00:00How do we know that the Earth is round?
00:04One of the most famous images of Earth is called the Blue Marble.
00:08It was snapped in 1972 from a distance of about 18,000 miles
00:12by the crew of the Apollo 17 spacecraft, and it shows our planet
00:16as a water- and cloud-covered sphere against the black backdrop of space.
00:20However, there are people who claim that this image is part of a
00:24vast conspiracy to trick people into believing that Earth is round,
00:28when in reality, they say, it's as flat as a pancake.
00:32Members of a group known as the Flat Earth Society point to the visible horizon
00:36and say that since they can't see the curve of the globe, that the planet must be a flattened disk.
00:40How do we know that it's not?
00:44Well, no one has ever documented this so-called edge of the Earth,
00:48which flat-earthers say is ringed with a giant wall of ice.
00:52And scientists have been explaining how we know the Earth is round since the 3rd century BC.
00:56Earth is so big that from a person's vantage point on the ground,
01:00its curvature is simply impossible to see.
01:02But the ancient Greeks were able to see Earth's curve by looking at the sun's position
01:06and comparing shadows that it cast in different places at the same time of day.
01:10The laws of gravity also explain how a spherical planet would form,
01:14with its mass attracting matter in space and building a shape outward from a central core.
01:19And on a spherical planet, gravity's pull from the center is what keeps our feet on the ground.
01:25Not to mention that in the 16th century, Ferdinand Magellan sailed completely around the world,
01:31which would have been impossible on a flat Earth surrounded by an icy wall.
01:35Earth isn't a perfect sphere, more like an irregularly shaped ellipsoid, according to the National Ocean Service.
01:41But for those arguing that it's pancake-shaped, that idea falls a little flat.
01:47The shape of the Earth, just one of life's little mysteries.
01:51Earth held ready for proof.
01:53They have no idea what did you think.
01:55There were only 100 membranes who are able to see through the stairs,
01:58there's nothing to use for any certain power.
02:00The other information can be better than the extensions take these encounters.
02:02The edge behind our investigation and to improve the path and build that way.
02:05This roadってる is a very limited 달�asy problem,
02:07and the natural layer was neverשובable at the height.
02:10This event arrives atро zap-limin and the terrain is certainly becomes a large piece of support
02:15through the ll Ekop уст, where there's an alternate.
02:17The Norway is only a natural superstar.
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