Geocentric Coordinate System Does not Imply Geocentrism

In astronomy, a celestial coordinate system is a system for specifying positions of celestial objects like satellites, planets, stars, etc. The origin of the coordinate can be anywhere, including Earth. If the coordinate system is Earth-centered, we call it a geocentric coordinate system.

Flat-Earthers are often triggered by the term ‘geocentric’. They would search inside astronomy books and scientific journals to find the word ‘geocentric’. If they can find it, they would use the fact as ‘evidence’ of geocentrism, or that the Earth is the center of the universe, and the Sun is revolving around the Earth.

They are wrong. In many cases, the term ‘geocentric’ refers to the origin of a coordinate system. And it has nothing to do with whether the Sun revolves around the Earth or the other way around.

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Geometry of a Full Moon

Some people are confused that a full moon is visible all night, and think 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 who have such spatial visualization problem take a step further and use it as ‘evidence’ that the Earth is not a sphere. They are wrong. The full moon phenomenon can easily be explained in the spherical Earth model.

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The Change of Constellations

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We can’t observe stars moving relative to each other, and the shape of constellations looks the same every night. The reason is not that stars are stationary, but their motions are very slow and cannot be observed over the timescale of human life.

Flat Earthers claim that the fact constellations don’t appear to change as proof the Earth is stationary. They are wrong. Stars have proper motion, but they can only be observed using precise instruments over a long time. Constellations do change, but the change is slow and cannot be perceived over the timescale of human life.

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Total Lunar Eclipse, Drawn to Scale

Any diagram showing two or more celestial bodies is almost never drawn in the correct scale. The reason is that in most cases, any two celestial bodies are spaced too far away relative to their sizes. It is just not possible to draw them in the correct scale and still effectively describes what we want to explain. We don’t have much choice other than drawing them not to scale.

The perpetrators of flat-Earth disseminate the allegations that the diagrams were drawn not to scale because of evil intentions, and not because of legitimate technical reasons. Some people don’t understand this and fell victim to flat-Earth indoctrination.

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

The orbit of the Earth and that of the Moon are not perfectly aligned in the same plane. The orbital plane of the Moon is inclined 5.145° from the Earth’s orbital plane. This is the reason an eclipse does not happen every month.

Sometimes we see flat-Earthers claim that an eclipse should happen every month. But it does not, and they take that as ‘evidence’ of the failure of modern science to explain the occurrence of an eclipse. Their mistake is that they don’t account for the orbital inclination.

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Total Solar Eclipse, Drawn to Scale

Any diagram showing two or more celestial bodies is almost never drawn in the correct scale. The reason is that in most cases, any two celestial bodies are spaced too far away relative to their sizes. It is just not possible to draw them in the correct scale and still effectively describes what we want to explain. We don’t have much choice other than drawing them not to scale.

The perpetrators of flat-Earth disseminate the allegations that the diagrams were drawn not to scale because of evil intentions, and not because of legitimate technical reasons. Some people don’t understand this and fell victim to flat-Earth indoctrination.

Continue reading “Total Solar Eclipse, Drawn to Scale”

The Galileo Affair was Never About the Shape of the Earth

Flat-Earthers often bring Galileo into the discussion. They treat him as a ‘villain’ who supported the spherical Earth but unable to prove it as he failed to demonstrate the occurrence of stellar parallax.

They are wrong. The Galileo affair was in fact not about the shape of the Earth at all. It was about geocentrism vs. heliocentrism. Everyone involved already knew that the Earth is spherical.

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Galilean Moons: The First Objects Observed to Orbit Another Object

Jupiter possesses four large moons: Io, Europa, Ganymede, and Callisto. These are called the Galilean Moons. They are easy to observe and the first objects found to orbit a planet other than the Earth.

Flat-Earthers are often seen demanding proof that an object can orbit another object. All they have to do is to use a telescope to observe Jupiter and its Galilean moons.

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The Distance to Polaris

Anyone who is in the northern hemisphere can observe the star Polaris, located very close to the north celestial pole. As a result, when observed casually, Polaris appears practically stationary in the same position.

Flat-Earthers claim that the fact Polaris appears stationary as ‘evidence’ that the Earth is stationary: if the Earth is in motion, then Polaris should appear in motion too. They are wrong. Polaris appears stationary because it is very far and its motion can’t be visually observed in the scale of a human life.

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