see this structure look scary and devoid
of any possibility of life but this is
our home the earth at the beginning of
its existence 4.6 billion years ago
and its formation and the formation of
the moon remains a mystery but today
we'll tell you about the theories that
scientists suggested you'll learn how
planets so different from each other
form from the same material what planet
crashed into the earth in the past
how much water there is on our planet
and where it came from and finally we'll
tell you how old the oldest organism on
earth is
we prepared the story of our planet from
a clump of dust and gas a few miles in
diameter to the appearance of life
when the sun was created gases and other
materials around it started colliding
with each other and forming small bodies
called planetesimals and as the
gravitational forces were growing more
material was pulled together and these
seeds of planets grew larger until they
became true planets the solar systems
gas giants jupiter and saturn uranus and
neptune were born much earlier than the
four known terrestrial planets mercury
venus earth and mars
but how exactly was our home planet born
[Music]
the earth story started about 4.6
billion years ago in a disc shaped cloud
of dust and gas rotating around the
early sun and we know it was that long
ago because of the fossil record one of
the most simple methods to determine the
age of our planet
scientists were able to find zircon
crystals that are roughly 4.3 billion
years old so far these crystals are the
oldest materials found on our planet but
how exactly our planet was formed
remains a scientific mystery however
there are two leading theories on
planetary formation
the core accretion model is the first
one and most widely accepted about 4.6
billion years ago there was a solar
nebula consisting of spinning gas and
dust particles from which our sun was
born then as the remaining material of
different sizes orbited our star at
slightly different speeds it started to
collide and stick together
under the effect of gravity smaller
particles grew into larger particles
that ranged from miles to hundreds of
miles in diameter
the solar wind would then sweep away
lighter elements such as hydrogen and
helium so that just rocky materials
would stay closer and turn into
terrestrial worlds the process continues
until these space objects reach
thousands of miles in diameter but far
away from the star the sun's constant
stream of charged particles doesn't have
a very strong impact on lighter elements
as a result these elements combine and
transform into gas giants
what's exciting is that nasa believes
that this is the way planetary formation
works small rocky worlds like the earth
are a lot more common throughout the
universe than gas giants
the thing with this theory is that it
works well to explain the formation of
terrestrial planets but has problems
explaining the creation of giant worlds
this is because scientists believe the
gas disk around our sun only lasted
about four to five million years and
simulations based on the core accretion
model show such planets form longer than
that however the second theory or the
disc instability model resolves this
issue
this newer idea suggests that chunks of
dust and gas clump together early in the
existence of the solar system and over
time these chunks slowly turn into a gas
planet but the difference is that this
way planets can form much faster than
those explained by the core accretion
model in fact according to this theory
it could happen within as little as 1
000 years a planetary formation this
fast makes it possible for such worlds
to trap the rapidly vanishing lighter
gases
a recent study suggests that proto-earth
was formed within about 5 million years
and on a cosmic scale it's nothing if we
converted the solar system's estimated
4.6 billion years of existence into a
24-hour period these 5 million years
would be equal to just about 1.5 minutes
if scientists are right about this water
could be just a byproduct of the
formation of a planet similar to our
home
this would mean that we're a lot more
likely to discover the ingredients of
our life outside our solar system
and what about our satellite what's the
story of the moon
[Music]
astronomers have proposed many
hypotheses for the origin of our
satellite and some of them are quite
bizarre
the fishing theory suggests that the
moon was once part of our planet
when the earth was still a hot ball of
spinning lava it may have ejected the
material our satellite is made of now
while most scientists remained skeptical
because of how fast our planet must have
been spinning to make this happen it
would have been a breathtaking
phenomenon to observe
the capture theory is yet another
interesting idea suggesting that the
moon could have been captured from a
different part of the solar system we
already know that some worlds have
gained their moons in such a way perhaps
before it was attracted by our planet's
gravitational pull the moon was orbiting
venus still this wouldn't answer the
question of why the earth and the moon
have almost identical oxygen and isotope
ratios but the next theory could
some astronomers think how satellite was
created side by side with the earth the
idea is that both were formed at about
the same time from the same gas and dust
and at the same part of our solar
system's protoplanetary disk the theory
is called co-formation and it fits
because of the isotopic similarities
between the two space objects but at the
same time it cannot explain the
difference in the size of their iron
cores
the leading and perhaps the most
mind-blowing theory is that the moon was
born as a result of a giant impact with
a different celestial body there's a
chance that earth wasn't the only planet
that was forming 150 million kilometers
from the sun
earth's creation may have been
accompanied by another planet dubbed
thayer this strange world must have been
smaller than our planet just about the
size and mass of mars at first it could
have had a stable orbit but as earth
increased its mass by gathering more
material thayer's orbit was destabilized
and so it swung back and forth towards
our planet until eventually the two
proto-planets collided the speed of
collision was low so the earth wasn't
destroyed however the impact must have
created a disc of debris of molten rock
and hot gas that became the building
blocks of the moon both thayer and the
earth could have been composed of a
combination of materials and more of the
lower density splatter would eventually
transform into the moon if this is the
case it explains why our planet has a
higher density and thicker core than our
satellite and why the earth and the moon
spin the way they do around each other
but let's get back to earth
throughout the next half a billion years
the earth resembled a ball of a molten
surface volcanism and asteroid impacts
and several things made it extremely hot
gravitational compression radioactive
decay and asteroid impacts a big amount
of this initial heat is still there deep
inside our planet but as it cooled
minerals started to crystallize and
because of the different densities of
materials the crust mantle and core were
formed
so how did water appear on a hot rock
floating through space
[Music]
oceans cover more than 70 percent of the
earth's surface this is
1.386 billion cubic kilometers of
surface water or ice
but the fact that there's more liquid
water on our planet than any other known
rocky world in our solar system isn't
fully understood and as with the earth
and moon there are several hypotheses as
to how water appeared here
one likely reason is extra planetary
sources such as comets trans-neptunian
objects or even proto-planets there's
actually a lot of water in our solar
system two-thirds of uranus and neptune
for example are made of ice so if our
planet was born hot and dry then water
must have come from somewhere else
brought by icy comets and asteroids
comets are made of dust and ice with
most of that ice being frozen water so
they might be the clue
but measurements show the comet water
has a lot more deuterium in it compared
to that found on earth what about
asteroids because their ratio of
deuterium to normal hydrogen water is
closer to that which we have on our
planet they're even a better candidate
also asteroids are 20 water but due to
their small size there must have been a
colossal number of impacts to explain
all the water on our planet to fill the
planet with
1.386 million cubic kilometers of water
might seem like a lot
to compare this much water would have
been enough to cover the contiguous
united states to a depth of roughly 145
kilometers but this still isn't a lot in
fact water amounts to only about
0.02 percent of our planet's mass and
since earth experienced periods of heavy
bombardment in the past this is actually
a possible scenario
researchers also think that when our
planet formed huge amounts of hydrogen
were captured in its rocks and minerals
and because of the mantle's heat
hydrogen and oxygen-rich minerals
started to melt this made it possible
for water to spew out from the earth's
crust
according to scientists estimates about
10 oceans of water could exist within
the mantle up to this date
probably the most astonishing of all is
the volcanic outgassing hypothesis
according to this idea water may have
come from volcanism in other words it
was always there in the form of minerals
with oxygen and hydrogen hidden beneath
the crust of our planet and volcanoes
only helped it break freya's vapor it
originated in volcanic eruptions then
condensed and fell as rain
scientists think that all volcanic
eruptions contain some water vapour and
that it may have been enough to account
for the earth's surface water
this still remains an open question but
whatever the case with water there often
comes life
life most likely began during the late
hadiyan or early archaean eon that
lasted from 4.0 to 2.5 billion years ago
there's evidence of life in at least 3.8
billion year old rocks from akila island
greenland and the oldest form of life
discovered by scientists a tiny hematite
tubes estimated to be 4.28 billion years
old
hypotheses include a chemical origin of
life in the early atmosphere
hydrothermal vents deep seas oceans and
even comets that came here from
somewhere in space
it's highly possible that life began
from the chemical environment of the
early atmosphere and oceans but they
were nothing like we have today the
atmosphere was oxygen free but was
abundant in methane carbon dioxide
sulfur and nitrogen compounds and some
space objects in our solar system are
known to have an atmosphere like this
in one experiment scientists simulated
our planet's early atmosphere and
lightning with a sealed vessel they
found that after igniting sparks amino
acids or the fundamental building blocks
of proteins were formed
life that could have started on the deep
ocean floor may have also been able to
survive without photosynthesis due to
another biological process called
chemosynthesis
instead of using energy from the sun
primitive life gained energy from the
heat that was coming from the earth's
interior
still there's always a possibility that
life initially originated in space and
was then carried here by comets or other
celestial bodies researchers have
already found amino acids within
meteorites and comets what's exciting
about this idea is that it means a high
likelihood of life exists somewhere in
space
we hope you enjoyed our story of the
formation of the earth and its satellite
the origin of water and of primitive
life but if you'd like to hear about
multicellular organisms and how
intelligent life evolved let us know in
the comments
you