The Great Filter and the three f's

In yesterday's post, we looked at how the Drake Equation predicts the number of intelligent civilizations out there in the galaxy, and that more than one of the variables has been revised upward in the last few years because of recent research in astronomy.  This suggests that life is probably super-common in the universe -- and intelligent life undoubtedly is out there, as well.

But we ended with a puzzle.  Physicist Enrico Fermi famously responded to Frank Drake with four words: "Then where is everybody?"  This was true back when it was said (1961) and is even more true now; in the intervening 57 years, we've done huge amounts of surveying of the sky, looking for any sign of an extraterrestrial intelligence, and found... nothing.

Now, to be fair, "huge amounts of surveying" still covers a minuscule fraction of the stars out there.  All that would have to happen is the radio signal saying, "Hi, y'all, here we are!" hitting Earth while our radio telescopes were aimed at a different star, or tuned to a different frequency, and we could well miss it.

Messier 51, the Whirlpool Galaxy [Image courtesy of NASA/JPL]

But there's a more sinister possibility, and that possibility goes by the nickname of "The Great Filter."

I looked at this concept in a post a while back, especially apropos of the variable "L" in the Drake Equation -- once a planet hosts intelligent life, how long does it last?  If we were to time-travel two thousand years into the future, would there still be a human civilization, or are we doomed to destroy ourselves, either by our own fondness for weaponry capable of killing large numbers of people at once, or because our rampant population growth exceeded the planet's carrying capacity, and we experienced what the ecologists somewhat euphemistically call "overshoot-and-rebound?"

But today I want to look at the Great Filter in a larger perspective.  Given that most astronomers think that the Drake Equation leads to the conclusion that life, and even intelligent life, is common out there, Fermi's quip is well taken.  And the answers to that question can be sorted into three basic categories, which have been nicknamed the "three f's":

1. We're first.
2. We're fortunate.
3. We're fucked.

Could we be the first planet in our region of the galaxy to harbor intelligent life?  It's certainly possible, especially given the time gap between our developing life (four-odd-billion years ago) and our developing the technology not only to send, but to detect, signals from other planets (about fifty years ago).  Consider, for example, that if there was a civilization on Alpha Centauri at the technological stage we had two hundred years ago, they would have a thriving society made up of individuals that are highly intelligent, but to us here on Earth, they would be completely silent (and also wouldn't know it if we were talking to them).

However, considering the number of stars with planets, even in our region of the Milky Way, I think that's unlikely.  Even if we were all on a similar time table -- a contention that is not supported by what we know of stellar evolution -- it's nearly certain that there'd be someone out there at, or ahead of, our level of technology.  Add to that the fact that there are a lot of planet-hosting stars out there that are much older than the Sun, and I think option #1 is really not that likely.

Might we just be fortunate?  There are a number of hurdles we had to overcome to get where we are, none of which were at all sure bets.  The development of complex multicellular life, the evolution of symbiosis between our cells and what would eventually become our mitochondria (allowing us not only to avoid the toxic reactiveness of atmospheric oxygen, but to hitch that to our energy production systems, an innovation that improved our energy efficiency by a factor of 18).  None of those are at all guaranteed, and although it's conceivable to have intelligent life that lacks those characteristics, it's kind of hard to imagine how it would advance this much.

Then there's the evolution of sexual reproduction, which is critical not only because it's fun, but because it allows recombination of our genetic material each generation.  This allows us to avoid the dual problems of genetically-identical individuals being susceptible to the same pathogens, and also Muller's Ratchet (a problem faced by asexual species that is best understood as a genetic game of Telephone -- at each replication, mutations build up and eventually turn the DNA into nonsense).

But no one knows how likely the evolution of sexual reproduction is -- nor, honestly, if it's really as critical as I've suggested.

The last possibility, though -- "we're fucked" -- is the most alarming.  This postulates that the Great Filter lies ahead of us.  The reasons are varied, and all rather depressing.  It could be the "L" in the Drake Equation is a small number -- on the order of decades -- because we'll destroy ourselves somehow.  It could be that there are inevitable cosmic catastrophes that eventually wipe out the life on a planet, things like Wolf-Rayet stars and gamma-ray bursters, either of which would be seriously bad news if one went boom near the Solar System.

Then there's Elon Musk's worry, that intelligent civilizations eventually develop artificial intelligence, which backfires spectacularly.  In 2017 he urged a halt, or at least a slowdown, in AI research, because there's no reason to think sentient AI would consider us all that valuable.  "With artificial intelligence," Musk said, "we are summoning the demon.  You know all those stories where there’s the guy with the pentagram and the holy water and he’s like, yeah, he’s sure he can control the demon?  Doesn’t work out."

But by far the most sinister idea is that we're doomed because eventually, a civilization reaches the point where they're able to send out radio signals.  We've been doing this ever since radio and television were invented, so there's an expanding bubble of our transmissions zooming out into the galaxy at the speed of light.  And the idea here is that we'll eventually attract the attention of a considerably more powerful civilization, which will respond by stomping on us.  Stephen Hawking actually thought this was fairly likely -- back in 2015, he said, "We don't know much about aliens, but we know about humans.  If you look at history, contact between humans and less intelligent organisms have often been disastrous from their point of view, and encounters between civilizations with advanced versus primitive technologies have gone badly for the less advanced.  A civilization reading one of our messages could be billions of years ahead of us.  If so, they will be vastly more powerful, and may not see us as any more valuable than we see bacteria."

Which, considering that the first traces the aliens will see of us are Leave it to Beaver and The Andy Griffith Show, is an understandable reaction.

So there you have it.  If we did contact another civilization, it would be good news in one sense -- the Great Filter hasn't wiped everyone out but us -- but could be a seriously bad one in another respect.  I guess stuff like this is always a mixed bag.

Me, I still would love to live long enough to see it happen.  If an alien spaceship landed in my back yard, man, I would be thrilled.  It'd suck if it turned out to be an invasion by Daleks or Cybermen or whatnot, but man, at least for the first three minutes, it would be a hell of a rush.

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This week's Skeptophilia book recommendation is from one of my favorite thinkers -- Irish science historian James Burke.  Burke has made several documentaries, including Connections, The Day the Universe Changed, and After the Warming -- the last-mentioned an absolutely prescient investigation into climate change that came out in 1991 and predicted damn near everything that would happen, climate-wise, in the twenty-seven years since then.

I'm going to go back to Burke's first really popular book, the one that was the genesis of the TV series of the same name -- Connections.  In this book, he looks at how one invention, one happenstance occurrence, one accidental discovery, leads to another, and finally results in something earthshattering.  (One of my favorites is how the technology of hand-weaving led to the invention of the computer.)  It's simply great fun to watch how Burke's mind works -- each of his little filigrees is only a few pages long, but you'll learn some fascinating ins and outs of history as he takes you on these journeys.  It's an absolutely delightful read.

[If you purchase the book from Amazon using the image/link below, part of the proceeds goes to supporting Skeptophilia!]

Fermi's Paradox, fast radio bursts, and extraterrestrial intelligence

Just because I believe that science works, and that its methods are sound, doesn't mean that I have to like its conclusions.  And one of my least favorite pieces of sound scientific reasoning is Fermi's Paradox.

Named after the Nobel Prize-winning physicist Enrico Fermi, Fermi's Paradox originally took the form of a succinct response to all of the speculation about life in other star systems.  According to everything we know about stellar evolution, planet formation, biochemistry, and evolutionary biology, life should be common out there.  And just considering the fact that some star systems with planets are likely to be considerably older than ours, it also stands to reason that there should be civilizations out there considerably more advanced than ours.

Upon hearing this sort of argument, Fermi responded with a simple question:  "Where is everybody?"  If life, and intelligent life, is as common as all that, we should be bombarded with signals from extraterrestrials.  And in fact, despite decades of searching the skies, there has never been a single unequivocal transmission found from an intelligent life-form.  (Although the "WOW Signal" might be a contender; it's yet to be explained.)

There are a number of possible explanations for the lack of extraterrestrial communications, and most of them are depressing.  It could be that the likelihood of intelligent life developing on planets is, for some reason, a great deal less likely than we think it is (i.e. we here on Earth were just damn lucky).  It could be that most civilizations destroy themselves shortly after achieving the capacity for long-distance communication.  Some astronomers even think that there are cosmic reset switches -- natural phenomena that periodically wipe the galaxy clean of life, requiring a prolonged reboot, and preventing most life ever from achieving technology.  (For example, consider gamma-ray bursters, but only if you want to spend the next few days worrying about the entire solar system suddenly getting fried.)

Being someone who would love nothing better than to witness the discovery of extraterrestrial intelligence, I find the Fermi Paradox a significant downer.  I do have one possible answer that may still allow for a rich diversity of intelligent life in the galaxy, however; because we are looking for communication in the radio region of the spectrum (the fashion in which we as a species first learned to do long-distance transmission of information), it might be that such discernible, signal-producing modes of communication are quickly superseded by more sophisticated technologies that produce much less in the way of a footprint when observed from light years distant.  In other words; societies might only be detectable during the first few decades of their technological existence, when they're communicating with each other by shouting from the rooftops.  After they learn more efficient means of transmitting information, they seem to go silent.

I hope.  Because otherwise, it's mighty lonely here, you know?

All of this comes up because of a paper published just last week by Michael Hippke, Wilfried Domainko, and John Learned called "Discrete Steps in Dispersion Measures of Fast Radio Bursts."  In this interesting bit of research, an analysis was done of the dispersion measures of microseconds-long pulses in the radio region of the spectrum.  The paper is quite technical -- even with a B.S. in physics, it was over my head -- but insofar as I understand it, the curious thing about the eleven radio pulses thus far detected is that their dispersion measures are all integer multiples of 187.5 parsec/cm3 -- something that admits of no particularly obvious natural explanation.

Carl Sagan, in his wonderful novel (and later movie) Contact, used the idea of encoding a signal with some mathematical pattern as a way of broadcasting a "We're Here" signal into space -- or, conversely, looking for such a signal as a way of detecting life that's out there.  If a radio signal could be encoded with the first ten digits of pi, or (as in Contact) the first few prime numbers, that would be instantly recognizable as an unequivocal signal from an intelligence.  So the discovery of the 187.5 pattern in dispersion measures for FRBs was immediately jumped upon as evidence that the radio bursts originate from some alien civilization.  (The International Business Times, for example, was all a-quiver with the possibility.)

The astrophysicists, of course, are being more circumspect.  All that Hippke, Domainko, and Learned concluded from their research is that the pattern is currently unexplained, if suggestive:

(A)n extragalactic origin would seem unlikely, as high (random) DMs would be added by intergalactic dust.  A more likely option could be a galactic source producing quantized chirped signals, but this seems most surprising.  If both of these options could be excluded, only an artificial source (human or non-human) must be considered, particularly since most bursts have been observed in only one location (Parkes radio telescope)...  In the end we only claim interesting features which further data will verify or refute. 

They also suggest that the FRBs might actually be perytons, signals that appear to originate from space when they actually are entirely terrestrial in origin -- i.e. human-generated signals that are being misinterpreted, or simple radio telescope glitches.

Whatever the explanation is, the FRBs are an interesting phenomenon, and give me hope that there might be an eventual answer to Fermi's Paradox.  I have to be careful about letting my desire for there to be intelligent life elsewhere in the universe get in the way of my objectivity in evaluating the evidence at hand; but even so, the strange mathematical pattern that Hippke et al. have discovered might be the best contender we currently have for an alien civilization saying, "Here we are!"