1) Go to the ocean, bring a pair of binoculars 2) Watch a ship sailing away 3) The hull will disappear before the mast 1) Watch the stars at night from North America or Europe - recognize the "big dipper" 2) Fly to somewhere in the Southern Hemisphere 3) Wow there's no more "big dipper", but I can see the "southern cross"? How's that work? Newsflash, flat earthers are useful idiots and trolls.