An Alien Civilisation Detection Simulation

I’ve just been playing with a piece of thought provoking software called the Alien Civilisation Detection Simulator (ACD). SETI (Search for Extra Terrestrial Intelligence) has been around for 50 years or so. In effect, it’s trying to answer a question posed by physicist Enrico Fermi who, incidentally, built the first nuclear reactor. The question is simple: “Where is everybody?”

Fermi’s point was that in a universe the size of ours, and that’s been around for as long as ours has, by now we should have seen some evidence of other intelligent species. But we haven’t. This in turn lead to the formulation of what is known as the Drake Equation, first formulated by Dr Frank Drake. This equation suggests that the number of alien civilisations that exist and which we can detect is governed by the following: the rate at which suitable stars form, the fraction of those stars with planets, the number of planets per system capable of supporting life, the fraction of those planets on which life appears, the fraction of life bearing planets on which intelligent life emerges, the fraction of those civilisations that release detectable electromagnetic waves (for example radio) into space, and finally the length of time such civilizations release the detectable signals into space.

Phew! There’s one important assumption in the equation that isn’t mentioned – it assumes that we are going to continue looking for the evidence for ever! ‘For ever’ is a long time (and very expensive). Currently we’ve been searching for radio wave evidence for about 50 years and already voices are being heard suggesting that’s long enough. ‘For ever’ may be an unwarranted assumption. If it’s not true, then the chances of discovering an alien civilization are even slimmer.

ACD is a simulation that allows you to fiddle with the values in the different parts of the Drake Equation (using dials – no typing of numbers!) and then run it to see how many civilizations you detect in a given time. You get a picture of the ‘local’ chunk of the galaxy with civilizations coming into existence as the equation specifies, then transmitting for a time. You see the radio waves spreading out and getting fainter as they go further, until they become indistinguishable from the general background noise of the universe. On the simulation they fade completely. You ‘discover’ an alien civilization if a radio signal reaches the Earth before it fades out.

To give you some idea of what’s involved, the first run I did was for 10,000 years and I left all the settings as they were when I got it, which represents our current best guess. The results were an eye opener. It took nearly 3,000 years to find the first alien civilization, and in the whole 10,000 years it simulated, I only found five lots of aliens! That’s not very many... If, like me, you are curious, I recommend that you have a play with ACD. You can get it via the author’s Dropbox, but you don’t need a Dropbox account.

Now for your homework. I mentioned about that there is an assumption in the Drake Equation. Actually, I can think of at least two others, both of which make the equation more pessimistic than it actually should be. Can you figure them out? Answers in next week’s issue.

Alan Lenton
29 January 2017

Return to the reviews page

Back to the Phlogiston Blue top page

If you have any questions or comments about the articles on my web site, click here to send me email.