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?

00:04One 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.

01:51part 2

01:55tr UX

02:01Method 3

02:05Part 2

02:09Part 3

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