how did the earth came into existence and get its present form
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Approximately 4.5 billion years ago, one part of a big cloud of dust and gas became a little more dense, and thus had greater gravity than the rest. It started to attract gas and dust, rotating faster and faster and gathering into an accretion disc swirling in towards the center. The center became dense enough and massive enough for fusion to start, and the Sun was lit.
In the accretion disk, matter gathered under gravity to form lumps that bumped into one another to form bigger lumps with more gravity, all while going around the disc. These lumps attracted matter that came swirling in, forming a local rotary motion as it gathered, and eventually became big enough to completely dominate their orbits and cleanse them of lesser lumps.
And by “cleanse”, I mean that the lesser lumps fell down on the bigger ones causing all imaginable hell. This period is even called the Hadean or the hellish period. One of these was to become Earth. Somewhere around this time, one huge lump, but still smaller than the early Earth, impacted the Earth. The ejected material from that impact eventually formed the Moon.
Slowly things calmed down. The early Earth had a hellish poisonous atmosphere and shallow oceans full of chemicals. Life appeared – we’re still not sure how – and evolved.
Some 2.5 billion years ago, something happened. The primitive single-cell life forms invented sex and photosynthesis, and the resulting oxygen killed off nearly every life there was. The first “Snowball Earth” period may have been caused by this “the great oxygenation event”.
But life finds a way, and the Earth eventually thawed. Life became multicellular colonies, then multicellular animals and plants and fungi, and eventually they crawled up on land.
And the rest is history.
Well, paleontology and geology, actually. History comes later, when one species of apes came up with the idea of making symbols that represented speech, and started to write stuff.
In the accretion disk, matter gathered under gravity to form lumps that bumped into one another to form bigger lumps with more gravity, all while going around the disc. These lumps attracted matter that came swirling in, forming a local rotary motion as it gathered, and eventually became big enough to completely dominate their orbits and cleanse them of lesser lumps.
And by “cleanse”, I mean that the lesser lumps fell down on the bigger ones causing all imaginable hell. This period is even called the Hadean or the hellish period. One of these was to become Earth. Somewhere around this time, one huge lump, but still smaller than the early Earth, impacted the Earth. The ejected material from that impact eventually formed the Moon.
Slowly things calmed down. The early Earth had a hellish poisonous atmosphere and shallow oceans full of chemicals. Life appeared – we’re still not sure how – and evolved.
Some 2.5 billion years ago, something happened. The primitive single-cell life forms invented sex and photosynthesis, and the resulting oxygen killed off nearly every life there was. The first “Snowball Earth” period may have been caused by this “the great oxygenation event”.
But life finds a way, and the Earth eventually thawed. Life became multicellular colonies, then multicellular animals and plants and fungi, and eventually they crawled up on land.
And the rest is history.
Well, paleontology and geology, actually. History comes later, when one species of apes came up with the idea of making symbols that represented speech, and started to write stuff.
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