The first ever image of a black hole came out in April 2019 and the Internet went insane. Voyager 2 left our heliosphere in December 2017, becoming the second object to ever do so, after its twin, Voyager 1. These are all significant milestones in our history of space exploration and certainly worth celebrating. However, I found myself wondering: we have come so far and yet why haven’t we found any signs of extra-terrestrial life?
Back in 1950, physicist Enrico Fermi asked the same thing (his exact words were “Where is everybody?” but you get the gist), which led to the coinage of the Fermi Paradox. It refers to how the high probability of life outside our Solar System contradicts the lack of evidence that intelligent extra-terrestrial life exists.
Simply put, there are billions of stars in our galaxy that are billions of years older and very similar to our Sun. It is also likely that some of those stars have Earth-like planets and therefore have intelligent life. It is possible that those civilisations have already developed interstellar space travel, just like we’re doing now. Astrophysicist Michael H. Hart stated that the Milky Way could be traversed within a few million years, even if space travel is really slow. So, by that line of reasoning, Earth should already have picked up some signs of aliens.
Scientists put forth all sorts of theories as to why that did not happen:
- Aliens possess different behaviour from us and do not want to travel across space.
- Aliens have already wiped themselves out (via triggering climate change or from not
evolving fast enough as hospitable environments are difficult to maintain).
- The aliens are trapped on “super-Earths” – a type of planet with a mass up to 10 times greater than Earth’s. They would have heavier gravity and therefore be more difficult to enter space.
- Dark energy is pulling the galaxies further away from each other and within a few billion years, we might not be able to meet any extra-terrestrial life at all.
- We are the first technological species to evolve in the galaxy and Earth is in a “quarantined zone”, a so-called protected zoo for aliens.
There are more arguments that are both wackier or more reasonable but let’s leave it at that. My personal favourite theory is the last one, because it is (sort of) in line with the Prime Directive, a fundamental protocol from the sci-fi series Star Trek. A Forbes article, The Philosophy of Star Trek: Is The Prime Directive Ethical? described it as “prohibition on interference with the other cultures and civilizations representatives of Starfleet encounter in their exploration of the universe”.
It makes sense. The Prime Directive is more of a philosophical concept rather than a scientific theory but maybe the reason why we have not encountered any aliens is because we are not allowed to. Maybe we are not at the right stage of our evolution. Maybe we are not technologically advanced enough and any extra-terrestrial life are forbidden from interfering with our natural development. Or maybe we’re just located in a really, really isolated part of the galaxy.
Honestly, it could be any of theories. It could be all of these theories but in the end, we just don’t know. It is unlikely that most of us will ever see the discovery extra-terrestrial life in our lifetime but judging from the enthusiasm surrounding the black hole photograph, that doesn’t stop us from trying or hoping otherwise.