Jupiter has four moons (Io, Europa, Ganymede, & Callisto) that we can easily observe using a binocular or telescope. They are the first objects found to orbit another, proving it is possible for a satellite to orbit planets other than Earth.
Flat-Earthers like to demand evidence of an object orbiting another. All they have to do is use a telescope to observe Jupiter. Its moons have short orbital periods (1.8 to 16.7 days), & thus, it is not hard to observe the orbiting motion.
Continue reading “Galilean Moons: First Objects Observed to Orbit Another Object”
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.”
Continue reading “Dark Part of the Moon & Its Visibility During the Day”
Earth’s gravity pulls things toward Earth. Satellites can stay up there because they are orbiting. They are moving at the right speed and right direction to counter the pull of gravity.
Flat-Earthers claim that satellites should fall down if gravity pulls toward Earth. In reality, we do not just launch satellites to space. We also give them the correct speed & direction, so they neither fall toward Earth nor keep going farther away.
Continue reading “How Satellites Can Orbit and Stay Up There”
Image noise is a random variation of brightness or color information produced by a photo film or digital sensor. Image noise is an undesirable by-product of photography and does not come from the actual objects in the picture.
Image noise can be in the salt-and-pepper type, forming bright dots in the dark parts of the image. When appearing in the dark part of the Moon, flat-Earthers incorrectly claim they are stars, “proving” that the Moon is transparent. In reality, these are just image noise, not part of the actual objects.
Continue reading “Image Noise and The “Transparent Moon” Misinformation”
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.
Continue reading “Earthrise”
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.
Continue reading “Stellarium”
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”