Every time when look up into the sky staring at the stars, one question comes to my mind. Are we the only living things in the entire universe? The observable universe is about 90 billion light-years in diameter. There are at least 100 billion galaxies each with 100 to 1000 billion stars. In our universe, there are trillions and trillions of habitable planets, which means there should be lots of possibilities for life to develop and exist. so why can’t we hear from the Alien ?
Let’s take a step back, even if there are alien civilisations in other galaxies and, even if we had fast spaceships, it would actually take billions of years to reach these places. So, for starters, let’s focus on the ‘Milky Way’ which is our home galaxy. Milky way consists of up to 400 billion stars and trusts me, that’s a lot of stars. Approximately 10,000 for every grain of sand on earth. There are about 20 billion sun-like stars in the Milky Way and estimates suggest that 1/5 of them have an Earth-sized planet in its habitable zone – the area with conditions that enable life to exist.
Another fact is that the earth is only 4 billion years old. So it is possible that life exists on other habitable planets within our own Milky Way galaxy, so where are all the aliens? Why can’t we see any signs of them? This is the Fermi Paradox and nobody has an answer to it. The Fermi paradox is named after Nobel prize winner physicist Enrico Fermi who introduced plain contradiction between the lack of evidence for and the high probability estimates of the existence of extraterrestrial civilisations.
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Distance is one of the main reasons why we and some alien species are not able to find each other. If someone could travel with the speed of light it would still take, 100,000 years to cross the Milky Way once or to visit some habitable planet. Even if some alien species sitting millions of light years away would see us with their telescope, they will not see any civilisation at all, because of the enormous amount of distance they will only see back or ahead in the time. This means that either we are not born yet or else in the future our civilisation is destroyed like dinosaurs.
We humans still lack much in our technological advancements. We’ve spent more than 90% of our existence as hunter-gatherers. 500 years ago we thought we were the centre of the universe. 200 years ago we’ve stopped using human labour as the main source of energy. 30 years ago we had apocalyptic weapons pointed at each other because of political discrepancies.
In the Galactic time scale, we are like embryos. We’ve come far, still have a long way to go. Maybe in future when time travelling, and interstellar voyages will be common, we can expect some extraterrestrial greetings. Till then, may the force be with us!