Shadow of Flame

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A flame can produce a shadow if the other light source is much brighter, then refracted by the temperature difference, or the flame produces soot, steam, or other combustion products.

Flat-Earthers discovered images of flames not casting a shadow, & when they saw in a photo that a rocket’s exhaust casted a shadow, they used it as “evidence” it was faked. In reality, a flame can produce a shadow under the right conditions. Rockets have opaque combustion products, & in daylight, are lit by the very bright sun.

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Earthshine Shows the Moon Obscuring the Sun During a Total Solar Eclipse

During a total solar eclipse, the Moon’s side facing Earth does not receive sunlight but still receives light reflected from Earth’s surface. The phenomenon is called Earthshine and can be captured using a camera with a long exposure.

Flat-Earthers demand visual evidence of the Moon blocking the Sun during a solar eclipse. Earthshine provides this visual evidence & shows that the Moon is blocking the Sun.

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Point Source

A point source is a source or reflection of light with a smaller angular size than the angular resolution of the observer. It is visible as a bright dot if bright enough against a dark background but not resolvable, or no detail is discernible.

Flat-Earthers claim the ISS should not be visible like a distant plane is not visible. In reality, aircraft lights can be seen from 60 km in a dark sky but are not resolvable. We can see them because they are point sources on a dark background.

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Dark Part of the Moon & Its Visibility During the Day

Black is a color that results from the absence of light. A dark or black object emits practically no light. It does not emit “black light.”

Flat-Earthers claim the dark part of the moon should appear black during the day. In reality, they fail to understand that black is caused by the lack of light, not by the emission of “black light.”

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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 claim that zooming in on a setting sun will reveal the full sun and somehow lift it out of the water. In reality, they used incorrect exposure settings, making the sun still above the horizon appear already half-obscured by Earth’s curvature.

Zooming on the setting sun will never reveal the sun already obstructed by Earth’s curvature.

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Bokeh

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

Flat-Earthers fail to take properly-focused photos of stars and planets because of their lack of photography skills and because their cameras are not suitable for the purpose. They are just getting bokeh, which tells us more about their equipment (and lack of knowledge) than the actual intended objects.

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Refraction of Laser Beam

Lasers are distinguished from other light sources by their coherence, or that their frequency and waveform are identical, and the output being a narrow beam. But lasers are still a form of light and exhibit the same characteristics as other light sources.

Flat-Earthers assume lasers always travel in a straight line, not affected by the medium. They use this incorrect assumption in their “experiments” to “prove” a flat Earth. In reality, like other light sources, atmospheric refraction can bend laser beams.

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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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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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Reflection of the Sun on Rippling Water Surface

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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 oriented correctly to reflect the sun’s light to the viewer.

Flat-Earthers use the long shape of the sun’s reflection on a water surface to “prove” Earth is flat. In reality, the shape of the reflection is the result of the rippling water surface. It can easily occur on a curved surface and does not prove a specific shape of Earth.

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Visibility of Objects in Space Compared to Those on Earth’s Surface

Visibility is a measure of the distance at which an object can be clearly discerned. Visibility depends on the transparency of the air. There is no air in space to disrupt the transmission of light, and therefore, light can travel very far in space practically undisturbed.

The ISS can be seen clearer than objects on Earth’s surface far closer than the ISS. Flat-Earthers use the fact as “evidence” that the ISS is much closer. In reality, only a fraction of the light path from the ISS travels through the dense lower part of the atmosphere that will significantly affect the transmission of light.

On the other hand, light emitted by objects on Earth’s surface has to travel the entire path through Earth’s atmosphere.

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Visual Albedo of the Moon and the Earth

Visual albedo is the measure of the reflection of sunlight 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 dark if the Earth also appears in the same photograph. Flat Earthers use the fact to dismiss such photos as fake. In reality, the Moon’s brightness in a photo is just a matter of choosing the correct camera exposure. But if Earth is also present, increasing the exposure will make the Earth appear too bright.

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Blood Moon: Why The Moon Turns Red During a Total Lunar Eclipse

The Moon becomes red during a total lunar eclipse because Earth’s atmosphere acts like a lens and refracts sunlight toward the Moon. It also scatters bluish components of sunlight more strongly and lets more reddish components reach the Moon.

The Moon does not become totally dark during a total lunar eclipse, and flat-Earthers use it as “evidence” the Moon is not in Earth’s shadow during a lunar eclipse. In reality, it occurs due to optical phenomena involving Earth’s atmosphere.

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Experiments Involving Flashlights, Laser, & Reflected Sunlight Over Water Surface

Atmospheric refraction is stronger near the surface. Additionally, a thermal inversion can form a duct guiding light ray to follow the curvature of Earth. These phenomena allow light rays to reach the viewer far behind the horizon, but the rays will be compressed, distorted, and scattered, and will not form the true image of the objects. However, a nondescript, intense point light source will stand out against a darker background.

Flat-Earthers like to perform experiments involving lasers, flashlights, and mirrors over the water surface. If the light is visible from the other side, they would wrongly conclude Earth’s curvature does not exist. In reality, atmospheric refraction causes the result they observed.

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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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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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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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