I'm 14 and I live in Newfoundland, Canada. (We even have a commercial that claims that The Flat Earth Society says we are one of the four corners of the world) This is an excerpt from Stephen Hawking's A Brief History of Time, please don't be too quick to dismiss!
Although as late as the time of Christopher Columbus it was common to find people who thought the earth was flat (and you can even find a few such people today), we can trace the roots of modern astronomy back to the ancient Greeks. Around 340 B.C, the Greek philosopher Aristotle wrote a book called On the Heavens. In that book, Aristotle made good arguments for believing that the earth was a sphere rather than flat like a plate.
One argument was based on eclipses of the moon. Aristotle ralized that these eclipses were caused by the earth coming between the sun and the moon. When that happened, the earth would cast it's shadow on the moon, causing an eclipse. Aristotle noticed that the Earths shadow is always round. This is what you would expect if the earth was a sphere, but not if it was a flat disk. If the earth were a flat disk, its shadow would elongated-in the shape of an ellipse.
The Greeks had another argument for the Earth being round. If the earth were flat, you would expect a ship approaching from the horizon to appear first as a tiny featureless dot. Then, as it sailed closer, you would graduall be able to make out more detail, such as its sails and hull. But that is not what happens. When a ship appears on the horizon, the first things you see are the ship's sails. Only later do you see its hull. The fact that the ship's masts, rising high above the hull, are the first part of the ship to poke up over the horizon is evidence that the earth is a sphere.
Thus I prove to you that the Earth isn't flat. Go Try This Experiment Yourselves!