Be very careful (Fermi Paradox edition)

Enrico Fermi, considering the billions of stars out there in the galaxy, noted to a number of physicists back in 1950 that the real mystery is why we haven’t seen any aliens yet. Even given a very low percentage of planets that have intelligent life which produces technology, the colonizing wavefront of at least one of these civilizations should have reached planet Earth. The Fermi paradox could thus be succinctly stated “Where is everybody?”

There are several postulates as to why they haven’t made it here yet, and it helps to review the Drake equation, from wikipedia:

The Drake equation states that:

N = R^{\ast} \times f_p \times n_e \times f_{\ell} \times f_i \times f_c \times L \!


N is the number of civilizations in our galaxy with which we might hope to be able to communicate;


R* is the average rate of star formation in our galaxy
fp is the fraction of those stars that have planets
ne is the average number of planets that can potentially support life per star that has planets
f is the fraction of the above that actually go on to develop life at some point
fi is the fraction of the above that actually go on to develop intelligent life
fc is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L is the length of time such civilizations release detectable signals into space.

For most of the numbers we have started to get a better and better guesstimate.  As we move from right to left, starting from the equal sign, our certainty about each variable decreases, until we get to “L”

We know almost nothing about L, except what we have observed from our planet. Some despair that L may be very low, because civilizations tend to self extinguish. Or it may be the case that even if they develop the technology, they might be uninterested in using that technology to communicate with us.  Imagine, for example that the Earth had cloud cover that never allowed inhabitants to see the night sky. Civilizations that arise on such a planet might be very inward looking, and never even consider what’s beyond. But it seems most likely that that would be rare.

As we find more and more suns that have planets, and some with ones that appear to be earth-like in some ways, the probability is that civilizations tend to self-extinguish once they develop technology cannot be ignored.

Why might that be? Why would L be very small, nearly uniformly?

There are several lines of thought here. All should develop non-idiosyncratic causes, because those could happen in any one given civilization, but not in others.

My favorites are:

1. Technology is developed by competitive species; those tend to be inherently war-like, to some degree. Once technology such as nuclear bombs become widespread, it is nearly inevitable that that civilization will wipe itself out.

2. There is a technology which is discovered, and its dangers are not realized until it has destroyed that civilization. Perhaps genetic engineering or nano-technology has some elementary danger, similar to the grey goo hypothesis.

Some other articles:

Where are they? Why I hope the search for extraterrestrial life finds nothing by Nick Bostrom

Be very careful (Fermi Paradox edition)

3 thoughts on “Be very careful (Fermi Paradox edition)

  1. rogue medic says:

    I think the problem is just a poor understanding of the size of infinity.

    If there is infinite space and more planets than we imagine, how much of that space is between these planets that potentially support intelligent life? Even with the development of travel through time/space warping media (wormholes and other stuff we do not yet know about), how much of infinity is likely to be explored, or traveled in a way that can be observed?

    Those with the technology to actually observe life on earth from close up, probably are much farther away than what we would consider close. We would not be able to observe them, while they are able to observe us.

    Maybe they’re just not that into us.

    And infinity is not just really really big, but big with “really” written a whole lot of times before big. And then some.

    Or maybe, Teresa is correct that we are unique, that everything is about us, but what are the chances of that?

    Another take on the small L size is presented by Ray Kurzweil and others. It does not even involve conflict among humans, but conflict between our creations and humans.

    As we develop intelligent machines, will they have a use for us?

  2. @Teresa:

    Yes, that is right, but the provisio which you propose requires the abandonment of the anthropic principle, essentially. As we discover more and more extra-solar planetary systems and develop telescops that would be able to see Earthlike planets, it looks like some of the variables on the left will become known shortly. It appears that F sub p could even be greater than .75 or so.

    And regarding F sub l, there’s reason to think that might be very high too:

    Mars rock contains evidence of fossils:

    See also the Aug. 16, 1996, issue of the journal Science.

    @rogue medic:

    You are right that travel through large distances is daunting, and may not be possible to develop faster than light travel. But some type of hibernation, coupled with available technology could make a star system accessible within 50 years or so of flight time.

    With regards to your statement “Maybe there just not that into us.” is something that is almost always ignored conceptually. Stanislaw Lem considered this possibility in two works: Solaris and even better work IMHO is Fiasco.

    Fiasco reviews at Librarything:

    Fiasco is probably one of the most important books in Science Fiction, and shows Lem as one of the great conceptual thinkers of our time, an opinion that isn’t mine alone.

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