This may seem like a strange statement, but I have arrived at this conclusion after a lot of thought. Many of the ideas that have led me to this conclusion are from all sorts of sources, and none of these ideas is originally mine. The conclusion though, is my own. I have never yet read anything like this before, which actually surprises me quite a bit.
I have not attempted great scientific accuracy in the text below, as I am quite convinced that any of what I am saying is readily available to all, and either scientifically accepted, or speculation in the first place. Please bear with me, the conclusion is more important than the facts.
Let me state from the beginning that I believe in science; this is a scientific problem, not a philosophical or even a theological one. I am not going to dismiss scientific theories, rather accept them as facts.
But if I have misrepresented any scientific theory, please tell me about it, and I will adapt what I write here, and if necessary, even my beliefs that are the conclusion of them.
I have written this in the form of a set of questions and answers. Let us begin with :
Firmly yes. Experiments have shown that under conditions, comparable to those on earth at the beginning of it's existence, amino acids naturally form. From this to the formation of "living" entities is just a matter of time, and time is what we have plenty of.
Another firm yes. Although not every part of the evolutionary chain on earth has been satisfactorily explained, I do believe that evolution, and nothing else, has created the higher life-forms present today.
I do not believe there is any fundamental difference between Man and the other animals, apart from a quantitative one in the intelligence area. I have no doubt that this is not the end of the line and that other species, or later evolutions of Man, can become even more intelligent. There is no quality "intelligence", which suddenly springs up. That is not to say that this quantitative property cannot be turned into a qualitative one, by defining a threshold. Let me define an intelligence as an entity, capable of formulating and attempting to answer the question : "are there other intelligences in the rest of the Universe ?". By that definition, Earth (and our Sun) has possessed "intelligence" for some centuries now (I will not enter the discussion whether this should be half, one, three, 25 or 100 centuries, all of these could be said to be true)
Again I don't hesitate in answering Yes. Planets around other suns have been proven to exist (at this time 18 according to the Extra-solar Planets Catalog), and although those discovered are quite unlike earth (much bigger and closer to their suns), this must be because of our limited capabilities in detection at this time. There are 100 billion stars in our Galaxy and I believe there must be (tens of) billions of planets out there, comparable to our own.
Another firm yes. There must be more than one set of possible chemical compunds that form a planet's athmosphere, but not an infinite number. Considering that Earth's athmosphere is made up of the most common elements in the universe, it is very probable that similar athmospheres abound.
Yes it does. I fully agree with the calculations that have been produced to solve this problem. They usually result in a giant number of planets with life such as ours, in this Galaxy alone. In the rest of this article, I will use a number of 1,000,000 as the number of stars, capable of evolving intelligent life. I believe that at all these stars, given enough time, intelligent life will evolve.
The main answer to that one is that the question is not complete. It should be completed to read "why do I believe there is no other life such as ours in the Galaxy _at this moment in time_".
This timescale is very rudimentary, the numbers may be wrong by several units, but the magnitude of each is rather well accepted by the scientific community :
let's extrapolate :
If this last figure seems small to you, considering the vast interstellar distances, remember that the Galaxy is only 100,000 light years accross - and with exponential growth to take into consideration, an average speed of 1/10th the speed of light should not be a major problem.
Since we are only talking about our Galaxy, the first 5,000,000,000 years do not count, and within our Galaxy, an additional 5,000,000,000 years are needed for first-generation stars to be born and die, and for second-generation stars to form. First generation stars do not possess heavy metals and cannot have planets, much less life on them.
We may of course consider that the first second-generation stars have been formed 6 or 7 billion years ago, but why not stick to the beautiful round figure of 5,000,000,000 years. Starting from then, all planets are on their own (I do not believe in extraterrestrial origins of life, but even so, the history of all civilisations begins 5,000,000,000 years ago).
5,000,000,000 years ago, evolution started on one star, and around the same time also on others. 5,001,000,000 years later, the life form that started on that star has colonised the entire Galaxy. Now we may say, why 5,001 ? Why not 4,937, or 6,285 ? We might say that evolution takes about that time to happen, but it is extremely unlikely that this 5,001 is a special number, and that at this moment in time, several thousands of intelligent races are about to take their first extrastellar steps. A universe with Humans, Vulcans, Klingons and Romulans, all at about the same point in their technological evolution, is a very unlikely event indeed.
Put this argument another way : at some moment in time, call it 0MY (million years), the first second-generation star, capable of evolving intelligent life, is formed. At some other moment, let's say 1,837MY, our sun is created. around 5 billion years later, life from our Sun has colonised the Galaxy, just put that at 6,928MY. If the same thing has happened on every of the 1 million earth-like planets in the Galaxy, don't you think the first of these colonisations must have happened earlier, say, at 5,246MY. That is 1,700,000,000 years ago! There was barely any life on our earth at that time!
Is the main point in my argument. If there are others, they should have visited us, and left some sign. If there are others, there are lots of them (maybe millions). Why, after all our searching (including decades of SETI), have we found not a single trace of any of them ?
Now some may think there is some "Prime Directive" at work. Aliens have visited us, seen that we show potential, and left us to our own evolution (and perhaps left a sentinel on the far side of the moon). All very nice, and precisely what we would do, if we found a planet with Ape-like animals on it.
But my main argument is that the first intelligence to wander out among the stars, must have found almost barren planets out there, and colonised them. If the main life-form on some beautiful planet you find is some moss, would you have ethical problems in colonising that world ? Especially if every single planet you find, has some different kind of moss on it ? You'd probably create a sanctuary for the indiginous life forms and terraform the rest of the planet.
Evolution takes 5 to 7 billion years to reach "intelligence", but 1 million years later that intelligence has colonised the entire galaxy, leaving no room for a second intelligence to evolve.
Or just the first? I conclude the latter. We have found no traces of Galaxy-wide civilisations, neither out there, nor on our own planet. But there must be life out there, and we are just the first to reach intelligence.
I don't believe so. If for some reason we are first (here at 6,998MY) and the second will come at some normal distribution rate, that would make it 7,013MY, or something. We might reach that planet and conclude that it will have a civilisation within the next 20,000,000 years, and leave it to itself. We just colonise all other 999,999 planets we find. So for all practical purposes, if we are first, we must also be alone. (I have elaborated on this argument in a separate piece on the statistics of my argument)
No it doesn't. Someone has to be the first. The second one does not get a chance to write this same essay. Since I am writing this, we can be the first.
No it isn't. I don't like to prove something by stating that the reverse would be impossible, if I cannot make at the same time the statement at least probable.
I have said that the evolution of life on earth is a natural phenomenon, which should happen on any of the 1,000,000 stars that are like our sun.
I don't believe in luck, not on this scale.
There must be something about our earth, or about our solar system, that is unique, or in some way "uniquer" than around similar stars.
Look up at night : the Moon.
Yes. The ratio of weight between primary and satelite is 1/81 in our system. The similar rate for any other body in our Solar system is very much larger (13,000 for Ganymede, 4,000 for Titan, 3,000 for Triton) Only the Pluto-Charon double planet is even closer (7), but that system is in such an eccentric orbit that it was probably formed through some form of collision. The earth and moon are in an almost circular orbit around the Sun, which seems to indicate that they were formed together, not the result of some later (near-)collision.
The fact that Science is not sure about how the Moon did originate also contributes to my belief that the earth-moon system is a very unlikely occurence. (Scientific theory seems to settle on a near collision with a Mars-sized object - also a quite unlikely event in my opinion)
Well, one solution is that we are here because of it. If the moon were not there, nor would I be, so I could not be wondering about it.
You would not believe that the Moon could directly be involved in the evolution of intelligence. But there is no need for it to be directly involved. As I said, we need not be alone, we need only be the first.
Maybe there is some direct (inverse) relation between the size of a planet's major satelite, and the time it takes for intelligence to evolve on it. Then if we have the biggest satelite in the Galaxy, this explains why we are the first, and thus able to write this.
So a better question is :
Well, I can think of several ways :
I am not saying that these are conclusive arguments, but they do help in making acceptable my opinion that we are alone.
Well of course many of these ideas have been mentioned in Science Fiction stories, of which I have read quite a few.
There are only a limited number of variations on the theme of extraterrestrials :
I am a great fan of all of these, but that has no bearing on my personal beliefs :
I have received two reactions so far, which I present here and here
Herman De Wael - Antwerpen, Belgium
written 1999-02-23 - last adapted 2000-04-06