Very cool, btw, about the ET. Just recently, my friend's brother mentioned tracking ISS as it flew across the sky in a matter of minutes the other night. Now I am going to have to commandeer my daughter's telescope some evening to take a look for myself.

On the subject of 'Colonizing Space,' thanks for providing a thread for so many interesting comments from this board's contributors.

Some afterthoughts.

Maybe 'Earths' exist, possibly even nearby, and maybe they don't. Now, do you think it will make a difference if there are or not?

Personally, I don't think it will. If humans are already out among the planets and migrating toward the edge of the Solar System, then at least one interstellar voyage to a nearby system becomes a possibility. But will they go? What would be the motivation? I am genuinely interested in what you think. My worldview obviously limits my own thinking on this.

By the time humans are ready to cross the interstellar void - if they ever are - they should already be aware of which nearby suns control living planets. By that time, perhaps one or two small but very, VERY expensive robotic probes may have been sent for a closer look. Curiosity, then, is the motivation in this case.

Another possible motivation might be that a sprawling interplanetary civilization may begin feeling 'done' and confined by the limits set by the Solar System. An interstellar project might go some distance toward injecting new life into a civilization in danger of stagnation. Expanding humanity's own sense of self might be the motivation here. Humans - or whatever they have become - might have run out of things to do, creating a psychological need to try something new. Maybe. I realize this is a stretch.

Any others? Because I'm out. I don't think an interstellar project can be justified on an economic basis. A manned starship is anything but practical. Something impractical must then serve as the pretext for such an awesomely challenging undertaking. In my opinion. But what's yours? Are there other motivations that might serve?

I've also given more thought to human autoevolution and am interested in what you think.

Let's say our AI successors head for the core, as Seth Shostak presumes they will. Might make sense. As Shostak says, there's plenty going on there. But since humans can't go, might autoevolved enhanced humans remain in some sort of contact with their AI kin? And one day step out into space to see what all the fuss has been about? But the AI life has congregated in the center of the Milky Way. Would enhanced humans deliberately choose the other direction? To explore the galaxy's thin habitable zone and beyond?

The lure of intergalactic space. It sounds like an oxymoron. What could be alluring about the vast empty void?

But maybe it will not turn out to be so empty. What, for instance, is the Great Attractor? What of the hidden structure of the universe, most of which lies between the galaxies?

The galactic bulge might be a known quantity by this time, thoroughly explored and inhabited by AI life. But what of the great Beyond?

Most of humanity will remain behind. Humans may, in fact, never leave Sol, having left that job to their AI cousins. But if humans do choose to depart the Solar System, they might set their sights on distant barely real Grails such as Andromeda, the LMC, the Dwingeloos, and others. Not so much to visit other galaxies, but to travel the spaces between.

To me, this twist is both unexpected and extremely intriguing. Then, as you say, humans would become the species that inhabits space rather than the stars.

Cobweb Between the Galaxies