Repulsive Force

Gravity does not possess repulsive force like magnetism. These are two different phenomena with different characteristics.

Flat-Earthers use the lack of a repulsive force in gravity to deny its existence. In reality, there is no requirement for an attractive force to have a repulsive force. Gravity does not act like magnetism, and the fact does not disprove gravity.

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Weightlessness, Free Fall, and Microgravity

In orbit, objects are weightless because both the objects and the spacecraft have the same speed and direction, and both are affected by the same gravitational influence. We use the spacecraft as the frame of reference. Because the objects are not in motion relative to the spacecraft, they appear to float.

In Earth orbit, the objects are still affected by Earth’s gravity, but yet they float. Flat-Earthers use it to disprove spaceflight. In reality, the objects float because we are using the spacecraft as the frame of reference, which is also moving by the same amount and is affected by the same gravity as the objects themselves.

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Eötvös Effect: Direct Evidence Earth is a Rotating Sphere

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

The slight difference in weight due to the Eötvös effect can be measured in an experiment on a flight. The Eötvös effect is direct evidence that the Earth is a rotating sphere.

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Flat-Earthers’ Alternative Facts for Gravity

Flat-Earthers reject gravity because it does not support the flat Earth model. To explain the various phenomena explained by gravity, they invented many different ‘alternative facts’ in place of gravity.

Flat-Earthers agree only on a single thing that the Earth is flat. However, as flat Earth is not fact-based, flat-Earthers cannot agree on practically everything else. Different flat-Earth denominations have their alternative explanations for gravity, all of which lacks predictive power and cannot adequately explain real-world facts.

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Airplanes Will Never Fly Into Space

An airplane relies on the lift from its wings, which depends on the airplane’s speed and the air density. As a result, a cruising airplane will fly at a constant altitude, following the curvature of the Earth.

Flat-Earthers claim if Earth is a sphere, an airplane has to dip its nose down periodically, or it would fly into space. In reality, an aircraft will follow Earth’s curvature and is unable to fly to space even if the pilot deliberately attempts to do that

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Curved Appearance of a Rocket Trajectory

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Rocket launches have a curved trajectory because their objective is not only to reach space but also to enter Earth orbit. To achieve it, a spacecraft needs to gain a sufficient horizontal speed, parallel to Earth’s surface.

Flat-Earthers claim the curved appearance of a rocket launch trajectory “proves” rockets never reach space. In reality, it is caused by the motion of the rocket parallel to Earth’s surface, perspective effect, and the curvature of the Earth.

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Fictitious Force

A fictitious force is a force that appears to act on every object when the frame of reference is accelerating. The term “fictitious” does not mean the force does not exist, but it is not an actual force that arises from an interaction between objects.

Flat-Earthers noticed gravity is considered a fictitious force and use the fact to “prove” gravity does not exist. In reality, we can feel a fictitious force. It is merely a term we use for forces that arise due to an accelerating frame of reference.

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Cavendish Experiment

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The Cavendish experiment was the first experiment to measure the force of gravity between masses in the laboratory and the first to yield accurate values for the gravitational constant.

Flat-Earthers are in a constant effort to discredit the Cavendish experiment. They would invent various “explanations” to “explain” the result of the experiments. However, the experiment was not only done once by Henry Cavendish in 1797-1798, and has been replicated numerous times by multiple independent parties for centuries, all yielding consistent results.

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Spirit Level on an Airplane

During cruising, an airplane is practically level. It is flying perpendicular to the direction of gravity. The aircraft is still flying following Earth’s curvature and continuously changes its orientation. However, not only its orientation changing but also the direction of gravity, having the same amount of change. As a result, a spirit level on a flight will not show us the difference in orientation of the airplane due to its motion following the curvature of the Earth.

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Electromagnetism

The electromagnetic force is a type of physical interaction that occurs between electrically charged particles. Electromagnetism is different from gravity. Both phenomena are real but have different characteristics.

Flat-Earthers refuse to accept gravity, and some of them use electromagnetism in place of gravity to explain the various phenomena that are explained by gravity. In reality, electromagnetism has different characteristic from gravity, and cannot explain the various phenomena that are explained by gravity.

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Egg and Salt Water

An egg will generally sink in freshwater, but if we pour salt into the water and stir it, then the egg will start to float. The reason is that after salt is added, the density of water increases. However, the relationship between density and if the egg floats or sinks is not a direct causality.

Flat-Earthers claim that the phenomenon “proves” things fall because of density, and that gravity does not exist. In reality, the density of the water determines the magnitude of buoyancy the egg receives. If the buoyancy is higher than the weight of the egg, the egg will float, and vice versa.

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Shell Theorem

Shell theorem is a simplification stating that a spherical body affects external objects gravitationally as though all of its mass were concentrated at a point at its center.

The direction of Earth’s gravity toward the center of the Earth made some flat-Earthers to assume that we think gravity is caused by something in the center, and that our inability to go there “disproves” gravity. They are wrong. Earth’s gravity is the result of the entire mass of Earth. Using the center of the Earth is merely a simplification.

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The Ball and Water ‘Experiment’

Gravity is the attraction between objects with mass. The higher the mass, the greater is the gravitational attraction. Gravity is not the result of the shapes of the objects.

Flat-Earthers like to perform the ball-and-water ‘experiment.’ They spray water to a ball, then observe the water does not stick to the ball the same way the ocean water curves over the surface of the Earth. They would wrongly conclude that “gravity does not exist.” Gravity does not come from the spherical shape of objects, Continue reading “The Ball and Water ‘Experiment’”

The Variation of Earth’s Gravitational Acceleration

The gravity of Earth varies on the different location on Earth. The variation is caused by the difference in latitude, altitude or depth, and local geology & topography. In most cases, the centrifugal acceleration from Earth’s rotation is also already accounted for in the value of Earth’s gravitational acceleration.

Flat-Earthers claim that according to science, the Earth’s gravitational acceleration is always constant at 9.8 m/s² everywhere on Earth. And they are using the claim to prove Earth is not a rotating sphere. In reality, the magnitude of Earth’s gravitational acceleration varies on the different location on Earth.

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Einstein’s Thought Experiments and Daydreaming

Albert Einstein used thought experiments as a tool for formulating his theories. His theories provided predictions that can be tested in observation and experiments. He did not perform the observation and experiments himself. Others did and confirmed his theories.

Some flat-Earthers dismiss Einstein’s theories —especially those about gravity— on the basis that they are founded on thought experiments and daydreaming. They are wrong. His theories have been repeatedly confirmed by various experiments and observation performed by many others, even to this day.

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Weight = Gravitational Force

The weight of an object is the force exerted on the object by gravity. The gravitational force exerted by the Earth on an object is what we refer to as ‘weight’.

Many flat-Earthers fail to understand that the gravitational force is just another name for ‘weight’. Many misconceptions in the communities of flat Earth victims arise from such a misunderstanding.

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Theories of Gravity

Gravity is a natural phenomenon by which all things with mass or energy are brought toward one another. Today, the phenomenon of gravity is explained by two theories: Newton’s law of universal gravitation and Einstein’s general relativity.

Flat-Earthers take the existence of the two explanations as inconsistency in science and use it as a “proof” of deliberate misconduct. Such allegation is obviously only a result of their prejudice. The two theories are the correct explanations of gravity, and can reliably predict the outcome of the phenomenon.

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Buoyancy

Buoyancy is an upward force exerted by a fluid (liquid or gas) that opposes the weight of an immersed object. Buoyancy happens because the fluid has a pressure gradient. Pressure gradient occurs because the fluid is affected by acceleration, such as the Earth’s gravitational acceleration.

Flat-Earthers makes buoyancy as an “explanations” on how things fall. They are wrong. Without Earth’s gravitational acceleration, buoyancy will not occur.

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Countering Gravity

Gravity is not the only force. There are other forces, too. Multiple forces can simultaneously affect a single object. Forces can counteract gravity, making an object move against the direction of gravity. Such facts do not disprove gravity.

Flat-Earthers take the fact there are objects that move against the direction of gravity as ‘evidence’ of the non-existence of gravity. They are wrong. There are forces other than gravity affecting the object, having the opposite direction from gravity, with at least the same magnitude.

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Orbital Station-Keeping

A satellite in a high enough orbit can remain operational for a very long time because in space there is practically no air resistance. This is a situation that never occurs in our everyday life. A car requires a constant consumption of fuel to keep running, but a satellite can remain in motion without consuming any fuel because there’s practically no force stopping it.

Flat-Earthers claim that satellites cannot stay up there for such a very long time because ‘we never refuel any satellites.’ They are wrong. In space, there is practically no drag, and satellites only need to consume fuel to adjust their speed periodically.

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