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Alien Invasion, The Likelihood Of (Real)It's The End Of The World As We Know It, Just Not Very Probable
Date: 1997/07/22 Agree? Disagree? : Have Your Say Buy Books About This Topic At: Amazon UK Amazon US Send This Article To A Friend: Email It Use Telepathy
On some occasions -- such as the ushering in of a new era with the most significant digit of the year being incremented -- a few people start to get a bit worried (a condition dubbed by some as PMT; pre-millennial tension). What they exercise their paranoia on is one of those oldest of science fiction chestnuts: that of alien invasion. If you just sit down and think rationally for a few minutes (assuming that you are capable of this), you should come to the conclusion that it isn't very likely, now is it? [1] Astronomer Dr Carl Sagan worked out from some rather dubious estimates that there ought to be around 10,000,000 advanced technological civilisations in our galaxy, the Milky Way [2]. From equally dubious assumptions we can also work out the likelihood of aliens invading, say, in the next century, in a worst-case scenario. If we assume: Then, as a worst case scenario, presume that aliens invade tomorrow (or some time in the next century, if they're held up by bad weather, traffic congestion, or the wrong type of interstellar hydrogen). From a total of 45 million and one centuries, we will then only have been invaded in one century. Thus the probability of being invaded in the next century is vanishingly small, at only one in 45 million [3]. The chance of an alien invasion commencing in the very minute that the year 2000 starts [4] is therefore even smaller, at about one in 2,368,000,000,000,000. [5] Sceptics might point out that the three assumptions I made earlier are wrong, which would make my estimate equally wrong. (What am I talking about? Real sceptics would be arguing the same as me!) However, I can justify these three premises. For (1), there is no proof, as yet, that the Earth has ever, in its history, been invaded by outsiders (notwithstanding Nazca plain figures). That also means ignoring, for the time being, any theories that say life on Earth was of extraterrestrial origin (which might count as an invasion of sorts). However, it is probably impossible to prove that the Earth hasn't been invaded at all, only that is has (which it probably hasn't). Remember: absence of proof doesn't mean proof of absence. As for (2), this is an estimate made by people with more geological, astronomical and cosmological knowledge than I (say that with your false teeth in). This can't be proven absolutely either, without being able to travel faster than light, which is impossible (although its impossibility cannot be proven, only extrapolated) [6]. Anyway, even if this estimate is out by several orders of magnitude, the chances of invasion are still slim. You might say that point (3) is the weak point in my argument; that the probability of an alien invasion hasn't been constant throughout our planet's life. Firstly you might point out that as any hypothetical alien race becomes more technologically advanced, the chance of them invading increases. This is true... well, probably: the aliens might become more benevolent and wise over time, but since we don't know if there are any aliens out there, their existence and frame of mind are effectively random -- their quantum wave function hasn't collapsed yet, you might say. Besides, aliens aren't really going to want to invade a planet just for us (what would give you that idea?). They wouldn't need to enslave us; if they had the necessary know-how to invade a planet, they could instead build a simple robot to make the tea and fetch their slippers for them. They wouldn't want the planet for its natural resources; if they've just travelled N light years to get here, expending <large-number> terajoules of energy in the process, they're not going to want Earth's <small-number> joules of fossil fuel energy. ConclusionFor those high-powered executives among you who haven't had time to read this entire article and have instead skipped straight to the conclusion, here is the bulk of the article presented in one easy-to-digest sentence: If the occurrence of alien invasions of Earth is random, Earth has not undergone alien invasion yet, and the Earth has been around for a long time, the probability of alien invasion over a small time scale is minute. So, throw away your T-shirt emblazoned with the slogan "the End of the World is Nigh", and invest in some lottery tickets! That'll give you a better chance of getting it right.
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