Archimedes’ principle states that the upward buoyant force exerted on a body immersed in a fluid is equal to the weight of the fluid that the body displaces. Today we usually use B = -ρgV to calculate the buoyant force, where ρ is the fluid’s density, g is the gravitational acceleration, and V is the volume of the displaced fluid.
Archimedes discovered buoyancy earlier than Newton discovered gravity, and flat-Earthers dispute the presence of g in the buoyancy formula. In reality, buoyancy depends on the weight of the fluid, and the distinction between weight and mass only occurred after Newton. Archimedes’ principle still applies, only that we now have a better understanding of what weight is.
Continue reading “Gravitational Acceleration in Archimedes’ Formula”
The flag and emblem of the United Nations is a map of the world in the azimuthal projection centered on the North Pole. Flat-Earthers wrongly claim that the UN uses the so-called “flat-Earth map” in their emblem and use it as “evidence” that the UN “knows Earth is flat.”
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The fallacy of appeal to worse problems (or relative privation) occurs when someone argues that efforts spent to solve a specific problem are a waste by pointing out that there are bigger problems that need to be solved.
Space research is a common target of appeal to worse problems. Flat-Earthers use it to discredit space research and to make people emotional. In reality, it is possible to care about multiple problems simultaneously, and solving the supposed smaller problems does not mean the bigger one is considered unimportant.
Continue reading “Fallacy of Appeal to Worse Problems / Relative Privation”
Rocket engines produce thrust by releasing mass rearward at a very high speed according to Newton’s third law, not unlike how discharging a fire extinguisher pushes us backward.
Flat-Earthers claim that rocket engines cannot possibly work in space because space if vacuum and there is no air to push against. In reality, it is possible to produce thrust in a vacuum by releasing mass —that we call “propellants”— rearward at a very high speed.
Continue reading “How Rocket Engines Work in A Vacuum”
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.
Continue reading “Earth Axial Tilt”
If a piece of information requires us to accuse others of malice before it is possible to believe it, then there is a high probability it is not true. Such information is usually highly emotional. It can be very tempting to believe it, and we need to be cautious.
Continue reading “Information that Involves Accusations of Malice”
The fall of an apple inspired Isaac Newton to understand that the same force that brought the apple falling toward the ground also keeps the Moon in motion around Earth. However, his work involved much more than just observing the falling apple.
Flat-Earthers downplay Newton’s contribution as if it was only about the falling Apple and use the episode as a means of ridicule. In reality, Newton’s works were much more than that.
Continue reading “Isaac Newton and the Falling Apple”
The Saros is a period of 18 years, 11 days, and 8 hours between related eclipses. The eclipses with the same Saros cycle are classified into a Saros series which is numbered for identification.
Flat-Earthers claim the usage of the Babylonian term Saros “proves” that eclipses are predicted using ancient Babylonian technology. In reality, the Saros is now used to classify related eclipses. For example, the solar eclipse on August 21, 2017 is the 22nd member out of 77 in the Solar Saros 145.
The term Saros was first used in association with eclipse by Edmond Halley in 1691. The Babylonians never used the term Saros to describe eclipses. And the numbering system of the Saros series was created by G. van den Bergh in 1955.
Continue reading “The Saros Cycle and Saros Series”
Airline pilots are educated to understand that Earth is a sphere and depend on the knowledge to do their job. They have plenty of opportunities to observe Earth’s curvature, either visually or using the airplane’s instruments. They are also aware that there are people out there that somehow believe in flat Earth, and some of the pilots even actively debunk flat Earth in their spare time.
Flat-Earthers asked some of the pilots if Earth is flat and rudely recorded the conversation. Then, they would brag online if they can get the pilots to “admit” in camera that Earth is flat. In reality, these pilots are professionals on the job and aware of the erratic behavior of the flat-Earthers. They were just trying to get rid of these people as quickly as possible without making a scene.
Continue reading “Asking Pilots”
Some people are confused that we can see a full moon all night. They expect if the full moon is the result of the opposition of the moon from the sun, then a full moon should be visible only at midnight.
Flat-Earthers with such a spatial cognition problem go a step further and use it to “disprove” spherical Earth. In reality, we can easily explain the phenomenon in the spherical Earth model.
Continue reading “Geometry of a Full Moon”
Flat-Earthers like to mention an astronomical event or a specific celestial geometry and insist it cannot possibly occur if Earth is a rotating sphere orbiting the sun. They would incorrectly proclaim it as “evidence” of a flat, stationary Earth.
We can ask them the time of the event and the observer’s location, then use Stellarium or a similar app to simulate the event. If it produces the same result as the actual observation, then they have nothing to complain about. And the problem was just caused by their failure to understand and to create the correct model.
Continue reading “Stellarium”
Saros is a period of 6585⅓ days separating the occurrence of two eclipses. One Saros after an eclipse, a similar eclipse will occur. The eclipses that belong to the same cycle are grouped in a Saros Series.
Flat-Earthers claim that we can only predict eclipses using the Saros Cycle. In reality, it is impossible to determine many characteristics of an eclipse from its Saros Cycle alone.
Continue reading “Saros Cycle and Prediction of Eclipses”
The images showing the progress of a lunar eclipse were taken in increasing exposures to compensate for the decrease in brightness. The exposure increase from full moon to totality can reach 12EV or 4000× increase in light-gathering power.
Images showing the progress of a lunar eclipse appear in a constant brightness, and flat-Earthers —presumably never seen it in person— use it to “prove” a lunar eclipse is not caused by Earth’s shadow. In reality, the images were kept in a constant brightness by increasing the exposure of the camera.
Continue reading “Constant Image Brightness in Images of a Total Lunar Eclipse”
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”
Diagrams of the Sun, Earth, and the Moon or any other celestial bodies are rarely made to scale because of their extreme smallness relative to the vast distances between them.
Flat-Earthers assume that the diagrams are not made to scale as a form of deception. In reality, it is just impossible to draw a diagram of celestial bodies with the real scale on physical media and still convey what we want to describe.
Continue reading “Scale in a Diagram of the Solar System”
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.
Continue reading “Variation of Earth’s Gravitational Acceleration”
The lunar phase is the shape of the Moon’s directly sunlit portion as viewed from Earth. The lunar phases change continuously, with a cycle over a period of 29½ days.
A lunar eclipse occurs when the Moon moves into Earth’s shadow. It is a rarer event that occurs only during a full moon and when the Sun, Earth, and Moon are very closely aligned.
Flat-Earthers claim it is impossible that the gibbous phase of the Moon is caused by Earth’s shadow, and they use it to discredit science. In reality, nobody claims Earth’s shadow causes it. They confuse the lunar phase with a lunar eclipse.
Continue reading “Lunar Phase and Lunar Eclipse”
The Sydney-Santiago flight route is one of the southernmost passenger flights. Such a route is impossible if Earth were flat and confirms that Earth is a sphere. It is easy to verify the existence of this route from flight websites.
On a flat Earth, this route should go across the United States. But the duration of the Sydney-Santiago route with a stop in the US is much longer than the non-stop route because Earth is a sphere, and this route does not go anywhere near the United States.
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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 shill gambit is a fallacy where someone dismisses another party’s arguments by proclaiming them to be on the payroll of some conspiracy without having evidence other than the arguments themselves. The shill gambit is a type of ad hominem and poisoning-the-well fallacy. It shifts from addressing the substance of the argument to attacking the person and their credibility instead.
Flat-Earthers would usually commit the shill gambit when they feel cornered. They would accuse anyone outspoken against flat Earth of having been paid by the global conspiracy. We at FlatEarth.ws get these accusations a lot.
Continue reading “Shill Gambit”