By PRAGYANSHARMA POLAVARAPU (Vrs.Somanchi)
Scientists say that it might have
taken earth a few hundred million years to cool–after its formation
about 4500 million years ago (from a hot sphere of molten
rock and molten metal) . Scientists say that as earth further cooled water till
then held in kilometer-thick clouds rained continuously for centuries with
occurrence of big dazzling lightning and the oceans formed. This was perhaps
the situation about 3000 million to 4000 million years ago.
Scientists examined oldest
rocks in western Australia and estimated their age with help of radioisotope
technology and also identified some fossils which were billions of years old .
They say that about 3000 million years ago the temperature of the
oceans cooled to around 30 to 40 degrees centigrade and that
there were many sulphur-spewing active volcanoes. Some bacteria managed to live
feeding on the sulphur-based compounds and even in waters near hot
springs . There was absolutely no oxygen in the air and there were no green
grass meadows on the stony land .
THE CHANGING ATMOSPHERE
Scientists say that in the oldest
atmosphere of earth 4500 billion years ago there were only helium and hydrogen
just as at similar places and similar situations in the universe
near stars. There was no oxygen in the air surrounding earth.This was the first
atmosphere of earth .
The planet earth was extremely
hot and in a molten state with even the rocks in a molten state.We should
understand that the earth moved more than a hundred and fifty million
kilometers away from the sun during the process of its formation
and entered a solar orbit at that distance. The earth started
to cool along with other planets and their satellites but the cooling
process perhaps took a few hundred million years!
The earth and planets now
entered an extremely cold space in the all pervading emptiness of
cosmic space . In this extremely cold environment of perhaps “minus 150”
or “minus 200” degrees centigrade temperature earth began to slowly solidify.
Thousands of kilometers thick semi-solid stony plates of continent-size (
thousands of miles long and thousands of miles wide ) were forming around
the hot metallic core of earth . Not just this. Above these huge
soft semisolid stone plates a solid stone crust of 20 or 30 miles
thickness formed. Scientists say that first rains fell about 3000 million years
ago . Before that time the earth being very hot all water hung in
kilometers- thick clouds and that the temperature was around 70
to 80 degrees. It might have rained for hundreds of years and the oceans
were filled. There were thousands of volcanoes . Volatile gases evolved
in unlimited quantities sending out pungent smelling vapours . The
vapours contained billions of tons of H2O, CO2, CO,ammonia,
nitrogen, sulphur oxides etc .This pungent and suffocating
atmosphere—(suffocating for us humans)– is called second atmosphere. It can be
said that that such atmosphere might have existed for about
three billion years. There was no oxygen at all.
Scientists say that by about 2700
million years back— (after millions of years of rains and cooling
of the stone layers of the earth and perhaps also due to the slow cooling
in the liquid metallic deep interior of earth) — the temperatures on earth’s
surface and in oceans cooled further down to 30 to 40 degrees . Everywhere
there were volcanoes spewing sulphurous gases, carbon dioxide, water vapor and
hydrocarbons and ammonia.
As already said, over hundreds
of millions of years— due to temperature adjustment and due to formation of
world’s oceans and the torrential rains —the weather cooled
.Scientists say that single-celled organisms without any nucleus and any
recognizable body shape and body parts might have appeared in the oceans and
seas even in those far away “thousands of millions of years”. All those
creatures lived only in water.
SOURCE OF WATER ON PLANET EARTH
Scientists have also studied the
question—where from did the huge quantity of water that accumulated in oceans
come? Some water might have come through the ices brought by
thousands of meteors and comets coming from millions of miles and flying by
very near to earth or crashing on earth. However from the large number of
ancient volcanoes limitless quantities of water vapor might have come
originating from the deep stony interior of earth. Scientists remind that
there were limitless quantities of hydrogen in atmosphere existing
since the start of time –from the time of formation of planets . Scientists say
that in the gases surrounding the primordial molten earth, oxygen might
also have been abundant.If there was abundant hydrogen and oxygen in air it may
be possible lot of water might have formed in earth’s
atmosphere in the presence of incessant electrical energy of the
lightnings in the clouds . The temperature of ocean water at the time
(when the first oceans formed) might have been high at 70 to 80 degrees
centigrade and there was no free oxygen. In the atmosphere there were
also abundant quantities of inert gas nitrogen ,carbon dioxide and carbon
monoxide and some hydrocarbons. The average depth of ocean might have
been 3.7 kilometers as per scientific opinion about such colossal quanties of
H2O.
THE BLEAK WORLD
Now a most surprising
fact may be mentioned here. Since in the beginning there was no
free oxygen in atmosphere and oxygen was available only in a dissolved
condition in water no creatures could live on land . All living beings
lived only in water in the oceans. All living creatures were also
microscopic in size and only lived in kilometers-long
and kilometers-wide floating colonies on the surface of the oceans. The winds
and storms and ocean currents carried them in every direction. The microscopic
living creatures breathed only the oxygen dissolved in water.
The floating and living
creatures were extremely small —of microscopic size or at most a
millimeter size. They were all “single celled creatures”. There was no
oxygen at all in the air. The plant kingdom was not yet born on earth at that
time. There was no green plant ,no trees,no grass. All land was only lifeless
stone where there was no greenery as we now know and there was not even one
four-legged living creature !
The microscopic size or millimeter
size living creature had no bones in body , no thinking mechanism,
no nerve system in body to feel pain etc, no eyes, no ears etc. The little
microscopic and millimeter size creatures only floated in the water. When
hungry -they simply devoured the neighboring creature. They devoured each other
.
In short ,to recollect again—there
was no oxygen ,there were no green plants, no green grasses, no green trees,
even no green mosses, no lions, no deer and rabbits and birds! The great
reason is that there was no plant kingdom to manufacture the carbohydrate
molecules in nature’s factories called “plant leaves”!
THE GREAT REVOLUTION CALLED
PHOTOSYNTHESIS
There was soon a great change. We may
call it a revolution . Some green bacteria (the cyanobacteria)
existing in water 2.3 billion years ago started to produce
carbohydrate in their bodies . The carbohydrates were tiny food material that
could be consumed as food by other living beings. Till then all the
microorganisms devoured each other when they were hungry. The cyanobacteria
started the new “photosynthesis” reaction to produce carbohydrate,
perhaps as tiny particulate food material in their bodies.
It is most interesting for modern
school students to note— that the cyano-bacteria just used
carbon dioxide gas and water vapor and sunlight
to synthesize in their bodies the carbohydrate particles —which became
the primary food of “universe”. Whether the carnivores or herbivores –all have
to depend on the carbohydrate for their existence.
But most importantly— from the view
point of all living creatures including humans which appeared only two
billions years later—a wonderful thing also started to happen and
continued for ever during all these billions of years. The green bacteria
which perhaps lived in kilometers- long floating colonies in oceans
enjoying sunlight released oxygen every second every day for two thousand
million years and lo the entire air was filled with oxygen. In addition to the
food particles called carbohydrate which became the basic food of the universe
the life giving oxygen gas filled the air . Living beings till then
living only in ocean waters spread also to the stony land and after hundreds of
millions of years the green tree cover(billions and billions of small and
big trees, the creepers,the greeses and mosses ) filled every inch of the earth
as the cool skies rained water . Not only the giant forest trees but also
the hundreds of billions of leaves of plants and the hundreds of billions of
green blades of grass in the millions of acres of land took over the duty of
photosynthesis from the tiny bacteria and lessened its burden. The planet earth
entirely underwent a change.
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