And now I think about it, I never really wanted to live forever. I just want to live well. - Charles Sheffield

Earth has been regarded for centuries as a giant self-regulating machine, absorbing all changes, great and small, and diluting their effects until they become invisible on a global scale. Mankind has taken that stability for granted. Careless of consequences, we have watched as forests were cleared, lakes poisoned, rivers dammed and diverted, mountains leveled, whole plains dug out for their mineral and fuel content. And nothing disastrous happened. Earth tolerated the insults, and always she restored the status quo.
Always—until now. Until finally some hidden critical point has been passed. The move away from a steady state is signalled in many ways: by increasing ocean temperatures, by drought and flood, by widespread loss of topsoil, by massive crop failure, and by the collapse of worldwide fishing industries.

To a logical entity, such as myself, the behavior of organic intelligences such as yourself, provides many anomalies. For example, the history of humanity, the species concerning which my data banks have most information, is replete with cases where humans, on little or no evidence, have believed in impossibilities. They have accepted the existence of a variety of improbable entities: of gods and demons, of fairies and elves, of 'good luck' charms, of magic potions, of curses and hexes and evil eyes."
"Tally, if you're going to blather about—"
"But at the same time, humans and other organic intelligences often seem unwilling to accept the implications and consequences of their own legitimate scientific theories.

If I’ve learned one thing wandering around inside and outside the Solar System, it’s this: Nature has more ways of killing you than you can imagine. When you think you’ve learned them all, another one pops up to teach you humility—if you’re lucky. If not, someone else will have to decide what did you in.