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Ask Slashdot: How Could We Actually Detect an Alien Invasion From Outer Space?
First time accepted submitter defiant.challenged writes As I was watching another sci-fi blockbuster about aliens wanting to harvest the life stock population on earth for their energy since we are such a robust species, I was wondering how likely and easy/difficult it would be currently to actually detect an outer space invasion (fleet). I am a firm believer that if we would be invaded, we would not stand a chance and would probably not even hit a single ship when it comes to fighting them. The aliens in the movie had the capability to space-jump right into our solar system and even very close to earth. My question is how good are we at the moment in detecting an alien ship/fleet that jumps into our solar system. Do we have radio dishes around the globe such that we can detect objects in space in all longitude and latitude degrees? I know we have dishes pointing to the skies but how far can they reach? Do we have blindspots perhaps on the poles? I also wonder if our current means, ie radio signals, are relatively easy to be compromised with our current stealth technology? To formulate it in more sci-fi terms, how large is our outer space detection grid, and what kind of time window can they give us?
Any race advanced enough to travel here to invade will have capabilities way beyond anything we could hope to combat or detect. I would imagine the first sign you would have would be if you were one of the lucky ones to see half the world wiped out a few seconds before you yourself were removed from this mortal realm.
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The usual example given to illustrate an Outside Context Problem was imagining you were a tribe on a largish, fertile island; you'd tamed the land, invented the wheel or writing or whatever, the neighbors were cooperative or enslaved but at any rate peaceful and you were busy raising temples to yourself with all the excess productive capacity you had, you were in a position of near-absolute power and control which your hallowed ancestors could hardly have dreamed of and the whole situation was just running along nicely like a canoe on wet grass... when suddenly this bristling lump of iron appears sailless and trailing steam in the bay and these guys carrying long funny-looking sticks come ashore and announce you've just been discovered, you're all subjects of the Emperor now, he's keen on presents called tax and these bright-eyed holy men would like a word with your priests.
Banks goes on to note that most civilisations tend to encounter an Outside Context Problem only once, at the point where that particular civilisation ends or is subsumed into the more powerful one. (Incidentally this is also the title of a series of eBooks by Christopher Nuttall which are satisfyingly geeky.)
Of course, there are plenty of fictional examples of invasion, I guess ranging from the barely-competent aliens in Niven & Pournelle's "Footfall" (who were easily detected) and the almost-Gods of Arthur C Clarke's "Childhood's End" who basically just turned up without warning. It's too varied a field to come up with an idea of how we could detect them.
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I once had two ducks. I wondered what I looked like to my ducks. I decided that I look like a duck. All the extra powers that make me more than a duck - speech, thinking, telphones, etc. - are beyond the duck's imagination. To a duck, I look like a duck.
Then I wondered what an alian would look like to me, a human. I decided that an alien would look just like another human. So I began to wonder what advanced characteristics I couild watch out for. Successful businessman, good luck, healthy long life, mysterious origin, that sort of thing.
I found one. At the time he was my boss. He pretends to be Chinese, but hey, what westerner really knows what Chinese people look like?
They have landed already; and they are friendly. I was friendly to my ducks, and that Chinese family is friendly to me.