You actually can tell if earth is curved with compass, automobile, stick, ruler, and maybe a clock. And math, of course. You need a little bit of trigonometry

You actually can tell if earth is curved with compass, automobile, stick, ruler, and maybe a clock. And math, of course. You need a little bit of trigonometry to do that. There is nothing dangerous telling people they can verify things themselves. That is how next generation of scientists is born. It is dangerous to tell it is dangerous.