The evolution of the Earth is a fascinating subject although the term Evolution is not quite accurate when describing the Earth. The Earth no more evolved than a mountain range evolves. It is beautiful yes, complex and born of our universe but it cannot fight against its environment, it simply reacts to it. But just like us the chances of it ever existing were vast beyond imagination. For humankind it is a rare and precious jewel hanging in the vast blackness of space. And since the first photographs taken of it from craft leaving here were seen it has become a symbol of home and all that, that, word stands for. But where did it begin?
In the beginning there was the big bang. Time it might be said stated then in our universe. As the Universe expanded the Hydrogen and helium that existed within it formed the first giant stars. Later, as these ran the course of the lives they exploded, throwing the many new heavy elements that had been forged in their hearts out deep into space. Again and again the cycle or recycling (The universe is a very green place. Sooner or later everything is recycled) of the stuff of stars continued until there reached a time when there were enough heavier elements for planets such as the ones we seen in our own solar system to form.
Some time about four and a half billion years ago in a swirling mass of stuff and gravity our little planet was formed. Life however in a young solar system is not a friendly place. It's hot, incredibly hot and there are meteors, asteroids and proto planets flying about every where. Shielded by the mighty gravitational pull of the sun on one side and Jupiter on the other the Earth and the other rocky inner planets survived this fire and brimstone birth. But they certainly didn't make it unscaved. At some point in the Earths youth a planet roughly the size of Mars hit it, re-melting the entire planet and tearing a piece off of it. That piece can still be seen today orbiting our planet every lunar month. It is our moon.
Not all the rocky planets survived out of the nursery however. Between the orbits of Mars and Jupiter there is a ring of rocks called the asteroid belt. Like the inner planets this too was once a rocky planet and is a heady reminder of how lucky we are to have a planet at all.
As the earth cooled comets of ice hitting the surface melted without burning off and the seas of our world were formed. A similar situation is now believed to have happened on Mars also. But with Mars' lower mass and weaker gravity I was unable to hold onto most of it water. Some water is still believed to be there beneath the surface of the planet and at its poles, where it is frozen. Venus and Mercury however are too close to the Sun and the temperatures are just too high to allow liquid water to form seas and oceans.
Later still, about three and a half billion years ago the first delicate life began on our world. In our then, carbon dioxide rich atmosphere, early algae's began respiration and slowly started to replace the carbon dioxide in our atmosphere with oxygen. This was the beginning of our world as we know it.
While I said at the start of this article that Evolution was the not an accurate word to describe the gradual formation of our world, it is however an apt one. While there were no genetics involved, its journey from the very beginning of time to the world we seen now is no less inspiring or humbling then the slow genetic evolution of mankind upon it. We are made of the things of Earth just as it is made from the things of the universe. This is our home, our world, our universe.