There are perhaps 10,000 stars for every grain of sand on Earth, in the known universe. We know that there are possibly trillions of planets. So the question is where is everybody? This is the Fermi Paradox.
Even if there are alien civilizations in distant galaxies, there is no way we’ll ever know about them. ( Well not with the technological level that we have now. ) Basically, all that stuff outside of our direct galactic region, the so-called, “Local Group” is pretty much out of our extent, because of the expansion of the universe. The thing is, even if we had truly fast spaceships it would simply take billions of years to reach these places, cruising through the emptiest areas in the universe.
So, let’s focus on our galaxy.
The Milky Way is our own galaxy, it consists of up to 4 hundred billion stars. There are around 20 billion sun-like stars in the Milky Way and evaluation suggests that a fifth of them have an Earth-like planet in its habitable zone, the area with conditions that permit life to exist. If only 0,1% of those planets housed life, there would be 1 million planets with life in our galaxy alone.
But wait, there’s more.
The Milky Way is about 13 billion years old. In its starting point, it would not have been a favorable place for life because things exploded a lot, but after 1 to 2 billion years, the first habitable planets were created. Earth is only 4 billion years old, so there were probably been trillions of chances for life to flourish on other planets in the past. If only a particular one of them had developed into a space traveling super civilization we would have seen by now.
What would such a civilization look like?
There are 3 levels according to the Kardashev Scale.
A Type I civilization would be capable to access the total energy available on its planet. In case you are wondering, we are presently around 0,73 on the scale and we should grasp Type 1 sometime in the next couple hundred years.
Type II would be a civilization competent of harnessing all of the energy of its home star. This would require some serious science fiction, but is achievable in principle. Concepts like the Dyson sphere, a giant complex structure surrounding the Sun.
Type III is the civilization that essentially controls its whole galaxy and its energy, an alien race this advanced would apparently be godlike to us.
But why should we be able to see if such an alien civilization exists in the first place?
If we were to create generations of spaceships that could nurse a population for around one thousand years we could colonize the galaxy in about 2 million years. This sounds like forever, but remember, the Milky Way is enormous. So, if it needs a couple of million years to conquer the entire galaxy and there are possibly millions if not billions of planets that sustain the survival of species in the Milky Way and these other life forms have had a significantly more time that we’ve had, then where are all of them?
This is the Fermi Paradox, and nobody has an answer to it … but we do have a few ideas.
Let’s talk about filters.
A filter, in this context, performs a barrier that is really hard for life to conquer. They come in various degrees of nasty.
One: There are Great Filters and we’ve transcended them. Maybe it is way more difficult for complex life to develop than we think. The process granting the chance life to begin hasn’t yet been completely figured out and the circumstances required may be really complicated. Maybe in the past, the Universe was way more inhospitable, and only recently things have calmed down to make complex life possible. This would also mean that we may be unique, or at least one of the earliest, if not the first civilization in the entire Universe.
Two: There are Great Filters and they are ahead of us. This one has the word “bad” written all over. Maybe life on our level exists here and there in the universe but it gets crushed when it reaches a certain point, a point that lies before of us. For example, impressive future technology exists, but when activated, it destroys the planet. The last words of every advanced civilization would be something like this: “This new device will fix all of our problems once I press this one button.” ( Dexter’s laboratory anyone?) If this is correct, then we are closer to the end then to the beginning of our existence. Or maybe there is an ancient Type III civilization that observes the Universe and once a civilization is advanced enough it gets eradicated, in an instant.
Maybe there is something out there that it would be better not to discover.
There is no way for us to know that.
Or maybe we are alone …
Right now we have no signs that there’s any life besides us. Nothing. The Universe appears to be barren and dead. No one sending us messages, no one responding to our calls. We may be totally alone, trapped on a tiny moist mudball in an eternal Universe.
Does that thought shock you? If it does, you are having the appropriate emotional reaction. If we let life on this planet perish, perhaps there would be no life left in the Universe. Life would be gone, probably forever. If this is the situation, we just have to take an adventure to the stars and become the first Type III civilization to keep the gentle flame of life existing and to distribute it until the Universe breathes its last breath and fade into oblivion.
The Universe is too beautiful not to be experienced by someone.