Fermi's Paradox III: Zookeepers, Alien Visitors, Or Simple Life; How Can We Explain Our IsolationNov. 29, 2001
by Seth Shostak - Senior Astronomer
We seem to have the Galaxy to ourselves. At least, thats the obvious conclusion from the apparent lack of aliens in the neighborhood.
But this conclusion might be a bit too obvious, and possibly wrong. In previous articles, weve considered why extraterrestrial intelligence even if common would have restrained itself from spreading to every half-decent star system in the Galaxy. Its possible that the aliens have done cost-benefit analyses that show interstellar travel to be too costly or too dangerous to warrant ambitious colonization efforts. An alternative suggestion that would explain our apparent solitude is that the Galaxy is urbanized, and were in a dullsville suburb.
Yet another resolution for the so-called Fermi Paradox is that weve been singled out for special treatment: we are an exhibit for alien tourists or sociologists. Our world may be known to the extraterrestrials, but they observe us through a sophisticated type of one-way mirror.
While theres no evidence to give credibility to this last idea (known as the "Zoo Hypothesis"), many would argue that evidence does exist for another possibility namely, that the Paradox is just a red herring because the aliens are in the neighborhood. In fact, theyre in our back yards, or just above them.
Many thousands of sightings of unidentified flying objects (UFOs) are reported each year, and polls show that one-third to one-half of the population believes that at least some of these aerial apparitions are alien spacecraft. The presence of aliens on Earth would neatly resolve the Fermi Paradox.
But while this is a prevalent idea among the public, the evidence for alien visitation has failed to sway most scientists. To convince researchers, who are inherently skeptical, unambiguous and repeated detection of flying objects by satellites or ground-based radar would be required. Better yet would be some indisputable physical evidence, such as the landing lights from an alien craft. In other words, something better than witness testimony is necessary, since such testimony isnt good enough, no matter how credible the witness.
Consider the fact that lots of people claim to have seen ghosts, and will be pleased to tell you what they saw. But the case for the existence of these shrouded spirits isnt what you would call convincing. You dont read a lot about the parameters of ghosts in scholarly journals.
Until and unless better evidence is collected, few scientists are inclined to accept the premise that the Fermi Paradox can be resolved by the claim that aliens are either soaring through the stratosphere, or are stashed away in meat lockers at Area 51.
Of course, theres no doubt that aliens in the neighborhood would be dramatic news, and thats part of the appeal of such claims. But the opposite circumstance would be similarly startling. What if we have failed to espy the extraterrestrials simply because there arent any? After all, the evolution of intelligence may be a rare occurrence, even if biology is common. Could it be that in the enormous reaches of the Milky Way, ours is the only planet with thinking beings? That would neatly solve the puzzle posed by Fermi. And no matter how discouraging (or otherwise) the thought of being unique may be, we still havent the proof that it isnt true.
While possible resolutions of Fermis Paradox are as plentiful as gas stations, we still have no idea which, if any, is correct. Perhaps the universe is teeming with societies so subtle we cant prove their presence. Or havent yet. On the other hand, maybe were alone.
Its all a bit perplexing, but in fact theres hope. SETI experiments offer the promise of relegating the Fermi Paradox to the dustbin of historical curiosities by proving that other intelligence is out there. So while its interesting and instructive to consider the pros and cons of galactic colonization, we should also make sure that we do some careful observing. In science, speculation is desirable, but experiment is definitive.