Flat earth

 Here's how we can prove the earth is round. 

The first way:

We get two big wooden poles. We stick one in the ocean floor, at the coast.

We get another, and stick it into the ocean floor 20 km away. Make sure both poles are the same height above sea level. 

Drill a hole in the one at the coast. Make sure the hole points towards the other pole. 

Shine a strong laser through the hole. 

Contact a person viewing the other pole. If the laser hit the other pole at where the hole should be, we can see that the eart is indeed flat. Otherwise, if it hit above the pole or above where the hole should be, the earth is round. This drawing should show it.

This experiment has actually been done, by a group of flat earthers. 

They ended up disproving themselves. They repeated it several times. Every time it said that the earth was round.

The second way.

Look out of your front porch. Do you see the Eiffel tower? The shard? The skytower? The empire state building? Mount everest?

No? Thats because they are all hidden behind the curviture of the earth. If the earth was flat, with some good telescope eqipment, we could all see things like this. 

The third way. 

Go for a walk. A very long one. A very, very long one. If the earth was flat, when you're at the middle of the earth, everything seems normal. But as you get further to the edge, it's like walking up a skateboard ramp. Everything feels like its getting steeper, but it's just the gravity trying to pull you back into the centre.

Here are some screenshots of a pysics simulation game i used to prove this

Flat earth:

The black dots are a gravity pulling surface.

Round earth:

Notice how none of the entities are inbalanced in the round earth one, whereas in the one where the ground was flat, the ones tothe far left and right were about to fall, while the middleone noticed no difference.

Obviously, we don't feel like we're on a sloped surface if we are far from the North pole, so we can see from what we've observed here that the earth probably isn't flat.