Iridium is a satellite constellation consisting of 66 satellites. It provides satellite phone services over the entire Earth surface. The first generation satellites have three door-sized reflective antennas. Because of their reflectivity, Iridium satellites will occasionally reflect sunlight to Earth’s surface. The Iridium flare will look like a bright flash over a few seconds.
Most flat-Earthers deny the existence of satellites. Iridium flares provide an easy opportunity to confirm the existence of satellites, at least until the end of 2018, when they are replaced by newer non-reflecting satellites.
Continue reading “Iridium Flare”
“If satellites exist, then why would mobile phone operators bother to install transceivers everywhere?” flat-Earthers asked this a lot.
The logic is that if using a satellite can get you a vast coverage area, then spending a lot of money and effort to install towers everywhere does not make any sense. Usually, they would follow-up and conclude that “satellites don’t exist.”
They are wrong. Satellites do exist, and there are good reasons why mobile phone communication utilizes cellular architecture.
Continue reading “Cellular Network vs. Satellite Communications”
Unlike other planets that were found by empirical observation, Neptune was found by mathematical prediction involving Newton’s law of universal gravitation.
Continue reading “Neptune and Newton’s Law of Universal Gravitation”
Some flat-Earthers mentioned the fact that graviton —the mediating particle of gravitation— is ‘not yet observed’. They took this fact as ‘proof’ that gravity does not exist.
Often they would triumphantly show us screenshots of the table of fundamental particles they took from Wikipedia and other sources. In the ‘gravitation’ column, they would point out its mediating particle has not been observed yet. And they would conclude that scientists are aware gravity does not exist, and we all have been lied to.
Obviously, they are wrong on all accounts.
Continue reading “The Hypothesized Graviton and Flat-Earthers’ Zeal to Disprove Gravity”
A cyclone or hurricane rotates in a different direction depending on which hemisphere it occurs. A cyclone rotates counterclockwise in the Northern Hemisphere, and clockwise in the Southern Hemisphere.
The phenomenon happens because of the Coriolis effect, which in turn occurs because the Earth is spherical and rotating.
Continue reading “Cyclonic Rotation: The Direction a Cyclone or Hurricane Rotates”
As the Earth is spherical, the horizon is below the eye-level (or the astronomical horizon). The angle between the eye-level and the horizon is the dip of the horizon. The angle becomes larger as we go higher.
Flat-Earthers often claim that “the horizon always rises to eye-level”, and thus ‘proving’ the flat Earth claim. Despite their insistence to use a water level to ‘prove’ water is flat, the same device can be used to demonstrate the dip of the horizon, proving the water surface has curvature, and consistent with the spherical Earth model.
Continue reading “Water Level Demonstrates The Dip of the Horizon and Proves Earth’s Curvature”
A widespread misunderstanding within the flat-Earth victims is related to velocity/speed. They seem to think velocity is absolute, while in reality it is measured from a specific frame of reference. Example:
“If the Earth is in motion around the Sun at 30 km/s, and Apollo traveled at only 11 km/s, then how could Apollo astronauts possibly make it back to the Earth?”
We used to measure velocity/speed relative to the surface of the Earth. But it is not always like that.
Continue reading “Velocity is Measured From Specific Frame of Reference”
Soundly’s pictures and videos of Lake Pontchartrain power lines and causeway stirred up the flat-Earthers’ nests. They clearly show the curvature of the Earth, where it is usually hard to discern. For the rest of us, those pictures are just the consequence of the fact that the Earth is a globe.
Flat-Earthers can’t take this, and they invented various excuses to attack the credibility of these pictures and videos. Some of them look for specific vantage point where it is impossible or very hard to discern the curvature. They would conclude if the curve is not seen from these vantage points, then it should not be visible from Soundly’s viewpoints.
Continue reading “Perspective Compression: Determining If a Curvature Exists”
High-altitude balloon footage is often abused by flat-Earthers to show us that the Earth is flat when seen from a high altitude.
We analyzed more than two dozens of footage taken from high-altitude balloons on YouTube, and we can easily conclude the curvature is there and usually easy to spot, including in the cases where flat-Earthers use the video as ‘proof’ of a flat Earth.
Continue reading “Curvature of the Horizon in High-Altitude Balloon Footage”
Flat-Earthers quoted Einstein’s statement out of context to give the appearance that he gave credence to the notion that Earth is stationary. In reality, Einstein never said the Earth is stationary.
The quote came from his Kyoto address “How I created the theory of relativity,” December 14, 1922.
Continue reading “Quote-Mined Einstein Statement”
Things fall down because of gravity. The mass of the Earth causes everything to fall down at 9.8 m/s² near the surface of the Earth. This constant is called ‘gravitational acceleration’ and usually denoted by ‘g’.
Most flat-Earthers deny the existence of gravity. According to them, things fall down because of density or buoyancy, not gravity. They are wrong.
Continue reading “Free Fall”
A candle gets its flame from combustion, a chemical reaction. The hydrocarbon that formed the candle reacts with oxygen, and we get carbon dioxide, water, and heat energy as the results. The oxygen is obtained from the air. If the air supply is cut off —for example by covering the candle with a glass— then the reaction will stop, and the flame goes out.
We hear flat-Earthers often claimed that it is impossible for the Sun to be in space. They said the Sun burns, and therefore it requires oxygen. Space is empty, so it is impossible for the Sun to be there. They are wrong. The reaction that is occurring in the Sun is not combustion. It works differently from what happens with the candle.
Nuclear fusion powers the Sun. It fuses hydrogen atoms into helium atoms. All the necessary component for the reaction to happen is in the Sun, and the reaction doesn’t require matters from external sources.
Continue reading “How the Sun ‘Burns’ Without Air in Space”
In 205 BC, Eratosthenes successfully determined the circumference of the Earth by measuring the length of the shadow cast by a rod. He did the measurement in Alexandria and timed it to coincidence when the Sun is directly overhead Syene.
2222 years after that, some flat-Earthers tried to refute the Eratosthenes experiment. They say the experiment can be applied to the flat-Earth model.
Continue reading “The Eratosthenes Experiment: Proving the Earth is Spherical”
Flat-Earthers mention the curvature of water a lot. According to them, the curve of the water can never be observed, and thus, the Earth is flat.
The problem with such an argument is that they usually conclude that from a very small amount of water. Water in a glass or a bucket will practically look flat. Not because there is no curvature due to Earth’s gravity, but because the water is in such small amount so that the curvature is minuscule and impossible to observe, let alone with the naked eye.
Continue reading “The Curvature of the Water Surface”
The Amazon never flows uphill, or in other words, ascend to a location farther from sea level anywhere in the Amazon basin.
Flat-Earthers often claim that if the Earth is spherical, then the Amazon will have to flow uphill to overcome the curvature of the Earth. They are wrong.
Continue reading “The Earth is Spherical and The Amazon Never Flows Uphill Anywhere”
The GPS system is one-way. The satellites broadcast signals. GPS devices receive and process the signals to determine their location.
Flat-Earthers often point out the fact we were unable to locate the ill-fated MH370 as ‘evidence’ GPS doesn’t work and therefore doesn’t exist. They are wrong. GPS satellites never receive any signal from GPS devices, and it is not possible for them to locate MH370.
Continue reading “The MH370 Disaster and the Inability of the GPS System to Locate It”
Gravity causes water to seek the lowest potential, which can be simplified as the position as close as possible to the Earth’s center of gravity. As a result, the surface of the water will have equipotential surface and form an approximately spherical surface which has the same center as the Earth. Every location along the surface has the same potential.
Continue reading “Equipotential: a Property of the Surface of Water”
We can use the duration of a flight route to roughly determine the distance between two locations. Then, we can use this to determine which model better represents reality: the flat-Earth model or the spherical Earth model.
In the flat-Earth Model, the distances between two locations become more unreasonable as we go further south. To illustrate this fact, we can use the flight route of Sydney-Santiago to help us with the calculations. This flight route is one of the most southernly flight routes. Continue reading “The Sydney-Santiago Flight Route: An Impossible Route on the Flat-Earth Model”
Light waves are not always moving in a straight line. When it passes through a medium of a different refractive index, the waves will deviate. The phenomenon is called refraction and described according to Snell’s Law.
Earth’s atmosphere has variation in air density that depends on the altitude. As the refractive index changes with the density of the medium, light waves passing through Earth’s atmosphere also experience refraction.
Continue reading “Atmospheric Refraction”
Sometimes, we can see clouds appearing as if they are behind the Sun or the Moon. Obviously, this is merely an illusion. But some flat-Earthers regard this as ‘evidence’ that the Sun and the Moon are close and apparently closer than some clouds. They are wrong.
Continue reading “The Illusion of Clouds Appearing ‘Behind’ the Sun or the Moon”