South Star

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The pole star Polaris is used to locate the position of the north celestial pole because it is a bright star that is conveniently located very close to it. However, there is no corresponding bright South Star near the south celestial pole. To locate the south celestial pole, we need to observe stars around it.

There is no South Star as useful as Polaris in the north. Flat-Earthers use it to “disprove” the existence of the south celestial pole, which cannot possibly exist if Earth were flat. In reality, the south celestial pole can be easily shown and located. There is simply no bright star near it.

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Richard Garriott’s “Pocket of Gravity” Magic Trick

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Richard Garriott is a video-game developer and entrepreneur who is also an avid magician. In October 2008, he flew to the ISS onboard a Soyuz rocket as a private astronaut. During his time on the ISS, he performed several magic tricks.

One of his magic tricks involves a hammer that floats and a card that seems to fall as if it is pulled down by gravity. Flat-Earthers were unaware it was a mere magic trick and wrongly assume it demonstrates things are falling in the ISS, despite other objects in the scene that float.

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The Impossible Eclipse

A selenelion is a rare lunar eclipse where the Sun and the Moon are both visible at the same time. An even rarer form of selenelion occurs if it is a partial lunar eclipse, and the upper part of the Moon is eclipsed. Some call this an “impossible eclipse.”

Flat-Earthers claim that such an eclipse should not be possible to occur because the Earth’s shadow is in the wrong position. In reality, it is possible to happen because the observer is looking slightly downward due to the dip of the horizon and atmospheric refraction.

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Missions to the Moon, Post-Apollo

After the Apollo moon landings, we continue launching missions to the moon, but with uncrewed spacecraft. The Apollo program was not entirely a scientific mission. It also served as a political mission due to the Cold War. We can research a lot of things about the moon without risking human lives by sending them to the moon.

Flat-Earthers claim that there have not been any missions to the moon after the Apollo missions, and they conclude that the Apollo missions were fabricated. In reality, we continue sending spacecraft to the moon to this day.

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Angular Resolution

Angular resolution is the minimum separation between distinguishable features in an image. Objects smaller than the angular resolution are indiscernible in the picture. The theoretical maximum angular resolution is determined by the diameter of the aperture of the optical instrument.

Flat-Earthers like to demand images of the lunar landers taken with a telescope as proof that the Apollo Moon landings did occur. In reality, no optical telescope on Earth is large enough to resolve the landers.

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2001 Mars Odyssey Launch Video

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Flat-Earthers often challenge us to provide a video of a rocket launch that was taken from the rocket itself, without interruption from launch to reaching space, as if it would convince them to accept that it is real and the Earth is a sphere.

The launch video of the 2001 Mars Odyssey mission easily fulfills their demand. But whether they can manage to accept the reality that Earth is a sphere is entirely another matter.

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Flight Dynamics: the Assumption of Flat & Non-Rotating Earth for Simplification

In making mathematical models, physicists often remove real-world details that have little influence over the final results for simplifications. In flight-dynamics, it is often perfectly adequate to assume Earth is flat & non-rotating, even if the final aircraft will be flying over spherical & rotating Earth.

Flat-Earthers claimed to have exposed ‘a secret document’ from NASA, saying that Earth is flat & non-rotating. In reality, the document is simply a derivation of a flight dynamics problem, assuming flat and non-rotating Earth, which is a common assumption made to simplify flight models. It does not imply the Earth is flat and non-rotating.

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Selenelion: The Phenomenon Where Both the Sun and Moon Are Visible During a Total Lunar Eclipse

A selenelion occurs during a lunar eclipse when the sun and moon are observed above the horizon. Atmospheric refraction bends light rays and lifts the image of the sun, and the moon typically up to 0.6°, so both can appear above the horizon.

Flat-Earthers assert that a selenelion should not be possible if Earth is a sphere due to the fact during a lunar eclipse, the sun and moon are 180° apart. In reality, a selenelion is possible because Earth’s atmosphere refracts light.

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Oblate Spheroid Shape of the Earth

The Earth is an oblate spheroid. Its diameter is longer across the equator than between the poles. The difference is tiny, only about 0.3%. It is not possible to notice the oblateness from photographs taken from space without careful measurement.

Flat-Earthers claim that in photos taken from space, Earth appears as a perfect sphere, unlike what science tells us, and they use it to discredit science. In reality, it is possible to notice the oblate shape with careful measurement of the images.

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Simulation and Observation

To determine if an observation is consistent with the spherical Earth model, we can create simulations to understand the expected result, and then see if they match the actual observation.

Flat-Earthers like to reject the results of simulation as being unreal, not real-world observation. In reality, the simulations are presented not to dispute their observation, but to demonstrate that their observation is consistent with expectation if Earth is a sphere.

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Subjectivist or Relativist Fallacy

The subjectivist fallacy occurs when someone claims that something is true for some people but not for someone else, when, in fact, it is true for everyone, as demonstrated by empirical evidence.

The shape of Earth is not a matter of belief or preference, but an objective truth from observations that applies to everyone. It is impossible Earth is both spherical and flat at the same time, depending on what we prefer or believe.

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Video Glitches

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In digital video, a missing or corrupted signal may result in glitches in the video. It can be caused by things like signal interference, scratches on Bluray discs, bad weather with satellite TV, damaged cables, Internet link congestion, etc.

Flat-Earthers like to scrutinize videos taken from space. If they find the glitches, they will swiftly use them as “evidence” of manipulation. In reality, such glitches in the videos are not unusual. We can easily encounter them on other occasions.

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Observation of Chicago From Michigan

Chicago’s skyline is visible on clear weather across Lake Michigan from Michigan as long as the observer is on high ground, or if atmospheric refraction is strong enough. This observation is consistent with the expectations if Earth is a sphere.

Flat-Earthers claim that the visibility of Chicago from Michigan is not possible if Earth is a sphere. In reality, they failed to account for the height of the observer or atmospheric refraction and ignored the fact that only the upper parts of the buildings are visible.

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Helical Motion of Planets

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The Solar System is in motion around the Milky Way galaxy, while the planets in the Solar System are in orbiting motion around the sun. As a result, from an observer outside the Solar System, planets will appear to move in a helical motion. Someone created an animation of this helical motion; it went viral and had a lot of media attention.

Flat-Earthers noticed the animation and use it to reinforce their arguments. They claim if the animation is correct, then stars should appear moving & star trails should be impossible. In reality, the animation does not show us the vast distances to the stars.

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Camera Entrance Pupil Size and the Zoom Factor

The entrance pupil is the opening in front of a camera that allows light to enter. If it is partially obscured, light can still come through the unobscured part, and the camera can still see the object.

In one of those “experiments,” flat-Earthers placed an obstacle in front of a camera, very close to the lens, so that an object is partially visible. At the widest angle setting, the person appears partially visible. But it turned out that zooming in will fully reveal the person. Flat-Earthers claim it is how objects can vanish behind the horizon if Earth is flat and how they can reappear by zooming in. In reality, zooming enlarges the camera’s entrance pupil, letting the camera to see over the obstacle.

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Human Senses

Human senses have limitations and cannot detect beyond a certain threshold of external stimuli. However, we humans possess intelligence that enables us to create instruments and allow us to perceive beyond the limitations of our senses.

Flat-Earthers argue if our senses cannot perceive a thing, then it does not exist. In reality, the instruments we made enable us to detect many things that our senses cannot.

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Eötvös Effect: Direct Evidence Earth is a Rotating Sphere

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Eötvös effect is the change in perceived gravitational acceleration when moving eastward vs. westward. An object will weigh slightly more when moving westward than when it is stationary or moving eastward.

The slight difference in weight due to the Eötvös effect can be measured in an experiment on a flight. The Eötvös effect is direct evidence that the Earth is a rotating sphere.

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Visibility Range vs Angular Resolution

Visibility range is a measure of the distance at which an object can be clearly discerned. Angular resolution is the ability of an optical system to resolve detail in the object.

Unlike the claim from flat-Earthers, there is no such thing as the “maximum range” of a camera. A germ on our hand is well within the visibility range, yet a regular camera lacks sufficient angular resolution to see it. On the other hand, an airplane is much farther away, but it has a larger angular size and can be seen by the camera.

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Conditions in School vs Science & Professional World

In an exam in school, students are expected to solve problems with limited references and tools to assess their knowledge. On the other hand, in the science & professional world, there are no such limitations. We are free to use any resources available to us to solve the problems at hand.

Some flat-Earthers become annoyed every time we use some things like computer simulations and other tools to solve problems, especially when they help us prove spherical Earth. They would proclaim because they feel they can solve their own specific problem with pen and paper, they think they are more right than these “cheaters” with computers and other technology. In reality, the tools being used do not decide which one is more right. These flat-Earthers are merely unfamiliar with real-world cases beyond school.

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Apparent Motion

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Apparent motion is the appearance that celestial objects move due to the motion of Earth. If all the objects that appear in the sky are moving similarly, then it is far more likely that the movement is only apparent and caused by the motion of the observer.

Flat-Earthers claim that the motion of celestial objects “proves” that Earth is stationary, and the celestial objects are moving. By the same “reasoning,” we can conclude that the train we are in is stationary, it is just all the objects outside, as luck would have it, are moving in a very similar fashion.

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