Serious thinkers pointed out that humankind was scarcely ready to colonize the stars, having solved none of its problems at home.

We weren't managed from the word go, like U2 or Simple Minds, to get bigger and bigger and take over the planet.

Human anatomy is horribly unsuited for outer space. The astroengineers lost sleep over this but not the science fiction writers, who being artists simply didn't mention it.

All the hundreds of millions of people who, in their time, believed the Earth was flat never succeeded in unrounding it by an inch.

We hadn't invented 'Not Invented Here', yet.

I couldn’t remember any science-fiction stories that actually dealt with how you’d handle timekeeping on a new planet.

For two hundred and fifty years the kzinti had not attacked human space. They had nothing to attack with. For two hundred and fifty years men had not attacked the kzinti worlds; and no kzin could understand it. Men confused them terribly.

Creating stars in laboratories on the very planets you inhabit turns out to be a bad idea.

When you compare Mars to Earth, and Venus to Earth, you can see the problem [earthlings face]. We do not want to become Venus.

...nor has any physical experiment ever proved that the Earth actually is in motion.

Mans can't make moons

I'm only sorry I was born three-quarters through this self-inflicted tragedy and not at the very beginning or at the very end. I'm fucking sick of watching this tragedy in slow motion. The other planets aren't though - they're on the edge of their suns. The reason we've never had visitors from outer space isn't that they don't exist but that they don't want to know us. We're the village idiots of all the teeming galaxies. On. quiet night you can hear their cackled laughter. And what are they laughing at? Let me put it this way: humanity is the guy who shits in his own pants and then walks around saying, 'So, do you like my new shirt?'

We thought nothing of running right ahead ten or a dozen miles before turning back; for we knew nothing about taking time by the sun, and none of us had a watch in those days.

But you've never even been as far as the Moon.