Great Filters, Part 9: Odds and Ends

Well, I think I've come to the end of my series on the Great Filters and the Fermi Paradox. There are a few bits which didn't quite fit into any of the earlier posts. So here they are, in more or less random order.

Have We Looked?

First, there's the issue of what Michael Hart called "Fact A" — we don't observe any extraterrestrial civilizations. But the actual fact is that we haven't detected them, not that they don't exist.

The shocking truth is that we haven't actually looked very hard. For the first fifty years of SETI, searches for extraterrestrial signals were small, spare-time affairs, involving a few hours of instrument time now and then, aimed at a handful of stars. More recently, donations by whimsical tech billionaires and a thin trickle of government funds have finally made it possible to set up dedicated radiotelescopes scanning the skies.

But even the mighty Breakthrough Listen project has only managed to search about 700 stars for signs of radio transmissions comparable to modern radar systems. That's the biggest SETI survey ever attempted, representing a decade of work. It represents one quarter of one-billionth of the stars in the Milky Way. Another billion years or so and they'll be done!

We don't know if there are any other civilizations in the Milky Way. We can't even really be sure there aren't any alien probes parked at Earth's Lagrange points or on the surface of a near-Earth asteroid, calmly watching us.

The actual, known facts are really as follows:

1: We are reasonably certain there are no giant omnidirectional beacons using the entire energy output of a star to power transmissions. At least not on this side of the Galaxy.

2: We are sure there are no civilizations within a few hundred light years beaming messages directly at us with an antenna the size of the Arecibo radiotelescope.

3: We know Earth was not colonized by an alien civilization eons ago (Or was it? See below!), nor dismantled by Von Neumann machines.

Other than that, we don't know!

Someone's Got To Be First

Someone's got to be the first species to reach a level of technology capable of interstellar communication. Maybe it's us. I've even toyed with a mathematical argument in favor of that. If you're born randomly in the Galaxy, which species are you most likely to be born into? Obviously, the odds favor the species which lasts the longest and exists in the greatest numbers. So the fact that I am a human supports the idea that humanity is the Elder Race of the Milky Way.

Of course the same argument can be used to demonstrate that we're on the verge of going extinct, since the odds favor being born at the time of humanity's greatest population. I suspect the entire argument is bogus, but I haven't been able to prove it yet.

Anyway, if my earlier estimates about the number of civilizations in the Milky Way are in the right ballpark, then there's about a 1 in 50 chance we're the oldest technological species. Those are long odds . . . but they're not impossible ones. Unless and until we do detect another civilization, this seems like the best assumption.

A Wizard Did It

Or God, or the programmer of the simulated reality we're all living inside, or whatever. The assumption, again, is that the Galaxy (if not the whole Universe) was either created specifically for us, or the simulation was run over and over and we're the first ones to appear this time (see above). Amusingly, one of the arguments in favor of the simulation hypothesis is exactly the same as my mathematical proof that we're the first.

Once you add a supernatural component, two things happen. First, any analysis based on the observed Universe becomes pointless, because the only elements that matter are the choices of whatever intelligence is directing and arranging things. Study theology instead of astronomy.

Second, all the questions just get moved up a level. Where did that creator or simulator come from? What are the rules of the "real" universe in which the simulation is running? Again, study theology.

We're Them

Or, perhaps we've been ignoring a key possibility. Maybe life didn't originate on Earth or in the Solar System. Maybe we owe our existence to some seeding expedition a couple of billion years ago. Rather than disproving the existence of ancient starfarers, maybe life on Earth is evidence they stopped off here.

That doesn't really negate any of the other Great Filters I've discussed, but it would change the numbers around. We could expect to find life everywhere, which makes intelligence and technology even less likely.

Of course, as Arthur C. Clarke suggested in 2001, perhaps our intelligence is also the result of alien meddling. Again, if we are made rather than the result of evolution, see the section on supernatural creators above.

They're Everywhere

One topic which keeps cropping up in discussions of the Fermi Paradox is that even if the aliens aren't interested in transmitting messages in our direction, we should still be able to detect any large-scale activities of theirs. Dyson spheres, stellar mining, laser-launched interstellar missions, and so forth. But (so far) we don't. See above for not looking much.

Unless, maybe we have but don't know it yet. One of my personal theories is that some astronomical phenomenon we've attributed to natural processes is really the work of intelligence elsewhere in the Galaxy. If any astronomers can think of something which is uncommon but shows up in other galaxies and has only tentatively been explained, maybe that should be re-examined as a potential sign of extraterrestrial intelligence.

All right, I'm done now. What now? Now we wait and see.

Comments

[MadRocketSci]

I suspect the entire argument is bogus, but I haven't been able to prove it yet.

The argument you're making is called a "Strong Anthropic Argument", which tries to infer some property of the likelihood of your existence from the fact of your existence.

There is a related line of argument: "Weak Anthropic Principles" (in this case weak as in it doesn't try to claim as much.) Weak Anthropic principles must be true. (Arguments of the flavor of "I think therefor I am".)

Wherever you go, there you are. Whatever sort of world you find yourself in must be a world that you *can* find yourself in.

Strong Anthropic Arguments have a problem with them though, and the problem is this: You can't define any measure over the set of possible situations that you find yourself in. Bayesian Reasoning isn't going to help you, because you can't define a prior probability. (No reasonable symmetry to use to distribute prior probability over a set evenly. Unless you've reincarnated a few times, you have no Frequentist sampling with which to develop a prior probability.)

(At least, I think that's what these two were called. I may be wrong. Engineer, not philosophy major.)

[MadRocketSci]

"Rather than disproving the existence of ancient starfarers, maybe life on Earth is evidence they stopped off here."

There's an infinite regress problem with this one. If the existence of life is evidence that it must have originated elsewhere, then there isn't anywhere where it could have originated. (Elsewhere keeps moving.)

[MadRocketSci]

PS: Not trying to nitpick or find fault, just trying to engage with your article.

[Cambias]

Oh, absolutely: panspermia doesn't explain the origins of life. But it does change a lot of the assumptions. If ancient aliens seeded the whole Galaxy, that means either intelligence is even less common than I posited . . . or there's some kind of really potent Great Filter about to filter us out of existence.

[Randomengineer]

As per my input on Centauri dreams one needn’t harness the power of a star to send a clear message. Here on earth in 2020 sober and rational types are discussing solar shades in orbit around the earth to address global warming. In a couple of hundred years it should be a realistic discussion to orbit larger shades around say alpha Centauri to form an unambiguous and clearly artificial optical message along the galactic plane. Keeping shades on orbit takes energy, yes, but not at the level of requiring the full output of a star. It seems to me that signaling can be done both relatively inexpensively and with tech not too far removed than our present capability. As such the lack of seeing a clear signal suggests we’re alone.