Some people seriously think that the Earth is flat. No one can save them. But the always thinking Vsauce explores the possibility and tries to figure out if the Earth actually could be flat in his latest video and details some rather interesting things about a flat Earth: that life would suck on it and that we couldn't fall off of it.
The way gravity works on a flat Earth is that the areas closer to the edge (and farther away from the centre) would be super annoying to live in. Moving closer to the edge would be like running up a steep hill. And once you get to the edge, you would have to worry more about tumbling back down to the centre because of the feeling of steepness.
And if you wanted to "fall off" the edge? You couldn't. After clearing the edge, you'd just reach a flat plane and stay on Earth. Gravity!