Originally posted by FOXMULDER147
Originally posted by TheOracle
OP, how would you react if I told you that we ARE aliens. That the life here came from space? Because that my friend is a fact
I missed that news bulletin.
Can you convince me in one post?
How was the Earth Formed
Our planet Earth is a third planet in the solar system. It has undergone several geological changes before it evolved to its present form. To know
more about how the Earth was formed, read on...
The Earth, at the beginning, was very different from what it is now. It did not have any atmosphere or water bodies. The common belief of scientists
is that our planet earth was formed some 4.5 billion years ago. The sun, the planets and their satellites in our solar system were all formed due to
the contraction of solar nebula. Solar nebula, from which our solar system is said to have formed, was a huge mass of spiral cloud made up of dust
particles and various types of hot gases. The constituent elements of the solar nebula were mainly hydrogen and helium and some other heavier
elements. Solar nebula began its contraction about 4.6 billion years ago. During the contraction process, its temperature came down and it began to
rotate very fast. As a result of cooling, shrinking and rapid rotation, the outer part of the cloud got detached from the main body in the form of
How was the physical structure of the Earth formed?
Each of the detached rings cooled and shrank further. Then, gradually the separated rings clustered together to form a globe. This globe or ball of
hot gases was by now, cooled so much that all the gases in it were condensed to liquid form or lava. Over a period of time, with further decrease in
temperature, the lava solidified to form the crust of the Earth. During the process of solidification, the heavy metals like iron, in their liquid
form, descended to the center due to high density, forming the core. The remaining separated lava formed the mantle, which lies just below the crust.
In this way, the layered structure of Earth was formed.
How were the oceans of the Earth formed?
Due to the cooling of earth, large amounts of steam escaped from its crust. As a result of the eruptions of volcanoes, substantial amounts of steam
and various types of gases were also released. Geologists believe that a good amount of water was imported to the Earth during its collisions with
several comets that contained ice. When the temperature on the Earth was very high, all the water remained in vaporous form above the atmosphere.
Then, as the temperature on Earth decreased, all the steam condensed to form clouds. The resulted rainwater got accumulated in the craters formed on
the surface by the impact of smashing of comets. This led to the formation of the oceans.
How was the atmosphere of the Earth formed?
The impact of collisions with comets enriched the Earth with water as well as many other essential gases like carbon dioxide, methane, nitrogen
ammonia, etc. The gases discharged from volcanic eruptions and collisions with comets led to the formation of the new atmosphere over the Earth. Free
oxygen was not available in the new atmosphere; it was either bound by hydrogen or some other elements. The ozone layer was absent in the newly formed
atmosphere. As a result of which, the Earth's surface was exposed to ultraviolet radiation.
How were the continents of the Earth formed?
According to theories of geology, the present-day continents were formed due to fragmentation of a huge, single mass of land. The broken pieces of
land masses then drifted away from each other. The Earth's crust comprises a number of large plates of solid rock floating on the liquid mantle. The
molten rock of the mantle is in constant motion due to convection of heat that occurs deep inside it. Due to this internal motion, some of the plates
are constantly sliding at the edges (more commonly) in relation to others. This kind of movement detached one plate from another and caused the
drifting of the continents. It is believed that the mountains were formed when one plate of the crust pushed the other, and the resultant pressure
thrust a part of the land upwards.
All the changes that contributed to the creation of the Earth, as we know it today, happened very gradually over a period of a few million years.
These geological features of the Earth made it suitable for evolution of life on the planet.
By Bidisha Mukherjee