Jan 152013

In 1950, the great physicist Enrico Fermi (Figure 1) asked a question that continues to puzzle astronomers, biologists, and philosophers to this very day.  In simple terms, the question is:  If our Milky Way galaxy and the universe at large (Figure 2) are indeed teeming with intelligent extraterrestrial (ET) civilizations, why haven’t we seen any sign of them yet?  In other words:  Where are they?  This mystery has become known as the “Fermi paradox.”  The paradox is compounded by the fact that estimates suggest that even an ET civilization that is only marginally more advanced than ours could have reached almost all corners of the Milky Way within a few tens of millions of years—a negligible period of time, considering the age of the Earth and the universe.

Figure 2. The spiral galaxy NGC 2841. Such galaxies are expected to harbor billions of planets orbiting Sun-like stars. Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration.

Figure 1. Italian-American physicist Enrico Fermi. Credit: Department of Energy. Office of Public Affairs.









Over the past decades, numerous attempts have been made to resolve the Fermi paradox.  Possible explanations range from suggestions that extraterrestrial intelligent life is actually extremely rare, to the idea that intelligent ET life could exist without making its presence detectable to humans.

At the present time, it is virtually impossible to determine whether any of the proposed explanations—or some combination thereof—is the correct one.  However, there are certain classes of explanations that I personally find less attractive than others.  These are the ones that find a plethora of reasons for why civilizations such as ours should be exceedingly rare.  To give a specific example of one of the more exotic arguments of this type, some have maintained that the fact that humans have developed technologies was a direct consequence of the availability of fossil fuels.  Without such fuels, this idea continues, even if an intelligent ET civilization develops it would not become technological, and therefore will remain undetectable.  The reason that I do not consider such arguments compelling is that so far, the history of science has continuously supported and even strengthened the concept known as the “Copernican principle”—the realization that humans are nothing special in the cosmos.

More likely, in my humble opinion, are the explanations based on the enormous gap in knowledge that is expected to exist between two Galactic life forms.  Chances are that another civilization is either more or less advanced than humanity by something like a billion years.  The probability that two such civilizations would be at about the same stage in their scientific development is miniscule (unless technological civilizations are extremely short-lived, in which case they may indeed be rare).  A huge gap in development means, however, that one civilization compares to the other rather like worms to humans.  In other words, not only would two such civilizations not be able to communicate, the more advanced one may have no interest in the other, and it would be easy for it to mask its presence from the inferior life form.  If this resolution of the Fermi paradox is indeed correct, the prospects of us ever finding an intelligent form of ET life may be slim.  This obstacle should not prevent us, however, from finding more primitive life.

All in all, there is no question that the best resolution of the paradox can only come from an aggressive search for ET life, using all the different strategies that are currently being pursued (described in “The Search for Extraterrestrial Life”).  As the ancient Biblical saying goes:  “Seek and ye shall find.”

  2 Responses to “Where Are They?”

  1. This idea that gamma rays cross the universe aimed at us is hard to accept. Dr Marmet says H2 fills interstellar space and so would delay light by impact. So our greatest danger from gamma rays is right next door, so to speak: the LMC
    In reading about WR stages of stellar death, I see that the majority of GRB are from the LMC so would it not be sensible to say that?
    And perhaps our Sol is capable of cycling emissions like jets? Venus was resurfaced 750 mya so what produced this enormous energy? A GRB from across the universe? Aimed for this tiny planet?
    Isn’t it more likely that Sol is a collapsed neutron star like O Manuel proposes in Iron Sun?
    That such a collapse can happen and the planets survive like the 2013 conference of astronomers suggests? http://blogs.discovermagazine.com/outthere/?p=28
    That the Oort shell is indeed evidence of this collapse? That by focusing on massive collapses that are supposed to follow WR star stages the energy levels down to Sol implosion are ignored?
    This scenario would be the simplest reason we do not see off world intelligence. And of course, the least favored.

  2. we need warp propulsion to seek

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