The (Im)possibility of Aliens

The universe is a pretty big place that has been around for a pretty long time. It contains billions of galaxies, like our Milkyway, which contain billions of stars, like our Sun. Orbiting these stars are planets, like our Earth. Billions and billions of planets. We've only just learned how to detect such 'exo-planets' by carefully measuring the variations in light emitted by distant stars. If they flicker a bit in a constant pattern, we deduce that this is caused by a planet orbiting the star and obscuring the light when it passes through our view-plane. This takes immensely sensitive equipment and some patience, but astronomers have already discovered some 778 exo-planets by this and other methods (as of June 15, 2012). Most are rather big, like Jupiter or even larger, since big planets are easier to spot, but we're discovering more and more Earth-sized planets as astronomers hone their skills and techniques.

Complex molecules, like sugars and amino acids; the building blocks of life, are now hypothesized to form in outer space and travel between the stars on comets. Sooner or later, these water-carrying comets will crash into a planet and seed it with the potential for life. This is not a rare event, it happens quite frequently. So, given that there are lots of stars, with lots of planets and lots of comets have seeded lots of these planets with the potential for life, then why is it that the aliens haven't come knocking at our door yet? In other words, as physicist Enrico Fermi stated: "If extraterrestrial aliens are common, why aren't they obvious?". This is known as the Fermi paradox.


Now, there's a whole cult of long-haired, unwashed, weed-smoking hippies who claim that ALIENS ARE AMONG US!!!!!!!11!!!1!! (Sorry, they tend to be very loud as well). I've inserted a picture of Hitler meeting with an alien ambassador below as proof. 

Hitler conspiring with an alien

I'm just going to ignore the alien conspiracies for now, but I might get back to them at some other time. A more reasonable explanation for the obvious lack of aliens is that complex life may actually be quite rare. Some guys have already written a book about that topic, so I'm not going to into that subject too much. Let's just say that there could be a whole bunch of reasons why Earth and the people on Earth, are rather unique. There's some truth in that, our species evolved through a series of extraordinary coincidences and if a whole lot of conditions would not have been met, I wouldn't have been here to question my existence (another theory holds that the universe only exists for us to question it). Fact is, however, we simply don't know how rare intelligent life is, since the only planet we can examine is our own and the only intelligent (well, somewhat intelligent) species on that planet is us. A sample size of one (1) is too small to draw conclusions, especially without controls. We must investigate some other earth-like planets for life first, before we can draw any conclusions about life's rarity. For that, we must travel to the stars and we can't. Simply can't. There's no way. Our technology doesn't allow it. I'll discuss the (im)possibility of interstellar travel another time, because for now I want to discuss the matter of time.


You see, as I mentioned before, the universe has been around for a pretty long time now. About 13.7 billion years. A few hundred million years later, galaxies began to form. Stars formed shortly after, and planets not long after these stars. The first stars were big and violent. Too violent to support life and they exploded not so long after they formed as supernovae, to disperse all the heavier elements throughout our galaxy (otherwise, all we would have to go by would be some hydrogen, helium and lithium; not much of an elemental table!). Our solar system and out home planet are rather young. The solar system only started 4.65 billion years ago, followed by the Earth, which needed some time to cool down, and the first forms of primitive life appear to have formed shortly after the Earth cooled. Some 3.9 billion years ago. I've put these dates into perspective on the graph below.

Now, it took some time for life to develop properly. It went through some false starts, getting killed by comet impacts, meteor strikes, ice ages. Or poisoning itself with oxygen. The first atmosphere was a nice mushy carbon-dioxide-rich soup, until some guys decided that photo-synthesis was the way to go and started converting all that carbon-dioxide into oxygen; killing themselves and everyone else in the process.  

Plankton celebrates his victory over life

Then some clever guys developed respiration in a collaborative effort. Consuming oxygen like that, using it as fuel, provided so much energy that complex life could develop, resulting in vertebrae, dinosaurs and, quite recently, us.

If you look at the graph above and consider everything in scale, we've only been around for an infinitesimally short amount of time. Some hundred thousand years, that's all. And we only developed some form of civilization after the last ice age, ten thousand years ago. Space flight was only developed about a minute ago, really.

We have no idea how long our current awareness will last. Our interest in space, our civilization or even our species. Historically, civilizations don't last very long. A thousand years at most, really, and even that is a stretch for the duration of the Roman empire. Sooner or later, the barbarians come knocking. In whatever disguise, extremists of some sort or another will destroy any given civilization. We will also happily destroy ourselves, sooner or later. We're very good at that. Peak oil, global warming, zombie apocalypse, whatever, we're doomed either way. Maybe we'll last a century, maybe another millennium or two, but sooner or later we'll be gone.

Now imagine an alien civilization. What are the odds that they're at our level? Hmm? Considering the age of the universe; they might have come and gone and we never would have noticed. I've put some in the graph. The first were around when dinosaurs roamed the Earth, had a good run but then destroyed themselves. The second were around when the Earth was young and nothing noteworthy was to be found here, on a planet with a poisonous carbon dioxide atmosphere. They had a really long run, but also left for greener pastures. The third aliens aren't here yet: they're in their proto-stage and will be around only long after we're gone. Simply put, the time-window in which two intelligent alien species can meet and communicate, understand each other and build meaningful relations, is very, very narrow. The odds of an alien species visiting our planet in the time that we would be here to greet them are very, very slim. Oh, there will be aliens, will have been aliens and will some day be aliens. Just not this very minute in which we're home.