Tuesday, February 10, 2004

And now… the astronomy post:

Today I am going to estimate how many extra terrestrial civilisations there are in The Milky Way.

During the penultimate entry I pondered upon the interesting notion that one can imagine a bookmaker taking odds on every aspects of my life. For instance, the odds of my death due to my friend Rob encouraging me to ride a motorbike over a cliff this year are probably fairly high and so on. Whilst writing this undoubtedly brilliant piece, I had wanted to compare the difficulty of calculating said probabilities with an equation set up by a scientist which referred to the likelihood of there being intelligent civilisations in our local galaxy The Milky Way (I always thought this name was more reminiscent of a drainage pipe leading out of a toilet in a Dutch brothel, but that is besides the point).

Alas, I had neither the information to hand nor the time required to investigate this equation at the time of writing. But now I have all the info in front of me via a lovely book I picked up at a second hand bookshop called “Making Contact: A Serious Handbook for Locating and Communicating with Extraterrestrials”. It’s a collection of articles ranging from guidelines and advice in case one should encounter an alien, to US Air force guidelines and how to administer alien first aid. In the main, the book takes a properly responsible view and understands that virtually all we know is conjecture and that the majority of all the alien stories we hear are certainly inventions. It does have lots of bollocks as well, but one must take the rough with the smooth when reading a tomb engaged in such a misunderstood and culturally curious subject.

Anyway, via this book I have found the relevant information and it all floods back to me from wherever I had heard it from before. It is called The Drake Equation. It is a formula that states that the number of Extra Terrestrial Civilisations in the Milky Way can be worked out by:

the rate of Sun-like star births per year, times *

the fraction of Suns with planets, times

the number of Earth-like planets per Sun, times

the fractions of Earths that form life, times

the fraction of ecologies that form intelligence and civilisation, times

the average duration of civilisations.

Now obviously, the figures for each part of this equation are in the main unknown – which is why it is not as famed in mainstream culture as it would otherwise be – but as we learn more our estimates grow more accurate and its importance will spread. Some of the figures are more easily worked out than others.

Way of the Milky

The rate of Sun-like star births is a relative cinch. There are two ways to estimate star birth rate, and both results are the same: the Milky Way has produced an average of 25 stars per year – currently it contains about 250 billion stars. Most of these are not Sun-like however; most are shitty brown stars or bulbous red ones. Others are binary systems** or are too close to the galactic core to give any real hope of providing a nice peaceful region like our nice rural star on the outskirts. If The Milky Way were represented as the whole of Europe, our Sun would be in the corner of the Shetland Islands down a disused gravel pathway and hiding in a ditch somewhere. Of course we would be the ones with the shotguns in one hand and the obscure cult symbols in the other nervously waiting in fear of nasty city types invading our precious space with their destitute morality and fancy technology. Meanwhile, next to our caravan homes, our land would be all dug up and bare of plant life excepting for countless weeds and the odd pot plant.

And once I again on these pages I find myself bringing you back from a digression with some more relevant words: subtracting all the unsuitable stars from 250 billion leaves us with a mere six to fifteen billion Sun-like stars in our Milky Way. A halfway figure is ten billion, which happens to be the number of years the Milky Way has existed. So the figure then is one Sun-like star birth per year. Lots.

Now the fraction of suns with planets is one of the things we are rapidly learning more about. A few years ago the mere existence of planets outside our solar system was merely a postulation, although a pretty obvious one. But soon enough, our technology became sophisticated and powerful enough to find evidence and more recently direct evidence. In fact this very week, the Hubble Space Telescope found a distant planet, analysed its light and found it’s atmosphere to be composed of oxygen and carbon! This, my friends, is how we will find the first evidence of extra terrestrial life. An array of several space telescopes, combining their images to massively increase magnification beyond that of a single telescope, will be able to directly see Earth-sized planets. The light will be analysed and such things as water and carbon dioxide can be detected using GCSE-standard light analysis. This is mere decades away – although actually finding the planet might take a bit longer.

Planets are being found at an increasingly speedy rate - it is not unreasonable to say that every Sun-like star has a planetary system, especially if you agree with the current star-creation theory. To be conservative (which I hate being, but it keeps my sums believable) we will state 0.75 – even though my book here claims it to be an entire 1.

We might reasonably think that an Earth-like planet is the most likely to produce life so we need to know how many Earth-like planets there are in every planetary system. It has been claimed that virtually every computer model of the evolution of a Solar System produces an Earth-like planet with a quarter producing two Earth-like planets. Basically certain elements naturally seem to set themselves at appropriate distances around their star, so gas planets would always be around where our gas planets like Jupiter are now. Gravity then divides up the material so the planets are fairly evenly spaced out leaving at least one planet within the perfect range of its star allowing water to exist in liquid form and stay on the planet. But I personally think these models reflect our anthropic view point which bias’ the analysis and therefore the results.

To clarify what I mean: speak to a man and ask him about his childhood. Will every man share his answers? Of course not, each person is different. If it is the only man there is to ask then one must extrapolate the view of all men from him, but it’s an extremely inexact method, and all conclusions must be treated with the realisation that you could be dealing with a distinctive case or an uncommon one. So with the theory of planets, we know almost all there is about Solar Systems from only the one example we have.

With some planets being mostly too big or occasionally too small, our guide tells us the figure is one in two – a number agreed with elsewhere. I remain dubious and will make it one in four since I want to account for my anthropic argument and stay conservative with my figures.

The next figure asks us the fractions of the Earth’s that evolve life. Probably the most debatable of the statistic required. My book ambitiously says the figure is one to one! It says that, given the understood process of planet building, all the ingredients for life would be there. Hmm, okay I can agree to that. It says that organic molecules occur naturally and are to be found on comets and meteors that would also fall onto planetary surfaces regularly. That is true. Subjecting these to planetary conditions would, they say, produce the necessary bio chemicals. Also very true. But do all these go on to form life? The book quotes a NASA researcher who says that life would almost certainly develop. It’s a strong argument but I don’t agree with their figure of one. I’m going for a quarter.

Next is also controversial. The ratio of planets with life that goes on to become intelligent and form civilisation is one to one according to my book!


As usual the Americans have misunderstood evolution. I witnessed one American ask on an Internet forum once “If evolution exists, how come animals aren’t changing into other animals?” Fuck me what a dumb arse! Evolution, basically put, is survival of the fittest. The fittest being the species that is most likely to survive. Intelligence isn’t necessarily the best survival tool. I see no reason why an entire lifetime of a planet should not be populated with various species no more intelligent than a humble housefly. I don’t know where the author of this article gets the idea that all life will eventually evolve into a civilisation. Actually I do, it is from a twentieth-century philosopher called Ilya Prigogine. Other evidence is sited, all directly from Earth. As I argued above, it is hardly conclusive scientific stuff to use evidence from one thing and use it to judge a billion others. Still, one Earth is all we can study. The author may be right and I may be wrong. But still I’m downgrading his one to 0.1.

The best picture of Alien Evolution I could find

Finally we ask what is the average duration of a civilisation? The mind boggles. We cannot even look to our one example. We might have been lucky to get this far. Else, perhaps we only need to wait another couple of centuries before we are advanced enough to virtually guarantee our existence for millennia. We have only just started ours, so even a species that lived dramatically short lives would hang around for a few years. My book says between two years and the lifetime of the Universe. Using their sums, if a civilisation lasts two years than one of them still remains. If they can last until the end of the universe than they reckon there are a billion of them in the Milky Way alone! So I’m going to say 100,000 years just for the fuck of it. Seems a good figure that might average out backward idiots like us who are one political misunderstanding away from Armageddon with more advanced civilisations that may have branched out and have flourished for a million years.

So (is anyone still reading this?):

1 (Sun-like star births per year)

times by 0.75 (the fraction of Suns with planets)

times by 0.25 (the number of Earth-like planets per Sun)

times by 0.25 (the fractions of Earths that form life)

times by 0.1 (the fraction of ecologies that form intelligence and civilisation)

times by 100,000 (the average duration of civilisations).

And my total:

I estimate that there are 88 civilisations currently in our Milky Way. If civilisations can muster a million years than we’re talking 46,875 of them. If they last a pathetic 2004 years than there are between nine and ten.

Remember folks, that the Milky Way is but one of many Galaxies in the Universe (if you are a regular reader you will realise that the term is simply Universe without the ‘the’), so to get the total number of civilisations in existence you will need to multiply the result by something to the order of another 200 billion or so.

There are far more stars in the Universe than there are grains of sand on the Earth.

A lot. ***


* = Three quarters of all women will have given up reading here.

** = Half of all men will have given up here.

*** = Those that remain will agree with my analysis of women readers.

No comments: