## Gravitational Acceleration vs Force of Gravity

Earth pulls all objects downward by the same gravitational acceleration of 9.8 m/s². But the force of gravity exerted by Earth on an object still depends on its mass. An object with a greater mass has a greater force of gravity (also called weight).

Flat-Earthers claim that if greater mass means a greater force of gravity, a bowling ball in a vacuum should fall faster than a feather. In reality, they confuse acceleration with force. Both fall at the same speed because the gravitational acceleration is the same on both, but their forces of gravity are different.

## Archimedes’ Principle and Gravity

Archimedes’ principle states that any object, totally or partially immersed in a fluid, is buoyed up by force equal to the weight of the fluid displaced by the object. Meanwhile, Newton’s law of universal gravitation states that every particle attracts each other with force directly proportional to their masses & inversely proportional to the square of their distances.

Flat-Earthers like to characterize gravity as if it was “invented” to “replace” Archimedes’ principle & that the two are competing theories. In reality, these are two different theories that explain different phenomena. Gravity does not explain anything that Archimedes’ principle explains and vice versa. Gravity does not replace Archimedes’ principle; both are valid and in use today.

## Reproduction of the Cavendish Experiment

The Cavendish experiment was the first experiment to measure gravity between masses in the laboratory. The experiment has been repeated numerous times over two centuries with consistent results. Many other types of experiments also confirmed it.

Flat-Earthers incorrectly claim the Cavendish experiment has never been reproduced. They focus solely on the original experiment to discredit it. In reality, there are far too many repeats of the experiment. To discredit the experiment, they have to address all and each of the repeats of the experiment.

## Attraction Between Masses

If gravity is the attraction between masses, then why two hanging masses do not appear attracted to each other? Because there is a really huge mass (the Earth) below both masses, attracting both masses with a much significantly larger force compared to that between each other.

The Schiehallion experiment used a massive mountain as one of the masses. And they were able to measure the effect, called the vertical deflection.

The Cavendish experiment controls the vertical attraction from Earth out of the equation. Therefore, we can observe and measure the weak and slow horizontal attraction between the masses, without interference from Earth.

## Theories of Gravity

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

Flat-Earthers treat the existence of the two theories as a supposed conflict, and they use it as “evidence” of wrongdoing. In reality, these are two separate theories that explain the phenomenon of gravity. Einstein’s is more accurate yet more complex. In contrast, Newton’s is simpler but less accurate. Despite having been superseded, Newton’s gravity continues to be used as an excellent approximation of the effect of gravity in most applications.

## Isaac Newton and the “Hypotheses non Fingo”

Isaac Newton formulated the law of universal gravitation, which adequately explained the motion of all bodies in space known at his time. He also showed it is the same law that is causing everyday objects to fall on Earth.

In his famous phrase “hypothesis non fingo,” Newton stated that he did not know what causes gravity and refused to speculate. Flat-Earthers use it to discredit him. In reality, just because he did not know what causes gravity, it does not mean his law of universal gravitation is wrong.

## Moving Vehicle Analogy and the Physical Barrier Excuse

We cannot feel the Earth rotating, and to explain the phenomenon, we usually use the moving vehicle analogy. If the vehicle is moving at a constant speed, we will not be able to sense the motion. We cannot feel the motion of Earth because of the same reason.

Flat-Earthers invented the excuse that we are standing on Earth, not inside it, to falsely reject the explanation.

## 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.

## Newton’s Law of Universal Gravitation

Gravity is a natural phenomenon by which all things with mass or energy are brought toward each other. In 1687, Isaac Newton explained the phenomenon as a force, which was formulated in Newton’s law of universal gravitation.

Flat-Earthers insist that gravity does not exist. But this is only a result of a mere ignorance on how gravity works. Everything in our lives is consistent with what is explained in Newton’s law of universal gravitation.