Our Ability to Perceive Speed and Acceleration

When we are aboard a plane flying at cruising speed, we will not be able to feel that the plane is in fact moving at speed of more than 900 km/h. But if the plane changes speed, turns or changes its altitude, we can easily feel it.

Same thing happens with the motion of the Earth. Because of the Earth’s rotation, the surface of the Earths moves at a speed of 1656 km/h near the equator. It also travels around the Sun at a speed of about 107000 km/h. We never feel any of these because the speed is constant, or in other words, the acceleration is zero.

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The Saros Cycle and Saros Series

A page on NASA’s website is at the center of the attention of flat-Earth followers. It is a page created by Fred ‘Mr. Eclipse’ Espenak, explaining the Saros cycle. Here’s the first paragraph from the page:

The periodicity and recurrence of eclipses is governed by the Saros cycle, a period of approximately 6,585.3 days (18 years 11 days 8 hours). It was known to the Chaldeans as a period when lunar eclipses seem to repeat themselves, but the cycle is applicable to solar eclipses as well.

After they discovered that the said ‘Chaldeans’ was a civilization from 25 centuries ago, they got excited and jumped to the conclusion that NASA used ancient technology to predict eclipses, and thus eclipses can’t be predicted from the motion of the Sun, Earth and Moon themselves.

Like other similar cases, this tells us more about the flat-Earthers themselves than about NASA.

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Difference in Entrance Pupil Diameter: The Real Reason Why An Obscured Object Appears When Zoomed In

Ever seen a video where a flat-Earther tries to demonstrate that a distant object that appears to be behind an obstacle can be brought back into view simply by zooming in? He would then conclude the same thing would happen when zooming in to a distant ship, and the reason a distant ship is not visible is not the curvature of the Earth.

Well, no. The real reason why the object in that experiment can be seen after zooming in is that the obstacle is close, and there’s difference in the camera’s entrance pupil size when the zoom changes. For a camera that has very long zoom range —like the Nikon P900—, the difference can be very dramatic.

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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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The topic of tide come up frequently in the flat-Earth community. Let’s examine some of the ‘issues’ they brought up about tides in Q&A format.

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Polar Circumnavigation

Flat-Earthers think there hasn’t been anyone who has circumnavigated the Earth by traversing both the north pole and south pole in the process. All we have are explorers who have circumnavigated the Earth to the east or west, parallel to the equator; explorers like James Cook or Ferdinand Magellan. They don’t really have the choice, because if polar circumnavigation is possible, then the flat-Earth assumption falls flat.

But, like a lot of assumption in the flat-Earth community, it is simply not true. There are in fact many people who have done a polar circumnavigation, and the information can be easily found on the Internet.

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Eötvös Effect: Evidence of Spherical, Rotating Earth

Eötvös effect is the change in perceived gravitational acceleration when moving eastward vs westward. An object will weigh more when moving eastward than when it is stationary or moving westward.

The effect was discovered by Loránd Eötvös in the 1900s after noticing the difference in gravity measurement on moving ships. He noticed that the readings were lower when the boat moved eastwards, higher when it moved westward. He identified this as primarily a consequence of the rotation of the Earth.

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Lake Pontchartrain Power Transmission Lines: Evidence of Earth’s Curvature

Lake Pontchartrain is a lake in Louisiana, United States. There are power transmission lines about 24.27 km (15 mi) across this lake. They are practically straight and each tower is uniform and has the same height, making these towers ideal for observing the curvature of the Earth.

They are first popularized by Soundly who presented evidence of Earth’s curvature using a series of photos and videos of the power lines in June 2017. As of now, the towers and other objects on the lake are probably the most popular Earth curvature tourism spot in the world.

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