It is remarkable that observation of the faint agglomerations of stars known as galaxies leads us, very directly and cleanly, to the conclusion that we live in a Universe of finite and determinable age. A century ago, no one could have offered even an approximate age for the Universe. For an upper bound, most nonreligious scientists would probably have said “forever.” For a lower bound, all they had was the age of the Earth.

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.

Darya was beginning to understand why she might be ruined forever for academic life. Certainly, the world of ideas had its own pleasures and thrills. But surely there was nothing to compete with the wonderful feeling of being alive, after knowing without a shadow of doubt that you would be dead in one second.

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.