[Earth ]Earth Observatory/NASA Humanity has known the Earth to be round for a few millennia and I’ve been meaning to show some of the methods of how we figured out the world is not flat. I’ve had a few ideas on how to do that, but I got an interesting incentive, when Phil Plait (The Bad Astronomer) wrote about a recently published BBC article about “The Flat Earth” society. Phil claims it’s ridiculous to even bother rebutting the flat earth society – and I tend to agree. But the history of our species’ intellectual pursuit is important and interesting, and it’s very much well worth writing about. You don’t need to denounce all science and knowledge and believe in a kooky conspiracy theory to enjoy some historical factoids about humanity’s quest for space. On we go to the top 10 ways to know the Earth is unequivocally, absolutely, positively, 100% not flat: 1. THE MOON Sagredo/Wikimedia Commons Now that humanity knows quite positively that the Moon is not a piece of cheese or a playful god, the phenomena that accompany it (from its monthly cycles to lunar eclipses) are well-explained. It was quite a mystery to the ancient Greeks, though, and in their quest for knowledge, they came up with a few insightful observations that helped humanity figure out the shape of our planet. Aristotle (who made quite a lot of observations about the spherical nature of the Earth) noticed that during lunar eclipses (when the Earth’s orbit places it directly between the Sun and the Moon, creating a shadow in the process), the shadow on the Moon’s surface is round. This shadow is the Earth’s, and it’s a great clue on the spherical shape of the Earth. Since the earth is rotating (see the “Foucault Pendulum” experiment for a definite proof, if you are doubtful), the consistent oval-shadow it produces in each and every lunar eclipse proves that the earth is not only round but spherical – absolutely, utterly, beyond a shadow of a doubt not flat. 2. SHIPS AND THE HORIZON Reuters/Mike Blake If you’ve been next to a port lately, or just strolled down a beach and stared off vacantly into the horizon, you might have, perhaps, noticed a very interesting phenomenon: approaching ships do not just “appear” out of the horizon (like they should have if the world was flat), but rather emerge from beneath the sea. But – you say – ships do not submerge and rise up again as they approach our view (except in “Pirates of the Caribbean”, but we are hereby assuming that was a fictitious movie). The reason ships appear as if they “emerge from the waves” is because the world is not flat: it’s round. Imagine an ant walking along the surface of an orange, into your field of view. If you look at the orange “head on”, you will see the ant’s body slowly rising up from the “horizon”, because of the curvature of the Orange. If you would do that experiment with a long road, the effect would have changed: The ant would have slowly ‘materialized’ into view, depending on how sharp your vision is. 3. VARYING STAR CONSTELLATIONS Moriel Schottlender This observation was originally made by Aristotle (384-322 BCE), who declared the Earth was round judging from the different constellations one sees while moving away from the equator. After returning from a trip to Egypt, Aristotle noted that “_there are stars seen in Egypt and […] Cyprus which are not seen in the northerly regions._” This phenomenon can only be explained with a round surface, and Aristotle continued and claimed that the sphere of the Earth is “_of no great size, for otherwise the effect of so slight a change of place would not be quickly apparent._” (De caelo, 298a2-10) The farther you go from the equator, the farther the ‘known’ constellations go towards the horizon, and are replaced by different stars. This would not have happened if the world was flat. SEE THE REST OF THE STORY AT BUSINESS INSIDER
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