Observing Earth’s Curvature From a Flight

At the cruising altitude of a jet airliner, Earth’s curvature is too slight for us to notice casually. But with planning and careful observation, it is not impossible to see the curvature. Continue reading “Observing Earth’s Curvature From a Flight”

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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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” (walter.bislins.ch/FED) 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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Sky

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The sky appears practically identical to all observers on Earth, except that the Earth obstructs the view to a different part of the sky to a different observer on Earth, and daylight obscures the view to most objects in the sky.

The fact that the sky appears identical everywhere on Earth can only be adequately explained if all the astronomical objects are very far from us and that the Earth is a sphere.

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Air Density vs Object’s Weight

At a lower altitude, the air is denser, and objects weigh more. On the other hand, at a higher altitude, the air is less dense, and objects weigh less.

Flat-Earthers deny gravity and invented the “explanation” that an object falls only because it is denser than the air surrounding it. But if it were true, objects should weigh more at a higher altitude where the air is less dense. But they weigh less instead, disproving flat-Earthers’ density theory.

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Curved Airplane Window and Observation of Earth’s Curvature

With careful planning, we can easily observe Earth’s curvature from an airliner. To “explain” the observation, flat-Earthers invented the excuse that it is caused by the distortion from the shape of the airplane’s window.

In reality, all camera lenses are curved, too, yet most of these lenses produce normal, rectilinear images. The fact that the shape of the window is curved does not mean looking through the window will produce a curved horizon.

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Lamp Illuminating a Dark Wall Demonstration

Flat-Earthers often show us images of a lamp illuminating a dark wall to demonstrate —incorrectly— how night can happen on a flat Earth.

In the images, the areas farther from the lamp appear dark. Due to the inverse-square law, areas farther than the source of light receive less light. However, these areas still receive light nonetheless. From these dark areas, the lamp is still visible. This contrasts with what happens at night, that sunlight is nonexistent and the sun is not visible.

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Stars in the Southern Sky Prove Earth is a Rotating Sphere

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If we look toward the south at night in any location in the southern hemisphere, we will see the same set of stars. We will see the stars rotating around the south celestial pole, in the Octans constellation, near the star Sigma Octantis.

The flat-Earth model cannot explain the phenomenon. Looking at the so-called ‘flat-Earth map,’ we should see another set of stars on a different location in the southern hemisphere. The reason is that the flat-Earth model is a false representation of the Earth.

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Qibla Direction Proves Earth is a Sphere

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

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

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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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Flying a Drone Inside a Moving Vehicle

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If we fly a drone inside a vehicle that is moving in a constant speed and direction, the drone will hover normally because it preserves the motion it gets from the vehicle. It will not abruptly move toward the rear of the vehicle.

Flat-Earthers claim that it should not be possible for drones to hover if Earth is rotating. In reality, drones follow Newton’s first law of motion and will preserve their inertia. It is easy to demonstrate the phenomenon by flying a drone inside a moving vehicle. The fact that drones can hover still in mid-air is not evidence of stationary Earth.

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Earthshine and Moon Phase

Earthshine is a glow in the dark areas of the Moon because sunlight reflects off Earth’s surface to the Moon’s night side. Earthshine can be easily observed with long-exposure photography.

Some flat-Earthers claim that the Moon is transparent or that it is not a sphere. By observing the earthshine using a camera with the correct exposure, we can easily disprove such claims.

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Rock Balancing

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Rock balancing is an activity in which rocks are balanced on top of one another. It is possible to do it if Earth is rotating because the speed is constant and the rocks are affected by a constant net acceleration from gravity and Earth’s rotation.

Flat-Earthers use rock balancing as “evidence” that Earth is stationary. In reality, it is possible to balance objects on a moving platform, as long as it is moving in a straight line with a constant speed, and there is no force —like wind, affecting it.

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Planets vs Stars

Planets are not stars. On casual observation, both planets and stars appear as bright dots in the night sky. But with careful observation, we know planets are different from the stars.

Flat-Earthers insist that planets are just stars. In reality, we can easily observe many of the planets’ attributes that set them apart from the stars —using minimal efforts and equipment.

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Ursa Minor

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Ursa Minor is a constellation in the Northern Sky. It is traditionally important for navigation because of one of its member stars, Polaris, being the north star. Ursa Minor is always visible north of the 18°N and hidden south of 18°S. Polaris is located very close to the North Celestial Pole, and only visible north of the Equator. The visibility of Ursa Minor and Polaris is only consistent if Earth is a sphere.

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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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Cavendish Experiment

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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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Sunlight Creates Umbral Shadow Smaller than the Object Casting the Shadow

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The sun is a huge light source. It is larger than anything on Earth. As a result, the umbral part of a shadow formed by sunlight will always be smaller than the object casting the shadow.

Flat-Earthers assert that a shadow cannot be smaller than the object casting the shadow. They would use that to “disprove” the scientific explanation about the occurrence of a solar eclipse. In reality, it is not difficult to demonstrate that the umbral part of a shadow can be smaller than the object casting the shadow, especially if the light source is the sun.

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