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Science and Technology, Class 8
History of Development of Living Beings in Earth
A hot earth cooled · Two eons, six eras · A story of 4.6 billion years
What We Will Know By The End
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How the hot early earth cooled down
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How water, gases and the first life were formed
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The geological time scale, and what eons and eras mean
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Which living things appeared in each of the three eras
The Early Earth
From Molten Rock to Falling Rain
STRUCK
Huge meteorites fell and made the earth extremely hot again and again.
SEPARATE
Heavy iron and nickel sank to the centre, light silicon and aluminium rose to the surface.
SHRINK
As it cooled the material shrank, forming plains, hills and hollows.
RAIN
Rain fell from the clouds and the surroundings became suitable for life.
Presenter notes: Today we look at how the earth cooled, how life began, and how scientists have divided the time that followed.