Aug 072016

Lying on the grass and looking into a sparkling star-filled summer sky. Can there possibly be anything more beautiful? But it also makes me think about how small we really are and are we truly alone in the universe. This question has bothered humans since the beginning of our existence.

In the observable universe, there are at least 100 billion galaxies containing 100-1000 billion stars each. Not to mention the gigantic number of existing planets surrounding those stars including trillions of habitable ones. Consequently, there must be plenty of opportunities for alien life to develop.

But is the contact with extraterrestrial life really that likely? It has to be mentioned, that a huge number of existing galaxies are completely out of reach because of the expansion of the universe. Only the ones being part of our local group come into consideration for a theoretical alien contact. Anyways, if life had developed only on 1% of all planets in habitable zones in the Milky Way, there would be millions of planets inhabited by aliens. Since life on earth emerged rather late compared to the age of the Milky Way, potential super-intelligent and technologically advanced aliens would have had much time to build powerful space ships and to make a trip to our blue planet. In fact, if those guys would have been able to build generation space ships, they could colonize the Milky Way in a few million years. And that is not a long time when we think that life on earth exists since 4 billion years and the fact that other planets might have had developed life long before earth did. So if only one of those theoretical alien races would have developed into a super-technological civilization, shouldn’t we know by now?

So where are all the aliens? Why did they not contact or – in a bad scenario – attack us so far? This lack of proof for aliens despite its apparently high probability is called the Fermi Paradox, named after the physicist Enrico Fermi.

There are different scenarios which can resolve the Fermi Paradox and some of them are quite amusing and imaginative. Here is a small selection:
1. In spite of the apparent high probability, we are alone in the universe. We might always have been and always will be. The condition for the emergence of life could be much harder and complicated than we assume.
2. There were intelligent aliens long before humans came into existence. They could have gone extinct before someone on earth ever thought about extraterrestrial life at all. Indeed, we do not know everything concerning different thresholds life has to overcome in order to survive. We might just be lucky that we do not yet have encountered one really tough barrier, like the dinosaurs obviously did. Or maybe at some point, every sophisticated culture will destroy itself by inventing a highly destructive super-weapon.
3. Our extraterrestrial friends want to observe us in order to do psychological studies or maybe we are just part of some “galactic zoo” for aliens. They also might just wait until we are a threat to them and then kill us. This has also been a topic in various science fiction books.
4. Life forms from outer space are already among us and we do not notice.
5. The aliens are simply not interested in having communication or imperialistic wars with anyone else and stay peacefully and happy on their home planet.
6. The universe is full of extraterrestrial signals but we are not advanced enough to detect them.

Maybe there will be a day in the future when we get a more definite answer to the Fermi Paradox. Let’s just hope it will be a salubrious one!

– Jennifer Heidrich

Read and watch more:
— M. H. Hart: Explanation for the Absence of Extraterrestrials on Earth. Quarterly Journal of the Royal Astronomical Society. 1975, 16, 128.
— A. Frank and W.T. Sullivan: A New Empirical Constraint on the Prevalence of Technological Species in the Universe. Astrobiology. 2016, 16, 359.
The Fermi Paradox — Where Are All The Aliens? (1/2)
Drake’s Equation – A Deep Dive | Answers With Joe

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