Drake Equation and the Search for Alien Civilization

Are we alone?

Are we alone?

Looking up into the night sky, us humans have the habit of going into all existential mode pondering about life in general. Philosophers and scientists throughout centuries have been wondering if we are really Alone in this universe. The question does form an interesting premise for a philosophical debates.

Then, early in nineteenth century, scientists started asking another more specific question, much more scientific one.

‘If they do exist, Where are they? And how many of them are technically advanced enough to reach out to us?’

Remember E.T? or the desi one called Jaadoo? What if civilizations such as that did exist somewhere in the cosmos?

Drake Equation and its Implications

Dr. Frank Drake in early 60s tried to mathematically estimate the number of civilizations that
might have beings with technology sufficient to communicate across the interstellar space.
He, thus formulated the Drake Equation. A very simple equation predicting the possibilities of Extra Terrestrial Intelligence.

N = R* fp ne fl fi fc L 

where N is the Number of Intelligent Civilization

  • R is the rate of star formation in the galaxy.
  • fp is the fraction of stars that form planets.
  • ne is the number of planets Earth-like planets (Where you can survive).
  • fl is the fraction of these planets on which there is Life.
  • fi is the fraction of these planets on which Intelligent life arises.
  • fc is the fraction of these planets with intelligent life capable of interstellar communication.
  • L is the length of time such a civilization remains detectable.

Seemingly a very simple equation, indeed.

Now, let’s put numbers into the equation. There are 100-400 billion stars in our galaxy (and there are estimated to be as much galaxies in the universe). And going by estimate that there are around 5% of stars that are Sun-like. We get around 20 billion sun-like stars. Going by the arguments in the scientific world, there is one earth-like planet orbiting at least 1% of these Sun-Like stars. Giving us 200 million planets in our very own galaxy. Let’s consider that 1% of these planet develop life forms and out of that 1% of those develop intelligent life forms like here on Earth.

Drake predicted around 10,000 intelligent civilizations in the Milky Way Galaxy. 10,000! civilizations  like ours, advanced enough to explore space and even much more, in our own cosmic backyard. The value of  N has been revised throughout the years. Yet, considering the number of galaxies in the universe, the number of intelligent civilization according to the equation is still significant.

Let’s assume even if a fraction of these civilizations are sending out signals into space, we should have been able to listen. The scientists at SETI (Search for Extra Terrestrial Intelligence), an institute dedicated to listen to signals from an Alien world initiated by Dr. Drake himself, is actively engaged in the cause hoping that maybe one day, there will be a contact.

Though forty years later, the search has still been fruitless. We have nothing.

So, Where is Everybody?

Fermi Paradox

Fermi Paradox is an argument of scale and probability that seem to favor Intelligent life on earth, and a total lack of evidence that seem to suggest otherwise.

Enrico Fermi in 1950 suggested that we may have cosmic company. He theorized that a civilization even with modest amount of rocket technology, could colonize an entire galaxy in ten million years. That time period may seem like a lot but is only a blink of an eye given the age of galaxy. If us humans could reach mars in only fifty years of research in space science, an elder civilization than ours surely had more time to carry out this process. But then we observe nothing. An obvious question popped up in his head ‘Where is everybody?’

Let us take into consideration all the advanced civilizations in our galaxy and leave the rest out. The civilizations with which a contact is possible. Karshadev Scale is a tool to measure the technological advancement of a civilization. The scale is measured as per their ability to utilize energy. According to this scale, a technically accomplished civilization can be divided into three categories.

Type-I Civilizations: A Civilization similar to our own, which is capable of harnessing all the energy resource of its host planet. According to experts, we are not even Type-I, though we are close.
Type-II Civilizations: A civilization capable of harnessing energy from its own Star (In our case that would be Sun).
Type-III Civilizations: The ones capable of harnessing energy resource of an entire galaxy. Yes. Ultimate bad-ass civilization prospect.

If 1% of these civilization which started out like us and has survived for thrice as long time as us, there is a small chance that they would have achieved Type-III civilization. If they did, they would have mastered intergalactic space travel. Even if 1 in 10,000 civilization has become a Type-III level, their presence would be quite noticeable given the power of such civilizations. But that’s not the case. It’s seems like there are no Type-III civilizations.

So what are the steps that needs to pass through to be a Type-III civilization? One way to look at it is having a Great Filter which need to be passed through before you get to the point of intelligent civilization. There are many filters along the way. First filter being Bio-genesis or origin of life, next filter is evolution of multi-cellular organisms, followed by evolution of an intelligent civilization… and this in itself could be almost impossible. The Great Filter theory says that at some point from basic Intelligence to Type III intelligence, there’s a wall that all or nearly all attempts at life hit. There’s some stage in that long evolutionary process that is extremely unlikely or impossible for life to get beyond. That stage is The Great Filter.

The great filter which reduces the possibility of an intelligent life to advance before it reaches Type-III

The great filter which reduces the possibility of an intelligent life to advance before it reaches Type-III


Us humans have just surpassed basic intelligence filter. We have to keep in mind that Earth is comparatively young and Humanity is a very recent phenomenon. Its been only fifty years since we actively started searching for extra terrestrial life. What is a mere fifty years in cosmic terms. There are planets far more older than Earth which probably boasts of an advanced civilization.

They could just be around and maybe we aren’t technically advanced enough to make a contact. Or maybe the communication processes as we employ is different than that of other lifeforms and its only a matter of time our technology becomes synonymous. Or maybe as theorized by much more creepier idea called Zoo Hypothesis, Advanced Civilizations are aware of us and they are observing us from a distance.

Or perhaps Earth is indeed the first planet to have a civilization this technically advanced while life across the galaxy are yet to cross the third filter. We are the first ones on the track to become a Type-III civilization.

Well, we may never know.

For the interested, a much more comprehensive study on this subject can be found here. A brilliant read.


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