Within the unimaginable depths of the universe there is a small family of worlds circling about a star we call the Sun; it is just a single star among the billions upon billions which are shining in the cosmos. Against the awesome backdrop of the infinite blackness of space, our world is just another planet; nothing more than an insignificant speck on the cosmological scale of things, but it is our home, and as of yet we have found no other planets which are remotely like Earth. The history of our world is a story which is still largely incomplete....