## Sweden Solar System

The Sweden Solar System is the largest scale model of the Solar System in the world. We can use it to get a better sense of the sizes and distances in the Solar System.

Flat-Earthers claim there is no scale model of the Solar System and use the fact to “prove” the failure of science to explain the world. The Sweden Solar System proves them wrong and gives us an idea about the problem of making a scale model of the Solar System.

## How Satellites Can Orbit and Stay Up There

Earth’s gravity pulls things toward Earth. Satellites can stay up there because they are orbiting. They are moving at the right speed and right direction to counter the pull of gravity.

Flat-Earthers claim that satellites should fall down if gravity pulls toward Earth. In reality, we do not just launch satellites to space. We also give them the correct speed & direction, so they neither fall toward Earth nor keep going farther away.

## Wet, Spinning Tennis Ball False Analogy

The gravitational acceleration exerted by the mass of a wet, spinning tennis ball is too small compared to the centrifugal acceleration generated by its rotating motion. As a result, the water escapes away from the tennis ball, unlike Earth.

A wet spinning ball is a sphere, spinning & wet, like Earth. But the water goes away from the ball, unlike Earth. Flat Earthers use it to “disprove” spherical Earth. In reality, the magnitude of the involved accelerations in the two cases are different.

## Where’s the Curvature?

A human eye can only visually perceive the curvature of the Earth if we are at a considerable altitude from the surface, which is still beyond the reach of most humans today. A commercial jet airliner is the highest position realistically attainable by most humans today. We can only perceive very slight curvature at such altitude and, even then, only in an ideal condition.

The basis of flat-Earthers’ belief is that the horizon appears flat. They would say if we cannot see the curvature, then there’s no curvature, and therefore, the Earth is flat. In reality, only a few people can travel high enough to see the curve.  The highest we can realistically go is by getting on a commercial jet airliner, which can only go about 11-15 km up, only a fraction of Earth’s radius.

## Observing Mercury and Venus

Mercury and Venus are inferior planets. Their orbits are closer to the Sun than Earth. We can see these planets if they are above the horizon, and it will be easier if the Sun is below the horizon. Generally, both planets can be seen early or late in the night.

Flat-Earthers claim we should not be able to see Mercury and Venus as they are closer to the sun, and at night we are facing away from the sun. In reality, early and late in the night, we can look toward the general direction of the Sun & observe both planets.

## Earthrise

Earthrise is a photograph of Earth that was taken from lunar orbit by William Anders during the Apollo 8 mission. It was taken just after Earth rises from behind the Moon.

From Earth, the Moon always shows the same face, and from a location on the Moon facing Earth, it is impossible to see Earth rising. Flat-Earthers use it to reject the Earthrise as fake. In reality, the photo was not taken from the lunar surface, but from the lunar orbit. Apollo 8 did not even land on the Moon.

## Visual Albedo of the Moon and the Earth

Visual albedo is the measure of the reflection of sunlight out of the total solar radiation received by an astronomical body, taking into account only the visible light. The visual albedo of the Earth is 0.37, and the Moon’s is 0.12.

The Moon appears dark if the Earth also appears in the same photograph. Flat Earthers use the fact to dismiss such photos as fake. In reality, the Moon’s brightness in a photo is just a matter of choosing the correct camera exposure. But if Earth is also present, increasing the exposure will make the Earth appear too bright.

## Frame of Reference

A frame of reference consists of an abstract coordinate system and physical reference points that uniquely fix the coordinate system and standardize measurements. Speed or velocity is relative to a specific frame of reference. It is possible that two speeds/velocities are measured relative to a different frame of reference and thus cannot be directly compared.

Flat-Earthers like to compare two different speed measurements like an airplane moving at 900 km/h (560 mph) and Earth’s surface near the equator at 1674 km/h (1040 mph). They would conclude the airplane should not be able to catch up with Earth’s surface and would not land if the Earth is rotating. In reality, both the speeds are measured relative to a different frame of reference, and therefore, cannot be compared directly.

## Perspective of Earth Due to Different Observer Distance

Because of a perspective effect, an observer in space can see more of Earth’s surface if they are farther from Earth.

Flat-Earthers noticed the different visible Earth’s surface in different Earth images and used it to “prove” they are fake. In reality, it is just a perspective effect caused by the fact that the Earth was seen from a different observer distance.

## Geometry of a Full Moon

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.

## Stellarium

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.

## Scale in a Diagram of the Solar System

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.

## Apparent Motion of Planets

Planets appear to move near the ecliptic —the line that marks the annual path of the Sun against background stars. From these motions, it is obvious that Venus and Mercury are in motion around the Sun. And the motion of the other planets can only be explained if Earth is in motion around the Sun.

Flat-Earthers claim that Earth is stationary. In reality, from observing the planets’ motion, the most plausible explanation is that all planets, including Earth, are in motion around the Sun.

## Earth Seen From the Moon vs the Moon Seen From Earth

Earth seen from the Moon will appear 3.7× larger than the Moon seen from Earth. However, if a photograph of Earth is compared to that of the Moon, the sizes of both objects also depend on the field of view of the cameras that were used to capture them.

Flat-Earthers discovered the size of the Earth in a photograph is not 3.7× the Moon in another picture. They used the fact as “evidence” of wrongdoing. In reality, the two photos were not taken with the same field of view, and cannot be compared directly.

## Geometry of a Crescent Moon

Some people are confused that the crescent moon can be visible at night, even though during the time, the Moon is closer to the Sun than Earth, and the part of the Earth is facing away from the Sun.

Many flat-Earthers have the same visualization difficulties, but they take it a step further and use it as ‘evidence’ as a ‘failure’ of science to explain the fact. In reality, the phenomenon can be readily explained in the spherical Earth model.

## Human Perception of Speed and Acceleration

When aboard an airplane flying at cruising speed, we will not be able to feel that the plane is, in fact, moving at speed of more than 900 km/h. But if the plane changes its speed, turns or changes its altitude, we can easily feel it.

The same thing happens with the motion of the Earth. Due to Earth’s rotation, the surface of the Earth is moving at 1656 km/h near the equator. We never feel it because the speed is constant, or in other words, the acceleration is zero.

## The Varying Earth-Moon Proportions in Different Pictures

How an object appears in a photograph depends on perspective —the position of the camera relative to the object—, and field of view of the camera. The farther the object, the smaller the object will appear in the resulting image; and conversely, the closer the object, the larger it will appear. The narrower the field of view, the larger the object will appear in the image; and conversely the wider the field of view, the smaller the object will appear.

Flat-Earthers take the varying proportions of the Earth & Moon in different pictures as a glaring inconsistency. They are wrong. The pictures were simply taken from a different perspective and field of view.

## Sunlit Objects and Visibility of Stars

Generally, sunlit objects are far brighter than any stars. It is the reason stars are not visible in a lot of photographs showing sunlit objects unless the objects are overexposed and made much brighter than the correct exposure.

Flat-Earthers take the lack of stars in photographs as evidence of misconduct. They are wrong. If the primary object in the picture is sunlit, then in most cases, stars will not be visible.

## Real Photos of the Earth

The first photo showing the entire Earth was taken in 1966 from the spacecraft Lunar Orbiter 1. Since then, there are too many photos showing the whole earth taken from various missions to space.

The advent of computers in the 80s introduced a new technique of generating such pictures. A satellite can be used to take many photos of the Earth from a low orbit, and computers can be used to assemble those pictures into a single photo of the Earth.

Flat-Earthers ‘discovered’ such technique, then they concluded that all pictures of the Earth taken from space are all composites, the results of manipulation or assembled by computers. They are wrong. Just because there were pictures created using such technique, it doesn’t mean there is no genuine picture showing the entire Earth, not composites, not stitched, and were taken from a single shot.

## 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.