Isaac Newton and the Falling Apple

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”

Variation of Earth’s Gravitational Acceleration

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”

What We Feel as “Weight” is the Force of Gravity

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 feel as the ‘weight’ of the object.

Many flat-Earthers fail to understand that the gravitational force is just another name for ‘weight’. Much misinformation in flat Earth communities arises from this misunderstanding.

Continue reading “What We Feel as “Weight” is the Force of Gravity”

Force Vectors

Many misinformation within flat-Earth communities is present only because of their lack of understanding on how forces work on an object.

Continue reading “Force Vectors”

Newton’s Cannonball

Featured Video Play Icon

Newton’s cannonball was a thought experiment Isaac Newton used to explain the principle of orbital motion. It was the first explanation of an orbit and still the easiest to understand.

Newton visualizes a cannon on top of a very tall mountain where the air resistance is no longer a factor. As more charge is used with each cannon shot, the speed of the cannonball will be greater, and the cannonball will hit the ground farther and farther. Finally, at a certain speed, it will not hit the ground at all. It will fall toward the spherical Earth just as fast as the Earth curves away from it. In the absence of drag from the atmosphere, it will continue forever in orbit around the Earth.

Continue reading “Newton’s Cannonball”

Hill Sphere

The Moon orbits the Earth —not the Sun— because the Moon lies well within Earth’s Hill sphere. Hill sphere is the region around Earth where Earth —instead of the Sun— dominates the attraction of satellites.

Flat-Earthers noticed the Sun exerts a stronger pull to the Moon than Earth does to the Moon. They incorrectly concluded that according to science, the Moon should orbit the Sun, then proceeded to use it to discredit science. In reality, they did not account for the centrifugal acceleration resulting from the motion around the Sun, which is one of the factors that determines Earth’s Hill sphere.

Continue reading “Hill Sphere”

Elegance

Our understanding of gravity explains a phenomenon clearly and directly. It is one idea, easy to understand, explains so many phenomena, can account for a large amount of data, and answers many questions. In other words, we can say that gravity is elegant.

In contrast, each of the different concepts in the flat Earth model requires a separate explanation and often in conflict with each other. We can say it is ugly. It is why flat-Earthers cannot accept that a single idea of gravity can explain so many phenomena.

Continue reading “Elegance”

“What is Gravity”

In a StarTalk episode, Neil deGrasse Tyson was given the question “what is gravity?” He quipped “we have no idea” before elaborating more. Flat-Earthers quoted it out of context to discredit Neil and gravity, completely disregarding what Neil explained afterward.

In reality, Neil did provide a very comprehensive answer to the question “what is gravity” but flat-Earthers only gave an emphasis to the “we have no idea” part of his answer, and skipped the rest of his answer.

Continue reading ““What is Gravity””

Pressure Difference Without a Barrier

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”

Density Tower

A density tower is formed by layering immiscible liquids of different densities on top of each other. It is possible because Earth’s gravitational acceleration pulls denser fluid particles stronger and displace less dense ones upward.

Flat-Earthers claim that the possibility to have density towers disproves gravity. In reality, a density tower cannot form without the presence of acceleration, like Earth’s gravitational acceleration.

Continue reading “Density Tower”

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.

Continue reading “Repulsive Force”

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.

Continue reading “Weightlessness, Free Fall, and Microgravity”

Richard Garriott’s “Pocket of Gravity” Magic Trick

Featured Video Play Icon

Richard Garriott is a video-game developer and entrepreneur who is also an avid magician. In October 2008, he flew to the ISS onboard a Soyuz rocket as a private astronaut. During his time on the ISS, he performed several magic tricks.

One of his magic tricks involves a hammer that floats and a card that seems to fall as if it is pulled down by gravity. Flat-Earthers were unaware it was a mere magic trick and wrongly assume it demonstrates things are falling in the ISS, despite other objects in the scene that float.

Continue reading “Richard Garriott’s “Pocket of Gravity” Magic Trick”

Eötvös Effect: Direct Evidence Earth is a Rotating Sphere

Featured Video Play Icon

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.

Continue reading “Eötvös Effect: Direct Evidence Earth is a Rotating Sphere”

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.

Continue reading “Flat-Earthers’ Alternative Facts for Gravity”

Geostationary Satellites

Featured Video Play Icon

If a satellite is placed in an orbit 35786 km above the equator, it will be in motion at the same speed as the Earth’s rotation. As a result, the satellite will appear practically motionless from an observer on Earth’s surface. Many communication satellites are in this orbit so that a satellite receiver does not need to track the satellite continuously.

Flat-Earthers often take the fact that satellites are in motion, and most satellite dishes have a fixed direction as ‘proof’ the receivers cannot be pointing to satellites. In reality, it is possible to place a satellite in a geostationary orbit to make it appear in a fixed position in the sky relative to an observer on Earth.

Continue reading “Geostationary Satellites”

Cavendish Experiment

Featured Video Play Icon

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.

Continue reading “Cavendish Experiment”

Atmospheric Pressure and the Vacuum in Space

Atmospheric pressure decreases as altitude increases. There is no visible boundary between Earth’s atmosphere and space in terms of pressure. There is no abrupt drop in pressure where space begins.

Flat-Earthers assert that it is impossible for the pressurized atmosphere to meet the vacuum of space without any barrier. In reality, the pressure changes gradually. There is no sudden pressure drop between the atmosphere and space.

Continue reading “Atmospheric Pressure and the Vacuum in Space”

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.

Continue reading “Spirit Level on an Airplane”

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.

Continue reading “Electromagnetism”