People have believed that the Earth is flat since the beginning of humanity, but the modern Flat Earth hypothesis stemmed from an experiment called the Bedford Level Experiment, conducted in the mid-1800s by a man named Samuel Rowbotham.[1] Rowbowtham, who wrote a book named Earth Not a Globe, started the modern movement by debating scientists publicly and accumulating followers. In the experiment, Rowbowtham attempted to measure the curvature of the earth by observing the curvatures at a local river. He took his results as disproving the theory of a round earth, but future scientists have said that the results he obtained could be accounted for by the parallax effect.[2]
20. The common sense of man tells him - if nothing else told him - that there is an "up" and a "down" in -nature, even as regards the heavens and the earth; but the theory of modern astronomers necessitates the conclusion that there is not: therefore, 'the theory of the astronomers is opposed to common sense - yes, and to inspiration - and this is a common sense proof that the Earth is not a globe
61) If the Earth were actually a big ball 25,000 miles in circumference, the horizon would be noticeably curved even at sea-level, and everything on or approaching the horizon would appear to tilt backwards slightly from your perspective. Distant buildings along the horizon would all look like leaning towers of Piza falling away from the observer. A hot-air balloon taking off then drifting steadily away from you, on a ball-Earth would slowly and constantly appear to lean back more and more the farther away it flew, the bottom of the basket coming gradually into view as the top of the balloon disappears from sight. In reality, however, buildings, balloons, trees, people, anything and everything at right angles to the ground/horizon remains so regardless the distance or height of the observer.
198) Some say the idea of an inter-generational world-wide conspiracy to delude the masses sounds implausible or unrealistic, but these people need only familiarize themselves with the works and writings of Freemasons themselves, for example John Robison who exposed this in his 1798 book, “Proofs of a Conspiracy Against All the Religions and Governments of Europe Carried Out in the Secret Meetings of the Freemasons, Illuminati and Reading Societies.” Supreme Commander of the 33rd degree Albert Pike was quite forth-coming in several letters regarding the Masons ultimate goal of world domination, and in the Zionist “Protocols of the Learned Elders of Zion” the exact plan by which this would be and has been carried out is completely disclosed.
69) The New York City skyline is clearly visible from Harriman State Park’s Bear Mountain 60 miles away. If Earth were a ball 25,000 miles in circumference, viewing from Bear Mountain’s 1,283 foot summit, the Pythagorean Theorem determining distance to the horizon being 1.23 times the square root of the height in feet, the NYC skyline should be invisible behind 170 feet of curved Earth.

53) At places of comparable latitude North and South, the Sun behaves very differently than it would on a spinning ball Earth but precisely how it should on a flat Earth. For example, the longest summer days North of the equator are much longer than those South of the equator, and the shortest winter days North of the equator are much shorter than the shortest South of the equator. This is inexplicable on a uniformly spinning, wobbling ball Earth but fits exactly on the flat model with the Sun traveling circles over and around the Earth from Tropic to Tropic.

Besides the above difficulties or incompatibilities, many cases are on record of the sun and moon being eclipsed when both were above the horizon. The sun, the earth, and the moon, not in a straight line, but the earth below the sun and moon–out of the reach or direction of both–and yet a lunar eclipse has occurred! Is it possible that a “shadow” of the earth could be thrown upon the moon, when sun, earth, and moon, were not in the same line? The difficulty has been met by assuming the influence of refraction, as in the following quotations:–

Astronomers tell us that, in consequence of the Earth's "rotundity," the perpendicular walls of buildings are, nowhere, parallel, and that even the walls of houses on opposite sides of a street are not! But, since all observation fails to find any evidence of this want of parallelism which theory demands, the idea must be renounced as being absurd and in opposition to all well-known facts. This is a proof that the Earth is not a globe.