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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A fictitious force is a force that appears to act on every object when the frame of reference is accelerating. The term “fictitious” does not mean the force does not exist, but it is not an actual force that arises from an interaction between objects.
Flat-Earthers noticed gravity is considered a fictitious force and use the fact to “prove” gravity does not exist. In reality, we can feel a fictitious force. It is merely a term we use for forces that arise due to an accelerating frame of reference.
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The Cavendish experiment was the first experiment to measure the force of gravity between masses in the laboratory and the first to yield accurate values for the gravitational constant.
Flat-Earthers are in a constant effort to discredit the Cavendish experiment. They would invent various “explanations” to “explain” the result of the experiments. However, the experiment was not only done once by Henry Cavendish in 1797-1798, and has been replicated numerous times by multiple independent parties for centuries, all yielding consistent results.
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Many sports involve launching balls into the air. Launched balls are projectiles and will be deflected by a tiny amount due to the Coriolis effect from Earth’s rotation.
Athletes never account for the Coriolis effect, and flat-Earthers use it to “disprove” Earth’s rotation. In reality, the deflection from the Coriolis effect in sports is very tiny. It does not mean the Coriolis effect does not exist.
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Teaching aids are used by teachers to help students learn a subject more easily. A scale model of an eclipse is a teaching aid. It is not presented as evidence about how an eclipse can occur, but to help students to understand the mechanism of an eclipse.
Flat-Earthers often incorrectly consider a teaching aid is presented as if it is evidence of a phenomenon, then demand a similar thing as “evidence” of another phenomenon. In reality, a natural phenomenon is studied from the observation of the phenomenon itself. A teaching aid is there merely to help students learn.
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Flat-Earthers use the phenomenon of refraction as a catch-all “explanation” every time they observe something not appearing in the expected position if the Earth is flat. They use the term “refraction” as mere technobabble without any underlying explanation.
The following are how we can distinguish real-world, scientific refraction from the technobabble used by flat-Earthers:
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Atmospheric pressure decreases as altitude increases. There is no visible boundary between Earth’s atmosphere and space in terms of pressure. There is no abrupt drop in pressure where space begins.
Flat-Earthers assert that it is impossible for the pressurized atmosphere to meet the vacuum of space without any barrier. In reality, the pressure changes gradually. There is no sudden pressure drop between the atmosphere and space.
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Switching is used to establish a telecommunication network between two non-adjacent communication nodes. The information is relayed by one or more intermediate nodes that might use very different means of data transmission.
In 1969, President Richard Nixon called the Apollo 11 astronauts from the White House using a landline phone. Flat-Earthers regard the fact as ridiculous. According to them, if we cannot reliably make a phone call to the next room, then it must have been impossible for President Nixon to make a phone call to a location 384000 km away using a corded phone. Such allegation only stems from their lack of understanding of telecommunication.
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Many natural phenomena cannot be explained if Earth were flat, including the observation that the bottom part of a distant object appears clipped. To “explain” it as if it can occur on a flat Earth, flat-Earthers invented the “explanation” that it is due to what they call “perspective.”
This supposed “perspective” that flat Earthers invented is different from the actual law of perspective. To distinguish it from the actual, real-world law of perspective, many people call it “flerspective,” a combination of the words flerf and perspective.
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The electromagnetic force is a type of physical interaction that occurs between electrically charged particles. Electromagnetism is different from gravity. Both phenomena are real but have different characteristics.
Flat-Earthers refuse to accept gravity, and some of them use electromagnetism in place of gravity to explain the various phenomena that are explained by gravity. In reality, electromagnetism has different characteristic from gravity, and cannot explain the various phenomena that are explained by gravity.
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The word ‘theory’ has several meanings and can be confusing. Its meaning in the scientific context can differ from that in the context of everyday communication.
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The Coriolis force is a force that acts on objects that are in motion within a rotating frame of reference. Because the Earth is a rotating sphere, an object traveling unattached to Earth’s surface is affected by the Coriolis force, depending on its speed and direction, as well as its latitude on Earth’s surface.
The rotating motion of the Earth causes the different parts of Earth’s surface to have different linear speeds, depending on its distance from the Earth’s rotational axis. An object moving from a location to another with a different linear speed will be affected by the Coriolis force because the motion of the object is now being observed from another location with a different linear speed/direction relative to Earth’s rotational axis.
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Polar areas have a lower temperature than areas closer to the equator because the same amount of solar radiation is dispersed over a larger area, and the surface of ice and snow reflects more sunlight than darker surfaces.
In the spherical Earth model, the distance to the Sun from the poles and the equator is practically the same because the sun is much farther than the distance between any two locations on Earth. Because of that reason, flat-Earthers then claim that the temperature in polar and equatorial areas should be the same. In reality, the distance to the sun is not the only factor that can determine temperature.
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Some people are confused that the crescent moon can be visible at night, even though during the time, the Moon is closer to the Sun than Earth, and the part of the Earth is facing away from the Sun.
Many flat-Earthers have the same visualization difficulties, but they take it a step further and use it as ‘evidence’ as a ‘failure’ of science to explain the fact. In reality, the phenomenon can be readily explained in the spherical Earth model.
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We cannot feel the Earth rotating, and to explain the phenomenon, we usually use the moving vehicle analogy. If the vehicle is moving at a constant speed, we will not be able to sense the motion. We cannot feel the motion of Earth because of the same reason.
Flat-Earthers invented the excuse that we are standing on Earth, not inside it, to falsely reject the explanation.
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A vacuum implosion can occur if a sealed enclosure has less pressure inside it than outside it, and the structure is not designed to withstand the pressure difference.
Flat-Earthers use vacuum implosions to ‘disprove’ space travel in the vacuum of space. In reality, 1. it is possible to engineer structures that can withstand such a pressure difference; and 2. in space, the inside is pressurized while the outside is a vacuum, which simplifies the engineering considerably.
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An egg will generally sink in freshwater, but if we pour salt into the water and stir it, then the egg will start to float. The reason is that after salt is added, the density of water increases. However, the relationship between density and if the egg floats or sinks is not a direct causality.
Flat-Earthers claim that the phenomenon “proves” things fall because of density, and that gravity does not exist. In reality, the density of the water determines the magnitude of buoyancy the egg receives. If the buoyancy is higher than the weight of the egg, the egg will float, and vice versa.
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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 aircraft is flying over spherical & rotating Earth.
Some flat-Earthers claimed to have exposed ‘a secret document’ from NASA saying that Earth is flat & non-rotating. They are wrong. 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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Light travels in a practically straight line over a short distance. We often use this property of light to determine if an object is flat or straight from visual observation.
Some flat-Earthers start with the wrong assumption that a specific object is flat, then attempt to redefine how our vision works from that. They are wrong. From visual observation, we can determine if an object is flat, not the other way around.
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‘Flat’ and ‘Level can mean approximately the same thing in everyday conversation. But in the context of science and engineering, they have different meanings. ‘Flat’ describes a planar surface. ‘Level’ means at the same height or perpendicular to the direction of Earth’s gravity.
Flat-Earthers interpret the word ‘level’ as if it always has the same meaning as ‘flat.’ However, in the scientific context, the two words have different meanings. Insisting that both words to have the same meaning is the fallacy of appeal to definition.
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