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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Zooming In On Distant Ships Does Not Disprove Earth’s Curvature

If we can’t see a distant ship, then it is because of one of these reasons:

  • Our eyes have limited angular resolution and are unable to resolve the ship at that distance.
  • The atmospheric condition is limiting our visibility.
  • The curvature of the Earth obscures the ship.

Flat-Earthers are keen to demonstrate that a previously invisible ship at a distance can be made visible by zooming in. They take this fact as ‘proof’ that the curvature of the Earth doesn’t exist. They are wrong. The curvature of the Earth is not the only reason a distant object is not visible.

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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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Selenelion: The Phenomenon Where The Sun and Moon Are Visible During a Total Lunar Eclipse

“The Sun and the Moon have been observed to appear in the sky at the same time during a total lunar eclipse. This cannot happen if the Earth is round because the Sun, Earth and Moon are supposed to be in a straight line during a total lunar eclipse. So, the globe Earth model is wrong!”

Some flat-Earthers observed the Sun and Moon appear at the same time during a total lunar eclipse. Predictably enough, they pick the most far-fetched explanation, and conclude the Earth is not round. But in reality, this phenomenon is well documented and clearly explained.

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Space Flight and Temperature In The Thermosphere

Thermosphere is a layer of the Earth’s atmosphere from about 95 km­ to 600 km. It is named ‘thermosphere’ because its temperature increases with altitude. Temperature in the thermosphere can reach 2500°C.

Flat-earthers question this fact a lot:

“If temperature in the thermosphere can reach 2500°C, then how is it possible for human to travel to space? Not to mention that many satellites —including the ISS— are in the thermosphere.”

Short answer: air density in the thermosphere is much, much lower than at the surface of the Earth.

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