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  • Hey there!

  • Welcome to Life Noggin.

  • Right now you're probably watching this video from somewhere on Earththat big,

  • round, beautiful planet you humans call home.

  • But how do you know the Earth is round?

  • Your senses would tell you that it's flat.

  • After all, if you stand in a large field, it actually looks pretty flat.

  • And if you walk through that field, it doesn't feel like you're going over a curve.

  • Could it be that the Earth is actually flat?

  • Well, let's try an experiment.

  • Say you're standing in a field outside of Chicago.

  • If the Earth is flat, you should be able to see southwest and see some of the tallest

  • points in the United States, the Rocky Mountains.

  • But the thing is, you can't.

  • That's because of the curvature of the Earth.

  • You'll notice a similar problem if you stand on a seashore and try to watch a boat sail

  • away.

  • After a while, it will disappear from view.

  • And not only that, but the bottom of the boat will vanish before the top as it

  • goes over what's called the horizon linethe place where the sky meets the Earth.

  • For someone who is six feet tall, the horizon line is only three miles away.

  • But the higher up you are, the farther you can see over the Earth's curve.

  • This is why standing on a tall mountain might allow you to see over 100 miles while standing

  • in a field will only let you see a short distance.

  • It also means that taller people can see slightly farther than shorter people.

  • Good thing my animator can make me any height!

  • See, I'm like that one ant dude.

  • The thing is, none of this is new information.

  • We've known about the planet's curvature for over 2000 years.

  • The Ancient Greeks figured out that the Earth is round based on several pieces of evidence,

  • including their observations of ships going over the horizon line. The scientist Aristotle,

  • writing in 350 BCE, noted that during an eclipse, the Earth makes a round shadow on the moon.

  • He also realized that stars appear in different places depending on where you are standing.

  • For example, he saw stars in Egypt that weren't visible farther north.

  • Roughly 100 years later, humans got their first measurements of the Earth's curve

  • from another Greek mathematician, Eratosthenes.

  • He had heard of a city in southern Egypt where, at noon on the summer solstice, the sun was

  • directly overhead and the buildings cast no shadows.

  • But at the same time in the northern city of Alexandria, the buildings DID cast shadows.

  • meaning the sun was at a different angle in the sky.

  • On the day of the solstice, Eratosthenes stuck a stick in the ground in Alexandria and measured

  • the angle of its shadow.

  • Using the distance between the two cities, he was able to calculate the curvature of

  • the Earth!

  • You could actually perform this same experiment if you have a friend living a few miles away.

  • Or, if your friend is several hours west, you can get more proof that the Earth is round

  • by calling them at sunset and asking how the sky looks.

  • It will still be daylight there because of the Earth's curve.

  • And there's one more piece of clear evidence for the planet's shapepictures taken

  • from space.

  • Maybe you're not on Earth after all and are actually watching this video from the

  • space stationin which case, please leave a comment, because that's so cool.

  • If that's true, you'll have a bird's-eye view of this giant blue and green globe.

  • What a beautiful place to live.

  • So what other myths about Earth do you want me to explore?

  • Let me know in the comment section below.

  • Do you love science?

  • Do you love video games?

  • If so, you'll HAVE to check out Play Noggin,

  • which is an excellent combination of the two.

  • Julian recently explored the idea of mind control.

  • Check it out!

  • If the colander our protagonist puts on his head allows him to hack into the mind of his less intellectual friends,

  • then in theory, he could exercise control over their actions at a basic level, it doesn't sound too complicated.

  • In order to control the activity in an area of the brain, you need to stimulate it with energy.

  • My name is Blocko, this has been Life Noggin, don't forget to keep on thinking

Hey there!

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B1 US earth curvature flat curve horizon field

This Is How We Know Earth Isn't Flat

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    Emily posted on 2018/09/13
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