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Planet Earth is the home of every lifeform,
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known to us, in the universe.
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Its age is about 1/3 of the age of the universe
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and, admitted,
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It is a thing of beauty.
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a slightly squashed fair with a heavy metal core,
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and a lighter surface crust,
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wrapped in a thin sliver of sweet air to breathe,
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with vast oceans,
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fertile plains,
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magnificent mountains,
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fresh water rivers, streams, lakes and aquifers,
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orbiting a star which warms us,
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and gives us energy.
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But how did our home come in to existence,
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and what's it made of?
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4.6 billion years ago,
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Earth was created from the remnants of dead stars,
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that collected in a giant, dirty gas cloud.
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The gas cloud became denser in its center,
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and formed an accretion disk.
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small particles started clumping together,
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and building larger and larger objects,
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until they form the objects we call "Planets" today.
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This process took 10 to 20 million years,
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and is still not very well understood.
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At about this time, when the solar system was young and chaotic,
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a giant object, about as big as Mars,
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collided with our home.
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The impact was violent,
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and if the object had been more massive,
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it might have destroyed Earth.
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Materials from Earth were smashed out into orbit,
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and formed the Moon,
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which is the biggest satellite in relation to its planet in the solar system.
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At this time, Earth was a hot hell,
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constantly being hit by asteroids,
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with seas of lava,
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and a toxic atmosphere.
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But something was about to change drastically.
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Earth cooled down.
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Water from the inside of the Earth
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wandered to the surface and rained down on Earth,
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only to vaporize again and become clouds.
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Millions of asteroids brought more and more water to our planet.
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All the water on Earth has about this volume compared to Earth.
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Today,
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the surface of Earth is 71% water,
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and 29% land.
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97.5% is saline water,
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while only 2.5% is fresh water.
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The Fresh water is 69% ice and snow,
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30% are ground waters,
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and only about 1% make up the remaining ground waters.
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But even this small part is mostly frozen.
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Only a tiny part of our water is actually lakes and rivers.
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and an even tinier part is bound in living things.
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So, gradually the Earth cooled down,
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and the surface formed a thin crust.
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But inside the earth, hot rock continue to swirl about,
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moving the crust from below and breaking it apart.
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This process is called "Plate Tectonics",
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and is happening right now.
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We'll make a whole video about it in the future.
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For now,
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let's just say that the crust of Earth consisted of
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separate giant plates that move around.
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As they meet, they crumble, and create mighty mountains.
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OR:
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violently plunge back down, deeper into Earth,
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creating deep trenches.
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That's the way the highest place on Earth was formed: Mt.Everest,
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and the deepest: the Mariana Trench.
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From our perspective,
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Earth's mountains and trenches are mighty indeed,
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but when you look at the Earth in cross-section,
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you can see how tiny they actually are.
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The part we stand on is the crust,
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which is about 50 kilometers thick,
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though it can vary between 5 and 70 kilometers
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By the way,
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the deepest hole ever drilled by man
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is 12.262 kilometers deep.
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After the crust, comes the mantle.
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It's a silicate rocky shell,
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and about 2,900 kilometers thick.
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The mantle consists of the upper mantle, and the lower mantle.
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The upper mantle has different regions, too.
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It's upper part, which is viscous and carries the crust,
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is called the "Lithosphere."
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After that, there comes the "Asthenosphere,"
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which consists of less mobile, mostly solid material.
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The lower mantle reaches deep down to the outer core of Earth.
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Earth's outer core is a liquid layer of iron and nickel,
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about 2,266 kilometers thick.
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Temperatures vary from 4,000℃(7,232℉)
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to 5,700℃(10,292℉).
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And in the center, is the inner core.
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It's mostly solid,
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a ball made of an iron-nickel alloy.
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with a radius of about 1,200 kilometers.
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70% of the size of the moon,
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and about the temperature of the surface of the Sun.
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It is slowly growing
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at an estimated rate of about 1mm/year.
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Now, for some respective,
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this small layer of crystallized melt products of former molten mantle,
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is where we live.
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Then, there's Earth's magnetic field.
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It's an invisible phenomenon
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that diverts high energy particles coming from the Sun and other sources,
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allowing for a stable environment
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with comparatively little radiation impact on Earth.
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But why is it there?
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Actually, we don't really know a terrible lot about that.
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We know, it has something to do with the core of Earth.
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Inside this metal sphere,
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large electrical currents flow in complicated patterns.
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They cause a magnetic field,
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that sort of stabilizes itself according to the laws of electrodynamics.
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This entire system is called the "Dynamo."
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But, don't let us fool you into thinking we have it all figured out.
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Speaking of breathtaking information,
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what about the airy stuff that surrounds us?
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By volume,
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dry air consists mostly of Nitrogen,
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Oxygen,
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Argon,
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Carbon,
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a variable mount of water vapor,
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and small amounts of other gases.
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Humans are very dependent on the lowest layer of the atmosphere:
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the Troposphere - Where the weather is.
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It's 12 kilometers thick on average.
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Above that is the Stratosphere,
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which is where the ozone layer protects us
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from the sun's most aggressive type of light.
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Above that is the Mesosphere - the coolest place on Earth,
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with an average temperature around -85℃(-121℉).
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At about 80 kilometers up, the Thermosphere starts.
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The transition to space is a fluent one, without clear borders.
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but humans decided that space starts here.
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At about 100 kilometers, Earth stops, and space begins,
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though the atmosphere extends a bit further.
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In this region, we find the Ionosphere,
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the aurora borealis,
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and the ISS,
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and the outermost layer is the Exosphere,
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stretching up to 10,000 kilometers.
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It merges fluently with outer space,
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where there's no atmosphere at all.
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The atoms and molecules in this area are so far apart,
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that they can travel hundreds of kilometers
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without colliding with each other.
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OK.
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Humans, in their present form,
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have only been around for 200,000 years.
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- that's 0.004% of Earth's history.
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Not long, really.
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And, here we are now,
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living in a thin, moist layer on a small, wet rock.
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We call this rock: Earth.
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It is the product of the universe's deepest workings,
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the result of a constant process of creation and destruction,
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happening all of the universe, all the time,
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helped by chance,
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the laws of the universe and random events,
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we are really lucky.12256
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