SETI: The Ultimate Search - Part 1

Well, it's been while since I last posted here, due to exams and such, but I should hopefully be able to write more frequently from now on. As the title suggests, this is about SETI (the search for extra-terrestrial intelligence if you really prefer), its worth, and its implications.


Where is Everebody?

SETI is what it says on the tin - the searching of the universe for other intelligent species like ourselves (at least some of the time), although not necessarily a lot like ourselves. Limitations on our current technology clearly prevent us from partaking in this search in person, so we've had to resort to listening for, and sending out, signals from and to outer space. We should first examine the likelihood that anyone is actually out there.

The good news is that someone has already beaten us to it, namely Frank Drake, with his formula know as the Drake equation, with which the number of communicating extra-terrestrial civilization can be estimated. The bad news is that the equation has seven variables, of which only two are known with any certainty, although we have some idea of the values of a couple of others. Here it is:

N here is the number of detectable extra-terrestrial civilizations in our galaxy, the Milky Way. Let's take each variable in turn, which become estimated with less and less certainty as you go on.

R, the average rate of star formation, is the one variable that we can be sure is about right. In our galaxy, around seven stars are formed each Earth year; no mean feat considering that each one is likely to last for many billions of years.

f_p , the fraction of good stars (meaning stars that aren't pathetic white dwarfs, or over-sized giants) varies from around 20% to almost 100%. For the sake of neutrality, I'll go for the value in the middle: 60%.

n_e, the average number of planets (or possibly moons, *ehem* Avatar *ehem*) that are capable of supporting life in those systems that have any planets at all, is a value that is only just now being investigated. Initial estimate suggest that perhaps around 10% of planets are capable of supporting life. If we take our own solar system as a rough guide, that works out to around one planet capable of supporting life. As a sample size of 1 isn't great, I'm going to use the, perhaps conservative, figure of an average of 0.2 earth-like planets per star.

f_l , the fraction of those planets where life actually develops. For the purpose of not resorting to pure guesswork already, I'll use the figure of 0.2, based on the time that it took for life to develop on Earth.

f_i , the fraction of planets on which life develops where a species evolves intelligence. I'm going to use an educated guess of 0.05, since, given enough time, the evolution of intelligence seems likely, but by no means certain.

f_c , the fraction of those species that possess, and are using, communications technology. Again, I'm going to use the figure of 0.1, based on the length of time that we have been using communication technologies as a fraction of our total length of existence, past and future, and the possibility that some intelligent species struggle to form a civilization.

L, the length of the 'communicative phase', which is likely to correspond to the length that the civilization exists. This is an interesting variable which warrants longer discussion. There have been several points in our recent history at which we have come close to the end of civilization, all of which have been due to the threat of nuclear weapons, and indeed our continued future is threatened by climate change. However, it isn't as simple as working how long, on average, it takes for someone to accidentally detonate a nuclear weapon, or how long a species can keep their climate stable. This is because a civilization even a little more advanced than ours would be able to establish colonies on nearby planets and moons, and given a little more time, on the planets of other stars. When a species reaches this stage of development, they could become essentially immortal, even if their home star died (they could simply migrate to another). Therefore, I'm going to tentatively suggest an average of 1,000,000 years; still a tiny fraction of the total age of the universe.

And now, the moment of truth:

(7 x 0.6 x 0.2 x 0.2 x 0.05 x 0.1 x 1000000) - 1 [us!] = 839 detectable civilizations in our galaxy, and therefore about 80 trillion in our universe. But where on Earth (well, not) are they?


The Fermi Paradox

From the above calculation, it would seem that our galaxy, and universe, are abuzz with life. Unless you happen to believe the UFO nuts, you might have noticed that we haven't seen much of these 800-something civilizations, and don't even have a smidgen of evidence. This apparent contradiction is known as the Fermi Paradox.

One way to resolve the paradox is glaringly obvious - the calculation seems to be really quite naff, and it is indeed! If we change the values for the percentage of life-supporting planets that develop life from 0.2 to 0.05, and the fraction of intelligent species using communicative technologies from 0.1 to 0.01 (these change are not at all unreasonable, and would still be considered very optimistic by many), we now come to a figure of just 21. With just a little more adjustment and we can come to a figure of 1 or less.

There are many other explanations that have been proposed, including that a majority of civilizations destroy themselves too quickly (although this has already been taken into account in the equation), that most species have a policy of non-interference, much like the 'Prime Directive' of Star Trek, or simply that they don't want to communicate.


First Contact

Let's imagine that somewhere amongst the hundreds of billions of stars of the Milky Way, there is an intelligent species other than our own. How might contact happen, and what would be the consequences?

As suggested earlier, it's likely that initial contact would occur via communication technology; either with us receiving a message from outer space, or with them receiving one of our messages, such as the Arecibo message. You might be wondering how this is going to work, since we are certain to use utterly different language. Instead of our own languages, we have used the universal languages, of mathematics and science, which (probably) are the same for all intelligent beings.

However, this method of communication is severely limited by the many tens, or hundreds, of years that it would take for a reply to travel back across the vast expanses of space. Regardless, this is the only line of inquiry pursued by SETI organisations.

The most interesting form of contact, popularised in countless books, films and games, is that of direct contact; as in aliens visiting Earth in person. You many have noticed that a theme running through the portrayal of direct contact in these media sources is that this first contact doesn't often end well for Humanity.

In my opinion, it is unlikely that this would be the reaction of another civilisation to out own. For a species to survive its technological adolescence, it cannot have been so bellicose that it would attack other species on sight. A more likely response would be similar to our own; that they've just discovered another intelligent species, perhaps the first they have ever encountered, and that annihilation is not the best course of action.

What might be the effect of first contact on our own species and society? You'll have to wait for part 2 to find out...



- Daniel