Desperately Seeking Extraterrestrials ~ Fermi's Paradox Turns 65 ~ Part 1

Excerpt from huffingtonpost.com


Introduction
 

65 years ago, in 1950, while having lunch with colleagues Edward Teller

and Herbert York, Nobel physicist Enrico Fermi suddenly blurted out,

“Where is everybody?” His question is now known as Fermi’s paradox.

Fermi’s

line of reasoning was the following: (a) Most likely there are numerous

(maybe millions) of other technological civilizations in the Milky Way

galaxy alone; (b) if a society is less advanced than us by even a few

decades, they would not be technological, so any other technological

civilization is, almost certainly, many thousands or millions of years

more advanced; (d) within a million years or so (an eye-blink in cosmic

time) after becoming technological, a society could have explored or

even colonized most of the Milky Way; (e) so why don’t we see evidence

of the existence of even a single extraterrestrial civilization?

Clearly

the question of whether other civilizations exist is one of the most

important questions of modern science. And a discovery of such life, say

by analysis of microwave data, would certainly rank as among the most

significant and far-reaching of all scientific developments. For one

thing, it would lend credence to the suggestion by some eminent

scientists, such as Freeman Dyson, that the universe is primed for intelligent life.

But

after 50 years of searching, the bottom line is that nothing has been

found. If there are indeed numerous technological civilizations in the

Milky Way, why have we not been able to detect any signals or other

evidence of their existence? Why are they making it so hard for us to

find them? In Fermi’s parlance, “Where are they?”

Proposed solutions to Fermi’s paradox

Numerous

scientists have examined Fermi’s paradox and have proposed solutions.

Here is a brief listing of some of the proposed solutions, and common

rejoinders [Webb2002, pg. 27-231]:

1. They are under strict orders not to disclose their existence.
   
   Rejoinder: This explanation falls prey to the inescapable fact that it
   
   just takes one small group in one extraterrestrial society to dissent
   
   and break the pact of silence. Given our experience with human society,
   
   it seems utterly impossible to think that a ban of this sort could be
   
   imposed, without a single exception over millions of years, on a vast
   
   extraterrestrial civilization dispersed over multiple stars and planets.


2. They exist, but are too far away. Rejoinder: Such
   
   arguments typically ignore the potential of rapidly advancing
   
   technology. For example, once a civilization is sufficiently advanced,
   
   it could send “von Neumann probes” to distant stars, which could scout
   
   out suitable planets, land, and then construct additional copies of
   
   themselves, using the latest software beamed from the home planet.
   
   Simulations of this scheme indicate that a single society could explore
   
   (via its probes) the entire Milky Way galaxy within at most a few
   
   million years, which is a tiny fraction of the galaxy’s lifetime.
   
   Communication can similarly be greatly facilitated by futuristic, but
   
   entirely feasible, high-tech means.


3. They exist, but have lost interest in interstellar communication and/or exploration.
   
   Rejoinder: Given that Darwinian evolution, which is widely believed to
   
   be the mechanism guiding the development of biology everywhere in the
   
   universe, strongly favors organisms that explore and expand their
   
   dominion, it is hardly credible that each and every individual, in each and every distant civilization
   
   forever lacks interest in space exploration, or (as in item #1 above)
   
   that a galactic society is 100% effective, over many millions of years,
   
   in enforcing a ban against those who wish to communicate or explore.


4. They are calling, but we do not yet recognize the signal.
   
   Rejoinder: While most agree that the SETI project still has much
   
   searching to do, this explanation doesn’t apply to signals that are sent
   
   with the express purpose of communicating to a newly technological
   
   society, in a form that this society could easily recognize. Indeed, the
   
   current SETI project program assumes that the remote civilization is
   
   making some effort to signal its existence using technology we can
   
   detect. And as with item #1, it is hard to see how a galactic society
   
   could forever enforce, without any exceptions, a global ban on such
   
   targeted communications.


5. Civilizations like us invariably self-destruct. Rejoinder:
   
   This contingency is already figured into the Drake equation in the L
   
   term (the average length of a civilization). In any event, from
   
   human experience we have survived at least 100 years of technological
   
   adolescence, and have not yet destroyed ourselves in a nuclear or
   
   biological apocalypse. Global warming presents a major challenge at the
   
   present time, and has recently been explicitly suggested
   
   as a negative solution to Fermi’s paradox. But we now understand the
   
   situation fairly well and are rapidly developing affordable green
   
   technologies, leading some, including Al Gore, to change their minds and be cautiously optimistic. Additional, more exotic, technologies
   
   are in the works, and at least some of them may bear fruit. In any
   
   event, within a decade or two human civilization will spread to the Moon
   
   and to Mars, and then its long-term existence will be largely
   
   impervious to calamities on Earth.


6. Earth is a unique planet with characteristics fostering a long-lived biological regime leading to intelligent life.
   
   Rejoinder: The latest studies, in particular the detections of
   
   extrasolar planets, point in the opposite direction, namely that
   
   environments like ours appear to be quite common.


7. WE ARE ALONE, at least within  our home in the Milky
   
   Way galaxy. Rejoinder: This hypothesis flies in the face of the
   
   “principle of mediocrity,” namely the presumption, dominant since the
   
   time of Copernicus, that there is nothing special about Earth or human
   
   society. This may be a philosophically satisfying answer to some, but
   
   scientifically speaking it is rather disquieting.

The great filter

Some writers have suggested that there is a great filter

that explains the eerie silence — some major barrier to a society

becoming sufficiently advanced to explore the Milky Way. Possibilities

here range from the hypothesis that it might be extraordinarily unlikely

for life to begin at all, or that the jump from prokaryote to eukaryote

cells is similarly unlikely, or that our combination of planetary

dynamics and plate tectonics is exceedingly unlikely, or, as suggested

above, that civilizations like ours invariably self-destruct, or that

some future calamity, such as a huge gamma-ray burst from a nearby star, invariably ends societies like ours before they can explore the cosmos.One disquieting aspect

of this line of thinking is that it then follows that either (a) we are

first such technological society, since the great filter is behind us,

or else (b) we are in deep trouble, since the great filter, possibly a

great catastrophe, is still ahead of us. Along this line, Nick Bostrom,

among others, hopes that the search for extraterrestrial life, either

on Mars or on an extrasolar planet, comes up empty-handed, because if

life were found, either ancient or present-day, this would reduce the

number of possible candidates for the great filter being behind us, and

it would increase the likelihood that the great filter still lies ahead

of us.
Conclusion

With every new research finding of extrasolar planets in the habitable

zone, or of potential life-friendly environments within the solar

system, the mystery of Fermi’s paradox deepens. Indeed, “Where is

everybody?” has emerged as one of the most intriguing scientific

questions of our time. There is no easy answer.
We will continue this discussion in a subsequent blog. Stay tuned!

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Desperately Seeking Extraterrestrials ~ Fermi's Paradox Turns 65 ~ Part 1