The idea that, instead of sailing horizontally round the Earth, ships are taken down one side of a globe, then underneath, and are brought up on the other side to get home again, is, except as a mere dream, impossible and absurd! And, since there are neither impossibilities nor absurdities in the simple matter of circumnavigation, it stands without argument, a proof that the Earth is not a globe.

A "Standing Order" exists in the English Houses of Parliament that in the cutting of canals, &c., the datum line employed shall be a "horizontal line, which shall be the same throughout the whole length of the work." Now if the Earth were a globe, this "Order" could not be carried out: but, it is carried out: therefore it is a proof that the Earth is not a globe.
The most commonly accepted explanation of this is that the space agencies of the world are involved in a conspiracy faking space travel and exploration. This likely began during the Cold War's 'Space Race', in which the USSR and USA were obsessed with beating each other into space to the point that each faked their accomplishments in an attempt to keep pace with the other's supposed achievements. Since the end of the Cold War, however, the conspiracy is most likely motivated by greed rather than political gains, and using only some of their funding to continue to fake space travel saves a lot of money to embezzle for themselves.