[js1138]

If you add 12 million years, 120 million years or even 1.2 billion years for travel time, you get the same result -- still a small fraction of the available time. If you postulate traveling at one percent the speed of light, and allow several centuries to colonize each new world, you still have time left over.

Perhaps not enough to colonize the entire galaxy, but certainly enough time to reach out several thousand light years.

[discostu]

But, you have to add time for the civilization to go from cavemen to that level of technology, which from what we're seeing is pretty long. And you have to assume they develop alone, uncontested (all spread times increase dramatically, possibly to the infinite when contested). And you have to assume they even want to colonize continuously until conquering the entire galaxy. Then finally you have to assume that either we have the technology to detect them, or they decided to communicate with us on our level of tech.

There are actually more assumptions in the "alone in the galaxy" arguement than in the "there's somebody else out there" position.