Is there life other than here? A possible answer

If there's an obsession that I have it's astronomy. To me nothing is as amazing, mind boggling and limitless.

I'm not sure if you share my enjoyment of staring at a clear night sky, and watching the twinkling stars. Looking at such a star filled sky logically begs the question, is there someone else looking at the sky from their planet and wondering if there is anyone else out there. Which brings me to the topic of this post: is there life somewhere else? I'll tell you right now, I don’t have an answer but I will speculate with the help of a simple equation I ran across about 5 years ago. Before you continue reading this, I ask you to look at the picture above and give the question a bit of thought. Every dot and bright spot in the picture represents a star, just like our sun, perhaps with little planets orbiting them as well. What makes us so special that our tiny planet is the only planet to harbour life from this vast ocean of matter? Or are we not special after all? I believe that our planet represents one of many planets harbouring life throughout the universe. Here’s a little (and simple) calculation to show how many different "advanced civilization" exist in our galaxy alone. An advanced civilization is defined as one that is technical, in other words possesses technology. The calculation is statistical, here are the different parts of the equation and what they represent:

- N, the number of advanced civilizations in the Milky Way
- N*, the number of stars in the Milky Way
- fp, the fraction of stars which have planetary systems
- ne, number of planets in a given system that are ecologically suitable for life (not too cold, too hot…)
- f1, fraction of otherwise suitable planets on which life actually arises
- fi, fraction of inhabited planets on which an intelligent form of life evolves
- fc, fraction of planets inhabited by intelligent beings on which a communicative technical civilization develops
- fL, the fraction of a planetary lifetime graced by a technical civilization

The equation is then N = (N*) (fp) (ne) (f1) (fi) (fl) where the brackets represent multiplication. It is important to note that just from reading the parameters of the equation you can see that the calculation is pretty thorough and well thought of.

So what are the numbers to be placed into the equations?

Well, we know N*, which is 4 X 10^11 (four with 11 zeros after it). Fraction of stars with planets is approximated at a third of all stars. We estimate ne, to be 2, just by looking at our own planetary system. We estimate f1 to be a third. The estimate of fi and fc are combined to equal 0.01. Which means that only one percent of planets on which life arises eventually produce a technical civilization. Lastly we estimate fL as one millionth of a percent. Which can be seen from our civilization, it took us hundreds of thousands of years to develop a highly technical civilization.

Multiplying all those numbers together we get about 10 civilizations. That is, 10 civilizations in the Milky Way alone. Consider now that there are 100 billion galaxies in the universe, and the number of civilizations becomes too much to comprehend. By the way, if you wonder how the estimates in the above paragraph were made, I can send you the full details or post them on the blog.
It took the author of Cosmos about 4 pages to describe what I have compressed in the last two paragraphs.

You may ask the question: so why haven't seen any of those life forms. I can think of two simple answers. One is that the furthest we have (closely) investigated for life is Mars, which is very close, especially when we talk about astronomical distances. The second explanation is that the universe is too large for two civilizations of actually meet by sheer coincidence. One other explanation is that civilizations may not use 'earthly' ways of communication, such as radio, or sound waves. So we may not be able to detect those civilizations.

Anyhow, I thought I would bring you into my mind and my interest. I hope it wasn’t too boring. But I do want to know what you think. Did the above information change your mind about life elsewhere? Strengthen your belief? Left you snoring out of boredom? Does any one care about this issue? Isn’t it boring to be the only existing life out there?

Sources: my thoughts, the equation and the numbers from Cosmos by Carl Sagan
The picture came from astronomy picture of the day website