The orbit of the Moon is tilted 5.145° to Earth’s orbit around the Sun. As a result, a lunar eclipse does not occur every month, and a full moon is never 100% illuminated.
Flat-Earthers claim a full moon should not be possible due to the tilt of its orbit, incorrectly assuming a full moon means 100% illumination. In reality, a maximum full moon is at least 99.8% illuminated, and we cannot tell a 98% illuminated moon from a 100% illuminated one. We call it a full moon, even if it is never 100% illuminated.
Continue reading “Illuminated Fraction of a Full Moon”
Earthrise is a photograph of Earth that was taken from lunar orbit by William Anders during the Apollo 8 mission. It was taken just after Earth rises from behind the Moon.
From Earth, the Moon always shows the same face, and from a location on the Moon facing Earth, it is impossible to see Earth rising. Flat-Earthers use it to reject the Earthrise as fake. In reality, the photo was not taken from the lunar surface, but from the lunar orbit. Apollo 8 did not even land on the Moon.
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The sunlit part of the moon is far brighter than the stars in the background. But cameras have dynamic range limitations. They cannot capture extremely bright and extremely dim objects at the same time. We can increase the exposure to reveal the stars, but then the moon will appear washed out, with no visible details.
Flat-Earthers use the lack of stars in photos taken from space to dismiss them as fake. In reality, the reason for the lack of stars is the same reason stars are also missing in photos of the Moon taken with the correct exposure.
Continue reading “Camera Exposure Settings to Capture the Moon and Stars”
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.
Continue reading “Visual Albedo of the Moon and the Earth”
A full moon can only occur if the Sun is directly opposite the Moon in the sky, and it will never appear near the Sun. There are photos on the Internet showing a full moon next to the Sun. These photos are fakes, and the phenomenon cannot possibly occur in the real world.
Flat-Earthers discovered images on the Internet showing a full moon next to the Sun, and they use it as “evidence” that moonlight is not reflected sunlight. In reality, these people are not aware that these photos are obvious fakes.
Continue reading “Images of Full Moon During Sunset”
Some people are confused that we can see a full moon all night. They expect if the full moon is the result of the opposition of the moon from the sun, then a full moon should be visible only at midnight.
Flat-Earthers with such a spatial cognition problem go a step further and use it to “disprove” spherical Earth. In reality, we can easily explain the phenomenon in the spherical Earth model.
Continue reading “Geometry of a Full Moon”
Flat-Earthers like to mention an astronomical event or a specific celestial geometry and insist it cannot possibly occur if Earth is a rotating sphere orbiting the sun. They would incorrectly proclaim it as “evidence” of a flat, stationary Earth.
We can ask them the time of the event and the observer’s location, then use Stellarium or a similar app to simulate the event. If it produces the same result as the actual observation, then they have nothing to complain about. And the problem was just caused by their failure to understand and to create the correct model.
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Saros is a period of 6585⅓ days separating the occurrence of two eclipses. One Saros after an eclipse, a similar eclipse will occur. The eclipses that belong to the same cycle are grouped in a Saros Series.
Flat-Earthers claim that we can only predict eclipses using the Saros Cycle. In reality, it is impossible to determine many characteristics of an eclipse from its Saros Cycle alone.
Continue reading “Saros Cycle and Prediction of Eclipses”
Diagrams of the Sun, Earth, and the Moon or any other celestial bodies are rarely made to scale because of their extreme smallness relative to the vast distances between them.
Flat-Earthers assume that the diagrams are not made to scale as a form of deception. In reality, it is just impossible to draw a diagram of celestial bodies with the real scale on physical media and still convey what we want to describe.
Continue reading “Scale in a Diagram of the Solar System”
The lunar phase is the shape of the Moon’s directly sunlit portion as viewed from Earth. The lunar phases change continuously, with a cycle over a period of 29½ days.
A lunar eclipse occurs when the Moon moves into Earth’s shadow. It is a rarer event that occurs only during a full moon and when the Sun, Earth, and Moon are very closely aligned.
Flat-Earthers claim it is impossible that the gibbous phase of the Moon is caused by Earth’s shadow, and they use it to discredit science. In reality, nobody claims Earth’s shadow causes it. They confuse the lunar phase with a lunar eclipse.
Continue reading “Lunar Phase and Lunar Eclipse”
The Moon orbits the Earth —not the Sun— because the Moon lies well within Earth’s Hill sphere. Hill sphere is the region around Earth where Earth —instead of the Sun— dominates the attraction of satellites.
Flat-Earthers noticed the Sun exerts a stronger pull to the Moon than Earth does to the Moon. They incorrectly concluded that according to science, the Moon should orbit the Sun, then proceeded to use it to discredit science. In reality, they did not account for the centrifugal acceleration resulting from the motion around the Sun, which is one of the factors that determines Earth’s Hill sphere.
Continue reading “Hill Sphere”
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.
Continue reading “Earthshine and Moon Phase”
The Sun and the Moon appear about the same size in the sky, but they are not perfectly the same size, and their sizes are not constant because their orbits are not perfectly circular.
Flat-Earthers claim it is too much of a coincidence that the Sun is perfectly 400× larger than the Moon and perfectly 400× farther, making them appear perfectly the same size. In reality, the Sun and the Moon are not perfectly the same size in the sky.
Continue reading “Apparent Size of the Sun & 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.
Continue reading “Zooming at the Moon”
Flat-Earthers claim that moonlight is cold and cools down objects exposed to it. It is merely a myth from the 19th-century flat-Earthers, reinforced by confirmation bias in various so-called “experiments” performed by today’s flat-Earthers.
Flat-Earthers experimented and insisted that moonlight has a cooling effect because they failed to control other factors affecting the experiment and maybe even deliberately introduced them to influence the results. They also did not account for measurement errors —the variation between several measurements— and cherry-picked the results that fit their desired outcome while ignoring the rest.
Continue reading “Moonlight and the Cooling Effect Myth”
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.
Continue reading “Earth Seen From the Moon vs the Moon Seen From Earth”
A selenelion is a rare lunar eclipse where the Sun and the Moon are both visible at the same time. An even rarer form of selenelion occurs if it is a partial lunar eclipse, and the upper part of the Moon is eclipsed. Some call this an “impossible eclipse.”
Flat-Earthers claim that such an eclipse should not be possible to occur because the Earth’s shadow is in the wrong position. In reality, it is possible to happen because the observer is looking slightly downward due to the dip of the horizon and atmospheric refraction.
Continue reading “The Impossible Eclipse”
After the Apollo moon landings, we continue launching missions to the moon, but with uncrewed spacecraft. The Apollo program was not entirely a scientific mission. It also served as a political mission due to the Cold War. We can research a lot of things about the moon without risking human lives by sending them to the moon.
Flat-Earthers claim that there have not been any missions to the moon after the Apollo missions, and they conclude that the Apollo missions were fabricated. In reality, we continue sending spacecraft to the moon to this day.
Continue reading “Missions to the Moon, Post-Apollo”
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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The Sweden Solar System is the largest scale model of the Solar System in the world. We can use it to get a better sense of the sizes and distances in the Solar System.
Flat-Earthers like to claim that we never see a scale model of the Solar System, and use it to “prove” the failure of science to explain the world. The Sweden Solar System proves them wrong, and also gives us an idea about the problem of making a scale model of the Solar System.
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