How Do We Know Earth is Round?

Live Science

Members of the Flat Earth Society claim to believe the Earth is flat despite scientists explaining how we know the Earth is round since the third century B.C.

Transcript

00:00How do we know that the Earth is round?

00:05One 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 by the crew of the Apollo

00:1317 spacecraft, and it shows our planet as a water- and cloud-covered sphere against

00:18the black backdrop of space.

00:20However, there are people who claim that this image is part of a vast conspiracy to trick

00:25people into believing that Earth is round, when in reality, they say, it's as flat as

00:30a pancake.

00:31Members of a group known as the Flat Earth Society point to the visible horizon and say

00:35that since they can't see the curve of the globe, that the planet must be a flattened

00:39disk.

00:40How do we know that it's not?

00:43Well, no one has ever documented this so-called edge of the Earth, which flat earthers say

00:48is ringed with a giant wall of ice.

00:51And scientists have been explaining how we know the Earth is round since the 3rd century

00:55B.C.

00:56Earth is so big that from a person's vantage point on the ground, its curvature is simply

01:01impossible to see.

01:02But the ancient Greeks were able to see Earth's curve by looking at the sun's position and

01:07comparing shadows that it cast in different places at the same time of day.

01:11The laws of gravity also explain how a spherical planet would form, with its mass attracting

01:16matter in space and building a shape outward from a central core.

01:20And on a spherical planet, gravity's pull from the center is what keeps our feet on

01:24the 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

01:40the 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.

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