An atmospheric duct is a horizontal layer in the lower atmosphere in which a thermal inversion causes light rays to be trapped and continuously guided near Earth’s surface. They tend to follow Earth’s curvature without escaping to space.
Water heats up slower than air and will be cooler than air most of the time. In turn, the colder water cools down the layer of air just above it, creating a thermal inversion that can form a duct.
It is the reason flat-Earthers like to perform observations from very close to the water’s surface. It will be easier for light to bend, revealing objects that are geometrically behind the curvature. Then, they will incorrectly attribute it to “the lack of curvature.”
Continue reading “Atmospheric Duct”
The strength of atmospheric refraction is not constant but varies depending on the weather condition. As a result, a distant object usually obscured by Earth’s curvature can sometimes be visible if the refraction is strong enough.
Lake Pontchartrain transmission towers demonstrate Earth’s curvature. Flat-Earthers like to cherry-pick moments where the towers appear straight, ignoring other cases. In reality, they look straight only because the refraction was strong enough.
Continue reading “Refraction Effect on the Lake Pontchartrain Power Transmission Line”
Different reasons can cause a distant object to be not visible:
- The angular resolution limit of the observer.
- The visibility limit imposed by the atmosphere.
- Obstruction by another object, including by Earth’s curvature.
Flat-Earthers incorrectly presumed “a distant ship is not visible only because of Earth’s curvature.” Incorrectly concluded if we can bring the ship back into view, the curve must not exist. In reality, Earth’s curvature is not the only thing that can cause a distant ship to be not visible; other reasons can also cause it.
Continue reading “Different Reasons Why a Distant Object is Not Visible”
Black is a color that results from the absence of light. A dark or black object emits practically no light. It does not emit “black light.”
Flat-Earthers claim the dark part of the moon should appear black during the day. In reality, they fail to understand that black is caused by the lack of light, not by the emission of “black light.”
Continue reading “Dark Part of the Moon & Its Visibility During the Day”
In photography, bokeh is the way a lens renders out-of-focus points of light. The shape of bokeh depends on the shape of the lens’s aperture more than the out-of-focus objects themselves.
Flat-Earthers fail to take properly-focused photos of stars and planets because of their lack of photography skills and because their cameras are not suitable for the purpose. They are just getting bokeh, which tells us more about their equipment (and lack of knowledge) than the actual intended objects.
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Lasers are distinguished from other light sources by their coherence, or that their frequency and waveform are identical, and the output being a narrow beam. But lasers are still a form of light and exhibit the same characteristics as other light sources.
Flat-Earthers assume lasers always travel in a straight line, not affected by the medium. They use this incorrect assumption in their “experiments” to “prove” a flat Earth. In reality, like other light sources, atmospheric refraction can bend laser beams.
Continue reading “Refraction of Laser Beam”
In an online lecture, an MIT professor explained the second law of thermodynamics. One of his examples is a container filled with gas next to another filled with a vacuum. If the wall is removed, the gas will rush to fill the newly available volume. However, it is only a simple model that does not attempt to explain everything about the system.
Flat-Earthers abuse the lecture to “prove” it is “impossible” for the atmosphere to exist next to a vacuum. It becomes a flat Earth talking point as if the lecture shows us that spherical Earth “violates” the second law of thermodynamics. In reality, the gas inside the container is also affected by gravity and will also have a pressure gradient, just like the gas outside. But it is not within the scope of the lecture.
And if we ask the lecturer if Earth is flat, he will surely say no.
Continue reading “Misconception about the Second Law of Thermodynamics”
Using a precise digital kitchen scale and a smartphone with a pressure sensor, we can easily measure the change in weight and atmospheric pressure in different locations.
Flat-Earthers claim that an object falls down because it is denser than the air surrounding it. However, simple measurements show that things weigh less at a higher altitude where the air is less dense, contrary to the expectation if their claim is true.
Continue reading “Weight and Air Density Experiment”
Some flat-Earthers discovered images of multiple suns in the sky. They jumped to the conclusion that it proves whatever they want it to confirm. In reality, we can explain them without going for farfetched scenarios.
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Flat-Earthers cannot understand why space appears dark if the Sun is in space, and they use their ignorance to discredit science.
In reality, sunlight does travel through space. However, space is a vacuum, and there is nothing to scatter and redirect the light toward our eyes like in Earth’s atmosphere. We can demonstrate the phenomenon using a low-powered red and green laser pointer in clean air.
Continue reading “Light Scattering Demonstration Using Laser Pointers”
Visibility is a measure of the distance at which an object can be clearly discerned. Visibility depends on the transparency of the air. There is no air in space to disrupt the transmission of light, and therefore, light can travel very far in space practically undisturbed.
The ISS can be seen clearer than objects on Earth’s surface far closer than the ISS. Flat-Earthers use the fact as “evidence” that the ISS is much closer. In reality, only a fraction of the light path from the ISS travels through the dense lower part of the atmosphere that will significantly affect the transmission of light.
On the other hand, light emitted by objects on Earth’s surface has to travel the entire path through Earth’s atmosphere.
Continue reading “Visibility of Objects in Space Compared to Those on Earth’s Surface”
Because of inertia, we cannot travel to another location by hovering inside a helicopter and waiting for the Earth to rotate below us until we are above our destination.
Flat-Earthers claim that we cannot do such a thing as ‘proof’ of a motionless Earth. In reality, when still on the ground, the helicopter is already moving at the same velocity as Earth’s surface.
Continue reading “Hovering Helicopter and Earth’s Rotation”
At a lower altitude, the air is denser, and objects weigh more. On the other hand, at a higher altitude, the air is less dense, and objects weigh less.
Flat-Earthers deny gravity and invented the “explanation” that an object falls only because it is denser than the air surrounding it. But if it were true, objects should weigh more at a higher altitude where the air is less dense. But they weigh less instead, disproving flat-Earthers’ density theory.
Continue reading “Air Density vs Object’s Weight”
The Moon becomes red during a total lunar eclipse because Earth’s atmosphere acts like a lens and refracts sunlight toward the Moon. It also scatters bluish components of sunlight more strongly and lets more reddish components reach the Moon.
The Moon does not become totally dark during a total lunar eclipse, and flat-Earthers use it as “evidence” the Moon is not in Earth’s shadow during a lunar eclipse. In reality, it occurs due to optical phenomena involving Earth’s atmosphere.
Continue reading “Blood Moon: Why The Moon Turns Red During a Total Lunar Eclipse”
Atmospheric refraction is stronger near the surface. Additionally, a thermal inversion can form a duct guiding light ray to follow the curvature of Earth. These phenomena allow light rays to reach the viewer far behind the horizon, but the rays will be compressed, distorted, and scattered, and will not form the true image of the objects. However, a nondescript, intense point light source will stand out against a darker background.
Flat-Earthers like to perform experiments involving lasers, flashlights, and mirrors over the water surface. If the light is visible from the other side, they would wrongly conclude Earth’s curvature does not exist. In reality, atmospheric refraction causes the result they observed.
Continue reading “Experiments Involving Flashlights, Laser, & Reflected Sunlight Over Water Surface”
The moving vehicle analogy is often presented to explain how Earth’s rotation does not seem to affect an object’s motion. Similarly, a ball released inside a moving vehicle will not fall rearward because it retains its inertia.
Flat-Earthers offer the moving open-air vehicle as if it is the “correct ” analogy. In reality, with their analogy, the air moves relative to the vehicle, which exerts an additional force that does not exist in the fact being explained. Their analogy fails to represent the fact being explained.
Continue reading “Moving Vehicle Analogy: Inside vs Outside of the Vehicle”
An airplane exists on Earth. It has the same motion as the surface of the Earth, including Earth’s rotating motion. The motion and speed of an airplane are measured relative to Earth’s surface.
Flat-Earthers claim that an airplane should not be able to fly eastward or land. In reality, an airplane is moving relative to the surface. It has Earth’s motion as a component of its motion and does not need to chase Earth’s rotation.
Continue reading “Airplanes and Earth’s Rotation”
Atmospheric pressure decreases as altitude increases. A pressure difference can occur without a barrier. Other factors, like gravity, can cause a pressure difference.
Flat-Earthers claim a pressure difference cannot possibly occur without a barrier, like Earth’s atmosphere next to the vacuum of space. In reality, it is not difficult to demonstrate that a pressure difference can exist without a barrier.
Continue reading “Pressure Difference Without a Barrier”
A selenelion occurs during a lunar eclipse when the sun and moon are observed above the horizon. Atmospheric refraction bends light rays and lifts the image of the sun, and the moon typically up to 0.6°, so both can appear above the horizon.
Flat-Earthers assert that a selenelion should not be possible if Earth is a sphere due to the fact during a lunar eclipse, the sun and moon are 180° apart. In reality, a selenelion is possible because Earth’s atmosphere refracts light.
Continue reading “Selenelion: The Phenomenon Where Both the Sun and Moon Are Visible During a Total Lunar Eclipse”
Visibility range is a measure of the distance at which an object can be clearly discerned. Angular resolution is the ability of an optical system to resolve detail in the object.
Unlike the claim from flat-Earthers, there is no such thing as the “maximum range” of a camera. A germ on our hand is well within the visibility range, yet a regular camera lacks sufficient angular resolution to see it. On the other hand, an airplane is much farther away, but it has a larger angular size and can be seen by the camera.
Continue reading “Visibility Range vs Angular Resolution”