The Fermi Paradox

There are billions of stars in our galaxy that are similar to our Sun. So at least some of these stars might have Earth-like planets, which leads to a foggy conclusion that there might be life on those planets.

When you look to the stars at a starry night, are you awestruck by its beauty and wonder about how big the universe is and how tiny we seem on a galactic scale or are you way past that feeling and now you just have one question in your mind like me, are we really alone?

And even if we aren’t, why haven’t we discovered extraterrestrial life yet?

Welcome to the Fermi Paradox

By definition a paradox is a seemingly absurd or contradictory statement which when investigated may prove to be true.

For instance, take a look at the images in the slide show below, you’ll get my point.

This slideshow requires JavaScript.

I hope you got the gist of it…now let’s get back to the Fermi Paradox..

Named after the physicist, Enrico Fermi.

The paradox goes like this;

We know that there are billions of stars in the galaxy which are similar to our Sun.

There is a high probability that some of these stars might have Earth-like planets, and if the Earth is typical, some might have intelligent life.

Now what if, some of these civilizations have already figured out interstellar travel?

It would take at least a few million years to completely traverse The Milky Way.

So the question is, why haven’t we met such intelligent extraterrestrial life yet? Or are we just assuming it blindly that they exist? But the chances of the existence of life sustaining planets is pretty high.

Now let’s try and break down the paradox to get some things out of the dark.

  • The observable universe; the universe as we know at the moment, is about 90 BILLION light years in diameter.
    • A light year is a unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.4607 × 1012 km (nearly 6 million million miles).
  • There are at least 100 BILLION galaxies each with 100 to 1000 BILLION stars.

To give an analogy to this; for every grain of sand there is on Earth, there are 10,000 stars in the observable universe.

on a scale of 1 to a billion, how mind-blown are you right now?

Consider a single galaxy with 100 billion stars for now. Let’s say there is not even a single planet from among these billion stars (and their systems like our own, The Solar System) with intelligent life on it.

Now consider 50 or more such galaxies together as a cluster. This makes the Local Group.

Isn’t there a 1 in a trillion chance that intelligent life might exist somewhere out there in one of these 50 galaxies?


Practically, it is impossible for us to reach other Local Groups besides our own, so they are pretty much out of our reach forever, reason being the expansion of the universe.

So even if we had really fast spaceships it would take billions of years to reach these places travelling through the emptiest areas of the universe.

Scaling down to our Milky Way which consists of about 400 billion stars. It is about 13 billion years old. In the beginning it would not have been a peaceful place because things exploded a lot! But after about 1 to 2 billion years the first habitable planets were born.

Earth is only 4 billion years old, so there have been trillions of chances for life to develop on other planets in the past. If only a single one of them had developed into a space travelling super civilization we would have noticed by now.

But what would such a civilization look like?

To explain this, we have to consider The Kardashev Scale.

A method of measuring a civilization’s level of technological advancement.

The method aims at dividing these into the following three categories;

TYPE 1 – planetary civilization

A civilization which would be able to access the whole energy available on the planet. Carl Sagan formulated this scale and it put us at a Type 0.7 civilization.


A civilization capable of harnessing all the energy from its planet’s parent star (the most popular hypothetical concept; the Dyson Sphere, a device which would encompass the entire star and transfer its energy to the planet(s)).


A civilization that can control energy on a galactic level.

Let’s take an example here to understand about the high probability of the existence of such civilizations.. but the lack of evidence for same.

As we already know, Earth is about 4.5 billion years old and as per the Big Bang theory the Universe is about 13.8 billion years old.


We shall compare our Earth to a hypothetical 8-billion year old planet. If it has a similar story to Earth, which is quite possible, as our Sun is said to be a young star and there have been Sun-like stars which might have their own Solar Systems as well. So basically if that planet ever existed, it would be way ahead of us at present. Also, if it were an intelligent species, they probably would have figured out interstellar travel, which means they would be busy colonizing the Milky Way by now.

If all of this had happened, it would take 3.75 million years to colonize the whole galaxy, a relatively small time on a geological scale itself, let alone the cosmological one.

So why the galaxy hasn’t been colonized already?


This, is the Fermi Paradox.

Although there aren’t any plausible answers for the uncertainty in the paradox but there are some hypothetical explanations as following;

  1. Extraterrestrial life doesn’t exist.
  2. Intelligence is uncommon. There might be life out there but none of them are as intelligent as us.
  3. Intelligent life exists, but lack technological advancements.
  4. They destroyed themselves with the weapons they created to save themselves from each other (a strange similarity, isn’t it?).
  5. Periodic extinction of such life by natural events; like the extinction of dinosaurs on Earth.
  6. Intelligent civilizations are just too far apart from each other in space and/or in time.
  7. It is physically expensive, or it is practically unachievable to travel across such long distances with such a slow speed or to harness energy from other planets. The reason being that the present scientific knowledge cannot enlighten us on the cost that incurs in such interstellar colonization.
  8. We are not old enough. On a cosmological scale we are an embryo.
  9. They are too alien.. Carl Sagan speculated that an alien species might have a thought process much much slower than us. Hence, a message broadcast by them would be undetectable to us, merely like a background noise.
  10. Everyone is listening but not responding. This is also known as the SETI Paradox. Extraterrestrial life exists everywhere, but they are unwilling to contact each other, everyone is receiving what others are transmitting but refrain from replying.
  11. Earth is purposely isolated; beyond a certain distance, there is nothing but virtual reality simulated by beings so that the universe appears to be dark and desolate.
  12. They are already here; but are undetectable by us.
An incredible shot of 10,000 galaxies by Hubble Telescope                                                        Image Credit : Nasa, ESA and the HST Frontier Fields team (STScl)                        Acknowledgement: Judy Schmidt

So, the Fermi Paradox is the contradiction between high estimates of the probability of the existence of extraterrestrial civilization and humanity’s lack of contact with, or evidence for, such civilizations.

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