The Fermi Paradox

The Universe is inconceivably huge. No human brain will ever actually understand what does its dimensions mean. Just a few numbers to illustrate: the observable Universe is estimated to be around 90 billion light years in diameter. One light-year is more than 5,8 trillion miles long. There are a least 100 billion galaxies, the smallest ones contain 100 billion stars. Almost every star have planets orbiting around it, which means that there are trillions and trillions planets. It takes a lot of effort to actually realise these numbers. People might ask: so, where are the aliens?

Our relatively "small" home
Let’s just stick to our galaxy, which is big enough to search for alien life. The Milky Way is 100 thousand light-years across., and the funny thing is that our galaxy is a relatively small one. Based on the Kepler telescope’s mission data, there could be 40 billion Earth-sized planets in the habitable zones of Sun-like stars in the Milky Way. (The habitable zone means that the planet is neither too close and nor too far from its star.) In contrast with these numbers, would it be possible that life only existed on the Earth? I do not think so. How is it that no aliens have ever visited us? This is called the Fermi Paradox, named after italian physicist, Enrico Fermi. Space scholars have several theories for this.

First, what if we are too small to be significant? Physically, we are nothing compared to the size of other space objects. Maybe there are gigantic forms of alien life somewhere around us and we are just not able to notice one others. Scientists have sent radio waves with coded message to outer space many times, but no one has answered. It might be possible that the message actually reached some forms of intelligent alien life but their machines work in a totally different way so they cannot decode our signals. What if we are not only too small, but also far away from everything? Theoretically, it is possible that alien species are using advanced technology and powerful spacecraft and travelling around planets, making up entire civilisations. However, they are simply existing in a very remote galaxy. We will never know. Even if human development will reach the technological singularity in the future, we will never be able to ever travel outside our galaxy. Imagine that we are very tiny ants on a leaf and the tree is our galaxy. We are wondering if other ants exist in a different tree located at a different continent. So this is our situation in the Milky Way. 

An alternative theory is that our planet and the human colony is too young. Entire civilisations might have existed billions of years ago, but they have all disappeared. There might be complete ruins of alien cities and edifices on a remote planet, too far away for us to ever explore. What if these civilisations have reached a certain point of intelligence and advanced technology so they have accidentally destroyed themselves in a nuclear disaster or war? If this is true, the human species will probably have the same future. This theory leads to the next point: The Great Filter.

The Great Filter is functioning like a tea-strainer. Some parts of the tea leaf pass through the strainer, some not. These parts land in the garbage bin. Here comes the astounding fact: 99% of the Earth’s species are extinct through the evolution. There must be something which stops most of the creatures from evolving and reproducius. We can be sure the human species passed at least one filter. We are the dominating living beings on our planet and we use its resources as we want. So what is next? What if evolution does not stop here? In the next century, our world will go through a transformation like never before. The technology is starting to be dangerous to us. We can see that nuclear weapons are getting more powerful every year and artificial intelligence scarier (but more fantastic at the same time). Human development is like a spire: it is taking faster and faster bends. Suppose that we will reach a certain point in advanced technology that we cannot sustain and this will lead to the human doom. Based on this theory, its probable that humans will not be the first to have been destroyed by this filter. 

There is one more thing worth to mention, called the anthropic principle. It says that the answer to the question “Why are we on the Earth and why can we observe the Universe?” is “Because otherwise we could not be here to ask this question.” For me, this means that it is useless to search for alien life because someone - a god - wanted us to be and if other forms of intelligent life exist, we would have meet them already. These things are really fascinating to think about, because they are beyond every science and knowledge. 

Why is there anything but nothing? Why do we see the space empty?