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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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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Refraction and Water

Refraction is the change in the direction of light due to the change in the medium’s refractive index traveled by the light. It is convenient to use water in a demonstration of refraction. But water alone is not the cause of refraction.

Flat-Earthers falsely claim that just because our atmosphere has water vapor in it, it will produce the same effect as any demonstration of refraction involving water. In reality, it requires far more reasoning than just that water is involved.

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Selenelion: The Phenomenon Where Both the Sun and Moon Are Visible During a Total Lunar Eclipse

A selenelion occurs during a lunar eclipse when the sun and moon are observed above the horizon. Atmospheric refraction bends light rays and lifts the image of the sun, and the moon typically up to 0.6°, so both can appear above the horizon.

Flat-Earthers assert that a selenelion should not be possible if Earth is a sphere due to the fact during a lunar eclipse, the sun and moon are 180° apart. In reality, a selenelion is possible because Earth’s atmosphere refracts light.

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Visibility Range vs Angular Resolution

Visibility range is a measure of the distance at which an object can be clearly discerned. Angular resolution is the ability of an optical system to resolve detail in the object.

Unlike the claim from flat-Earthers, there is no such thing as the “maximum range” of a camera. A germ on our hand is well within the visibility range, yet a regular camera lacks sufficient angular resolution to see it. On the other hand, an airplane is much farther away, but it has a larger angular size and can be seen by the camera.

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Inferior Mirage

An inferior mirage is a phenomenon in which atmospheric refraction bends light rays to produce a mirrored image below a real object. It occurs when a hot surface heats the layer of air above it, placing it below a colder & denser layer of air.

Flat-Earthers like to use inferior mirages to “explain” how a distant object can appear partly obstructed if the Earth is flat. In reality, an inferior mirage cannot produce an appearance similar to an object partially obscured by Earth’s curvature.

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Refraction: Only a Baseless Technobabble in Flat Earth Community

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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Earth’s Shadow and the Belt of Venus

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Earth’s shadow is the shadow that Earth casts into its atmosphere, toward the opposite point from the sun. Above Earth’s shadow is the Belt of Venus, a pink band from the scattering of sunlight through the atmosphere.

Earth’s shadow lies at the antisolar point —the point opposite the sun. It rises when the sun sets and sets when the sun rises. The phenomenon shows us that the sun really goes below the horizon and disproves the flat Earth model.

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Distance to the Horizon & the Black Swan Observation

The distance to the horizon depends on the height of the observer and atmospheric refraction. The variability in atmospheric refraction can make the horizon appear in front of a distant object sometimes, and behind it in other times.

Some flat-Earthers raised a case —dubbed the “black swan” case— in which the horizon appears to be behind a distant object which is farther than the distance to the horizon according to calculation, and they use the fact to “disprove” Earth’s curvature. In reality, they did not account for atmospheric refraction, and that the amount of refraction varies.

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The Appearance of Sunset and Atmospheric Refraction

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The appearance of sunset depends on atmospheric conditions. Thermal inversion can irregularly refract light coming from the sun and distort the image of the Sun seen from an observer.

Some flat-Earthers observed a specific appearance of sunset and presented the fact as if it “proves” a receding sun in the flat-Earth model. They are wrong. The appearances of the sunsets are the results of atmospheric refraction.

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Lighthouses and the Loom of the Light

Lighthouses are equipped with powerful lights. In a dark night, even if Earth’s curvature obscures the entire structure of the lighthouse, the phenomenon of the loom of the light allows their lights to be visible beyond the horizon; not unlike how the beam of a green laser is visible to our eyes.

Flat-Earthers like to point out the cases where the light from a lighthouse is visible even if the lighthouse should be completely obscured by Earth’s curvature. They would claim it as “proof” that the Earth is flat. They are wrong. The loom of the light lets us see the light even when the lighthouse itself is below the horizon.

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Flat-Earthers’ Laser Tests are Misleading

Flat-Earthers like to perform the experiment involving lasers to ‘disprove’ Earth’s curvature. If they observe a laser beam from the other side of a lake or an ocean, they would wrongly conclude Earth’s curve does not exist. It was merely a misunderstanding of how lasers work.

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Zooming-In on the Setting Sun

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Camera zoom works by enlarging the center portion of the image, or in other words, by making its field-of-view narrower. Zooming in on the setting sun will not reveal more of the sun, and will only enlarge the size of the sun in the resulting image.

Flat-Earthers are claiming that zooming in on a setting sun will reveal the entire sun, and somehow lift it out of the water. They are wrong. They simply used the incorrect exposure settings. In reality, zooming on the setting sun will never reveal the sun that is already obstructed by Earth’s curvature.

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Sun Dog

A sun dog is an atmospheric optical phenomenon that consists of a bright spot separated by 22° from the Sun to one or both sides of the Sun. It is caused by the refraction of sunlight by ice crystals in the atmosphere.

Flat-Earthers claim that a sun dog is caused by the reflection of sunlight by the mythical dome enclosing the flat Earth, that there are multiple suns, or other equally implausible reasons. They are wrong. A sun dog is simply an optical phenomenon that occurs in cold locations where ice crystals can accumulate in the atmosphere.

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Visual Albedo of the Moon and the Earth

Visual albedo is the measure of the reflection of solar radiation out of the total solar radiation received by an astronomical body, taking into account only the visible light. The visual albedo of the Earth is 0.37, and the Moon’s is 0.12.

The Moon appears darker if the Earth also appears in the same photograph. Flat Earthers use the fact to “prove” that the picture is fake. They are wrong. The Moon appears darker because it reflects less sunlight than the Earth.

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Solar Filter

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A solar filter is utilized to reduce the intensity of sunlight and enable a camera to capture the image of the sun with the correct exposure, even under bright daylight. Without a solar filter, sunlight can be too bright to be correctly exposed by a camera.

Some flat-Earthers made their observation of the sun using a camera without a solar filter. As a result, in some of their images, the sun appears much larger due to the fact the camera cannot distinguish the sun and the sun glare around it.

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Specular Reflection and Diffuse Reflection

An object is visible if it is either reflecting light or a light source itself. Furthermore, a reflecting object can have specular reflection (glossy finish, mirror-like), diffuse reflection (matte), or the combination of both.

Some flat-Earthers like to compare the appearance of the Moon to a glossy, metallic ball. Then, the difference in how the two objects look is taken as “proof” that the Moon is not reflecting light. They are wrong. A shiny metallic ball reflects almost all incoming light in mirror-like fashion, or that it has predominantly specular reflection. On the other hand, the Moon reflects incoming light to every direction, or that it has only the diffuse reflection.

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In photography, bokeh is the way a camera lens renders out-of-focus points of lights. The shape of bokeh depends on the camera lens more than the out-of-focus objects themselves.

Some flat-Earthers do not know how to take correctly focused pictures of distant planets and stars due to their lack of knowledge and the unsuitability of their camera for the purpose. All they are getting are bokeh, which does not tell us much about the intended objects.

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Rayleigh Scattering

Earth’s atmosphere glows in blue because of Rayleigh scattering. It scatters sunlight to every direction. Bluish colors are scattered more than reddish colors. This results in the bright blue color of the sky in the daytime.

There are many misconceptions in the flat Earth community that arise from the lack of understanding of Rayleigh scattering.

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Sun Glitter

Sun glitter is a bright, sparkling light formed when sunlight reflects from water waves. A rippled by a locally smooth surface such as water with waves will reflect the sun at different angles at each point on the surface of the waves. As a result, a viewer in the right position will see many small images of the sun, formed by portions of waves that are oriented correctly to reflect the sun’s light to the viewer.

Flat-Earthers take the long shape of the reflection of a sunset on an ocean surface as ‘proof’ that Earth is flat. They are wrong. Sun glitter is the result of rippling water. The difference in curvature between the flat and spherical Earth model is not that far to cause the difference in the shape of sun glitter.

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