Tag: earth-rotation

Earth Axial Tilt

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Earth’s axis of rotation is tilted. The tilt is relative to Earth’s orbital plane. Therefore, it only affects the apparent positions of objects in the solar system, but not that of the distant stars. Both of Earth’s celestial poles still point to the same location in the sky.

Flat-Earthers fail to understand why the stars are unaffected by Earth’s tilt, and they use it to discredit science. In reality, Earth’s axis of rotation is practically constant in the short term, only not perpendicular to Earth’s orbital plane. As a result, it only affects the apparent positions of the Sun, planets, moon, and other objects in the solar system.

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Variation of Earth’s Gravitational Acceleration

The acceleration of free-falling objects on Earth varies. It depends on various factors. The figure of 9.8 m/s² is just a nominal value to use if the actual local value is unknown or unimportant. These variations can only be explained using the law of gravity and that the Earth is a rotating sphere.

Flat-Earthers claim that science tells us that Earth’s gravitational acceleration is always 9.8 m/s² everywhere on Earth, and they use it as “evidence” Earth is flat and stationary. But, in reality, Earth’s gravitational acceleration does indeed vary in different locations.

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Ptolemy’s Almagest and Earth’s Axial Precession

Due to Earth’s axial precession, the positions of Earth’s celestial poles shift gradually in a cycle of approximately 26000 years. These days, Polaris is very close to the north celestial pole. However, 19 centuries ago, Kochab is much closer to the celestial pole than Polaris.

Flat-Earthers claim that the stars are always in the same position proves the Earth is stationary. An ancient star chart like Almagest from the 2nd century shows them wrong. The stars today were not in the same place as stars 19 centuries ago.

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Ring Laser Gyroscopes are Sensitive Enough to Measure Earth’s Rotation

A ring laser gyroscope (RLG) is an instrument for measuring the change in orientation and rotational velocity. It is sensitive enough to measure Earth’s rotation easily.

Flat-Earthers claim that there is no instrument able to measure Earth’s rotation. Such claim arose from their ignorance. Ring laser gyroscopes —which are installed in some airplanes and ships— can easily detect and measure Earth’s rotation.

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Old Star Charts and Earth’s Axial Precession

Due to Earth’s axial precession, the positions of Earth’s celestial poles shift gradually in a cycle of approximately 26000 years. These days, Polaris is very close to the north celestial pole. However, 2000 years ago, Kochab is much closer to the celestial pole than Polaris. In the next 2000 years, Errai will replace Polaris as our pole star.

Flat-Earthers claim that the stars are always in the same position proves the Earth is stationary. They are wrong. By observing old star charts from a few centuries ago, the shift of celestial poles can be determined. It proves stars are not always in the same position as today, and that the Earth is rotating.

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