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“Dissolving the Fermi Paradox”

Jonathan Falk writes:

A quick search seems to imply that you haven’t discussed the Fermi equation for a while.

This looks to me to be in the realm of Miller and Sanjurjo: a simple probabilistic explanation sitting right under everyone’s nose. Comment?

“This” is a article, Dissolving the Fermi Paradox, by Anders Sandberg, Eric Drexler and Toby Ord, which begins:

The Fermi paradox is the conflict between an expectation of a high ex ante probability of intelligent life elsewhere in the universe and the apparently lifeless universe we in fact observe. The expectation that the universe should be teeming with intelligent life is linked to models like the Drake equation, which suggest that even if the probability of intelligent life developing at a given site is small, the sheer multitude of possible sites should nonetheless yield a large number of potentially observable civilizations. We show that this conflict arises from the use of Drake-like equations, which implicitly assume certainty regarding highly uncertain parameters. . . . When the model is recast to represent realistic distributions of uncertainty, we find a substantial ex ante probability of there being no other intelligent life in our observable universe . . . This result dissolves the Fermi paradox, and in doing so removes any need to invoke speculative mechanisms by which civilizations would inevitably fail to have observable effects upon the universe.

I solicited thoughts from astronomer David Hogg, who wrote:

I have only skimmed it, but it seems reasonable. Life certainly could be rare, and technological life could be exceedingly rare. Some of the terms do have many-order-of-magnitude uncertainties.

That said, we now know that a large fraction of stars host planets and many host planets similar to the Earth, so the uncertainties on planet-occurrence terms in any Drake-like equation are now much lower than order-of-magnitude.

And Hogg forwarded the question to another astronomer, Jason Wright, who wrote:

The original questioner’s question (Thomas Basbøll’s submission from December) is addressed explicitly here.

In short, only the duration of transmission matters in steady-state, which is the final L term in Drake’s famous equation. Start time does not matter.

Regarding Andrew’s predicate “given that we haven’t hard any such signals so far” in the OP: despite the high profile of SETI, almost no actual searching has occurred because the field is essentially unfunded (until Yuri Milner’s recent support). Jill Tarter analogizes the idea that we need to update our priors based on the searching to date as being equivalent to saying that there must not be very many fish in the ocean based on inspecting the contents of a single drinking glass dipped in it (that’s a rough OOM, but it’s pretty close). And that’s just searches for narrowband radio searches; other kinds of searches are far, far less complete.

And Andrew is not wrong that the amount of popular discussion of SETI has gone way down since the ’90’s. A good account of the rise and fall of government funding for SETI is Garber (1999).

I have what I think is a complete list of NASA and NSF funding since the (final) cancellation of NASA’s SETI work in 1993, and it sums to just over $2.5M (not per year—total). True, Barnie Oliver and Paul Allen contributed many millions more, but most of this went to develop hardware and pay engineers to build the (still incomplete and barely operating) Allen Telescope Array; it did not train students or fund much in the way of actual searches.

So you haven’t heard much about SETI because there’s not much to say. Instead, most of the literature is people in their space time endlessly rearranging, recalculating, reinventing, modifying, and critiquing the Drake Equation, or offering yet another “solution” to the Fermi Paradox in the absence of data.

The central problem is that for all of the astrobiological terms in the Drake Equation we have a sample size on 1 (Earth), and since that one is us we run into “anthropic principle” issues whenever we try to use it to estimate those terms.

The recent paper by Sandberg calculates reasonable posterior distributions on N in the Drake Equation, and indeed shows that they are so wide that N=0 is not excluded, but the latter point has been well appreciated since the equation was written down, so this “dissolution” to the Fermi Paradox (“maybe spacefaring life is just really rare”) is hardly novel. It was the thesis of the influential book Rare Earth and the argument used by Congress as a justification for blocking essentially all funding to the field for the past 25 years.

Actually, I would say that an equally valid takeaway from the Sandberg paper is that very large values of N are possible, so we should definitely be looking for them!

So make of that what you will.

P.S. I posted this in July 2018. The search for extraterrestrial intelligence is one topic where I don’t think much is lost in our 6-month blog delay.


  1. Jag Bhalla says:

    Intriguing twist… any globe-girdling civilization will likely have to survive a tech-generated climate crisis. As Adam Frank’s recent book, Light of the Stars: Alien Worlds and the Fate of the Earth, argues. Here’s a short interview

    And that usefully connects to a way to think about the moral (=social coordination) problems faced by anything that seeks to survive in an environment with limits.

    Extending Turing, and Constructor Theory…. The Logic of Universal Survivors

  2. Chenowith says:

    or, Boltzmann Brain

    or, “Reality is an illusion” — Albert Einstein

    • Ethan Bolker says:

      Hungarians and the Fermi Paradax


      “They are among us,” it is reported that Hungarian-born physicist Leo Szilard responded [to Fermi], “but they call themselves Hungarians.”

      Apparently, Szilard’s comment had some cultural and historical basis. The following passage is from The Curve of Binding Energy by John McPhee (1973, Farrar, Straus and Giroux, pp. 104-105):

      “Not all the Los Alamos theories could be tested. Long popular within the Theoretical Division was, for example, a theory that the people of Hungary are Martians. The reasoning went like this: The Martians left their own planet several aeons ago and came to Earth; they landed in what is now Hungary; the tribes of Europe were so primitive and barbarian it was necessary for the Martians to conceal their evolutionary difference or be hacked to pieces. Through the years, the concealment had on the whole been successful, but the Martians had three characteristics too strong to hide: their wanderlust, which found its outlet in the Hungarian gypsy; their language (Hungarian is not related to any of the languages spoken in surrounding countries); and their unearthly intelligence. One had only to look around to see the evidence: Teller, Wigner, Szilard, von Neumann — Hungarians all. Wigner had designed the first plutonium-production reactors. Szilard had been among the first to suggest that fission could be used to make a bomb. Von Neumann had developed the digital computer. Teller — moody, tireless, and given to fits of laughter, bursts of anger — worked long hours and was impatient with what he felt to be the excessively slow advancement of Project Panda, as the hydrogen-bomb development was known. … Teller had a thick Martian accent. He also had a sense of humor that could penetrate bone.”

  3. Dan F. says:

    Given the size of the universe, the number of stars, and so forth, there is near certainty that there is other intelligent life in the universe. The is even greater certainty that we will never be able to confirm such a statement. The distance to the nearest star that could possibly have in its orbit a planet supporting life is so great that communication with such life, even via the fastest signals possible (light) is impossible in the lifetime of those now living … No other form of communication is physically (!) possible.

    These aren’t wild speculations, they are relatively obvious statements to someone who knows a bit of physics. People look for all sorts of ways around them, but this is just the religious impulse manifesting itself.

    • Kyle C says:

      +1 to this, plus, the “relevant” neighborhood is at best our galaxy, not the whole universe, and there is no reason to think that other intelligent life in our galaxy would overlap with the short flicker of time that we’ve been, or will be around.

    • some guy says:

      “Given the size of the universe, the number of stars, and so forth, there is near certainty that there is other intelligent life in the universe.”

      Not necessarily. My gut feeling would be that there is intelligent life elsewhere, but we simply can’t assign a probability to it. It’s easy to assume that life is elsewhere based on the immensity of stars in the universe, but this reasoning doesn’t consider that the probability of intelligent life developing may be infinitesimal. Maybe we are simply an extreme fluke in the universe? Several evolutionary biologists have chimed in on the SETI project and argued that intelligent life is likely improbable. Of all the lineages on earth, only ours has developed the capacity for abstract thought and tool-making that suggests that interstellar travel may be possible. If the evolution of higher intelligence was more probable, we would have expected it to have arisen more than once through convergent evolution.

      • Kyle C says:

        Hmm. Well it’s hard to debate subjective probabilities, I suppose. Yet given that there are around 10^24 planets in the observable universe alone, and the unobservable universe probably looks about the same, and most planets will exist for billions of years, even if the probability of intelligent life emerging in a given place is “infinitesimal,” it would seem overwhelmingly likely to happen at least twice in the life of the universe. In our own galaxy, not so much, I could easily believe we are alone.

    • Dzhaughn says:

      The “religious impulse” is almost certainly correct, but it is vastly more certain that it cannot be confirmed by empirical methods.

    • David L. says:

      Even worse, we wouldn’t be able to recognize a signal from a fellow intelligent being even if we saw one. Spread spectrum signals are indistinguishable from noise unless you know the pattern of the frequency hops, thanks to Heddi Lamar, and intelligent aliens are presumably more advanced than movie actresses (so decoding the signal could be even hairier than that). Next there’s the language problem. Since we don’t know what their vocal chords look like, we have no idea of what sounds they differentiate, let alone how relevant/irrelevant current linguistic theories might be. (And the basic “clock rate” of their brains could be one or more orders of magnitude slower or faster than ours.) And then there’s the problem of what fellow intelligent beings would be talking about and interested in; we sent popular songs and TV shows on one of our extra-solar-system probes, stuff that would make no sense to even ourselves 50 years later.

      To the best I can tell, SETI makes no sense.

  4. Mark Palko says:

    For a bit of historical perspective, speculation about extraterrestrial life and how to contact it gained a serious foothold in the 19th century, arguably peaking with Lowell’s Martian Canals []. I’ve got a post coming up about the NYT announcing the major accomplishments of Martian engineers.

  5. Mark Palko says:

    Important to remember that Lowell and Tesla weren’t as far out of the mainstream on this as you might think.

    “Assuming that Richard A. Locke was the author, his intentions were probably, first, to create a sensational story which would increase sales of The Sun, and, second, to ridicule some of the more extravagant astronomical theories that had recently been published. For instance, in 1824, Franz von Paula Gruithuisen, professor of Astronomy at Munich University, had published a paper titled “Discovery of Many Distinct Traces of Lunar Inhabitants, Especially of One of Their Colossal Buildings.” Gruithuisen claimed to have observed various shades of color on the lunar surface, which he correlated with climate and vegetation zones. He also observed lines and geometrical shapes, which he felt indicated the existence of walls, roads, fortifications, and cities.

    However, a more direct object of Locke’s satire was Rev. Thomas Dick, who was known as “The Christian Philosopher” after the title of his first book.[6] Dick had computed that the Solar System contained 21,891,974,404,480 (21.9 trillion) inhabitants. In fact, the Moon alone, by his count, would contain 4,200,000,000 inhabitants.[7] His writings were enormously popular in the United States, his fans including intellectual luminaries such as Ralph Waldo Emerson. “

  6. Anoneuoid says:

    I always thought it strange that people assumed these civilizations would just be sending out raw data signals that would be easy to distinguish from noise. To be efficient you would want to compress the data during transmission, and the better the compression the higher the entropy (more like noise the signal appears). And that isn’t even mentioning encryption…

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