The “Wait But Why” blog takes an in depth look at something some of us were discussing on another thread: the Fermi Paradox.
Everyone feels something when they’re in a really good starry place on a really good starry night and they look up and see this:
Some people stick with the traditional, feeling struck by the epic beauty or blown away by the insane scale of the universe. Personally, I go for the old “existential meltdown followed by acting weird for the next half hour.”
But everyone feels something.Physicist Enrico Fermi felt something too—”Where is everybody?”
full article at The Fermi Paradox – Wait But Why.
I’ve written myself about the Fermi Paradox, and my belief that the simplest explanation is that intelligent life is very rare. But I’ll fully admit that this is an area where there’s still lots of rooms for possibilities. That said, I think we can be pretty confident from the paradox that the Star Trek version of reality, with scores of alien civilizations within a few dozen light years of Earth flying around faster than light, doesn’t exist.
SelfAwarePatterns 
The nice thing about “Intelligent Life is rare” as the Filter is that it’s going to get more testable over time, in the comparatively near future. If we direct image a couple of Earth-like planets around relatively nearby stars and find strong evidence that they have biospheres at work, it would be good evidence for that particular Filter unless we found some strange signs at work indicating the use of technology.
Well, if we could somehow find some negative mass-energy . . . ;D
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Good point. Of course, even with thousands of civilizations in the galaxy, the nearest would still likely be thousands of light years away, so it might still be a bit before we know for sure. But the longer we go without detecting any, the rarer they’re likely to be.
If we do detect nearby civilizations, that will likely have depressing implications for the possibility of interstellar travel, since most of them should be more advanced than us, and they’re not here.
Ah, if only we had that negative mass. Maybe the NASA research will come through.
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That’s what I’m worried about too. What if we find out that interstellar travel is basically impossible for engineering reasons, short of crazy thousand-year-generation ship set-ups? I’d still be happier with that than with intelligent life and civilizations being ultra-rare, but still . . .
I think dark energy generates negative pressure (possibly negative mass?). Problem is that it’s both very thinly and completely evenly distributed – no idea if we can change that.
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We should also keep in mind that there’s no guarantee that intelligent life evolved on other planets at the same time as us. We might find dozens of extinct civilizations out there, or it could turn out that we’re among the first few species to get this far.
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I agree. Though I think I’d change the wording in your first sentence from “no guarantee” to “almost certainly”. Stars and planets are constantly forming, and evolution would proceed at different rates. The chances of us running into another species at or near our rate of development seems nil. Other species we run into would likely be either at the level of apes or gods.
If we did find dozens of extinct civs, I think that would have depressing implications for our long term survival.
I see the possibility of us being the first evolved intelligence as something of a restatement of the rare intelligence theory. We might well be the first intelligent species in our corner of the universe.
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What does “same time” mean? Consider that there is no better way to synchronize clocks than sending a light signal. Photons moving at speed of light do not “experience” time. Although we know that some galaxies are millions light years away, we can’t quite say that what we see in them happened millions of years ago. No. What we see is what is happening there now. Simply because we don’t have a better definition of “now”. Photons from MBR are the photons created during the big bang. For those photons, big bang is “now”. Again, we attempt to extrapolate our very local “feel” of space and time to the whole universe, but how space and time is experienced out there can be very different and mind-boggling. I could not have imagined my life today 20 years ago. We contemplate what civilization might be like 4 bln years from now. It’s like a child imagining his life at 200 years old not knowing that humans rarely live beyond 100 years, and many die young. What if there is a natural time limit for existence of life on a planet? Unfortunately, we will never know that, leave alone collect any statistics.
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I see an issue with the article. A major one for me. It attempts to extrapolate the experience of our civilization which spans over less than 100,000 years to 4 billion years (!). It also extrapolates what we know about life on Earth to, excuse me, how many possible planets? I didn’t quite comprehend that number. These speculations and calculations seem to have astronomically small credibility. Extrapolations based on such a small sample don’t have a chance to have anything to do with reality. I thought, we don’t even quite know what the universe is made of and call most of the stuff “dark matter”. Blame me for lack of imagination and curiosity, but I simply refuse to draw any conclusions to this effect.
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Agreed. We don’t even know what dark matter or dark energy are, so extrapolating anything we think we know about ourselves to a cosmic scale is not a very quantitative science.
But even if those numbers are wildly inaccurate, we can still speculate about why they might be inaccurate, and the great filter theory seems the most logical explanation, if we have to pick one. To prove it, we would need to find a number of Earthlike planets with no life, or just very primitive life. Since that would probably involve sending remote probes to the planets, it’s going to take a few hundred years, I would guess.
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I didn’t get the implied certainty from the article that you did. Certainly, the information we have to work with is profoundly limited. All we can really do is assess broad possibilities, and I perceived the article to be honest about that. Ultimately though, we don’t know what we don’t know. But the alternative is simply not to speculate at all, and where’s the fun in that?
As Steve notes, those possibilities will become more constrained over time as we continue to make observations. I think we’ll have telescopes in the coming decades that will be able to tell us if we have a technological civilization nearby (less than 100 light years). And whether or not we find any will obviously affect our view of these possibilities.
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I did not say that the article implies certainty and the speculations are fun. I think, this stuff belongs in science fiction. It’s not about the article, it’s about my attitude to such questions. For me, it’s more interesting and exciting to consider what is (what we do observe), how it came to be, and what will become of it, rather than contemplating what is not (what we do not observe) and why.
As for Fermi paradox, I don’t see a paradox there. Consider the Powerball lottery with chances of winning the jackpot of 1 in 175,223,510. Eventually, someone wins it (most certainly). But I see no paradox that I never do. It does not mean, though, that I should not buy the tickets.
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Sorry, didn’t mean to put words in your mouth. I do have a higher regard for this kind of reasoning than you do, but I definitely agree we have to keep its highly speculative nature in mind.
In my mind, the Fermi paradox is just the observation that all the calculations about how many civilizations should be out there, simply aren’t consistent with the observation that zero of them are here. It’s really only a “paradox” if you hold those calculations to a much higher level of certitude than they warrant, failing to appreciate how little we know.
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I think, what struck me as odd is the Kardashev’s classification of undiscovered civilizations. How good can be a classification of something that we have never seen?
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I think the Kardashev types should be regarded purely as a thought experiment. Certainly, we don’t even know if a Type I civilization is possible, much less a Type II or III. But if any of them should exist, thinking through the implications might give us ideas on what to look for.
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That’s an extremely comprehensive article. There are other theories I’ve come across, but they’re all very silly. The only ones that make any sense to me are 1) the great filter, and 2) we’re completely wrong about reality.
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I agree on the great filter. The question is where it lies. It could be at the start of life itself, or perhaps in the development of complex organisms, or (more darkly) in the tendency of intelligent life to destroy itself.
One possible filter I’ve thought about is sexual reproduction. It was billions of years before it evolved, and I wonder how complex life would have become without it. It might be that most life never reaches the complex stage because it doesn’t happen to evolve this complex process.
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Life appeared on Earth amazingly quickly after the planet was created, so that doesn’t seem to have been much of a filter. But then nothing much happened for a long time. The jump to multi-cellular life and sexual life were great filters.
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