Apparent Motion of Planets

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Planets appear to move near the ecliptic —the line that marks the annual path of the Sun against background stars. From these motions, it is obvious that Venus and Mercury are in motion around the Sun. And the motion of the other planets can only be explained if Earth is in motion around the Sun.

Flat-Earthers claim that Earth is stationary. In reality, from observing the planets’ motion, the most plausible explanation is that all planets, including Earth, are in motion around the Sun.

ISS Size Compared to an Airplane in a Photograph

Flat-Earthers compared the apparent size of the ISS and an airplane that appeared in photographs and then incorrectly concluded that the ISS could not be 410 km above us. Their mistake was equating altitude with distance and failing to account for both the ISS’ and the airplane’s downrange distance.

If an airplane is at an altitude of 12 km, it does not mean its distance from an observer is also 12 km. Its altitude and distance are equal only if the airplane is directly above the observer. If the plane is not directly above, then its distance is greater than its altitude.

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Misconception and Strawman Arguments About Foucault’s Pendulum

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The Coriolis effect acts on objects moving closer to or away from Earth’s axis of rotation. A swinging pendulum does that continuously while staying in the same place. Foucault’s pendulum is built very large to swing for a very long time so that we can observe the slow precession of the pendulum caused by Earth’s rotation.

Earth’s rotation does not cause a pendulum at rest to begin swinging, and flat-Earthers use that as “proof” that Foucault’s pendulums are manipulated. In reality, nobody claims the swinging motion of Foucault’s pendulum is caused by Earth’s rotation. The fact that Earth’s rotation does not cause a pendulum to swing does not disprove Earth’s rotation or the Coriolis effect.

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Usage of Animation to Visualize Space Missions

Many space missions use animations to visualize the state of the missions because it is impossible to record a video of the event. Spacecrafts continuously send telemetry data to Earth informing the status of their mission, and from the data, an animation can be constructed to illustrate the spacecraft’s current situation.

Flat-Earthers accuse that the animations are “proof” that the missions are faked. In reality, the animations are faithful depictions of the missions and are made to visualize the real state of the mission. Animations are used because it is not viable to send another spacecraft only to record a video of the mission. Furthermore, in the cases where the video is available, it is still too difficult for these flat-Earthers to accept reality.

Location Crowdsourcing

In addition to satellite navigation, mobile phones can also use crowdsourced cell sites and WiFi access points location data. Phones help each other by creating a centralized database of the locations of cell sites and WiFi access points. If satellite navigation is unavailable, then the phones can utilize this database to determine their positions.

Some documentations explain how a phone or device without GPS can determine its location. Flat-Earthers incorrectly use these documentations to “prove” GPS does not use satellites. In reality, there are various methods of determining location, not just GPS. These documentations explain location service using cell & WiFi crowdsourcing, which is different from GPS.

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Appeal to Ancient Wisdom

The appeal to ancient wisdom is a fallacy where someone assumes that concepts and knowledge from ancient times are superior to modern ones. In reality, just because they are from ancient times, it does not mean they are better than modern ones. On the contrary, in practically all the cases, we know a lot more than our predecessors.

Flat-Earthers often show us that in the past, people from various cultures believed that Earth is flat. Using it as “evidence” of a flat Earth is the fallacy of appeal to ancient wisdom.

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Curvature App

Curvature App is a web application we can use to create a simulation of the horizon’s shape and the visibility of distant objects on a flat and spherical Earth. Curvature App is available at

When determining a distant object’s visibility, flat-Earthers often use wrong calculators that fail to account for all the important variables and give them incorrect results. Curvature App accounts for all of these variables, and not only it gives us the numbers, but also the simulated view.

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ISS Construction Video

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The International Space Station (ISS) was not constructed overnight. It is built gradually, and new components are still arriving after more than 20 years since it was first launched.

The ISS is one of humankind’s greatest achievements, but there is no video showing its construction from start to finish. Flat-Earthers use the fact to “disprove” the existence of the ISS. In reality, the ISS was constructed gradually in years. There is no such video the same way there is none for New York City, for example. It does not mean New York City does not exist. On the other hand, we can find plenty of videos showing the assembly of its specific modules on the Internet. Continue reading “ISS Construction Video”

Beyond Horizons: World Records of Farthest Pictures Taken on Earth

We can see an object farther over Earth’s curvature if we and the object are higher. Mountain peaks are the highest points on Earth. As a result, from a mountain peak, it is possible to observe another peak very far away, even over hundreds of kilometers. The website Beyond Horizons discusses these records of observation.

Flat-Earthers use some of the world records of the farthest peak to peak observation as “proof” of flat Earth. In reality, these observations are possible because the peaks are very high, and atmospheric refraction helps the observation. These observations agree with the expectation if Earth is a sphere.

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Singapore–New York and Melbourne–Santiago Flight Routes

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As of 2020, the Singapore–New York flight route is the world’s longest flight route, while the Melbourne–Santiago route is the most southernmost route. The real-world durations of these routes are only consistent if Earth is a sphere.

On the flat-Earth model, the Melbourne–Santiago flight route should be a longer flight than the Singapore–New York route. These routes’ real-world durations disprove the flat-Earth model.

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Statue of Liberty

The Statue of Liberty was once used as a lighthouse. Its light can be seen from 24 miles away. Like other lighthouses, it can produce the loom of the light due to scattering in the atmosphere, which allows its light to be seen from much farther away.

Flat-Earthers use the visibility of the Statue of Liberty from 60 miles away as “evidence” of flat Earth. In reality, the effect of the loom of the light is what might be visible under clear weather, but the structure itself is not. Today, the Statue of Liberty is no longer used as a lighthouse, and nothing of it can be seen from that far away. But the information still spreads in flat-Earth communities as a hoax.

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Camera “Maximum Range”

There is no such thing as the “maximum range” in the specification of any camera. Just because a camera cannot see something at a certain distance, it does not mean it must not be able to see another thing farther away.

Flat-Earthers claim that the Moon cannot be 384400 km away because a camera cannot see another thing much closer than that. In reality, an object’s distance is not the only thing that determines if a camera can see it, but the object’s size also matters.

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Earthrise in President Nixon’s Oval Office

Earthrise is a photograph of Earth taken from lunar orbit during the Apollo 8 mission, seven months before the first Moon landing by the Apollo 11 mission. President Nixon hung a copy of Earthrise on the wall next to his desk in the Oval Office.

The picture of Earthrise was prominently visible during news coverage of President Nixon’s call with Apollo 11 astronauts on the lunar surface. Flat-Earthers find it strange Nixon already had the photo hung on the wall when the mission was still ongoing. These people are unaware that there are already several Apollo missions before Apollo 11, and Apollo 11 was only the first to land on the Moon.

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James Cook’s Second Voyage

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The second voyage of James Cook was commissioned to search for the hypothetical continent Terra Australis in the Southern Pacific Ocean.  He explored the Pacific and Atlantic oceans in the process and proved there is no such continent unless it is over the South Pole itself, which we now call Antarctica.

Some sources stated that Cook traveled over 60000 miles in his second voyage. Flat-Earthers use the figure as Antarctica’s circumference and claim it as “evidence” that Antarctica is much more than a continent. In reality, James Cook explored the vast ocean and did much more than just circumnavigating Antarctica.

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Uniform Circular Motion

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The motion of a specific location on Earth due to Earth’s rotation is a uniform circular motion. We can separate it into a uniform linear motion and a centripetal acceleration toward Earth’s center. From the reference frame of an observer on Earth, the latter results in a constant centrifugal acceleration, which is felt simultaneously with Earth’s gravitational acceleration.

We often use the uniform linear motion of everyday objects to explain the effect (or the lack of thereof) of uniform motion of Earth’s rotation. Flat-Earthers incorrectly reject it just because “it is not a circular motion unlike Earth’s rotation” In reality, a uniform linear motion is one component of a uniform circular motion. And these explanations are correct and still apply.

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Nautical Almanac

A nautical almanac is a publication that describes the positions of stars to enable navigators to use celestial navigation to determine their position at sea. Because the positions of stars are not fixed, a nautical almanac needs to be continuously revised.

Flat-Earthers claim that the positions of stars are fixed, and they only circle the celestial pole. In reality, stars’ positions do change, and we can find the historical positions of various stars from old publications of a nautical almanac.

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Airplanes Do Correct for the Coriolis Effect

Airplanes do correct for the Coriolis effect. They constantly make adjustments to counter forces that try to push them away from the planned route, including the Coriolis force.

Flat-Earthers claim the Coriolis effect does not appear to affect airplanes, and they use it to “prove” that Earth is stationary. In reality, the Coriolis effect does affect airplanes, and we do have to correct for it. But the effect is tiny, and we can safely ignore it in flight planning.

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Sydney-Johannesburg Flight Route

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The existence of the non-stop Sydney-Johannesburg flight route is only possible if Earth is a sphere. We can find that out by comparing its duration to the same route but with a stop.

There are other Sydney-Johannesburg flight routes, but with a stop, like in Dubai. Flat-Earthers use the existence of these routes to “prove” a flat Earth. In reality, it does not mean the non-stop route does not exist & it is not difficult to verify that the non-stop route exists.

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Moving Vehicle Analogy: Inside vs Outside of the Vehicle

The moving vehicle analogy is often presented to explain how Earth’s rotation does not seem to affect an object’s motion. Similarly, a ball released inside a moving vehicle will not fall rearward because it retains its inertia.

Flat-Earthers offer the moving open-air vehicle as if it is the “correct ” analogy. In reality, with their analogy, the air moves relative to the vehicle, which exerts an additional force that does not exist in the fact being explained. Their analogy fails to represent the fact being explained.

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Bonneville Salt Flat and Earth’s Curvature

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Interstate 80 traverses the Bonneville Salt Flat, Utah, in a practically straight segment. From the hilly terrain to the west of the highway, we can observe the highway’s curve following Earth’s curvature using a long-zoom camera.

Flat-Earthers incorrectly claim that salt flats are perfectly flat and use them to “prove” a flat Earth. In reality, salt flats form a curve following Earth’s curvature, like the ocean’s surface.

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