The Speculist today alerts us to an interesting article in The Independent called, "Meet the neighbours: Is the search for aliens such a good idea?"
The article, which was very well researched by astronomer David Whitehouse, examines the issue of whether or not human civilization should announce itself to the larger galactic community. Whitehouse cites the opinions of such notables as Freeman Dyson, David Brin, Ronald Bracewell, and many others. Understandably everyone has a strong opinion on the subject.
Here's my own take: If advanced extraterrestrial civilizations wanted to, they would have destroyed us by now. It's the Fermi Paradox all over again -- but this time, instead of wondering, "where is everybody," we find ourselves asking, "why haven't we be destroyed already?" There are several considerations which make the observation of our ongoing presence in the Universe a pertinent one.
First, it's largely believed that intelligence may have emerged in the Milky Way as long as 4.5Gyr ago. As has been argued on many occasions, this, in conjunction with the possibility of self-replicating probes, cuts the size of the Galaxy to manageable proportions; the Galaxy could have been colonized many times over -- but it's not.
This has also led to speculation about so-called berserker probes (a term attributed to Fred Saberhagen). These self-replicating probes could sterilize the Galaxy in relatively short order -- and the process would be fairly easy. A berserker could poison each planet such that life would never be capable of emerging. If the berserker should discover a planet with life already on it, all it would have to do is cause a global ecophagy through the use of molecular nanotechnology; an entire ecosystem could be destroyed in as little as 20 months.
If this seems like a rather excessive and 'uneconomical' way of sterilizing the Galaxy, keep in mind that we're talking about exponentially self-replicating probes. Berserkers could reproduce themselves using material found in asteroid belts or dead planets. There would be little cost involved, aside from the production and dissemination of the first probe.
If, on the other hand, an ETI was both malevolent and frugal there is another possibility: the use of hibernating berserker probes. Much like the monolith of 2001: A Space Odyssey, self-replicating probes could be lying dormant in every solar system in the Galaxy waiting patiently for intelligence to emerge. It could easily detect the presence of a civilization by listening for their radio signals. Swift destruction would ensue.
Which brings up an interesting consideration. Seeing as we have been transmitting radio signals for almost 100 years, any dormant berserker probe would be well aware of us by now. If it is going to destroy us, it should probably get going; we are only about 50 years away from a Singularity (a cosmologically insignificant amount of time).
I would think that the point of sterilizing the Galaxy would be to eliminate the possibility of any rival post-Singularity intelligences. And if you don't like the Singularity moniker, just substitute Kardashev I civilizations into your calculations.
Consequently, the berserker should have wiped us out by now. But it hasn't, which likely means there is no berserker hanging out in our neighborhood. Moreover, the fact that we're still inhabiting a life-rich Earth is an indicator that we don't reside in a sterile galaxy. We can thus conclude that advanced extraterrestrial civilizations do not embark on such nefarious campaigns. As Robert Freitas has stated, "The present observational record can only support the much more restricted conclusion that no rapacious galactic civilisations are currently loose in the Galaxy."
So, we don't need to worry about sending our radio signals out into space. We can transmit all we want -- it won't make a bit of difference.
Nobody is listening and nobody cares.
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