You know, we human beings are great ones for standing ourselves upon a pedestal and making out that we're something special. First of all, we told ourselves that a god made all the creatures of the earth, in their various shapes and forms, but then made man in his very own image and likeness. Wrong. Then, we told ourselves that the earth was at the centre of the cosmos, which subordinately revolved about us once a day. Wrong. Next, we convinced ourselves that, ok then, the sun was at the centre of the cosmos. Wrong again.
It does seem that each time we stand up on that pedestal, we get rather rudely knocked off it. But the experience has taught the proud ape humility, at least to the extent that he now knows that he inhabits just a small planet orbiting a rather ordinary star in the dusty suburbs of a mediocre galaxy. And when he also realised that he is made of nothing but the cheapest, most abundant elements in the entire universe, he naturally swallowed again and asked, "Well, are we alone??".
In all that huge expanse, this is also thought to be most unlikely. Our galaxy contains 400,000 million stars, each one a sun which probably has its own family of planets. We now know that planet formation around a star is an intrinsic part of the star's own formation process, and is therefore a common rule rather than some rare freak of nature. The observable part of the cosmos further contains 1 million million other galaxies. And the latest theories and cosmological models all point to there being countless other universes too.
But, so far, there is still no proof that we are not alone.
It was not until after the Second World War that radio astronomy first began. Some Dutch astronomers commandeered some German radio and radar equipment and converted it into the world's first radio telescope. They first predicted, discovered and then began to study the 21cm line of neutral hydrogen in the radio spectrum, but confined their work to these natural phenomena in the Milky Way and beyond.
Then in 1960 Dr. Frank Drake of the Green Bank Observatory in West Virginia U.S.A., suggested that it might be possible to search not for natural but for artificial signals from intelligent life elsewhere in the cosmos. He eavesdropped on some nearby stars, notably Epsilon Eridani and Tau Ceti, but with no success. Then in 1973 a convention of scientists from both the U.S.A. and the Soviet Union met to discuss the search for extraterrestrial intelligence (SETI) at length, and eventually the SETI project itself was born.
Today, large radio telescopes engaged on that project are routinely searching the skies for any signal which may sound artificial; millions of radio frequencies are scanned every second and advanced computers are constantly processing all the received data.
But so far, despite all these efforts, not a single artificial signal has ever been detected.*
Now this is absolutely my old university subject, and on this page I would like to put forward my own thoughts and theories as to just how abundant intelligent life is (or isn't) in this galaxy, just what our chances are of making contact with life beyond the earth in the forseeable future, and just what the chances are that we have been visited in the past.
Back in 1960, Frank Drake derived his now famous equation for the number of extant advanced civilizations in the galaxy. Its a pretty obvious piece of work, comes in various versions, and it says,
N = N1 x fp x Np x Fi x L/T
where N= the number of intelligent civilisations now extant in the galaxy, N1= the number of stars in the galaxy, fp= the fraction which has planets, Np = the average number of planets each star has, Fi = the fraction of these which have intelligent life, L= the average lifetime of the civilisation, and T= the age of the cosmos.
But the problem with this equation is that we have to estimate the likely value of most of the factors in it. We know for sure that N1= 400,000 million, and that T= 14,000 million years, but the rest we have to guess.
Therefore, we can end up with a very wide range of answers, depending on how pessimistic or optimistic we are. Some people consequently think there are a million extant technical civilisations in the galaxy, while others still think there's only us.
But for pessimists and optimists alike there is a very spooky problem here-- which I have called "The Spooky Problem" (my God, Holmes). In theory, a tiny few civilisations may avoid self destruction in nuclear wars, or succumbing to massive disease epidemics or cataclysmic natural disasters, and become so incredibly advanced that they cannot realistically be destroyed. When this happens, a situation will develop in the galaxy whereby these super-civilisations appear, but they never go away again, and so the galaxy will begin to fill up with them.
Now I suggested a phenomenon years ago which I called the "39 steps" (nothing to do with the book!) It so happens, that if a civilisation begins at its home star, and colonises 2 neighbouring stars after a time T years, and then from each of those 2 stars a further 2 are colonised after another T years, and so on, then the entire galaxy can be colonised after only 39T years (as 2 to the power of 39, or 2x2x2x2…..39 times… is very close to 400,000 million, the number of stars in this galaxy). If T is therefore, say, 2000 years (and even we on this planet seem to be advancing much faster than that), then the entire galaxy can be colonised in only 78,000 years. But the galaxy has been here for nearly 14,000 million years!! And this train of thought is only based on one initial civilisation doing this. Suppose there were a million civilizations to begin with, all doing this? And so, the galaxy has had plenty of time to fill up, hundreds of thousands of times over, in fact.
So where are they then??**
The most popular explanation for this is the claim that maybe they are here, (and from the foregoing have been here for a very long time), but that they are very aloof, and have this principle whereby they must never interfere in the development of fledgling civilisations like ours. But I think this is most unlikely. After all, it only takes one of these civilisations to disagree with this "ethic", and they would make themselves known to us. Moreover, if only some of them are benevolent beings, then for as long as there are children on earth dying of incurable diseases like cancer or AIDS, then there would be many such cases of disagreement and these beings would be very much in evidence and openly helping us--- if they were here.
So again, where are they then? And why on all those millions of wavelengths are the skies silent?
Now suppose we assume that there will always be room for good old Yorkshire commonsense in science, and that we conclude that they are not here. We still have this spooky problem, that they should be! Because of the sheer age of the cosmos, they have had more than enough time to completely fill up the galaxy.
Maybe there is a hint here. Maybe there is no such thing as a super-civilisation. Time for a story.
One Christmas a boy gets a Meccano set. It isn't the biggest set in the range, or the smallest, and he looks in his box and he sees that there are 6 different types of piece that he can use. He unfolds his instruction leaflet and reads that he can do 100 different projects with his set. So he starts with a simple project, then moves on to a more complex one, and then he progresses to a more complex one still, etc, until he finally completes the most complex project possible with his set, and of course at that point he effectively completes the course and can advance no further.
Now suppose, just suppose, that our universe is like the boy's Meccano set. We look into our box, and we see that there are only about a dozen or so elementary pieces. We have proton piece, electron piece, neutrino piece, photon, 6 types of quark, and a few more.
Now it appeals to the common sense, --and again I believe that there will always be room in science for common sense-- that there will only be a certain finite number of "projects" which a civilisation will be able to do, before it "completes the course" and hits a "technological ceiling", beyond which it cannot progress further. Now at last we have an answer to The Spooky Problem! The galaxy has not filled up with super-beings because nobody ever gets to be a super-being. The Meccano set just isn't up to it. Instead, the beings in the galaxy are always rather more mortal, and therefore more destructible, than that. They reach a upper limit of technical advancement, and that's as far as they can go.
Now this is only Michael Theory; I haven't ever heard any of this being discussed elsewhere --- however it does sound very real. After all, whoever first supposed that with so few elementary particles we can just advance and advance forever without limit? I'm surprised that this supposition wasn't fundamentally questioned long ago.
But we are still faced with the question of how many advanced technical civilisations there currently are in the galaxy, and to answer this we must return to Drake's formula.
Having regard to very many discussions with compatriots on the matter, and having read much material from other competent thinkers, both in amateur and in professional astronomy, I think that the values in Drakes formula might be approximately,
N1 = 400,000 million, T= 14,000 million years, fp = 0.66 (from angular momentum studies), Np =8 (taking our solar system as average), fi = 0.0005 (assessed from the overall chances of intelligence having arisen on earth), and L= 1000 years only (for bearing in mind that there are no super-beings, and that the beings in the galaxy are more fallible, and less advanced than we thought, and the beings which have reached their technical ceiling are all technically equal, then they are all quite capable of wiping each other out. Also, can you imagine, at present rates of advancement, the human race going for another 1,000 years without reaching a ceiling? Or without wiping itself out?).
This when evaluated gives the value N = 75 civilisations in this galaxy.
Also, for any value above 0 and below infinity there must be a kind of equilibrium situation, whereby these civilisations seem to be popping themselves (or each other ) off at about the same rate that they are coming online in the first place. Otherwise at one limit, intelligent life would decline and vanish from the galaxy altogether, while at the other limit the galaxy would fill up, which in all commonsense it has not. This bodes ill for those who want to find intelligent life elsewhere because such an equilibrium would be very delicate and would probably not last long, and if the galaxy hasn’t filled up, then it has probably emptied.
However let’s just see how far apart, on average, our 75 civilizations would be. Now the galaxy has a volume of 100 million million cubic light years, giving each civilization a spacial domain of 1.3 billion cubic light years, which places the civilisations about 11,000 light years apart. This may be why the skies are silent. If the civilisations are so far apart, and we know them to be less advanced than we thought, then their radio emissions, which are bound to be emanating from their factories, bases, power stations and industrial equipment (even equipment 1000 years more advanced than ours will get hot, or have alternating currents, and emit radio waves) will be so feeble at this distance, that we can say at once that our radio telescopes are nothing like big enough to detect them. In fact, the very largest we have is only 2000 feet or 0.4 miles in diameter while my own calculations suggest a collecting dish more like 20 miles in diameter would be required, which in the case of receiving artificial radio transmissions perhaps no more powerful than those of your local television transmitter, over a distance of many thousands of light years, seems more realistic.
If this is how far away they are, it also follows that none of them know about us. We first began transmitting radio waves about 130 years ago, and of course those first radio waves are still traveling outwards from the earth at the velocity of light, and have now reached an outward distance of 130 light years. But, "they" are 11,000 light years away and therefore will not receive our first signals for another 10,870 years. Further, the light from the earth which they are presently receiving left here 11,000 years ago, at about the end of the last ice age, when we had no advanced technology and were therefore leaving no signs of our presence (in the composition of our atmosphere etc.).
So it seems, from my thinking at least, that the SETI project in its current form is in vain, and that if for any reason we do not want contact with extraterrestrials then we can breathe easy for a while longer.
But of course there remains one last seductive question. The cosmos is very ancient, and as the star systems all wheel around the centre of the galaxy, once every 225 million years, and as civilisations are born and die, like tiny lights switching on and then going out at random throughout the galaxy, what are the chances that, at some time during the earths entire life, one of these lights has switched on close enough, for them to come over here and visit us?
We can work this out, if my 75 civilisations model, with L in the region of 1,000 years, is anything like the truth. But first we have to make another assessment. On a great map of the galaxy, as each tiny light of civilisation switches on, its sphere of colonisation will begin to spread outwards, like a little bubble, before it inevitably bursts and the light is extinguished. By definition, the earth will only get a visit if at sometime during its entire history it finds itself inside somebody's little bubble. (Then, for a brief period of history, the solar system will be a well-trodden place, before they go away again and leave us in peace). And so, we have to estimate the likely average size of these colonization bubbles, in order to calculate the chance that the earth has ever found itself inside one.
Upon first glance, the chances of the earth finding itself inside such a tiny localised bubble might appear very small. But we must remember that the earth has existed for a third of the lifetime of the entire cosmos, and so perhaps there is after all a finite chance that something, in all that time, might just have been here. Of course, all traces upon the earth's surface of any of their bases may long since have disappeared, but it is not beyond the bounds of possibility that some geologist might, one day, haul a length of cable out from between two layers of rock, billions of years old, and find to his utter astonishment that the material of the cable is a room temperature superconductor. I wouldn't put my beer money on it, -- but nor would it particularly surprise me.
But the moon is the place to look for traces of past visitations. In the absence of air and running water, even a footprint will not erode away for billions of years (it will eventually fill up with micrometeoric dust) and any equipment left behind by extraterrestrials will still be there. Strangely, there is a group of features on the moon which was first photographed by NASA in the 1960s and so far has defied all rational explanation. The objects themselves, called the Blair Cuspids, stand upon a low hill and are are too small to be seen from Earth. But the strange thing is, that they are all casting long, thin shadows. "Well so what?", you may think. But the problem there, is that on a world without any erosion, nobody can think of any natural features at all which cast long, thin shadows. I'm darned if I can, despite the fact that I studied geology alongside astronomy at university.
To calculate the chances, then, of the earth's ever having had a visit from extraterrestrials, we have to assume that my 75 civilisations estimate and my 1,000 years survival estimate are near the truth, and then further estimate the maximun size to which each civilisation's "bubble" will expand during that civilisation's lifetime.
In order to do this, we only have one example to go on-- us. The average distance between star systems in this galaxy is 4 light years, and perhaps we might realistically expect to reach the nearest one, the Alpha Centauri system, by about 2100 AD. This would mean that on average we are spreading outwards into the cosmos at the rate of very roughly one light year per 25 years, which assuming a linear expansion would mean a maximum "bubble radius", for us, of 40 light years over the next 1,000 years, beyond which, as we have seen, we cannot realistically expect to survive.
So all that remains now is to calculate the chances, that at anytime during the entire 5 billion year history of the earth, a civilisation has appeared within 40 light years of us. For that civilisation, as we know, will probably at one point have absorbed us into its colonisation sphere.
Well, a sphere radius 40 light years has a volume of 270,000 cubic light years and so the number of such spheres which can fit into the galaxy (volume 100 million million cubic light years) is 370 million. Now new civilisations appear at the rate of 75 every 1,000 years, i.e. 1 every 13 years (and the bad news is that we know they must be destroying themselves just as fast), and so every 13 years the earth has a 1 in 370 million chance that the new civilisation will appear within 40 light years. In other words, very approximately, the earth will have to wait for 13 x 370 million years, = 4.8 billion years, before one single civilisation appears within 40 light years. This is very close to the age of the earth (4.65 billion years) and therefore the result is very tantalising-- perhaps, just perhaps, on just a single occasion which lasted maybe no more than 1,000 years, the earth was colonised.
This would explain the strange long shadows on the moon. But remember, all of this is only possible if the equilibrium between civilizations being born and civilizations dying, has remained stable over billions of years, instead of gravitating to “galaxy full”, or to “galaxy empty”.
Anyhow, at the time these alien colonists arrived here, there would most probably have been nothing living on earth but ancient bacteria; we can be reasonably sure of this because this was the case for nine-tenths of the earths history and therefore there is only a 10 per cent chance that they arrived after this era. Fish, amphibia, reptiles, mammals and mankind were far into the future. Any of their spacecraft or satellites left in earth orbit would have long since returned and crashed onto the surface, due to the finite resistance of the incredibly tenuous atmosphere even at great heights. But anything in orbit around the airless moon would still be there.
Other than this episode in its history, it is very unlikely, due to the sheer vastness of the cosmos, that anything has ever been here. Notice how far away these realities are, from the stories we hear about UFOs being sighted last week or last year. If we were to receive visits with anything like that frequency, then truly the cosmos would have to be absolutely brimming with intelligent life...which clearly it is not.
This piece of thinking has been, I respectfully submit to you, the best that I can do (and rather better and more realistic, dare I say, than some of the current professional theories) to put the finger as realistically close as possible to the truth -- and there is only one truth-- concerning life in the cosmos and visitations from space.
For
those who would worry about such visitations, as the Carib Indians would have
been right to worry about the coming of Columbus, I believe that
"they" are farther away than some scientists think, and so, although
their absence might deny us their answers to many of the scientific and medical
problems which vex us today, at least we will be able to afford ourselves the
peace of sleeping safe in our beds, until distant tomorrows.
A bit of a pooper
However, having read all of the foregoing, a smart-ass called Michael Alan
Marshall put forward, to an astronomical society some years ago, that the human
brain has evolved 100 billion neurons, all by way of random genetic mutations,
and the chances of a circuit randomly evolving which is actually conscious, as
we are, are 1 in X where X is probably greater than the number of atoms in a
million universes (think of how many random ways 100 billion points can connect
themselves to make a circuit, then imagine that only one, or at most a few, are
conscious). This means that when consciousness evolved here on earth, it did so
as a freak chance, so incredibly rare that it has not occurred anywhere else in
our entire universe -- and we are entirely alone.
This may be disappointing for some, but it does answer many questions, such as for instance the Von Neumann paradox, which states that any civilization, even those not very far ahead of ours, could manufacture self-replicating probes, called Von Neumann probes, which by making copies of themselves could spread throughout the galaxy. But if each probe makes several copies of itself, the multiplication of their numbers will be exponential (remember the ’39 Steps’ above?) and in only a short time on the geological timescale they would have filled the entire galaxy. In fact, even if they were microscopic in size, they would still proliferate so much that in far less time than the age of the galaxy we’d be having to sweep them off the driveway to get the car out. The fact that this has not occurred proves almost categorically that of all the civilizations that have ever existed, nobody has ever built one, which is odd because out of thousands or even millions of civilizations spread out over the history of the galaxy, there’s always a joker, a tyrant, a malicious warmonger…. Is commonsense telling us here that nobody has ever built one of these relatively simple devices because these civilizations never existed and we’re alone?
--- Michael Alan Marshall
*
There was the famous “Wow” signal, which was a modulated extraterrestrial
signal picked up in 1977 by the Big Ear radio telescope in the USA. This signal
lasted for just 72 seconds and has not been detected since. It is now thought to
have been a reflection of an illegal terrestrial signal (it is not lawful to
transmit on that wavelength but students have been known to put oscillators
together which, by simply changing its resistors and capacitors, can do this).
**
This problem is also known as "Fermi's Paradox".