Curvature of Water Surface

If Earth is a sphere, why is the surface of water always flat?

Due to Earth’s gravity, water seeks the lowest potential or as close as possible to the center of Earth. It forms a practically spherical surface centered on Earth’s center. The width of the surface in everyday cases is tiny compared to Earth’s radius. Thus, the water surface looks practically flat but not perfectly flat.

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Misconception about the Second Law of Thermodynamics

In an online lecture, an MIT professor explained the second law of thermodynamics. One of his examples is a container filled with gas next to another filled with a vacuum. If the wall is removed, the gas will rush to fill the newly available volume. However, it is only a simple model that does not attempt to explain everything about the system.

Flat-Earthers abuse the lecture to “prove” it is “impossible” for the atmosphere to exist next to a vacuum. It becomes a flat Earth talking point as if the lecture shows us that spherical Earth “violates” the second law of thermodynamics. In reality, the gas inside the container is also affected by gravity and will also have a pressure gradient, just like the gas outside. But it is not within the scope of the lecture.

And if we ask the lecturer if Earth is flat, he will surely say no.

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Where’s the Curvature?

A human eye can only visually perceive the curvature of the Earth if we are at a considerable altitude from the surface, which is still beyond the reach of most humans today. A commercial jet airliner is the highest position realistically attainable by most humans today. We can only perceive very slight curvature at such altitude and, even then, only in an ideal condition.

The basis of flat-Earthers’ belief is that the horizon appears flat. They would say if we cannot see the curvature, then there’s no curvature, and therefore, the Earth is flat. In reality, only a few people can travel high enough to see the curve.  The highest we can realistically go is by getting on a commercial jet airliner, which can only go about 11-15 km up, only a fraction of Earth’s radius.

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Qantas QF14 Flight: Buenos Aires – Darwin

In early October 2021, Qantas flew a one-off repatriation flight from Buenos Aires, Argentina, to Darwin, Australia. It was the southernmost long-haul flight closer to the South Pole than any other passenger flight.

If Earth were flat, the flight should fly over South America, Canada, Russia, Japan, and Indonesia. But it flew over Antarctica instead, because the Earth is a sphere, not flat.

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Weight and Air Density Experiment

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Using a precise digital kitchen scale and a smartphone with a pressure sensor, we can easily measure the change in weight and atmospheric pressure in different locations.

Flat-Earthers claim that an object falls down because it is denser than the air surrounding it. However, simple measurements show that things weigh less at a higher altitude where the air is less dense, contrary to the expectation if their claim is true.

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Why Fisheye Lenses Are Used

Cameras with a fisheye lens are used in the ISS, high-altitude balloons, rocket bodies, and other purposes. The reason is that fisheye lenses have several advantages over rectilinear lenses.

Flat-Earthers claim there is an evil intention behind the usage of fisheye lenses. In reality, the use of fisheye lenses is not unreasonable. If it is desired to have a rectilinear image output, then it is not hard to defish fisheye images to rectilinear ones..

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Images of Multiple Suns

Some flat-Earthers discovered images of multiple suns in the sky. They jumped to the conclusion that it proves whatever they want it to confirm. In reality, we can explain them without going for farfetched scenarios.

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Illuminated Fraction of a Full Moon

The orbit of the Moon is tilted 5.145° to Earth’s orbit around the Sun. As a result, a lunar eclipse does not occur every month, and a full moon is never 100% illuminated.

Flat-Earthers claim a full moon should not be possible due to the tilt of its orbit, incorrectly assuming a full moon means 100% illumination. In reality, a maximum full moon is at least 99.8% illuminated, and we cannot tell a 98% illuminated moon from a 100% illuminated one. We call it a full moon, even if it is never 100% illuminated.

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Cherry Picking Experts and Appeal to Authority

Out of millions of people with an advanced degree, we can find someone, somewhere, who believes a crackpot proposition, including flat-Earth. Citing these very few experts to “prove” the crackpot proposition and ignoring the much larger body of experts who disagree is the fallacy of cherry-picking and appeal to authority.

The scientific consensus is determined by the collective position of the community of scientists in a specific field of study, not just by a few individuals.

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ETOPS is a safety regulation that prohibits airliners from flying too far from the nearest diversion airport. A higher ETOPS rating allows the flight to fly farther from the closest airport but has more stringent requirements, demanding higher operational costs.

As of 2021, there is no flight route over Antarctica, and flat-Earthers use it to “prove” a flat Earth. In reality, a reason for that is the lack of diversion airports in Antarctica, requiring aircraft with a higher ETOPS rating. Due to costs & the lack of market, no airliner considers it commercially viable yet.

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Shadows in Photographs Taken on the Moon

Flat-Earthers and other conspiracy theorists incorrectly claim that the shadows in photos taken on the Moon in the Apollo missions are inconsistent. In reality, it is just due to their confirmation biases, and we can easily explain how the shadows were formed.

The perspective effect can cause parallel shadows to appear angled to each other and converge to a distant point. Conspiracy theorists incorrectly claim that non-parallel shadows can only be caused by a nearby light source.

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Sun Outage

A Sun outage is a disruption of geostationary satellite signal caused by interference of the sun when it falls directly behind a satellite with which a receiver is communicating. Sun outages occur around the March equinox and September equinox.

Flat-Earthers fail to understand how the schedule of a Sun outage depends on the satellite and the receiver’s location. And they use it to discredit the fact. In reality, it is not difficult to visualize how a Sun outage occurs, and it will be consistent with the expectation.

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Theodolite and the Dip of the Horizon

Because Earth is a sphere, the horizon always lies below eye level. We cannot see it near Earth’s surface with the naked eye. But with a precise instrument like a theodolite, we can observe the dip of the horizon.

Flat-Earthers claim that the horizon always rises to eye level. In reality, even from very close to Earth’s surface, it is still possible to observe that the horizon lies below eye level.

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Flat Earth Dome Model

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The “Flat Earth Dome Model” ( is an app created by a fellow flat Earth debunker, Walter Bislin. The app attempts to map observed reality to the flat Earth model. Lines in the app portray how light rays must have traveled if Earth were flat. They demonstrate that light must bend in a physically impossible way if Earth were flat, disproving a flat Earth.

Videos of the app are circulating in flat-Earth communities, and flat-Earthers fail to understand what the app is showing. They incorrectly assume the app “proves” a flat Earth when in reality, it thoroughly disproves the flat Earth model.

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Meaning of the Term “New World Order”

The term “New World Order” has two meanings. The original, benign meaning is a period of history evidencing a dramatic change in world political thought and balance of power. It refers to periods like after the First World War, the Second World War, and the fall of communism.

The second meaning is the one used by conspiracy theorists. In this case, “New World Order” means a secretive power elite with a globalist agenda conspiring to eventually rule the world through an authoritarian one-world government. This second meaning is just a conspiracy theory, which is not an actual fact but believed as true anyway by its adherents.

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Flying Over Antarctica: Airliner vs Private Flight

Commercial passenger airliners are similar to public transits. The operator determines the route, and passengers take them if they fulfill their needs. On the other hand, a private flight is similar to a taxi. The passenger determines the origin and destination of the flight.

There is currently no airliner providing a route over Antarctica, and flat-Earthers use it to “prove” that it is impossible to fly over Antarctica. In reality, the airliners simply decide not to provide such routes due to commercial or other reasons. Not because it is impossible to fly over Antarctica. We can take private flights if we really want to fly over to Antarctica, just like we take taxis to go to a location not serviced by public transit.

Determining the Authenticity of a Photo

It is impossible to positively prove the authenticity of a photo beyond any doubt unless we take the photos ourselves. Instead, we gather as much information as possible related to the photo, evaluate the information, then use inductive reasoning to determine if the photo is real. And the conclusion will always be a probability, not a certainty.

Flat-Earthers like to demand us to prove that a particular photo is real, and if we cannot, they will conclude the photo is fake. In reality, while we might be able to prove a photo is not real, at the very best, we can only say there is no reason to believe the photo is not real from all the available information. This applies to practically all photos and also plenty of other things in everyday life.

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Neutral Buoyancy Pool for Astronaut Training

A neutral buoyancy pool is a pool of water in which neutral buoyancy is used to train astronauts for the difficult task of working outside a spacecraft in a weightless environment. Some of these pools contain full-scale mock-ups of ISS modules and other spacecraft.

Flat-Earthers discovered videos of astronauts in a pool of water, and they jumped to the conclusion that it is how they faked videos of astronauts in space. In reality, these are videos of astronauts in a neutral buoyancy pool, in training for their upcoming mission to space.

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Sarcasm, Irony, Satire

Sarcasm, irony, and satire are figures of speech involving statements that are untrue in a literal sense. However, it is expected the audience should understand that the remarks are not true, and will consider them insulting or humorous.

The gullibility of conspiracy theorists is a popular subject of sarcasm, irony, and satire. But being so gullible means many of them are unaware that the remarks are not really true. Many of these people wrongly consider the sarcastic, ironic, and satirical messages as true, and the messages spread as hoaxes in their community.

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Light Scattering Demonstration Using Laser Pointers

Flat-Earthers cannot understand why space appears dark if the Sun is in space, and they use their ignorance to discredit science.

In reality, sunlight does travel through space. However, space is a vacuum, and there is nothing to scatter and redirect the light toward our eyes like in Earth’s atmosphere. We can demonstrate the phenomenon using a low-powered red and green laser pointer in clean air.

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