JROA: I'd like you to perform a simple exercise for me, you'll need a powerful laser pointer and a friend who lives a couple hundred kilometers away. Lasers fire a beam in a straight line minus some very slight curvature due to Earth's gravity, I want you to place the laser pointer 2 meters off the ground, level with the Earth, and turn it on, pointed in a direction free of obstructions in the line of sight of the laser pointer.
Have your friend a couple towns over look up, make sure he is in line with the laser's beam, and have him measure its height above the ground. Also make sure you're both at the same height above sea level.
Now, I'm going to give you a moment to get yourself seated before I give you some fair warning, what you will see is going to completely blow your mind. The measurement your friend will return is going to be significantly higher than 2 meters! But you're both at the same height above sea level! How can this be, if the Earth is flat?!?
Simple answer is that it's simply not. If you send a camera up into space (Which you can do with a few thousand dollars nowadays), you can even take a picture of the Earth as it appears; a sphere.
Now, here's a slightly less practical experiment that you can try if you want to corroborate the ludicrous findings in the previous one. I want you to board an airplane heading East, make sure you're going to the same latitude as you're leaving from. Now, when you land there, take another plane heading East, again, making sure that you're landing at the same latitude. Do this until you find that your next plane ticket is for the place you took off from. But wait, how is this so? The Earth is flat, you can't circumnavigate it without coming to a sharp corner, and if you watched carefully, it was just smooth as far as the eye can see! Now, you may be thinking to yourself "Well IO just traveled around the rim of the disc!". Just to make sure, do it again, but with planes only going North, or as close as you can get to North. You'll notice the same effect! But that's impossible, no edges?!?
Now, I bet you'll assume that government spy satellites have been beaming false memories into your brain to make you think you didn't see any edges, but let's be honest here, the government doesn't have mind-altering satellites yet, come on, that's silly! Those go up in 2016.