- [Narrator] With a five billion year old history,
the Earth is a pretty interesting place.
We understand a lot about it, but there's plenty more
we're just beginning to understand.
These are the 10 things you didn't know about planet Earth.
While the Earth has only one satellite, the moon,
it also has several close friends.
Several asteroids, the largest being three miles
in diameter and shares orbits roughly the same size,
speed and distance from the sun as the Earth.
The result is that these objects remain
relatively near the earth throughout their
orbital cycle with their distance from our
planet remaining relatively stable.
This results in a series of asteroids
essentially sharing our orbit with the sun
constantly remaining with us as the Earth
revolves around the sun each year.
Some people erroneously describe these bodies
as small moons, but this is incorrect.
Moons would have to orbit the Earth
and these objects all technically orbit the sun.
Either way, the existence of these bodies
is something that most people don't know about.
According to the giant impact hypothesis,
an unidentified body collides with
the Earth 4.5 billion years ago.
This body shattered upon impact
and ejected massive amounts of material.
This debris eventually coalesced and fell
into orbit around the Earth becoming the moon.
This means that when we look up at the moon,
we're really looking at material which used to be the Earth.
This origin may explain why the moon
is so incredibly big in relation to the Earth.
No other planet has a moon as proportionally big.
If the moon was a more average size,
we'd never have solar eclipses among other things.
From sea level, Mt. Everest has no rival
with it rising five miles above it.
But the surface of the Earth does not begin at sea level.
It starts at the sea bed.
Mauna Kea in Hawaii is more than six miles
tall from the base to summit,
making it the largest mountain on Earth.
While the Andes Mountains in South America
form the longest mountain range on land,
it pales in comparison to the 40,000 mile long ocean ridge.
This formation weaves its way through every ocean
and makes the edges of several tectonic plates.
Magma forces its way up at these edges,
cools, and forms new land.
In addition, there are several mountain ranges which branch
off of the ocean ridge adding another 10,000 to the system,
and none of that is counting the numerous smaller ridges
that can be found on the seafloor throughout the world.
With five mile high mountains and ocean trenches miles deep,
the world seems a rather rough place.
However, if you shrank the Earth down to the size
of a billiard ball while maintaining its proportions,
those imperfections would be even less pronounced
than those allowed on a pool cue in tournament play.
However, while the Earth is actually very smooth,
it isn't actually a round body.
Centrifugal forces generated by the planet's spin
have caused the equator of our planet to be more pronounced.
The diameter of the planet, the equator,
is 27 miles longer than the diameter
of the planet from pole to pole.
This bulge has distorted gravity on our planet as well.
A 200 pound person is half a pound heavier
at the equator than he is at either of the poles.
Antarctica is full of snow and ice.
The Antarctic ice sheet averages a mile
in thickness even with global warming.
The continents glaciers contain 90% of the world's fresh
water supply, and yet, Antarctica is classified as a desert.
Snow and ice have built up over millions of years
forming the vast ice fields we see today.
But the process has been a slow one.
While the coast receives considerable snow,
the interior of this continent sees almost none.
Some places receive less than an inch per year,
which is the definition of a desert,
a place with very little precipitation
regardless of its temperature.
While estimates vary widely,
sea water likely contains a minimum of 15,000 tons of gold.
The bad news is that it's diluted
to roughly 10 parts per quadramillion.
To date, no one has figured out how to extract
it in a commercially viable quantity,
although a variety of scams in the last century
have promised to skim gold from sea water.
Ever dive under water and feel your ear pop?
That's the pressure of increasing
amounts of water on top of you.
Now imagine diving down thousands of miles
and the material surrounding you being rock, not water.
That is the environment at the center of the Earth,
and that pressure shapes a core which is molten
on the outside and solid on the inside.
Earth may have once been molten.
Over time the outer surface cooled and solidified.
However, heavier elements, particularly iron
sank towards the core.
The deeper it went, the greater the pressure.
The greater the pressure, the higher the temperature.
And that temperature continues to keep
a tremendous amount of this material molten.
Eventually, however, this pressure brings about a process
whereby iron reverts to a solid state,
so a 1,500 mile diameter iron core sits in the middle
of our planet surrounded by super heated magma
which will never be able to liquefy the inner core
of our planet because the pressure will never lessen.
The Earth possesses a gigantic magnetic field,
which is fortunate because it prevents solar wind
from ripping off the ozone layer
and flooding the planet with radiation.
Like a regular magnet, it has a north and a south pole.
However, these poles do not line up
with the planet's axial poles.
They also move, sometimes many miles in a single year.
They don't even have to be on opposite sides of the world.
Finally, periodically the poles flip positions
with the southern pole in the north
and the northern pole in the south.
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Thanks for watching and thanks for learning.
(tranquil music)