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So Where Is ET, Anyway?


While having lunch with colleagues at Los Alamos National Labs in 1950, physicist Enrico Fermi mused about the likelihood of intelligent life existing elsewhere in the Universe.  Fermi, one of the most astute scientists of his day, thought the size and age of the Universe means many advanced civilizations should have already colonized the galaxy, just as humans colonized and explored the Earth.   But if such galaxy-wide extraterrestrial civilizations exist, he wondered, where are they?

Some believe this problem, called the Fermi Paradox, means advanced extraterrestrial societies are rare or nonexistent.  Others suggest they must destroy themselves before they move on to the stars.

But this week, Jacob D. Haqq-Misra and Seth D. Baum at Penn State University proposed another solution to the Fermi Paradox: that extraterrestrial civilizations haven’t colonized the galaxy because the exponential growth of a civilization required to do so is unsustainable.

The researchers call their idea the “Sustainability Solution”.  It states: “The absence of ETI (extra-terrestrial intelligence) observation can be explained by the possibility that exponential or other faster growth is not a sustainable development pattern for intelligent civilizations.”

The researchers base their conclusions on a study of civilizations on Earth.  Historically, rapid growth of societies means rapid resource depletion and environmental degradation, usually with dire results.  They cite the example of Easter Island, where resource depletion likely caused a collapse of the local population.  And they conclude that while there are examples of sustainable growth like the !Kung San people of the Kalahari Desert, exponential growth in population and spatial expansion of a society is almost always linked to unsustainable growth and eventual collapse.

This principle has implications for our current global civilization.  Since Earth’s resources are finite and it receives solar radiation at a constant rate, human civilization cannot sustain an indefinite, exponential growth.  But even if we survive and advance as a civilization, we may have trouble colonizing the galaxy should we ever decide to do so.  And if this limitation applies to us, it may apply to other civilizations as well.

But the Sustainability Solution doesn’t mean ET is not out there.  Slower-growth extraterrestrial societies might still communicate by radio or other wavelengths, so current SETI programs still make sense.  Or ETI may result in chemical bio-markers in planetary atmospheres which may leave spectroscopic signatures detectable with upcoming generations of Earth and space-based planet-hunting telescopes.

The Sustainability Solution also allows that advanced civilizations may indeed colonize the galaxy, then collapse as resources are consumed at an unsustainable rate.

And some civilizations may send small messenger probes to other stars, which suggests a search for extraterrestrial artifacts (SETA) within our own solar system might be just as fruitful as radio-based SETI.  Searches might involve radio or visible detection of extraterrestrial probes orbiting the sun.  Or artifacts may even be embedded within planets or moons of our solar system, just like the giant black monoliths in Arthur C. Clarke’s 2001: A Space Odyssey.

In any case, the discovery of artifacts from a slow-growth extraterrestrial civilization would be an example “sustainable development” on a galactic scale.

You can read the original article here.

Comments on this entry are closed.

  • Lawrence B. Crowell June 7, 2009, 7:31 PM

    This matter I don’t think can be mathematically analyzed particularly. Yet a few suggestions could be made. If we get a radio signal from ET, or a spacecraft from them makes it here clearly they have at least some parallels to us. Such intelligent life is able to solve problems, which means that they can remove any environmental constraints on them. Homo sapiens started this about 4 million years ago when australeopithicus took themselves off the menu (throwing rocks at leapords etc) and figured how to get more on their plate. Then can stone tools, fire, and so forth. With each of these advances our homonid ancestors liberated themselves from the negative impact of the biological world around them, and learned to exploit more of that world.

    The result in our case is that we have expanded our population and control over the planet in unprecidented ways. it is the way of biological species, they largely are controlled in their dominion over the environment by the action of other species, preditors, parasites, etc. Yet we can figure our way around them. This is the nature of biology, and maybe any alternative self-regulating chemical system similar to life: they push to expand their influence and energy access. I would well imagine that any ET out there might well enough do much the same as we have.

    E.O Wilson wrote about the bottleneck the human race faces in the future. In a nutshell we are similar to the demonstration where a mold or bacillus on an agar plate grows and consumes its medium until there is a black crisp of waste left. We are in a much larger and complex manner following a nearly identical course — rather than using up agar on a plate we are using up the biological and mineral wealth of this planet. It would not surprise me at all if the vast majority of ETs that are technological do much the same.

  • Pedantic June 9, 2009, 6:58 AM

    This is not really a new idea. It’s been kicked around in several SF novels/short stories (For the best example, see RAMA REVEALED by Arthur C. Clarke (and please forgive the lack of title–I would rather leave it off than put something on that would be incorrect and offensive).

    Painting the properties of intelligent life with one brush stroke seems to me a bit foolish. Just as terran fauna comes in a myriad of forms, I suspect the same for sapience.

    As regards the original article, I find it reporting on a paper that is overly pessimistic, and narrowly focused on human failures. Anyone who has studied demographics will admit that WRT population growth, once a high standard of living is achieved in a society, birthrate drops off precipitously.

    Additionally, we are slowly learning how to control the consumption of our resources, not to mention that we have barely begun to tap the resources of the whole solar system. Ditto for our passions. I have said in other places that I suspect we have a critical 100 years to get through, and then we will enter a golden age.

    As to the original question, “Where are They?” We still have several good possible explanations:

    1.) We’re alone (not a popular explanation, but what does science have to do with popularity?)

    2.) They’re out there but they use a different form of communication.

    3.) They’re out there but they choose not to communicate with us barbarians.

    4.) They’re out there, friendly, chatty and willing to share, but we haven’t come across them yet.


  • bernardz June 9, 2009, 9:14 AM

    I tend to agree with Pedantic although I go much more for (1) as I have been convinced for years that Fermi Paradox leds to the conclusion we are alone or among the first.

    Not I do I think much of these writers comments that today “Amazon Basin, Siberia, and Indonesian islands are largely untouched by the global human civilization.”

  • Dark Tzar June 9, 2009, 6:06 PM

    I’m with bernardz, if the galactic age is considered correct, we are among the first, therefore effectively alone.
    If galactic age is assumed as incorrect (that is, greater than current thought) then considering the size of the universe and difficulty in performing said travel you can chose any of 2 – 4 from pedantic’s post.
    Also, considering Sagan’s great mathematical postulation about the probable number of civilisations out there, that needs to be measured against the size, again we come back to being alone, at least in this quadrant/area/locale/whatever.
    So, to go back to whether expansion is limited by sustainability, who knows? How would other civilisations consume or utlise resources? How can we even guess? As already noted above, how can we consider or even be able to understand an alien civilisation when we have a hard enough time understanding ourselves?
    So, again from pedantic above, go for option (1) as unpopular as it seems, but make the most of what we have and keep looking anyway. Who knows what you might find!

  • Lawrence B. Crowell June 10, 2009, 6:52 AM

    I tend to think that the density of intelligent-technologically capable life is fairly low. So the ratio of ET per galaxy is maybe at best around one at any given time of the Hubble frame. So if we humans mangage to contact an ET it might be a matter of great fortune and coincidence.

    Some issues have been raised about identifying exactly what is intelligent life. The objection is made that all of this involves comparisons to oursleves that might be wrong. In one sense I would agree, and in fact we do have what might be called other intelligent species here on Earth. Compare the brains of humans with dolphins, their brains are larger and more complex. Cetacians in general might be regarded as intelligent life, but their intelligence is different from ours. Then there are cephalopods, where some species of octopi have brains the size of basket balls which constitute 1/4 their body mass. These guys have complex communication by skin color and are capable of quick problem soliving skills. Yet they are not social and are short lived.

    I estimate the galaxy might have a few thousand bio-planets at any time, where maybe some subset of these have complex life forms. So there might be some intelligent life form on a planet just 500 light years from here that communicates to each other forms of mathematics we can’t imagine. Yet they might also not have the ability to manipulate things (such as whales etc) and so are not technological. We are likely to never know about them.

    Any technologically capable ET is likely to have developed those skills largely as a way to access energy and material from their environment, much as we have. The ability to communicate across great distances will also likely be a sort of indirect by product and not a primary focus of their activities.

    Lawrence B. Crowell

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