Some people say that the Big Bang began it. This, however, is just a theory. To this day, scientists, still do not know how humanity and life on our planet came to be.
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The Big Bang Theory models the Universe as a whole, and so far at least is the nearest theory to fit observations and calculations; but it leaves the uncomfortable "What came before?" question.. The Solar System is much younger.
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The two nouns in the second sentence ought be the other way round - Life in general came first, almost certainly as single-celled organisms first, but you are right that the actual mechanism has not been determined. We hominids appeared within the last 3 or 4 million years, very recently in geological terms, with our own species probably less than 1 million. It's hard to know because land animals from the time did not leave many fossils, compared to the rich assemblages of marine fossils.
1.4 million plants exist on earth
The earth doesn't spin because of gravity, and gravity has not ceased to exist.
It is estimated that there are approximately 390,000 species of plants on Earth. This number includes a wide variety of plants, ranging from tiny mosses to towering trees.
Gravity ! The gravitational pull of the Earth 'traps' the atmosphere close to the ground.
Yes, without the moon live as we know it would not exist on earth.