Want to know why Nick Bostrom is “hoping that our space probes will discover dead rocks and lifeless sands on Mars, on Jupiter’s moon Europa, and everywhere else our astronomers look”? Well then, read on.
It’s an interesting idea, this Great Filter (or what Chris McLaren, who posted about this way back in May, calls the “Doom Constant”), and it’s one full of scary implications for the survival of the human species. Bostrom suggests that if the emergence of intelligent life in the universe is not itself a rare event, then we surely have to wonder why none of it has been in contact with us. Is there a cataclysmic event waiting to kill off all advanced species, or have we already crossed that threshold and beaten the odds?
As McLaren notes, Bostrom “never gets near the possibility that the ‘Great Filter’ might actually be intelligent, outside action, rather than a self-destructive tendency.” (Having recently read Alastair Reynolds’ Revelation Space, I can totally get behind that idea.) But he also doesn’t get too close to the possibility that maybe advanced alien cultures have been in contact — not through alien abduction or even radio waves, but in exactly what Bostrom calls the likeliest method of space colonization.
“Even if [the aliens] failed a thousand times before they succeeded,” he writes, “they still could have arrived here hundreds of millions of years ago.”
My question is this: how do we know they didn’t? If “so-called von Neumann probes” indeed are the most likely means of colonizing other planets, how do we know they didn’t already colonize Earth? Maybe some species here — maybe humans, maybe even all life — is a direct descendant of that first probe.
Granted, this kind of exogenesis might not factor into Bostrom’s thinking at all, even if there was anything like credible evidence to support it. Regardless of where life on this planet began, the probability, one way or another of it, ending is of definite concern. But as a fan of science fiction, as someone who can’t help but wonder the “what if,” it’s an interesting thought.
And when you add in this (via Warren Ellis)…
Molecular “robots” have been developed by chemists to explore the unmapped chemical environments of living cells and transmit back the results.
…well, it just opens up all sorts of interesting scenarios…
I’ve never really bought into the whole “Where are they?” school of thought. Yes, the observable universe is incredibly immense, and yes we have discovered who knows how many possible solar systems in it. But our technology is so limited that we can’t make any sort of reliable statements about anything that is not in our own solar system — and even a lot of that is still speculative.
And all those trillions and trillions and quadrillions of stars out there? Most of them are billions of light years away. Even if we could reliably observe them from our vantage point, we’d be seeing them as they were billions of years ago, not as they are today. And the same goes for observers on those planets looking at us. From that distance, all they’d see of us (if they could see us at all) is a primordial soup at best.
If there is any sort of “Great Filter,” I have a hard time believing it’s anything as romantically science fiction-y as an evolutionary leap. It makes more sense to me that it’s just a matter of basic limits, both physical (being unable to travel or communicate faster than the speed of light) and biological (life spans that are significantly less than the millions or billions of years required to travel between star systems).
The simple fact is, we have no way of knowing if anyone else is out there, and we probably never will. In an infinitely vast universe, there could conceivably be millions of intelligent civilizations out there, but spread out so thin that they will never be able to know each other.
I think I mentioned this earlier, too, but Stephen Baxter’s Manifold: Space covers this idea in great depth, talking about advanced alien species and the scars they might have left on our solar system.
Baxter is incredibly smart, and his books sometimes read like dissertations on theoretical physics with characters, but they’re really good reads if you like Hard SF, and you always go away with more knowledge about the cutting edge theories of some school of thought.