So this time I talking about that staple of science fiction; aliens. Specifically the questions of why haven't we found any yet? And of course if they are out there why haven't they come calling?
The simplest assumption is of course that the reason we haven't found any is there aren't any. Now this can't be ruled out based on the current evidence but I don't personally find it very likely since here on Earth we have a number of unrelated species who demonstrate at least rudimentary tool using behaviour and the history of evolution shows the same concepts reappearing time and again independently. Wings have developed several times in unrelated groups; birds, bats, and insects so I don't see any good reason to assume intelligence is some sort of singular aberration that only occurred here on Earth.
So lets assume the alien civilizations are out there, why haven't we found any trace of them despite scanning the skies with telescopes both optical and radio? I mentioned part of the answer in a previous blog, that is it's just over two decades since we first detected planets around other stars and we are just barely at the point where we might be able to detect the presence of an atmosphere around a planet. Trying to detect the traces of an industrial civilization; probably still decades away.
radio signal are apt to be even worse since as much as we think of it as empty space is filled with dust, gas, and radiation that makes picking up signals even a few light years away a lottery.
Of course the above assumes that the aliens aren't just going to turn up on our doorstep; or as the UFO believers would have it that haven't already done so. I must admit I was fascinated by the UFO phenomena when I was young; convinced that there had indeed been alien visitors to Earth. that belief crumbled in the face of the misrepresentation of so much of the alleged evidence and a greater understanding of the way in which human perception and memory can be so easily confused and deceived. On top of which there is the fact that with the rise of the cameraphone one would expect an upsurge in the quantity and quality of UFO image. Instead the number of UFO reports has declined almost in step with the increasing ubiquity of the cameraphone. So under the circumstances I'm putting UFO's to one side and assuming that the aliens haven't made contact with humans; at least not so far.
So assuming the aliens exist but haven't actually flipped any cows or carved up corn fields where the heck are they? Here's my top five possibilities:
You can't get there from here...
There may be a myriad of alien civilizations out there but there is no guarantee that they can cross the distance between the stars easily if at all. That dust and gas I mentioned earlier may be incredible tenuous but at the kind of speeds needed to travel to another star within a human lifetime they could be like flying into an endless series of concrete walls. There are ideas like generation ships that would travel far slower and avoid those problems but they would have to be vast and aren't likely to be cheap or numerous so our aliens might not stray far from home at all. Of course I write science fiction so I can't just dismiss the possibility of FTL out of hand.
A long time ago...
The simple fact is that a technologically advanced species might have arisen near to our own sun a 100,000, or a 1,000,000, years ago, come to Earth and colonized and we might well never know. The forces of nature have eroded the the cities of earthly civilizations to rubble in 10 or 20 centuries imagine what would happen over 100 or 1000 centuries? The species might well be extinct never mind their civilization. The galaxy might be littered with alien civilizations but they may be the province of archaeologists rather than diplomats.
...Far far away
Even if our aliens have FTL that's no guarantee that they will turn up and ask to be taken to our leaders; the galaxy after all is huge and liveable world may not be all that hard to come by. The vast interstellar empire (or Republic) spanning 1000's of stars might be out there right now; there could even be a number of them existing at the same time and yet in terms of the scale of the galaxy they would all be a drop in the ocean. The chances that they would interact let alone fight each other over territory is unlikely. Of course there's nothing to stop them having internal falling outs so there could be epic space battles being fought as I type and we will never know about; which is probably for the best.
Does it come in red?
There was a movie that shall remain nameless that had aliens visiting Earth who it turned out were 'allergic' to water. leaving aside the aliens stupidity it raised an important point; that is we rather assume Earth is a beneficent abode of life that other species would find every bit as appealing. I've mentioned the Asimov classic 'Nightfall' before and if the civilization from the world found Earth would they stop or hurry on by from a nightmare world that plunged them into darkness every twelve hours? There are so many possible variations in gravity, atmosphere, and climate that it's entirely possible our putative aliens simply find Earth an uninhabitable hellhole and have carried on to greener pastures.
Yes it's a cliché but the aliens might not have come to visit for cultural reasons rather physical reasons. Now the Starfleet Prime Directive of non-interference might seem impossibly altruistic but such a directive needn't be so high minded; maybe the aliens are afraid we're going to start stealing their jobs and begging for aid if they make contact. It could also be that Earth is the interstellar equivalent of a bad neighbourhood and is off limits. Perhaps it's simply that the aliens have more in common with feudal Japan or ancient China and have no desire to meet other species and expose them selves to other cultures.
So there's my top five but I'm sure there's plenty more where they came from...