Pictured Above: ET from the movie ET
The universe is almost infinitely large, and there are many planets that appear habitable in our astronomical observations. These worlds are commonly a comparable distance from their parent star, replete with suitable levels of specific elements, and in many ways are indistinguishable from Earth.
Despite all of this, however, we have not communicated with any other intelligent life from any other world. This brings about the Fermi Paradox, which points out that because the universe is nearly infinitely big, with infinitely many opportunities for the rise of intelligent life, we have not received any communication and have no evidence for other intelligent life.
There are a couple of possible views that seek to answer this paradox. One is the Rare Earth Hypothesis, which is the idea that though the size of the universe is very large, the chance of intelligent life developing is so slim that it essentially “cancels out” the vastness of the universe. This idea would posit that Earth is the only world with intelligent life.
Another possible view is the Great Filter hypothesis, which says that even if intelligent life develops on a planet, there is some major filtering event that causes civilizations to die out or not be able to exist outside their planet. This means that either we have overcome this filtering event already (in which case, we would be the only one to do so, creating a “forever civilization”) or we will have this filtering event on our horizon. This event could be related to climate change, asteroid impact, or some other unforeseen circumstance that would threaten humanity’s attempts to exist in perpetuity and expand past the Earth.
Because we have not seen evidence for other intelligent life in the galaxy, one might be tempted to conclude that this is sufficient evidence to reject the possibility of life outside of Earth. This, however, would be foolish, and does not treat the Fermi paradox in good faith. There are scenarios where other intelligent life could exist and us not know about it, such as aliens visiting/observing Earth before humanity had fully developed, but choosing not to establish a colony because they did not want to interfere with our development, or aliens visiting before humanity altogether. Another conclusion from the Fermi paradox is that it is not fair to say that the only logical development of intelligent civilization is the colonization of the entire galaxy just because that seems to be what humanity would do if we had the resources available.
In conclusion, while the Fermi paradox creates an interesting discourse around whether intelligent life exists, and what they are doing if it does, it should not be taken as evidence in and of itself for or against the existence of extraterrestrials. Instead, it is a framework that can be used to generate ideas about why we do not yet have evidence of aliens in our galaxy.
