Should we devote resources to trying to expand across the galaxy and thus influence events millions of years in the future? I say no.

I've been thinking about this question for many years, and it's just in the past few days I've learned about the Singularity. I don't at the moment assign a very high probability to that -- yes, I'm ignorant, but I'm going to leave it out for the moment.

Suppose we posit that from some currently unavailable combination of technology, physics, psychology, politics and economics (for starters) we can have "legs" and cover interstellar ground. We also crucially need a density of planets that can be exploited to create the vibrant economies that could launch other expensive spacecraft to fuel exponential growth. If we're going to expand using humans, we have to assume a rather high density of not just planets that can support intelligent life, but planets that can support our particular form of intelligent life -- earth-like planets. We have to assume that those planets have not evolved competent, intelligent life of their own -- even if they are far behind us technologically, their inherent advantages of logistics could very well keep us from displacing them. But on the plus side, it also seems highly likely that if we can get such a process of exponential growth going in our corner of the galaxy, it could then be expanded throughout our galaxy (at the least).

If we can do it, so can they -- actually, they already did.

To expand that, I attach great importance to the fallacy of human exceptionalism. Over history we've had to give up beliefs about cultural and racial superiority, humans being fundamentally different from animals, the earth being the center of the universe, the sun being the center of the universe... The list is familiar.

We've discovered stars with planets. Perhaps fewer have small, rocky (non-gas giant) planets than theories initially suggested, but there are a few (last I knew) and that's just a small adjustment in our calculations. We have no evidence whatsoever that our solar system is exceptional on the scale of the galaxy -- there are surely many millions of rocky planets (a recent news story suggests billions).

Just how improbable is the development of intelligent life? I'd be interested to know how much deep expertise in biology we have in this group. The 2011 survey results say 174 people (16%) in the hard sciences, with some small fraction of that biologists? I claim no expertise, but can only offer what (I think) I know.

First, I'd heard it guessed that life developed on earth just about as soon as the earth was cool enough to allow its survival. Second, evolution has produced many of its features multiple times. This seems to bear on how likely evolution elsewhere is to develop various characteristics. If complicated ones like wings and eyes and (a fair amount of) intelligence evolved independently several times, then it wasn't just some miraculous fluke. It makes such developments in life on other planets seem far more probable. Third, the current time in earth history does not have a special status. If intelligent life hadn't evolved on earth now, it had a few billion more years to happen.

Based on those considerations, I consider it a near certainty that alien civilizations have developed -- I'd guess many thousands in our galaxy as a minimum. It's a familiar argument that we should assume we are in the middle of such a pack temporally, so at the least hundreds of civilizations started millions of years ago. If expansion across the galaxy was possible, they'd be here by now. The fact that we have detected no signals from SETI says virtually nothing -- that just means there is nobody in our immediate vicinity who is broadcasting right now.

Since we haven't observed any alien presence on earth, we would have to assume that civilization expansion is not independent -- some dominant civilization suppresses others. There are various possibilities as to the characteristics of that one civilization. They might want to remain hidden. They might not interfere until a civilization grows powerful enough to start sending out colonies to other worlds. Perhaps they just observe us indefinitely and only interfere if we threaten their own values. Even in some benign confederation, where all the civilizations share what they have to offer, we would offer just one tiny drop to a bucket formed from -- what, millions? -- of other civilizations. What all of these have in common is that it is not our values that dominate the future: it's theirs.

It seems likely to me that my initial assumption about exponential space colonization is wrong. It is unfashionable in futurist circles to suggest something is impossible, especially something like sending colonists to other planets, something that doesn't actually require updates to our understanding of the laws of physics. Critics point out all the other times someone said something was impossible, and it turned out that it could be done. But that is very different from saying that everything that seems remotely plausible can in fact be done. If I argued against interstellar colonization based on technical difficulties, that would be a weak argument. My argument is based on the fact that if it were possible, the other civilizations would be here already.

This argument extends to the colonization potential of robots produced in the aftermath of the Singularity. If their robots could do it, they'd be here already.

To achieve the huge win that would make such an expensive, difficult project worthwhile, exponential space colonization has to be possible, and we have to be the first ones. I think both are separately highly unlikely, and in combination astronomically unlikely.