Do we live in a "galactic ecosystem"? Once we evolve into a true space-faring, interstellar race, will we bump into other alien species competing for the bounty of our galaxy's resources?
Could such a competition define mankind as a Milky Way heavyweight? Or due to our willingness to "reach out" to extraterrestrials, might we get exterminated/assimilated/eaten faster than we can say "You were right, Stephen Hawking!"?
Should we just stay quiet, in case our ET neighbors don't like us?
This scenario is being pondered by Adrian Kent of the Perimeter Institute in Waterloo, Ontario, Canada, in a paper on the arXiv titled, suitably, "Too Damned Quiet?"
Why we haven't discovered an extraterrestrial civilization, despite decades of listening out for a telltale signal, is known as the "Fermi Paradox." If advanced extraterrestrial civilizations are out there, why haven't they made themselves known by now?
Kent think he knows why: Perhaps only the wiliest of alien species survive the interstellar version of evolution. Survival of the fittest, in this context, means that to make it in the Milky Way of hard knocks, you need to keep your head low.
Staying quiet means you avoid the attention of potentially aggressive alien species, thereby ensuring survival.
Could it be that the most advanced extraterrestrial civilizations are actually, by their nature, quiet? Is this why we haven't heard from them?
Perhaps, but I suspect there might be other, simpler explanations. Maybe the signal from ET just hasn't been detected yet. Also, we probably need a bigger, more sensitive listening device, such as the recently commissioned SETI's Allen Telescope Array. The Earth may exist in an underpopulated portion of the Milky Way, meaning we might not encounter another alien intelligence for a long, long time, if at all.
In a 2009 study, Reginald Smith of the Bouchet-Franklin Institute, in Rochester, N.Y., pointed out that ET's radio signal may degrade, becoming too weak to detect over the natural radio background noise. Likewise, our attempts at Messaging Extraterrestrial Intelligence (known as METI) may not reach very deep into space with the transmitting technology we currently possess.
Therefore, there needs to be a minimum number density of transmitting civilizations within our galaxy for anyone to be heard.
In an Astroengine.com blog on this topic, I concluded:
...unless our galaxy has over 300 civilizations, each one transmitting (for over 1000 years), there is a very high chance that (unless some of these advanced alien civilizations lived very close to one another) no two civilizations may ever know of anyone else's existence. The huge galactic distances coupled with signal degradation leads to a situation where, if communicating civilizations remain static, within their home star system, without interstellar travel, the likelihood of forging alien relations will forever remain unlikely.
Kent admits that discussing the nature of a hypothetical alien species - let alone the potential existence of aliens that could kill us - is pure speculation.
Although the idea of "staying quiet to avoid extermination" was made popular by Stephen Hawking in last year's Discovery Channel documentary "Into the Universe," there's also the argument that if we don't make contact with sufficiently advanced aliens, perhaps our survival in the Milky Way will be pretty limited without the help of technology beyond our own.
So, it's a "damned if you do, damned if you don't" situation. We have no clue if there are any aliens out there. We could be the only life-forms in our entire galaxy (so far, there is little evidence otherwise). Likewise, we could belong in a galactic ecosystem, where alien civilizations compete for resources, co-exist and evolve accordingly.
If the latter is true, should we be keeping our collective mouths shut until we evolve into a force to be reckoned with? Who knows.
Publication: "Too Damned Quiet?" Adrian Kent, 2011. arXiv:1104.0624v1 [physics.pop-ph]
via Mark Buchanan, New Scientist