From the top of a mountain, we can easily see the other peaks afar. And from the visibility and the orientation of the peaks relative to each other, it is easy to conclude that the Earth is a sphere.
Muslims perform their prayers by facing the Qibla —or the direction to the Kaaba in Mecca, Saudi Arabia. The direction of the Qibla is traditionally determined from the direction to the Sun when the Sun is directly overhead the Kaaba. If during the time the Sun is visible, it will indicate the direction of the Qibla.
If the results of the observation are drawn on the so-called ‘flat-Earth map’, the Qibla will not consistently point to the Kaaba. Only the calculation using the spherical Earth model will give us consistent results that conform to centuries of observation, from various locations on Earth. The reason is that the Earth is a sphere.
Because the Earth is a sphere, the surface of Earth obstructs distant enough objects. Climbing to a higher altitude allows us to see farther and more of the previously obstructed objects will become visible, starting from the tops first.
This phenomenon would not occur if the Earth were flat. In a flat Earth, it would not be possible for Earth’s surface to obstruct more of an object —starting from the bottom portions first— if the observer is closer to the surface.
The same thing also happens for objects nearby a large body of water. The surface of the water —which is obviously lower than the object— can obscure the object if the viewer is far enough. Flat-Earthers often invent the “explanation” that Earth’s contour causes the obstruction. This phenomenon can easily prove them wrong.
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.
On many flights, they would give away leveling devices to all passengers for free, so that everyone would be able to observe the dip of the horizon and proves Earth is a sphere. And as a nice side effect, to quench our thirsts, too!
Such devices are called ‘bottled water’. Using these simple ‘instruments’ on a flight, we can demonstrate that Earth is a sphere.
Earth’s curvature is hard to observe from the surface. Even from the altitude of a commercial passenger flight, about 30000-40000 ft, Earth’s curvature is still too small to notice. However, under careful observation, it is not impossible to confirm the curve from the cruising altitude of a jet airliner.
If the Earth were flat, then the Sun has to be visible above the horizon all the time, from the entire Earth. This does not occur, and the simple fact should have been sufficient to rule out any possibility of a flat-Earth.
But instead, flat-Earthers invented various convoluted chain of ad-hoc hypotheses and presented them as “explanations” to prevent the flat-Earth model from being falsified. None of the “explanations” are proven nor correspond to the way our world works.
The apparent size of the Moon remains constant in a single day. This can only happen if the Moon is practically at the same distance all day.
In the flat-Earth model, the Moon is thought to be moving in a circle above the flat Earth. Such a notion should cause the Moon apparent size to vary in a day. However, in reality, the Moon appears in the same size all day, and it proves that the flat-Earth model does not represent reality and that the Moon is much farther.
The Moon is tidally locked. Half of the Moon is always facing the Earth. However, due to libration, we can take a glimpse of areas of the moon that are not always visible.
Flat-Earthers invented many “scenarios” to “explain” how the so many lunar-related phenomena can happen on the flat Earth model. Some of these “explanations” include “transparent Moon”, “hemisphere-shaped Moon”, “flat circular Moon”, etc. Lunar libration rules out the majority, if not all, of these “explanations.”
Due to Earth’s curvature, ships traveling over an ocean disappear from the bottom up. This fact is one of the first evidence to confirm the Earth is a sphere, and one of the first facts of which flat-Earthers had to invent various “explanations” for.
Some of the popular “explanations” are: refraction, perspective, zooming reveal distant ships and visibility limitations. None can explain away the fact.
At any time, the Sun illuminates one half of the Moon and the other half dark. The phase of the Moon is the shape of the sunlit portion of the Moon as viewed by observers on Earth.
The phase of the Moon can never be adequately explained using the flat Earth model. To deal with this inconsistency in their theory, some perpetrators of flat Earth invented an ‘explanation’ that the phase of the Moon is not caused by sunlight. They are wrong. We can observe the Moon very carefully using telescopes of high-zoom cameras, and it will be evident how the lunar craters are lit. And this can only happen if the Moon is sunlit.
A circumpolar star is a star, as viewed from a given latitude on Earth, that never sets below the horizon due to its apparent proximity to one of the celestial poles. Circumpolar stars stay up there in the sky, even during the day.
Flat-Earthers claim the Earth is stationary because the same stars are always visible in the sky. They are wrong. Only circumpolar stars are always in the sky. There are others that are not circumpolar. Some are only visible during certain times in a year.
In the Northern hemisphere, the Sun appears to move to the right. In the Southern hemisphere, it appears to move to the left. During sunrise and sunset, the path of the Sun forms an angle that roughly corresponds to the latitude of the observer. This phenomenon occurs because observers on the different locations on Earth’s surface is not standing on the same plane.
The path of the Sun observed from many different locations on Earth’s surface is evidence of spherical Earth. This observation cannot possibly occur on a flat Earth.
Flat-Earthers reject the existence of satellites. They are wrong. To prove the existence satellites, we can attempt to take pictures of the ISS when an ISS transit happens, or the ISS passes in front of the Sun or the Moon.
Sunspots are darker spots on the surface of the Sun. The location where sunspots appear is unpredictable, but the appearance of sunspots is always the same when observed from anywhere on Earth; only the orientation is different on different observer location. Observers on the opposite position on the Earth will see the sunspots reversed. The reason is that the Earth is a sphere. Any two observers on Earth’s surface are not standing on the same plane.
Some flat-Earthers have spatial awareness difficulties and present the difference of the appearance of sunspots as ‘evidence’ the Earth is not spherical. They are wrong. If the Sun were close as in the flat Earth model, we would see the different appearance of sunspots on the different observer location. In reality, everyone on Earth observes the same appearance of sunspots, only with the different orientation that corresponds to the position of the observer.
The Moon looks practically identical from everywhere on Earth because the Moon is very far relative to the distance between observers on Earth. However, its orientation is different when observed from the various locations across the globe. The reason is that the Earth is a sphere: the different observers are not on the same plane and have the different orientations themselves.
Some Flat-Earthers have spatial awareness difficulties and present the difference of the orientation of the moon as ‘evidence’ of a flat Earth. They are wrong. If in their model the Moon is close, we should be able to see the different face of the moon on the different location on Earth. But we clearly don’t.
Flat-Earth is a concept initially intended for the potential victims in the northern hemisphere. At a glance, some of the claims are seemingly in line with reality in the northern hemisphere, but they would fall apart when verified and tested in the southern hemisphere.
90% of all humans live in the northern hemisphere. It made sense for the creators of the flat-Earth notion to invent their ‘facts’ with the northern population in mind.
In the 11th century, Al-Biruni successfully determined the radius of the Earth by measuring the dip of the horizon from the top of a hill.
In the 21st century, we can easily repeat the same experiment with practically no effort. All we need are a smartphone and an opportunity to observe the horizon from a high altitude, like during a flight.
If we were to observe the direction to the Sun over the entire course of the day, on multiple locations on Earth’s surface, and then plot the results on the so-called flat-Earth map; then they would not consistently point to the position of the Sun that is calculated from its location on such map.
This fact happens because the flat-Earth map is not the correct description of the real Earth.
Polaris is a bright star that is close to the north celestial pole. Currently, Polaris is only 0.74° apart from the north celestial pole and the only star visible to the naked eye that is close to the celestial pole. This is why Polaris is popular as a navigational aid in the northern hemisphere.
Some flat-Earthers think that Polaris is stationary and that it is a ‘special star’ because other stars are in motion around it. They would take that as ‘evidence’ that the Earth is motionless. They are wrong. Polaris is merely a regular star, just like the others.