The universe is immense, quite literally. Let’s try to understand how huge the universe really is. Our galaxy (the Milky Way) is a mid-sized galaxy with something around 100 to 400 billion stars, the Sun being just one of them. There are around 150 to 200 billion other galaxies in the observable universe, each with another 100 to 500 billion stars of their own. That is just a rough estimate. Some galaxies have only a few million stars, while the biggest galaxy ever found (IC 1101) has around 100 trillion stars. The total number of stars from all these galaxies roughly come around 1 billion trillion.
However, not all stars are sun-like or have a solar system. Scientists estimate that there are about 500 quintillion sun-like stars and about 50 sextillion habitable Earth-like planets. There is an estimated 100 billion earth-like planet in the Milky way galaxy alone. So, the real question is, with so many habitable planets, is there a possibility that we are not the only life form in the universe?The answer to that question is- we don’t know. Scientists and astronomers all around the world are trying to find the answer to that question. It is true that we have not discovered any tangible proof of life anywhere beyond our planet. But that does not mean that there are none. The absence of proof does not imply proof of absence.
However, until there is any proof all we can do is speculate, and different scientists have taken different educated guesses at the probability of the presence of life in the universe. Some of them, such as the famous astronomer Carl Sagan, say that there are about a million intelligent life forms in the Milky way galaxy alone. Others , such as, Frank Drake put the number at 10,000 while sceptics like Benjamin Zuckerberg refuse to believe that there is any intelligent life form at all in the entire universe.
Given the size of the universe and the little amount knowledge we have about it, it seems more and more likely that there are intelligent life forms out there. But if so, where are they and why haven’t we been able to contact them despite trying so hard for so long?
The answer or rather explanation to that question is given by the Fermi Paradox. The Fermi Paradox is the conflict between the high probability and the total lack of any evidence of extraterrestrial life. Like we saw earlier in this article, there are probably hundreds of thousands of intelligent life forms out there. Some of them might even be much more advanced than humans because the sun is a relatively new star and there are stars billions of years older than the sun and many habitable planets around those stars. If life developed in any of those planets, they have had billions of years worth of evolution more than humans.Different people have different answers when it comes to the Fermi Paradox. Some think that there are absolutely no intelligent life form anywhere in the universe or else we would have noticed something by now. Others argue that there are intelligent life forms out there but establishing contact with them may not be possible. Still others say that it is possible that the earth has been visited by aliens in the distant past when humans may not have been there or they had no way of recording what happened. Another popular opinion is that there are many higher civilizations out there but our technology is too primitive to even comprehend their signals.
Whatever the case may be, most scientists and thinkers tend to believe that humans are not the only intelligent form of life in the universe and the probability of life outside earth is quite high. In all possibility, there are civilizations which are much more advanced than the human race. But until we find proof of their existence, all we can do is wonder and speculate.