Sciency Words A to Z: The Fermi Paradox

Welcome to a special A to Z Challenge edition of Sciency Words!  Sciency Words is an ongoing series here on Planet Pailly about the definitions and etymologies of science or science-related terms.  In today’s post, F is for:


The birth of the Fermi Paradox is, perhaps, one of the most poorly documented scientific events in recent history.  Nuclear physicist Enrico Fermi did not present his famous paradox at some scientific symposium or write it up for some academic journal. No, the whole thing started (apparently) with a comment Fermi made half-jokingly over lunch.

I normally draw all the illustrations on this blog, but I’m making an exception today.  In 1950, New York City was suffering an epidemic of disappearing garbage cans.  No one could figure out where the city’s garbage cans were going or who was taking them, so the New Yorker published this cartoon offering one possible explanation:

According to the historical narrative reconstructed in this report, that summer (or sometime thereabout) Fermi was visiting the Los Alamos National Laboratory in New Mexico.  He and a bunch of old friends from the Manhattan Project had seen that cartoon and were joking about extraterrestrial life over lunch.

As the conversation progressed, Fermi suddenly, almost out of the blue, said these fateful words: “But where is everybody?”  He then proceeded to lay out the fundamental problem that is now known as the Fermi Paradox.

In short, our galaxy is old—over ten billion years old by most estimations.  Earth is less than half that age, and our civilization—why, we’ve been around for barely a blink of an eye on the cosmic scale.  If civilizations like ours can pop up so suddenly, so abruptly, then over the last ten billion years advanced civilizations should have filled up the whole galaxy.  The aliens should be everywhere, and yet we can’t seem to find any evidence of their existence.

So where is everybody?

Many answers to that question have been proposed over the years.  Fermi and company are said to have run through most of them that day while they finished up their lunch.

  • Maybe Earth is part of a galactic nature preserve, or maybe intergalactic law forbids anyone from making contact with “primitive” cultures like our own.
  • Maybe Earth is out in the boondocks of the galaxy, far, far away from where all the aliens like to hang out.
  • Maybe interstellar travel is harder than we think, and so all the alien civilizations tend to keep to themselves and never leave their home planets or home solar systems.
  • Maybe intelligent life has an innate tendency to destroy itself.

That last one is a sobering thought, especially when you remember that these were the people who worked on the Manhattan Project!

Personally, I kind of like the notion that we’re part of a nature preserve.  I have no scientific justification for thinking that; I just find it comforting to suppose that maybe the aliens do know about us and think we’re worth preserving.  But what do you think the solution to the Fermi Paradox might be?  Let me know in the comments!

Next time on Sciency Words: A to Z, why is Earth “just right” for life?

Correction/Clarification: After reading some of the responses to this post, I think I may have been a little too flippant about the galactic nature preserve thing. I think that’s a cool idea, and I think it’s a fun thing to think about. But there is absolutely no scientific evidence to support that hypothesis at this point, and I do not actually take the idea seriously. I should have been clearer about that.

19 thoughts on “Sciency Words A to Z: The Fermi Paradox

  1. For me the most compelling explanation is that advanced lifeforms are rare. It took 1 billion years for the first known single-celled organisms to appear on Earth, but something like 4 billion years for multicellular animals and plants to evolve. From there it was a brisk 500 million years until humans appeared.
    So, even if earthlike planets are commonplace, and even life is relatively common, intelligent life may still be extremely rare.

    Liked by 3 people

    1. From a purely rational standpoint, that’s my best guess as well. The nature preserve thing is fun to think about, but it’s not good science. We know it was really hard for intelligent life to develop on this planet and that we sort of got lucky. Going back to the Drake equation, that would mean the rate at which intelligent life develops must be a very low number, which seriously reduces the number of communicative civilizations we should expect to find out there.

      Liked by 1 person

      1. Indeed! It doesn’t make sense to me to think we’re all alone in the universe, though if our nearest neighbors are galaxies away we may never be able to make contact with them.

        Liked by 2 people

  2. It’s probably a matter of distance. There are two many obstacles to an interstellar journey that could span the distance from the nearest highly evolved civilization to Earth. Radio signals are a possibility but the speed of light is slow compared to the distances needed to travel. Probably someday if we are still alive we will detect a signal.

    Liked by 1 person

    1. I think that’s a reasonable guess. As much as I like the “nature preserve” thing, I know it’s not a very scientific explanation. But if there are others out there, I hope I’m around when we first hear from them.

      Liked by 1 person

  3. At this point, you know my position on this. It’s similar to Steve’s, for all the reasons he mentions. Life is probably fairly common, but complex life is rare, and intelligent life involving symbolic thought, is probably profoundly rare, so rare that the nearest other civilization is probably millions, if not billions of light years away.

    If interstellar travel is impossible, civilizations could be more prevalent. But “impossible” is a very strong word. Even if it’s only possible to hop between star systems as they pass relatively near each other, a civilization should still be able to spread around the galaxy over a time span of hundreds of millions of years.

    Liked by 2 people

    1. Yes, and in reality my feelings about this are much the same. I do like the nature preserve idea. I think it’s a fun thing to think about, but it has no basis in science and I do not actually take it seriously.

      It was very hard for intelligent life to develop on this planet, which suggests that it would be very hard for it to develop elsewhere. And if you plug that information into the Drake Equation, we should expect the number of communicative alien civilizations out there to be a vanishingly small number.

      Liked by 1 person

  4. I have heard an interstellar chip was spoted in the solar system for a millisecond then disappeared from the solar system, it might be sign of an interstellar civilization.

    Liked by 1 person

    1. I hadn’t heard about a chip, but there was an interstellar object that passed by recently. Astronomers named it Oumuamua, and there was some speculation that it might be an alien probe. I think it’s far, far more likely it was an interstellar asteroid or comet, though; not a space probe.

      Liked by 1 person

  5. I think interstellar travel is the big problem. Going at the speed of light it would take tens of years to get to another hibitable planet, but we haven’t a technology that could get anywhere near that fast.
    Also, I think our reliance on radio waves may be misplaced. There may be better ways of communicating that more advanced civilisations will have found, like quantom spin (or something like that).

    Liked by 1 person

    1. I’ve been reading a lot of older SETI papers for this A to Z series, and you’re absolutely right about the radio wave thing. Almost every paper I read claims that aliens will communicate via radio, because obviously that’s what they’d do. Obviously! Some papers even single out specific radio frequencies that the aliens would obviously use.

      It seems very presumptuous to me to think we know what aliens would or would not do.


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