Hello all,
I am a sea captain and I have circumnavigated. I am a master navigator. If the earth was a flat plane and not a globe, my navigation tools would not work, the math would not compute and I would be incapable of reaching my destination.
I have looked into your wiki and apart from some stuff about compasses, you do not address this flagrant flaw in your reasoning. My claim here is that you can prove to yourself that the Earth is round by learning to navigate on it. Navigating at sea and staying safe requires precision. Math and geometry don't lie. I have yet to meet a sailor or a navigator who believes the Earth is flat.
Please let me elaborate with a few examples:
Celestial navigation is about measuring angles from stars and planets in the sky to the horizon and inferring from those angles a triangulation of your position. The math is complicated because it needs to take into account the roundness of the planet, using spherical trigonometry. If Earth was flat, the math would be much simpler. Not only the math would be wrong if you used spherical trigonometry to navigate a flat earth and you would not know where you are, but frankly what kind of masochist would do spherical trigonometry at sea on a rocking boat if he didn't absolutely have to? Celestial navigation disproves flat earth. If you do not believe me, just learn celestial navigation and use it, you'll find out for yourself. If you assume a round earth, it works, if you assume a flat earth, it doesn't.
Stars used for celestial navigation are distinctly different in the northern and southern hemisphere in a way that is consistent with a round earth. You'd have to do some serious mental gymnastics to make it coherent with a flat earth model.
Gps is the modern equivalent to celestial navigation, it operates on roughly the same principles only using satellites instead of stars, radio waves and accurate time keeping to measure distances and communicate the signal and electronic means to do the triangulation instantly without having to do the math. The principle of GPS could work on a flat earth and we wouldn't know since we are not doing the math ourselves, but the thing with GPS is that it only works in line of sight. You do not get signal from a GPS satellite that is below the horizon. To work everywhere, it needs a minimum of about 24 satellites, otherwise there are areas of the globe that are not covered. On a flat earth, 3 or 4 satellites would be enough as you would have line of sight to them anywhere on the map.
Navigators monitor closely the distance they cover and the speed they go, using various means, including mechanical ones that cannot possibly be biased by a conspiracy as a GPS signal could be for example. Sometimes, using the navigating technique known as dead reckoning, we use only our speed to measure how far we've gone. As a result of personally monitoring distances all over the planet, I can say with confidence that distances around the globe are consistent with a round earth. For example the distance between Africa and South America at 25 south latitude is roughly 3200nm while the distance at 25 North latitude between Africa and the Bahamas is also roughly 3200nm, as expected with a round earth and from my sea charts. Under a flat earth model, the distances in the southern ocean would be very much bigger than in the north and all my charts would be wrong. That is simply not the case. Assuming similar conditions, it takes about the same amount of time to sail across the north Atlantic than it does to sail across the south.
As a matter of fact, because the southern ocean is open all the way round, this is the route for solo non stop round the world sailing races. The current sailing record is just over 42 days (amazing, really...), sailing at an average of 27.2 knots over 27,859.7 nautical miles. This is consistent with a round Earth, not with a flat Earth. There is no way a boat doing a max speed of about 35 knots could go around flat earth non stop in 42 days. Do the math yourself using whatever distances your flat earth model say the southern ocean should be. And keep in mind these are closely monitored races with high stakes in glory and fortune for the winners, followed by millions on TV. No cheating possible.
So, to recap, if you are passionate about truth and yet for some reason believe the earth is flat, I encourage you to learn celestial navigation and then to crew on a yacht and cross the Atlantic once in the north and once in the south. The trip should take about one month each, so you can do it on a holiday, and many private yachts do it regularly, taking inexperienced crew along. It is a very nice adventure in any case and the costs are usually very reasonable so it is accessible to most people. You will have a captain keeping you safe but you will also be able to do your own navigating and take your own measurements. And I guarantee you you will then be able to see for yourself that the concept of a flat earth is simply nonsense. As a sailor, you will be forced to accept the fact that Earth is round.