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All technology is Flat Earth technology.

Not hardly. Nothing that exists and is used today relies on the earth being flat. I can tell you something that only works if the earth is a spinning sphere though. Have you heard of a Foucault pendulum? It was invented in the 1800 and you could build one yourself to test out the spin of the earth if you wanted.

https://en.wikipedia.org/wiki/Foucault_pendulum