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The myth of the flat Earth is the modern misconception that the prevailing cosmological view during the Middle Ages in Europe was that the Earth is flat, instead of spherical.^[1][2]
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During the early Middle Ages, virtually all scholars maintained the spherical viewpoint first expressed by the Ancient Greeks. From at least the 14th century, belief in a flat Earth among the educated was almost nonexistent, despite fanciful depictions in art, such as the exterior of Hieronymus Bosch's famous triptych The Garden of Earthly Delights, in which a disc-shaped Earth is shown floating inside a transparent sphere.^[3]
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According to Stephen Jay Gould, "there never was a period of 'flat Earth darkness' among scholars (regardless of how the public at large may have conceptualized our planet both then and now). Greek knowledge of sphericity never faded, and all major medieval scholars accepted the Earth's roundness as an established fact of cosmology."^[4] Historians of science David Lindberg and Ronald Numbers point out that "there was scarcely a Christian scholar of the Middle Ages who did not acknowledge [Earth's] sphericity and even know its approximate circuмference".^[5]
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Historian Jeffrey Burton Russell says the flat-Earth error flourished most between 1870 and 1920, and had to do with the ideological setting created by struggles over biological evolution. Russell claims "with extraordinary few exceptions no educated person in the history of Western Civilization from the third century B.C. onward believed that the Earth was flat", and ascribes popularization of the flat-Earth myth to histories by John William Draper, Andrew Dickson White, and Washington Irving.^[6][7][2]
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History
In Inventing the Flat Earth: Columbus and Modern Historians, Jeffrey Russell describes the Flat Earth theory as a fable used to impugn pre-modern civilization and creationism.^[6][2]
James Hannam wrote:Early modern period
French dramatist Cyrano de Bergerac in chapter 5 of his Comical History of the States and Empires of the Moon (published 2 years posthumously in 1657) quotes St. Augustine as saying "that in his day and age the Earth was as flat as a stove lid and that it floated on water like half of a sliced orange."^[9] Robert Burton, in his The Anatomy of Melancholy^[10]wrote:Thus, there is evidence that accusations of Flatearthism, though somewhat whimsical (Burton ends his digression with a legitimate quotation of St. Augustine: "Better doubt of things concealed, than to contend about uncertainties, where Abraham's bosom is, and hell fire"^[10]) were used to discredit opposing authorities several centuries before the 19th. Another early mention in literature is Ludvig Holberg's comedy Erasmus Montanus (1723). Erasmus Montanus meets considerable opposition when he claims the Earth is round, since all the peasants hold it to be flat. He is not allowed to marry his fiancée until he cries "The earth is flat as a pancake". In Thomas Jefferson's book Notes on the State of Virginia (1784), framed as answers to a series of questions (queries), Jefferson uses the "Query" regarding religion to attack the idea of state-sponsored official religions. In the chapter, Jefferson relates a series of official erroneous beliefs about nature forced upon people by authority. One of these is the episode of Galileo's struggles with authority, which Jefferson erroneously frames in terms of the shape of the globe:^[11]19th century
The 19th century was a period in which the perception of an antagonism between religion and science was especially strong. The disputes surrounding the Darwinian revolutioncontributed to the birth of the conflict thesis,^[4] a view of history according to which any interaction between religion and science would almost inevitably lead to open hostility, with religion usually taking the part of the aggressor against new scientific ideas.^[12]
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Irving's biography of Columbus
In 1828, Washington Irving's highly romanticised biography, A History of the Life and Voyages of Christopher Columbus,^[13] was published and mistaken by many for a scholarly work.^[14] In Book II, Chapter IV of this biography, Irving gave a largely fictional account of the meetings of a commission established by the Spanish sovereigns to examine Columbus's proposals. One of his more fanciful embellishments was a highly unlikely tale that the more ignorant and bigoted members on the commission had raised scriptural objections to Columbus's assertions that the Earth was spherical.^[15]
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The issue in the 1490s was not the shape of the Earth, but its size, and the position of the east coast of Asia, as Irving in fact points out. Historical estimates from Ptolemy onwards placed the coast of Asia about 180° east of the Canary Islands.^[16] Columbus adopted an earlier (and rejected) distance of 225°, added 28° (based on Marco Polo's travels), and then placed Japan another 30° further east. Starting from Cape St. Vincent in Portugal, Columbus made Eurasia stretch 283° to the east, leaving the Atlantic as only 77° wide. Since he planned to leave from the Canaries (9° further west), his trip to Japan would only have to cover 68° of longitude.^[17][18]
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Columbus mistakenly assumed that the mile referred to in the Arabic estimate of 56⅔ miles for the size of a degree was the same as the actually much shorter Italian mile of 1,480 metres (0.92 mi). His estimate for the size of the degree and for the circuмference of the Earth was therefore about 25% too small.^[19] The combined effect of these mistakes was that Columbus estimated the distance to Japan to be only about 5,000 km (or only to the eastern edge of the Caribbean) while the true figure is about 20,000 km. The Spanish scholars may not have known the exact distance to the east coast of Asia, but they believed that it was significantly further than Columbus's projection; and this was the basis of the criticism in Spain and Portugal, whether academic or amongst mariners, of the proposed voyage.
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The disputed point was not the shape of the Earth, nor the idea that going west would eventually lead to Japan and China, but the ability of European ships to sail that far across open seas. The small ships of the day (Columbus's three ships varied between 20.5 and 23.5 m – or 67 to 77 feet – in length and carried about 90 men) simply could not carry enough food and water to reach Japan. The ships barely reached the eastern Caribbean islands. Already the crews were mutinous, not because of some fear of "sailing off the edge", but because they were running out of food and water with no chance of any new supplies within sailing distance. They were on the edge of starvation.^[20] What saved Columbus was the unknown existence of the Americas precisely at the point he thought he would reach Japan. His ability to resupply with food and water from the Caribbean islands allowed him to return safely to Europe. Otherwise his crews would have died, and the ships foundered.
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Advocates for science
In 1834, a few years after the publication of Irving's book, Jean Antoine Letronne, a French academic of strong antireligious ideas, misrepresented the church fathers and their medieval successors as believing in a flat earth in his On the Cosmographical Ideas of the Church Fathers.^[2][21] Then in 1837, the English philosopher of science William Whewell, in his History of the Inductive Sciences, identified Lactantius, author of Institutiones Divinae (c. 310), and Cosmas Indicopleustes, author of Christian Topography (c. 548 ), as evidence of a medieval belief in a Flat Earth. Lactantius had been ridiculed much earlier by Copernicus in De revolutionibus of 1543 as someone who "Speaks quite childishly about the Earth's shape, when he mocks those who declared that the Earth has the form of a globe".
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Other historians quickly followed Whewell, although they could identify few other examples.^[22] The American chemist John William Draper wrote a History of the Conflict between Religion and Science (1874), employing the claim that the early Church fathers thought the Earth was flat as evidence of the hostility of the Church to the advancement of science.^[23]The story of widespread religious belief in the flat Earth was repeated by Andrew Dickson White in his 1876 The Warfare of Science^[24] and elaborated twenty years later in his two-volume History of the Warfare of Science with Theology in Christendom, which exaggerated the number and significance of medieval flat Earthers to support White's model of warfare between dogmatic theology and scientific progress.^[25] As Draper and White's metaphor of ongoing warfare between the scientific progress of the Enlightenment and the religious obscurantism of the "Dark Ages" became widely accepted, it spread the idea of medieval belief in the flat Earth.^[26]
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The widely circulated engraving of a man poking his head through the firmament surrounding the Earth to view the Empyrean, executed in the style of the 16th century, was published in Camille Flammarion's L'Atmosphère: Météorologie Populaire (Paris, 1888, p. 163).^[27] The engraving illustrates the statement in the text that a medieval missionary claimed that "he reached the horizon where the Earth and the heavens met". In its original form, the engraving included a decorative border that places it in the 19th century. In later publications, some of which claimed that the engraving dates to the 16th century, the border was removed.
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20th century and onward

Front Cover of Daniel Boorstin's The Discoverers (1983), bearing a copy of the Flammarion engraving

Since the early 20th century, a number of books and articles have docuмented the flat earth error as one of a number of widespread misconceptions in popular views of the Middle Ages. Both E. M. W. Tillyard's book The Elizabethan World Picture and C. S. Lewis' The Discarded Image are devoted to a broad survey of how the universe was viewed in Renaissance and medieval times, and both extensively discuss how the educated classes knew the world was round. Lewis draws attention to the fact that in Dante's The Divine Comedy about an epic voyage through hell, purgatory, and heaven, the earth is spherical with gravity being towards the center of the earth. As the Devil is frozen in a block of ice in the center of the earth, Dante and Virgil climb down the Devil's torso, but up from the Devil's waist to his feet, as his waist is at the center of the earth.
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Jeffrey Burton Russell rebutted the prevalence of belief in the flat Earth in a monograph^[6] and two papers.^[7][2] Louise Bishop states that virtually every thinker and writer of the 1000-year medieval period affirmed the spherical shape of the Earth.^[28]
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Although the misconception was frequently refuted in historical scholarship since at least 1920, it persisted in popular culture and in some school textbooks into the 21st century. An American schoolbook by Emma Miller Bolenius published in 1919 has this introduction to the suggested reading for Columbus Day (12 October):Previous editions of Thomas Bailey's The American Pageant stated that "The superstitious sailors [of Columbus's crew] ... grew increasingly mutinous ... because they were fearful of sailing over the edge of the world"; however, no such historical account is known.^[30]
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A 2009 survey of schoolbooks from Austria and Germany showed that the Flat Earth myth became dominant in the second half of the 20th century and persists in most historical textbooks for German and Austrian schools.^[31]
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As recently as 1983 Daniel Boorstin published a historical survey, The Discoverers, which presented the Flammarion engraving on its cover and proclaimed that "from AD 300 to at least 1300 ... Christian faith and dogma suppressed the useful image of the world that had been so ... scrupulously drawn by ancient geographers."^[32] Boorstin dedicated a chapter to the flat earth, in which he portrayed Cosmas Indicopleustes as the founder of Christian geography.^[33] The flat earth model has often been incorrectly supposed to be church doctrine by those who wish to portray the Catholic Church as being anti-progress or hostile to scientific inquiry. This narrative has been repeated even in academic circles, such as in April 2016, when Boston College theology professor and ex-priest Thomas Groome erroneously stated that "the Catholic Church never said the earth is round, but just stopped saying it was flat."^[34]
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The 1937 popular song They All Laughed contains the couplet "They all laughed at Christopher Columbus/When he said the world was round". In the Warner Bros. Merrie Melodiescartoon Hare We Go (1951) Christopher Columbus and Ferdinand the Catholic quarrel about the shape of the Earth; the king states the Earth is flat. In Walt Disney's 1963 animation The Sword in the Stone, wizard Merlin (who has traveled into the future) explains to a young Arthur that "man will discover in centuries to come" that the Earth is round, and rotates.
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This is like posting the main stream media news for consumption as if it were true.  There is so much wrong with this article historically and factually, I haven't the time to fully tear it apart. That this piece dares to characterize Columbus' crew as superstitious and on the verge of mutiny is utterly false. Many of his men were self-sacrificing Catholics who prayed continuously to Our Lady throughout their journeys. And really, who cares what Louise Bishop or Jeffrey Burton Russel thinks? Rest assured, the modern world does not want anyone to know what the truth is, and this reflects that perfectly.

I've looked at the results of the Hungarian (Lake Balaton laser) experiment and it appears to be rather convincing ... unless it was completely hoaxed.

Advocates for science
In 1834, a few years after the publication of Irving's book, Jean Antoine Letronne, a French academic of strong antireligious ideas, misrepresented the church fathers and their medieval successors as believing in a flat earth in his On the Cosmographical Ideas of the Church Fathers.^[2][21] Then in 1837, the English philosopher of science William Whewell, in his History of the Inductive Sciences, identified Lactantius, author of Institutiones Divinae (c. 310), and Cosmas Indicopleustes, author of Christian Topography (c. 548 ), as evidence of a medieval belief in a Flat Earth. Lactantius had been ridiculed much earlier by Copernicus in De revolutionibus of 1543 as someone who "Speaks quite childishly about the Earth's shape, when he mocks those who declared that the Earth has the form of a globe".

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You did not read far enough in the metabunk forum. A few posts accused them of not having a level laser. BTW a few dozen meters with one centimeter's error (or even one millimeter!) would not ensure a level instrument for projection across several kilometers. They would have needed to establish less than one millimeter variation over 300 meters, by checking in opposite directions, before they would have reasonable assurance of an adequately level laser. Then their accuracy would have been within 3 millimeters in one kilometer or 6 in two or 9 millimeters in three kilometers.
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Be that as it may, the ultimate accusation on the metabunk site is in regards to the distortion that occurs over such surfaces as bodies of water, especially when there is an inversion layer (warm air on top of cold air). The cold air is commonly found lying over the surface of water, and a warm layer of air is not infrequently found above the cold layer. They explain that differences in air density causes the bending of light, just as it does when a laser is pointed into the surface of water at an angle. Viewed from the side, one can see that the laser striking the surface of water at a low angle (like a flashlight held in a boy's hand pointed out over a lake) when it penetrates the surface of the water the laser bends downward since the water is of a greater density than the air. If you have ever tried poking a long, straight stick or fiberglass pole into the water (like a swimming pool cleaning net) you see the pole appear to bend upwards from above the water looking down the length of the pole -- but the pole is not bending, the light is doing the bending. Or, if you attempt to shoot a fish with a bow and arrow, you have to aim much LOWER than the fish for your arrow to hit the target since the arrow will continue to fly through the water in a straight line but from the position of the bow the arrow will appear to bend upward in its flight under water, since the light coming off the fish bends when it hits the water's surface at an angle.
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Consequently, over the surface of water, where this condition is very likely to occur, objects that are far away over the water's surface and very low down and close to it, might appear to be higher up than they really are, due to the higher density of air that's near the surface of water, in part due to humidity increase and in part due to lower temperature. They post several photographs that demonstrate this phenomenon, which they identify as "looming." Additionally, tall objects with identifiable features at various heights can be seen to appear compressed when viewed through a telescope, such that the parts of the object close to the water's surface will appear shorter in height than they do when photographed at close range without the telescope. For example, the rungs of a standing ladder which are equally spaced will appear closer together near the bottom of the ladder, and gradually further apart as one looks higher up on the ladder, until at some point, perhaps 30 feet high, the rungs all appear to be equally spaced. This gradual change is comparable to the logarithmic scale of a slide rule, but it only applies to the lowest parts of the image in question. At about one or two miles, for example, it applies to the lower 20 or 30 feet. Objects close to the water's surface appear distorted and compressed vertically.
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Extending this principle to the whole picture of what is being viewed, it becomes clear that since the light traveling close to the surface of the water but still through air, can be bending downward toward the water, it is possible that this bending can be close to, equal to or greater than the curvature of the surface of the water. They provide figures on the site for what amount of bending light would be needed to equal the earth's curvature.
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Not to say this is conclusive, but only that the three different experiments shown (only one of which is the Balaton lake video - there are two more they refer to as well) were conducted by well-meaning people but they used inadequate methods. They only made one observation. They only did it at one time. They only did it over the same surface of water.
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They should have done several observations, on different days, at different times of year and different temperatures and humidity; they should have done some laser shots over dry land and in opposite directions, to demonstrate and discover what the consequence of having a laser slightly out of level would be. They are also accused of having a target on the boat that has a diffusely reflective surface such that the place the laser hits the panel on the boat is clearly seen from shore where the laser is coming from (in a way like a traffic sign on the highway has diffusely reflective paint which shines your headlights right back at you from any direction whatsoever). They are accused of then perhaps moving the laser down to meet the boat's target so they could get a favorable reading. I'm not making this accusation, I'm just reporting what the metabunk thread says.
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My question was, since they were riding in a small boat on the surface of water with a laser beam shining on their white board, why was the laser beam so steady on the board when you know that small boats on the water are bobbing up and down, right and left, fore and aft CONSTANTLY, and this cannot be controlled -- EVER. If it were real, that laser dot would have been all over the place, never standing still. But they showed it standing still almost all the time, with very little movement, if any.
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Also, on the metabunk site they refer to a well-known laser in Greenwich, England, which is a beacon for scientific use, and it shines out into the air above the land for all to see. It is observed some kilometers away where it comes close to striking a tall building, where they say it is actually two inches away from the building, nonetheless, there is a visible glow all around the beam which makes a splash of ambient light spilling across the perpendicular side of the tall building. The center of this glow is quite bright and would appear to be the laser itself, but perhaps the resolution of the image is wanting. In any case, there was no similar ambient glow in the Balaton boat's white panel or screen. This makes me wonder why the laser appeared therefore to be much closer to the boat than what they said it was. The laser in England is said to be shining through some dust clouds, the particles of which scatter the laser light by the time it reaches the tall building. But there are particles of moisture lying near the surface of water, so wouldn't that have the same effect at Balaton?
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Kiwi,

Just to clarify you said that, "The biggest problem we have therefore is people who are so dogmatically insistent on the globe, (or secretly so like even steven), when it has clearly been condemned."

Isn't it conflating shape with heliocentrism?  Wasn't Galileo condemned because helio was strongly suspected of heresy?

Was the globe specifically condemned?