To most, the fact that sailors have been able to take a trip around the Earth is proof enough that the planet is round. But, believe it or not, the debate surrounding whether the Earth is round or flat still exists. Despite scientific evidence to the contrary, a recent poll found that nearly 2% of people surveyed have never believed that the Earth is round. While this number is still relatively low, 2% is much higher than you might expect.

Are you one of the 2%? Are you trying to convince a flat-Earth-believing friend that they're wrong? Here are four scientifically-backed facts that prove that the Earth is not flat.

No One Has Ever Found the End of the Earth

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Let's take a minute to think about the theory that the Earth is flat. If this is indeed the case, then there are two possibilities.

One — if you keep going, you will eventually find the end of the Earth. But if the end of the Earth did exist, wouldn't we have pictures? Wouldn't it be some hot tourist spot? And what exactly happens at the end of the Earth? Does it fall off into nothingness? Is there this big wall that says, "The End," on it? No one has ever presented any evidence to show where the Earth starts and where it ends.

Which brings us to option two — the Earth doesn't end, it just keeps going and going and, well you get the picture. If the Earth was indeed flat and there was no end, we would constantly be discovering new people, new species, and new countries at the edges of our maps. However, these discoveries don't seem to happen.

The Lunar Eclipse Makes the Earth's Roundness Clear

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Let's start with a recap of astronomy. The Earth has one moon. This moon revolves around the Earth (assuming you believe the Earth is round, but we'll get to that proof in a minute). The Earth revolves around the sun. During a lunar eclipse, the Earth lines up between the moon and the sun. When this happens, the Earth's shadow is cast upon the moon.

If you have ever seen a lunar eclipse, or at least seen pictures of a lunar eclipse, you will see that this shadow is curved. If the Earth were flat, we wouldn't get this rounded shadow. Plus, if the world were indeed flat, we wouldn't see the different phases of the moon. Instead, it'd always be full.

If you're looking for a little more proof from outer space, take a look at the sky, either with your naked eye or a telescope. There are other planets in the solar system, and all of them appear to be round. It doesn't really make sense that the Earth is the only flat planet unless we are trying to debunk the whole idea of the solar system as well.

There's Something Interesting About the Way Ships Sail Away

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When a boat sails away, it seems to sink out of sight. We know that these ships are most definitely not sinking — no one would ever ride a boat if that were the case. The boat appears to sink because of the Earth's curvature. This phenomenon is more evident if you are watching a boat approach the shoreline. These boats look as if they are coming straight up out of the water. If the Earth were flat, why would ships appear to sink and rise from the water instead of just getting bigger as they come closer in to view?

While we're talking about boats, several people have sailed around the world. Some of the first were Ferdinand Magellan's crew in 1519. Their records, and later accounts, should end the discussion about the end of the Earth. You'd think if the Earth was flat, that one of these sailors would have come to the end of it. And if there were no end, they'd have never made it home.

The Higher You Go, the Further You Can See

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If the Earth were flat, you should be able to see the same amount of distance, whether you were standing on the sidewalk, or atop of New York City's highest building (assuming there are no obstacles). But interestingly enough, the higher you get up, the greater the distance you can see. Why? Because the Earth is round. From the lower vantage point, the Earth's curvature will eventually prevent you from seeing any further. When you are further up, you can see above some of this curvature.

Not convinced? If the Earth were flat, you'd be able to see neighboring states, across rivers, and oceans. It's the human eye that can't see that far, you say? Take a look up in the sky. Those airplanes, stars, planets, and clouds, they're much further away than the objects that seem to disappear from sight when looking straight ahead. That's because the curve of the Earth stops us from seeing anything further than about 3.1 miles ahead.