong. Under geocentrism, the Earth is a sphere, located at the center of the universe. It is not remotely compatible with the flat Earth model, which is an even more archaic understanding of the Universe.

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Air Distance vs Surface Distance

The cruising altitude of a jet airliner is about 33000-42000 ft or 10000-12800 m. It is very tiny compared to the radius of the Earth of 6378 km. Therefore, the distance measured at the cruising altitude does not differ much compared to the surface distance.

Some flat-Earthers claim that if Earth is a sphere, the distance traveled by a jet airliner would have been multiple times the surface distance. They are wrong. The air distance at 33000 ft is only 0.16% farther compared to the surface distance.

Sunset on Mountains

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During a sunset, mountain peaks lose sunlight later than areas around them. From a viewer observing a mountain, a shadow can appear ascending from the base to the peak. And conversely, during a sunrise, mountain peaks get sunlight before the areas around them and a shadow can appear descending from the peak to the base.

This phenomenon occurs because the Earth is a sphere. As the altitude increases, the hours of daylight become longer. It makes the sun rise earlier and set later.

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The Direction of the Qibla Proves Earth is a Sphere

Muslims perform their prayers by facing the Qibla —or the direction to the Kaaba in Mecca, Saudi Arabia. The direction of the Qibla is traditionally determined from the direction to the Sun when the Sun is directly overhead the Kaaba. If during the time the Sun is visible, it will indicate the direction of the Qibla.

If the results of the observation are drawn on the so-called ‘flat-Earth map’, the Qibla will not consistently point to the Kaaba. Only the calculation using the spherical Earth model will give us consistent results that conform to centuries of observation, from various locations on Earth. The reason is that the Earth is a sphere.

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Level, Higher and Lower

A higher position is farther up, away from the center of the Earth, relative to sea level. Conversely, a lower position is closer toward Earth’s center, relative to sea level. Two positions are level if they are at the same height from sea level.

Some flat-Earthers are unable to understand this. To them, ‘level’ means straight. They are wrong. In Earth sciences, height is measured from a plane of reference, usually the sea level.

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Suez Canal

The Suez Canal is a waterway connecting the Mediterranean Sea to the Red Sea. The level of water on both seas is practically the same, and the Suez Canal contains no locks system.

Flat-Earthers are claiming that the Suez Canal was constructed without accounting for curvature. They said if the Earth were spherical, then the middle of the canal should have been 1666 ft deep. This is merely a misconception. The surface of the water is equipotential. It has roughly the same distance to the Earth’s center of gravity. It is not necessary to dig 1666 ft in the middle of the Suez Canal. The engineers only need to ensure the base of the canal is below sea level for sea water to flow.

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Salar de Uyuni and Other Salt Flats

Salt flats are flat expanses of ground covered with salt and other minerals. Salar de Uyuni in Bolivia is the world’s largest salt flat. Salt flats are visibly very flat, but like every other geology features, they all follow the curvature of the Earth.

Flat-Earthers take the flatness of Salar de Uyuni and other salt flats as ‘evidence’ of a flat Earth. They are wrong. While most salt flats appear flat, they still gradually curve and follow the curvature of the Earth.

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The False Dilemma of the Figure of the Earth

There are several models explaining the figure of the Earth. These models vary in the way they are used, in their complexity and in the accuracy with which they represent the size and shape of the Earth. These models are sphere, ellipsoid, and geoid.

Flat-Earthers often take the existence of these multiple models as evidence of disagreement among scientists, and that the shape of the Earth is still in contention. They are wrong. All these models are valid models, only with different complexity and accuracy.

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Seismic Waves: Mapping the Interior of the Earth

Seismic waves are waves of energy that travel through the Earth’s layers and are a result of earthquakes, volcanic eruptions, massive landslides and large human-made explosions. Some types of seismic waves travel through the interior of the Earth and are detected by seismic stations on the other side of the Earth. By analyzing the types of waves that are received by seismic stations, we can determine the interior of the Earth.

Flat-Earthers are often seen saying that it is impossible to determine the interior of the Earth as nobody has gone there. They are wrong. Using seismology, we can determine the interior of the Earth without going there physically.

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A Glass of Water

The surface of the water in a glass of water is practically flat. Some flat-Earthers claim this is ‘evidence’ that the surface of the water is flat, and it will always be flat no matter how wide the container. They are wrong.

If the Earth is a sphere with the radius of 6371 km (3960 miles), then the surface of the water in a 10 cm (4 in) wide glass will have a bulge of 0.00000002 cm as the result of gravity, excluding other effects like the surface tension.

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Grid Corrections — How the Spherical Figure of the Earth Affects Land Partitioning

Some countries decided to partition their territories into a rectangular or square grid. But the Earth is spherical, and it is not possible to divide a spherical surface into a perfect rectangular grid while maintaining the perfect angles, distances, and areas.

To solve this problem, land surveyors implemented grid corrections. Every certain distance, parts of the grid are shifted away from each other. Therefore, an equal area in each division is maintained as much as possible by giving up an entirely lined up grid.

If the Earth is flat, it is not necessary to have this compromise. It would be possible to divide the land into a perfect square grid system.

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“Earth is a Sphere” Semantic Games

The Earth is spherical, but not perfectly spherical. Its diameter is longer across the equator than between both poles. The shape is called ‘oblate spheroid’. The difference between both diameters is tiny, only about 0.33%. It is perfectly fine to say that the Earth is round or spherical.

Some flat-Earthers take this issue very seriously. They think if that’s the case, then we can’t say the Earth is spherical. They are wrong. If we can’t say the Earth is a sphere, then we can’t describe every other spherical object as spherical, because nothing is perfectly spherical.

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