Proper Motion

Proper motion is the apparent motion of stars, caused by the movement of the stars themselves, relative to the solar system. Stars will appear to shift over time, relative to other, more distant stars.

Flat-Earthers assume stars are only in motion around Polaris, or the north celestial pole. They are wrong. Stars have other apparent motions, one of which is proper motion.

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How the Sun ‘Burns’ Without Air in Space

A candle gets its flame from combustion, a chemical reaction. The hydrocarbon that formed the candle reacts with oxygen, and we get carbon dioxide, water, and heat energy as the results. The oxygen is obtained from the air. If the air supply is cut off —for example by covering the candle with a glass— then the reaction will stop, and the flame goes out.

We hear flat-Earthers often claimed that it is impossible for the Sun to be in space. They said the Sun burns, and therefore it requires oxygen. Space is empty, so it is impossible for the Sun to be there. They are wrong. The reaction that is occurring in the Sun is not combustion. It works differently from what happens with the candle.

Nuclear fusion powers the Sun.  It fuses hydrogen atoms into helium atoms. All the necessary component for the reaction to happen is in the Sun, and the reaction doesn’t require matters from external sources.

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The Eratosthenes Experiment: Proving the Earth is Spherical

In 205 BC, Eratosthenes successfully determined the circumference of the Earth by measuring the length of the shadow cast by a rod. He did the measurement in Alexandria and timed it to coincidence when the Sun is directly overhead Syene.

2222 years after that, some flat-Earthers tried to refute the Eratosthenes experiment. They say the experiment can be applied to the flat-Earth model.

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Stellar Parallax

Stellar parallax is the apparent shift of the position of any nearby star against the background of distant stars. It is caused by Earth’s orbital motion around the Sun. It is so small and hard to observe. Successful measurement of stellar parallax was done only after 19th century.

Flat-Earthers like to think stellar parallax doesn’t exist, and that it is ‘evidence’ the Earth is stationary. They are wrong.

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Polaris: Our Current North Pole Star, But Not For Forever

Flat-Earthers often claim that the fact Polaris not appearing to move is ‘evidence’ that the Earth is flat and stationary. If the Earth is a rotating sphere, then Polaris —as they say— should appear to be in motion.

In reality, Polaris is indeed moving across the sky. Though it is not something we can observe in a single night, or even in our entire lifetime.

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Not to Scale: Depictions of the Solar System

Practically every depiction of the Sun, Earth and Moon is drawn not to scale. Flat-Earthers sometimes use this fact to point out the alleged “failure of modern science” to describe motion of celestial bodies, or something like that.

But in fact, the reason is simply that it is practically impossible to create a model of the solar system with real scale, using static images, that is still effectively describes the objects it is trying to explain.

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