Once we lose our fear of being tiny, we find ourselves on the threshold of a vast and awesome Universe which dwarfs — in time, in space, and in poten… - Carl Sagan

In the long run, the aggressive civilizations destroy themselves, almost always. It's their nature. They can't help it.

If we're stuck on one world, we're limited to a single case; we don't know what else is possible. Then — like an art fancier familiar only with Fayoum tomb paintings, a dentist who knows only molars, a philosopher trained merely in NeoPlatonism, a linguist who has studied only Chinese, or a physicist whose knowledge of gravity is restricted to falling bodies on Earth — our perspective is foreshortened, our insights narrow, our predictive abilities circumscribed. By contrast, when we explore other worlds, what once seemed the only way a planet could be turns out to be somewhere in the middle range of a vast spectrum of possibilities. When we look at those other worlds, we begin to understand what happens when we have too much of one thing or too little of another. We learn how a planet can go wrong.

The beauty of a living thing is not the atoms that go into it, but the way those atoms are put together.