Billions and Billions, by Carl Sagan (1997)

Because of the power of this exponential increase, dealing with global poverty now will be much cheaper and much more humane, it seems, than whatever solutions will be available to us many decades hence. Our job is to bring about a worldwide demographic transition and flatten out that exponential curve—by eliminating grinding poverty, making safe and effective birth control methods widely available, and extending real political power (executive, legislative, judicial, military, and in institutions influencing public opinion) to women. If we fail, some other process, less under our control, will do it for us.

If you understand exponentials, the key to many of the secrets of the Universe is in your hand.

Competitive sports are symbolic conflicts, thinly disguised.

After 10,000 generations in which the killing of animals was our hedge against starvation, those inclinations must still be in us. We hunger to put them to use, even vicariously. Team sports provide one way.

Some part of our beings longs to join a small band of brothers on a daring and intrepid quest. We can even see this in role-playing and computer games popular with prepubescent and adolescent boys. The traditional manly virtues—taciturnity, resourcefulness, modesty, accuracy, consistency, deep knowledge of animals, teamwork, love of the outdoors—were all adaptive behavior in hunter-gatherer times. We still admire these traits, although we've almost forgotten why.

Many hunter-gatherers organized egalitarian democracies. They had no chiefs. There was no political or corporate hierarchy to dream of climbing. There was no one to revolt against. So, if we're stranded a few hundred centuries from when we long to be—if (through no fault of our own) we find ourselves, in an age of environmental pollution, social hierarchy, economic inequality, nuclear weapons, and declining prospects, with Pleistocene emotions but without Pleistocene social safeguards—perhaps we can be excused for a little Monday-night football.

Eventually, we invented phonetic writing so we could put our sounds down on paper and, by glancing at a page, hear someone speaking in our head—an invention that became so widespread in the last few thousand years that we hardly ever stop to consider how astonishing it is.

Isolation breeds diversity; [...]

In the eighteenth century, it took about two years to sail from Europe to China.

How can light simultaneously be a wave and a particle? It might be better to think of it as something else, neither a wave nor a particle, something with no ready counterpart in the everyday world of the palpable, that under some circumstances partakes of the properties of a wave, and, under others, of a particle.