Even if they reached a habitable world, would there be enough of them to create a viable community?

The world was a watery one, as almost all habitable worlds were.

"Isn't it nice that these monuments always seem to be on habitable worlds?"

Where was the star with habitable worlds not yet known?

If there's a habitable world, one seed is bound to hit it.

Yet this still leaves an estimated four million habitable worlds.

The ground there is too hot to touch; all reminders of a habitable world are gone.

And at the most basic level, the habitable worlds were just too different from each other.

But there were sectors in which the best hope was to find a merely habitable world.

Unless we make planet-fall on some habitable world soon, you will all be dead.