Just a thought experiment, let’s say the earth is flat, looks like many professionals would know, including

  • Pilots/ATC/sea captain

  • Land surveyor and civil engineers

  • Astronomers and Geologists, at least the one dealing with experimental data

  • Militaries, at least radar operator and artillery

Just these categories are already a lot of persons, I assume I miss a lot of others. So how many person does it make in total ? 10 % of the population ?