In this vast universe, there must be countless planets teeming with life somewhere, but why can't we find any evidence? This is a famous question posed by Enrico Fermi in 1950: Where is everyone?
The observable universe is approximately 93 billion light-years in diameter, and there are at least 100 billion galaxies in the universe. Each of these galaxies hosts between 100 billion and 1 trillion stars. In recent years, we have learned that planets are also quite common.
There are probably trillions of habitable planets in the universe, providing numerous opportunities for life to exist and thrive, right? Fermi Paradox
So where is life?
Even if there are extraterrestrial civilizations in other galaxies, we have no way of seeing them. In fact, we will never reach anything outside our local neighborhood, the "Local Group."
The reason for this is the expansion of the universe. Even if we had spaceships traveling at the speed of light, it would take billions of years to reach places beyond our local group. We would be traveling in the emptiest regions of the universe. So, let's focus only on the Milky Way.
The Milky Way is our galaxy and contains about 400 billion stars. There are about 20 billion Sun-like stars in the Milky Way. According to estimates, one-fifth of these stars have a planet the size of Earth in the habitable zone.
Even if life existed on only 0.1% of these planets, there would be around a million inhabited planets in the Milky Way Galaxy.
The Milky Way Galaxy is 13 billion years old. Our galaxy was not initially a suitable place for life because there were many explosions, but about 1-2 billion years later, the first habitable planets were born.
Earth, on the other hand, is only 4 billion years old. So, before life could exist in our galaxy, there were probably trillions of opportunities. If life had developed on one of them in a way that could create super civilizations capable of space travel, we would have noticed.
So, what would such a civilization look like?
There are three categories related to civilization levels:
A Type 1 civilization is a civilization that can access all the energy of its planet and use it. If you're curious, we are about 73% at this scale. We will reach the Type 1 civilization level within the next century.
A Type 2 civilization is a civilization that can use all the energy of its star. While it requires some science fiction to achieve this, it is possible in principle. Concepts like a Dyson Sphere - a massive structure surrounding the star - are plausible.
A Type 3 civilization is a civilization that can control and use the entire galaxy's energy. Such an advanced civilization would be god-like for us.
Why should we have seen such a civilization?
If we could build spaceships that could carry a certain number of people for tens of thousands of years, we could have colonized our galaxy in 2 million years. This time may sound very long, but remember, the Milky Way is a very large galaxy.
So, if it takes millions of years to colonize a galaxy and there are millions of planets supporting life and these life forms appeared and had more time than us, where are these aliens?
This is the Fermi Paradox, and there is no definitive answer to this paradox. But we have some ideas. Let's talk about filters.
What we are talking about here is a filter representing a barrier where life's passage is very difficult. There are filters with different levels of danger.
1: There is a significant and major filter, and we have passed this filter. Perhaps the development of complex life is much more difficult than we thought. The process that allows life to start is not yet fully understood. The conditions necessary for the development of life can be very complex.
Perhaps the universe was much wilder and hostile in the past. But in the recent past, the environment has calmed down, allowing the emergence of complex life. This may mean that we are unique and one of the first civilizations in the universe.
2: There is a significant and major filter, and this filter may be in front of us. This would be quite bad. Perhaps life exists everywhere in the universe at our level, but when it reaches a certain point, this major filter causes the extinction of life.
For example, there might be tremendous future technology, but when activated, it destroys the planet. If this is true, it means we are closer to our end than our beginning.
3: Another possibility is that there is an ancient Type 3 civilization that watches over the entire universe, and when a civilization becomes advanced enough, it is suddenly eliminated. Maybe there are things out there that we shouldn't discover. We have no way of knowing this.
One last idea, maybe we are alone in the universe. Right now, we have no evidence of life beyond our planet. The universe looks dead and empty. No one is sending us messages, no one is responding to us.
There could be entirely lonely beings in a moist, spherical Earth, surrounded by an infinite universe. Does this idea scare you? If it does, you are showing the right emotional response. If we allow life on this planet to die, maybe life in the universe will be gone forever.
If that's the case, until the universe breathes its last breath and disappears forever, we must boldly sail towards other stars, maintaining and spreading the delicate light of life. Experiencing the universe without someone to experience it, without tasting it, is too beautiful.
Possible solutions to the Fermi Paradox:
In the observable universe, probably 10,000 stars fall on every grain of sand on Earth. We also know that there could be trillions of planets. So where are all these aliens? This is the Fermi Paradox.
So are we going to be destroyed, or is a magnificent future waiting for us? Space travel is difficult, possible, but reaching other stars is almost impossible. It requires an incredible amount of material to be launched into orbit and assembled.
Maybe a journey that requires thousands of years and a sizeable human community to survive. Building a spaceship that will survive this journey is incredibly difficult. Settling on a distant planet may be impossible. Consider time, our environment is quite old.
Life has been on Earth for at least 3.6 billion years. Intelligent humans have been around for about 200,000 years. However, we have had communication technology for long-distance communication for only a century.
We are embryos at the galactic time level.
We have come a certain way, but we have a long way to go. The idea that we are still at the center of the universe is still prevalent among people, so it's not impossible for us to make unwarranted extrapolations about life in the universe. But eventually, there is only one way to learn this, isn't there?
