“Simple and cheap, like onion dip.” That’s how Seth Shostak (SETI Institute) refers to our early optical search systems, which have involved limited equipment in the hunt for extraterrestrial intelligence, at least when compared to the much more demanding resources deployed by the radio search. Cheap is good, but not when you can only check one part of the sky at a time. All this gets Shostak pondering in a recent article about the parameters of a laser signal from an extraterrestrial civilization.
For if we might miss a faint signal, what about a really big one? Suppose an intelligent species somewhere out there is deliberately trying to contact our planet. Wouldn’t it make sense, Shostak muses, to create a huge optical impression, a signal that would catch our attention so obviously that we could then focus in to detect whatever message might be streaming from that same location? Bright objects in the sky do appear and are usually recorded, as witness historical records of supernovae.
And so it may be telling us something that we have no records of recurring bright objects. Sure, it would take huge resources to make a signal from such a civilization bright enough for the average person to see it without any equipment (Shostak estimates 5 X 1025 watts to push such a signal from 1000 light years away). That’s well beyond our resources, but not those of a Kardashev Type II civilization (one capable of using the entire power output of its Sun), which could imply there is nothing more advanced than a Type I civilization near us.
But whatever its Kardashev type, an advanced civilization may have no interest in beaming a signal to us in the first place. Or perhaps we remain simply undiscovered in a galactic backwater. Whatever the case, ‘naked eye SETI’ adds another twist to the ‘where are they’ question that Fermi posed, and at least seems to be saying that if a Type II culture wanted to reach us, it could have made its presence so blindingly obvious that we would be sure not to miss it. “…it strikes me as paradoxical,” says Shostak, “given the vastness of the cosmos, that such a simple signal has not been recognized, a signal that even a cow could see.” Welcome to the ‘Cow Paradox.’
Centauri Dreams‘ take: Long-time readers know I think there are few technological civilizations in our galaxy to be detected. When asked, I always settle on a number like 5-10 instead of Sagan’s 1 million. That’s the thought of a writer with no scientific qualifications other than a keen interest in these topics. But we’re all just guessing at this point, and this writer is not at all surprised our SETI efforts have so far come up short.