Many FET enthusiasts state that photographic evidence of a round Earth has been doctored, and there exists a global conspiracy preventing people from believing that the Earth is flat. My question here: What are the advantages for the parties involved, and what are their motivations to do such a thing. (This is more speculation, but I'd like to hear it nonetheless)
The more out-there FEers usually rely on religious reasons: people trying to hide God's word, or imply it's false etc, claiming some holy text says the Earth is flat, and so some nebulous cabal of satanists and such try to convince everyone it's round.
The less bizarre FEers claim that there is no intentional FE/RE conspiracy, there's only a space travel conspiracy. Space agencies couldn't get to space, but for political and financial gain they pretended otherwise, and as they expected to see a RE, that's what their falsified pictures showed.
Have any scientific papers been written on FET?
I remember seeing one done in theory, on whether an infinite planar Earth would be able to exert gravity, but generally there isn't much on actual FET. To be fair though, that's understandable: what academic publication would you expect to advocate FET?
What is the most convincing scientific experiment I can carry out to support a Flat Earth hypothesis? Make sure it follows the scientific method, i.e. it makes a hypothesis, carries out an experiment, collects data, and draws conclusions from results.
The Bedford Level Experiment is the most often quoted. The idea is that someone looked in a straight line along a canal, and saw no curvature when it would be expected: however there's little consistency in the results. Some people doing the experiment saw curvature, some did not. Even so, a lot of FEers appeal to this.
What is the most convincing scientific argument that disproves a round Earth hypothesis?
Most often they argue that there is no curvature, or that gravity cannot exist.