what is earth why human comed in earth why going life in human on earth ?
Answers
Answer:
A cataclysm may have jump-started life on Earth. A new scenario suggests that some 4.47 billion years ago—a mere 60 million years after Earth took shape and 40 million years after the moon formed—a moon-size object sideswiped Earth and exploded into an orbiting cloud of molten iron and other debris.
Explanation:
How did life begin? There can hardly be a bigger question. For much of human history, almost everyone believed some version of "the gods did it". Any other explanation was inconceivable.
That is no longer true. Over the last century, a few scientists have tried to figure out how the first life might have sprung up. They have even tried to recreate this Genesis moment in their labs: to create brand-new life from scratch.
So far nobody has managed it, but we have come a long way. Today, many of the scientists studying the origin of life are confident that they are on the right track – and they have the experiments to back up their confidence.
This is the story of our quest to discover our ultimate origin. It is a story of obsession, struggle and brilliant creativity, which encompasses some of the greatest discoveries of modern science. The endeavour to understand life's beginnings has sent men and women to the furthest corners of our planet. Some of the scientists involved have been bedevilled as monsters, while others had to do their work under the heel of brutal totalitarian governments.
This is the story of the birth of life on Earth.
Dinosaurs actually lived quite recently (Credit: Oleksiy Maksymenko/Alamy)
Dinosaurs actually lived quite recently (Credit: Oleksiy Maksymenko/Alamy)
Life is old. The dinosaurs are perhaps the most famous extinct creatures, and they had their beginnings 250 million years ago. But life dates back much further.
The oldest known fossils are around 3.5 billion years old, 14 times the age of the oldest dinosaurs. But the fossil record may stretch back still further. For instance, in August 2016 researchers found what appear to be fossilised microbes dating back 3.7 billion years.
These wavey patterns could be 3.7-billion-year-old fossils (Credit: Nutman et al, Nature)
These wavey patterns could be 3.7-billion-year-old fossils (Credit: Nutman et al, Nature)
The Earth itself is not much older, having formed 4.5 billion years ago.
If we assume that life formed on Earth – which seems reasonable, given that we have not yet found it anywhere else – then it must have done so in the billion years between Earth coming into being and the preservation of the oldest known fossils.
As well as narrowing down when life began, we can make an educated guess at what it was.
The tree of life (Credit: Hug, Banfield et al, Nature Microbiology)
The tree of life: most of the branches are bacteria (Credit: Hug, Banfield et al, Nature Microbiology)
Since the 19th Century, biologists have known that all living things are made of "cells": tiny bags of living matter that come in different shapes and sizes. Cells were first discovered in the 17th Century, when the first modern microscopes were invented, but it took well over a century for anyone to realise that they were th