Where is everyone?- The Fermi paradox

On a clear night we can see about 2500 stars and almost all are less than 1000 light years away. Our galaxy has 100-400 billion stars and the observable universe has that much number of galaxies. That is for each star of our galaxy there is a galaxy in the observable universe. There are 10 thousand stars for each grain of sand on earth. If you can conceive the numbers we are talking about then well and good.

The number crunching

The most conservative estimate by scientists is that there are 5% ‘sun like’ stars, even that makes 500 billion billion 'sun like' stars that are out there. Again as per the most conservative estimate there are 100 billion billion habitable 'earth like' planets, that is 100 'earth like' planets for each grain of sand on earth.

Now we have reached the level of probability and speculation. If 1% of those planets actually develop life form and thereafter intelligent life form as on earth then there are 10 million billion such planets in the observable universe. If we talk about our galaxy only then that would mean 100,000 intelligent civilizations in Milky Way only.

So where are the alien- that is the Fermi Paradox?

Our star is a relatively new one and there are many far older stars, that means far older habitable planets. If we compare the progress made by us in the last 400 years then we can very well imagine the level of progress a civilization will make that is more than a thousand years ahead of us. A civilization that is 50,000 years ahead of us will seem like comparing humans to monkeys. Earth is 4.5 billion years old and there are 'earth like' planets which are way older than our solar system.

The Kardashev scale groups human civilization into 3 categories as per the energy consumption.

The type 1 civilization can or has the ability to use all the energy of its planet and we are not there still but close to it.

The type 2 civilization has the ability to use all the energy of the of its host star, for us that would be the sun. For us that is now way beyond our imagination. It is something like ‘Dyson sphere’.

A type 3 civilization will have the ability to harness the energy of the host galaxy, something which we cannot comprehend.

An 'earth like' planet if they survive up to type 3 will have mastered inter galactic travel and even colonize an entire galaxy. Such type of civilization could travel to another planet and occupy it for about 500 to 700 years and use its resources and thereafter launch missions to another planet and this could go on and on until the whole galaxy is colonized. This would take about 3.75 million years which actually quite a small time considering the timeline of universe. Even if 1% of civilization cross the type 3 level then there should be about 1000 type 3 civilization in our milky way only.

If scientists are asked to explain this paradox then we will get different answers. But these can be broadly classified into 2 categories.

Explanations and possibilities

Explanation 1 – those who believe that there is no type 2 and 3 civilization out there. They believe that if the math is correct and we have not been contacted then maybe there are no such advanced civilizations.

Here comes the great filter. It says that from the smallest life form to the stage 3, life has to pass through filters which are invariably almost impossible to cross. This filter can be extinction of life due to climate change, getting hit by a large asteroid, a super volcano eruption, gamma ray bursts etc.- basically extinction level events which wipes out the whole life forms of a planet.

Some possibilities for explanation 1 can be:

• We have crossed the great filter. We are the rare species. The great filter might be at the very beginning and the creation of life is in itself the rarest of rare event.

• Another possibility is that the great filter is in between growing from single celled organism to multi celled organism.

• We are the first ones destined to come so far and continue our journey. Or it can be that the great filter is ahead of us and we are approaching it.

Explanation 2- those who believe type 2 and 3 level civilizations are out there but for some reason we have not encountered them.

Some possibilities for explanation 2 can be:

• Those advance civilizations visited us but we were not evolved then. We think we have been here for a long time but by the galactic time scale we as an intelligent species have only lived for a very very short time.

• Or it might be that we are living in a remote and uneventful area of the galaxy which is not visited by them.

• Or the physical colonizing is an old concept for them and they have some way of remotely visiting the outer space. With the level of advancement we conceptualize about them, they surely have conquered the biology and mortality of life. They have the capability of advance virtual reality and they live in those realms. Visiting primitive life forms like us is not there priority.

• Or those intelligent civilizations are not broadcasting themselves so that they do not attract advanced predatory civilizations which might destroy them.

• Or our technology is too primitive to receive their signals.

• Or we are receiving signals but government is hiding them.

• Or higher civilizations are around us on earth and we cannot perceive them.

• Or we are living in one of the reality created by them. The blue pill effect.

These are all in the realms of science fiction. But once the earth going around the sun was also a science fiction, or the earth is round was also a science fiction. One thing is for sure that the truth will always be what we cannot conjure. The Fermi paradox is a combination of math and speculation but it surely opens up a Pandora’s box of possibilities.