OP, if you want proof the Earth is not flat, you can go to a harbor where there are lots of ships. From the ground, watch the ship sail off, and eventually you will see that it will appear to sink, and will not "fade off". You will see the bottom of the ship disappear, and eventually will see the top of the flag disappear.

After the ship has appeared to disappear, move to higher ground near where you are -- go to the top level of a building and look towards the ship. You will be able to see more of the ship than you could when you were on the ground.