David Brin is a smart guy. And if his guest editorial of last month is any indication, he is worried about "active SETI." While an enthusiastic supporter of passive SETI, he has initiated (or at least tried to initiate) a dialog with the increasing number of commercial ventures that will, for a price or for entertainment, "beam your message into space." I'm reluctant to put words into the mouth of one of the outstanding writers of our time, but I think it's fair to summarize his thinking thus:
The counter argument (if one can argue against serious consideration before irrevocably committing potentially disastrous folly) is along the lines of "freedom of speech" and "it can't be stopped anyway, so why try." As with most arguments, there is merit on both sides. (Brin has called for a dialog, not a prohibition.)
Since the oft-cited "I Love Lucy" transmissions at the beginning of television, Earth has had an electromagnetic footprint, one that is expanding through the galaxy, and losing intensity as it does so. At some distance, perhaps less than the ~60 light-year sphere, it has already reached, it will no longer be practically detectable. At some greater distance it will no longer be even theoretically detectable, at least not without receiving systems measured in light years, or "magic" technology. Since these and subsequent transmissions can't be recalled, the real question with regard to "active SETI" is whether it's wise to do anything that will make us significantly more detectable than we already are. Are we with Brin? Do we feel making the Earth stand out - even "gaudy" as he puts it referring to the hypothetical ET beacons that we have failed thus far to find - is unwise, perhaps terminally so? Or is he being a nervous Nelly?
See above. David Brin is a smart guy. That's not the beginning of a "But..." clause. He may be right. He certainly makes some good arguments in this paper. His issue is a valid one propounded by a person who is not unreasonably concerned for our continued existence.
There is a third side to this discussion, however. It may be that, instead of the Great Silence being caused by inimical intelligence of whatever form, it may be caused by Brin's argument! As we as a civilization get smarter, more secure in our own existence, and happier with our toys and culture, will we progressively share his concern? Already we develop more lawyers and diplomats than explorers and pioneers. (This sounds like sarcasm, but it's happening and spreading as the world develops.)
If you believe the "principle of mediocrity" - the largely accepted theory that neither Earth nor Earthlings inhabit a special or privileged place in the universe - you have to think that any technological race will go through a similar process as it discovers how dangerous the physical universe already is, even without the presence of menacing space aliens. If Brin's argument gains adherents, the tendency toward caution will overwhelm the cowboy culture we have now where even individuals can send messages into space. As our technology makes it easier to beam messages, our culture transmogrifies from cowboy to wimp; by the time an individual or tiny group commands the power and hardware to send a serious active SETI message, laws, custom, and police powers prevent it.
In the Drake Equation, L is the factor that expresses the lifetime of a communicating civilization. This is one of the greater Drake imponderables, since we have only ourselves as an example, and we don't even know the answer for us. Not only have we been "able" to communicate for only the past few decades, we have not even had the notion of communicating for longer than that. One potential limitation to the value of "L" has been "civilizations destroy themselves." While this remains a possibility, it doesn't seem inevitable. However, announcing ourselves via electromagnetic radiation is strictly optional. Our communication technology is such that high-power, readily detectable transmissions are voluntary. Even if you say "don't we need high power radar to protect earth from asteroid collisions" and similar projects, I would respond that, given the necessity to transmit high power, the signals could easily simulate noise and hence be undetectable at any meaningful distance. Despite the possibility that our civilization will remain extant, we could easily decide that we don't want it to be detected, or at least not detected as one that is "intelligent." (Our atmospheric composition, detectable from interstellar distances, gives sufficient clues that we have a "biosphere.")
If Brin's suggestion has merit, making ourselves easily detectable should be avoided. Given the principle of mediocrity, and that we and our presumed aliens live in the same universe, with the same physical laws, would they not have their Brin's (let's call them "Nirbs - I like the sound), with the same concerns? Would not caution overwhelm any society as it learns just how dangerous the universe is even without biological or mechanical intelligence bent on deliberate destruction? We used to have comets. Now we have supernovae, gamma ray bursters, and who knows what else that could destroy us (literally) without a thought.
Regardless of how advanced a civilization might be that's capable of communicating, it can never be sure that predatory ETs aren't around the corner. If Drake's "L" is defined as the time between a civilization is capable of communicating and the time it becomes scared to do so, L might be zero, or even negative! The deadlock could only be broken if one ET race could prove there was no danger, which is presumably a logical impossibility.
The principle of mediocrity demands hordes of intelligent aliens. Where are they? Hiding! Why are they hiding? Because their Nirbs know something we don't? Or perhaps because their Nirbs don't know something we don't.
I am a strong proponent of passive SETI and had been agnostic on active SETI until Brin's discussion thread. I'm not unduly concerned that currently proposed active SETI projects will increase our footprint in a meaningful way. I've been beaming signals into space for years with my ham radio and my moonbounce beacon, and I don't embody sufficient constructive paranoia to believe that they will be the ones latched onto by Ixtl from ancient Glor. Even so, as we technologically decrease our footprint by converting to digital TV and cable and getting rid of those power wasting narrowband carriers in our communications systems, is it possible that we are saving our civilization? With little effort we can make ourselves electromagnetically inconspicuous, even from nearby. Should we embrace active SETI by creating our own beacons? Or should we eschew serious programs involving long duration with high power and narrow beamwidth? Should we join what may be a Universe of Wimps by hiding out on our own planet? Has everyone already made the same decision? Will universal fear doom SETI to a continuation of the Great Silence?
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