Constant Image Brightness in Images of a Total Lunar Eclipse

The images showing the progress of a lunar eclipse were taken in increasing exposures to compensate for the decrease in brightness. The exposure increase from full moon to totality can reach 12EV or 4000× increase in light-gathering power.

Images showing the progress of a lunar eclipse appear in a constant brightness, and flat-Earthers —presumably never seen it in person— use it to “prove” a lunar eclipse is not caused by Earth’s shadow. In reality, the images were kept in a constant brightness by increasing the exposure of the camera.

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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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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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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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Zooming at the Moon

At the longest zoom, the Nikon P1000 has a field of view of 0.2°, which is equivalent to 1342 km at the Moon’s distance.

Flat-Earthers zoomed their Nikon P1000 at the Moon and claimed that they could not find flags and landers from the Apollo missions. In reality, the smallest objects on the lunar surface they can observe using their cameras are large city-sized objects.

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Sun Glare

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Sunlight is very intense. It can cause glare to appear around the sun, and as a result, the sun can appear larger than its actual size. To observe the sun’s actual size, we need to eliminate the glare by reducing the camera’s exposure or using a solar filter.

During sunset, sunlight gradually becomes less intense, and sun glare gradually becomes smaller. If the glare is not eliminated, the sun can appear as if it is shrinking, and flat-Earthers incorrectly use it as “evidence” that the sun is moving away from us.

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Objects Obscured by Earth’s Curvature and Zoom Factor

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From an observer on a shore, the distance to the horizon is 5 km (3 miles), or more if the observer is higher. Therefore, Earth’s curvature obscures objects starting from that distance. If the objects are not large enough, we need an optical aid, like zooming in using a camera, to see them in the first place.

Flat-Earthers often show us wide-angle photos to demonstrate that objects are not obscured by Earth’s curvature. In reality, in such photos, objects far enough to be obscured by Earth’s curvature cannot be resolved. It is hard to see objects obscured by Earth’s curvature if the objects themselves are not visible in the picture.

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Coin on a Table “Experiment”

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Flat-Earthers performed the coin on a table “experiment” to “explain” how a sunset can occur on a flat Earth. Instead, it tells us more about their confirmation bias.

This is probably one of the most ridiculous flat-Earth arguments. It is so obviously wrong that many of us are having trouble explaining it and cannot accept that a member of the human race can fall for it.

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Earth Seen From the Moon vs the Moon Seen From Earth

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Earth seen from the Moon will appear 3.7× larger than the Moon seen from Earth. However, if a photograph of Earth is compared to that of the Moon, the sizes of both objects also depend on the field of view of the cameras that were used to capture them.

Flat-Earthers discovered the size of the Earth in a photograph is not 3.7× the Moon in another picture. They used the fact as “evidence” of wrongdoing. In reality, the two photos were not taken with the same field of view, and cannot be compared directly.

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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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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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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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Observing Geostationary Satellites

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Geostationary satellites orbit the Earth with the same rate as Earth’s rotation, 35786 km (22236 miles) above the equator. They are too far and too dim for the naked eye. However, we can observe them using a mounted telescope and a camera.

We can observe many of them by:

  • using an equatorial mount,
  • aiming the telescope at a star that lies in the orbit’s path, and
  • use a camera with a long exposure setting.

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Telephoto Lenses and the Appearance of Earth’s Curvature

A telephoto lens is a type of lens in which the physical length is shorter than the focal length. A telephoto lens has a narrow field of view, and as a result, the curvature of the Earth is less pronounced if taken using a telephoto lens compared to another lens with a wider field of view.

Flat-Earthers like to bring up pictures taken from the ISS that show a practically flat horizon, and use them as evidence of inconsistency. In reality, the images were taken using a telephoto lens with a narrow field of view.

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Infinity Focus

To an optical device, like a camera, there is little difference between an airplane at 20000 ft and the Moon at 384400 km (238855 mi). The aperture of the lens is far too small compared to the distance of either object. Focusing on either object will make the other object in focus, too.

Flat-Earthers claim that because both objects appear in focus in a photograph, then the Moon must be close to the airplane. In reality, both can be considered at infinity. And it will be easy to make both objects to be in focus simultaneously.

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Magnifying Images Vertically to Reveal Earth’s Curvature

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The horizon appears flat because the curvature is too small when observed from near the Earth’s surface. However, in some cases, we can exaggerate the curve by taking photographs of the horizon and then magnifying the results vertically.

Magnifying in such a way will also magnify the distortions introduced by the camera lens. We will need to control these distortions using proper photography techniques, or by placing a known straight object as a control object in the frame, close to the horizon. If successful, then the remaining curvature in the photograph can only come from the curvature of the Earth.

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Fisheye Videos

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In images taken using a fisheye lens, a straight line will remain straight if it crosses the center of the image. We can use this attribute to determine if a line is straight in reality.

In any fisheye videos taken from a high altitude, there should be plenty of moments where the horizon crosses the center of the image, and we can use those to determine that the horizon line is curved in the real world.

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Zooming In On Distant Boats Does Not Disprove Earth’s Curvature

If a distant boat is not visible, then it is because of at least one of these reasons:

  • Our eyes have limited angular resolution and are unable to resolve the ship at that distance.
  • The atmospheric condition is limiting our visibility.
  • The curvature of the Earth obscures the ship.

Flat-Earthers like to demonstrate that a previously invisible ship at a distance can be made visible by zooming in. They would use it to disprove Earth’s curvature. They are wrong. There are reasons other than Earth’s curvature that can obscure a distant boat.

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Sunset with a Solar Filter

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The apparent size of the Sun is constant throughout the day, from sunrise to sunset, seen from anywhere on Earth. This fact disproves the flat Earth model and is only consistent with the spherical Earth model.

Flat-Earthers like to show us videos of the Sun that appears shrinking during a sunset. They merely failed to control the exposure. Using a solar filter or the in-camera exposure settings, the size of the Sun will appear constant during a sunset.

The apparent size of the Sun is constant throughout the day, seen from anywhere on Earth, from sunrise to sunset. This fact is only possible if the Sun is very far compared to the distance between any two observers on Earth.

Observation of Earth’s Curvature from Near the Surface

Observing Earth’s curvature is more difficult when we are too close to Earth’s surface. The highest place within reach of the general public is a commercial passenger flight. Even then, it is still difficult to casually discern the curvature of the Earth from an airplane. With some effort, it is possible to observe the curve of the Earth from a location closer to the surface, as long as we are willing to do some planning and careful observation.

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