The Saros Cycle and Saros Series

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The Saros is a period of 18 years, 11 days, and 8 hours between related eclipses. The eclipses with the same Saros cycle are classified into a Saros series which is numbered for identification.

Flat-Earthers claim the usage of the Babylonian term Saros “proves” that eclipses are predicted using ancient Babylonian technology. In reality, the Saros is now used to classify related eclipses. For example, the solar eclipse on August 21, 2017 is the 22nd member out of 77 in the Solar Saros 145.

The term Saros was first used in association with eclipse by Edmond Halley in 1691. The Babylonians never used the term Saros to describe eclipses. And the numbering system of the Saros series was created by G. van den Bergh in 1955.

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Stellarium

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 Cycle and Prediction of Eclipses

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.

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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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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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Scale in a Diagram of the Solar System

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.

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Lunar Phase and Lunar Eclipse

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.

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Orbital Inclination: The Reason an Eclipse Does Not Occur Every Month

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The plane of the Moon’s orbit around Earth does not coincide with the plane of Earth’s orbit around the Sun. The two orbital planes form an angle of 5.145°. This is the reason an eclipse does not occur every month.

Flat-Earthers claim an eclipse should occur every month, but it does not, and they use it to discredit the science. In reality, they are unaware of the inclinations of the orbits.

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Eastward Direction of the Path of a Solar Eclipse

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The path of a solar eclipse moves eastward because the Moon moves in its orbit faster than the motion of the observer due to Earth’s rotation. The path is influenced more by the Moon’s linear speed, not its angular speed.

The Moon rises from the east and moves westward. Flat-Earthers incorrectly claim if the Moon moves westward, then its shadow should also move westward. In reality, the Moon’s shadow moves across the Earth, not around it. The path is influenced more by the Moon’s linear speed, not angular speed, as in the case of the Moon’s motion across the sky.

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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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Umbra, Penumbra, and Antumbra in an Eclipse Diagram

Light generally travels in a straight line. We can use this property of light to determine the umbra, penumbra, and antumbra part of a shadow by drawing lines from the edges of the light source toward and past that of the occluding object.

Flat-Earthers regard the lines in an eclipse diagram as a violation of the fact that a light source emits light in every direction. In reality, the lines are there only to determine the boundaries of the shadow’s regions in an eclipse diagram.

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Sunlight Creates Umbral Shadow Smaller than the Object Casting the Shadow

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The sun is a huge light source. It is larger than anything on Earth. As a result, the umbral part of a shadow formed by sunlight will always be smaller than the object casting the shadow.

Flat-Earthers assert that a shadow cannot be smaller than the object casting the shadow. They would use that to “disprove” the scientific explanation about the occurrence of a solar eclipse. In reality, it is not difficult to demonstrate that the umbral part of a shadow can be smaller than the object casting the shadow, especially if the light source is the sun.

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Lunar Phase: Earth’s Shadow has Nothing to do with It

It can be surprising that many people believe that the lunar phase is caused by the Earth casting its shadow on the surface of the Moon. Flat-Earthers are no exception. But they take it one step further and use the misconception do “disprove” the fact that Earth is a sphere. They are wrong. The lunar phase is the shape of the sunlit part of the Moon seen from the observer.

On the other hand, the phenomenon where the Earth casting its shadow on the surface of the Moon is called the lunar eclipse. Moon phase occurs all the time and undergoes a monthly cycle, while a lunar eclipse happens only a couple times in a year.

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Sunrays are Practically Parallel, but not Perfectly Parallel

The Sun emits sunrays to every direction. But as the Sun is very far, the sun rays that reach us are practically parallel. To an observer on Earth, the rays of light coming from the Sun form a maximum angle of about 0.53°. They are practically parallel, but not perfectly parallel.

Flat-Earthers often question the fact we say sun rays are parallel, but in any diagram of an eclipse, they are drawn at an angle. They merely confuse practicality with perfection. Sunrays are practically parallel, but they are not perfectly parallel.

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The so-called “Experiment” Done by Flat-Earthers

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We often see flat-Earthers create a ‘miniaturized physical model’ of a real object and present them as ‘proof’ in support of flat-Earth and against spherical Earth. Their M.O. is to observe if the model remotely resembles the actual object in a particular way. If it does, then it is enough for them to conclude the model describe how the real object works.

Conversely, if a real object cannot be miniaturized and still have the same behavior as the original object, they would conclude that the behavior of the original object doesn’t exist.

They would wrongly call creating such models “doing an experiment”.

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Atmospheric Refraction

Light waves are not always moving in a straight line. When it passes through a medium of a different refractive index, the waves will deviate. The phenomenon is called refraction and described according to Snell’s Law.

Earth’s atmosphere has variation in air density that depends on the altitude. As the refractive index changes with the density of the medium, light waves passing through Earth’s atmosphere also experience refraction.

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Earthshine Proves the Moon Obscures the Sun During a Total Solar Eclipse

During a total solar eclipse, the Moon is right between the Earth and the Sun. Thus, the near side of the Moon does not receive any sunlight. But while it is dark, it still gets some light reflected by the surface of the Earth. This phenomenon is called Earthshine.

Some flat-Earthers argue that a solar eclipse is not caused by the blocking of the Sun by the Moon, but by another, mysterious celestial body. The reason is that eclipses are incompatible with their beliefs about the motion of the Sun and the Moon.

Earthshine proves that they are wrong.

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