Those who would have to refute the sphericity of the earth are actually the flat earthers, since the current evidence is that the earth is round. People have already explored and measured the planet in a thousand ways, there are daily plane flights between all points on the map and the distances are known. There are about 5,000 satellites orbiting the earth taking photos every day that show it is round, but many flat earthers claim that all of these photos are fake. In other words, this discussion ceases to be a scientific question if there is no trust in the evidence suggested by others. I think it’s like we’re all looking at an orange and the Flat Earthers say what you’re seeing isn’t believable and go on to protest that the orange is actually flat.
It has been known that the earth is spherical for more than 2,000 years, long before satellites and the first orbit around the world. There are many mathematical proofs that the Greeks calculated using their knowledge of geometry and navigation. However, to answer your question, I was looking for simple arguments that are easily testable in everyday life and that wouldn’t fit on a flat earth. There are many, but I will give you five:
First: We all know that the higher we climb, the further we can see. If the earth were flat, this would not be the case. On a flat earth, you would have to see to the ends of the earth in any place without relief, such as in the sea. From Galicia you should be able to see America with a sufficiently powerful telescope, but this is not possible due to the curvature of the earth’s surface. As has been known since ancient times, lighthouses are placed on top of a tower so that they can be seen from a greater distance. And conversely, when you are in a harbor and see a ship coming in, you see the tallest part of the ship appearing first, the mast; then the sails and finally the hull.
Second: Sunrise and sunset times are different in every part of the world. If you think about it, this wouldn’t be the case on a flat earth either. Additionally, and related to the previous point, the time the sun sets in any location also depends on the height from which you are looking at the horizon. Muslims have studied this very well. Sunset time charts are available online for almost every location in the world to know exactly when to break your fast during Ramadan. If you are looking for these tables for Dubai, you warn right from the start that in the Burj Khalifa, the tallest building in the world at 828 meters, the sun sets three minutes later on the top floor than on the bottom floor .briefly. That wouldn’t happen on a flat planet either.
Third: the swamp water. On a flat, non-rotating earth, the water should fall uniformly everywhere toward the center of the sink, but it doesn’t. When you empty a sink (better if it’s a big round one), the Coriolis effect creates a whirlpool that can only be explained by the rotation of the earth. Flat earthers might say that a flat earth could also rotate on its own axis and that this could create a whirlpool like the one we see. The problem is that the vortices of the pools rotate in opposite directions in one hemisphere and in the other (also the storms and anticyclones). For that, on a flat earth, we would need two oppositely rotating poles, each affecting half of the earth.
Fourth: the movement of the night sky. This argument is similar to the previous one. In the northern hemisphere, the entire night sky revolves counterclockwise around the Pole Star, in the southern hemisphere everything revolves in the opposite direction around the Southern Cross. For this to be the case on a flat earth, there would need to be two celestial spheres, one for each hemisphere, rotating in opposite directions.
Fifth: The duration of long journeys is different if you travel east or west. This fact has no explanation on a flat earth. I’ll give two very different examples, but both have to do with a spherical earth rotating on itself. A fairly common example is that the flight from Madrid to New York is longer than that from New York to Madrid because the return flight is assisted by the eastward-flowing jet stream originating from the Earth’s rotation. The other argument, a little more distant but very strange, is the paradox of the circumnavigator. This paradox is that going around the world does not take the same amount of time to go west as it does to go east. In this case, no matter how long it takes you to go all the way, you gain a day if you travel east, like Phileas Fogg in Jules Verne’s novel, while you lose it if you travel west, like Elcano and his Crew the end of the first circumnavigation. This paradox is inexplicable on a flat earth, where the sun rises at the same time for everyone and everyone has the same calendar date.
Maria Belen Munoz Garcia She is a PhD geologist, professor and researcher at the Faculty of Geological Sciences at the Complutense University of Madrid.
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