Dark Forest Theory: Where are all the aliens?

image by Martina Badini / Shutterstock

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liens, amidst killer robots and mad scientists, have never really ranked high on my list of favorite sci-fi tropes. While little green men and alien abductions fail to captivate me, discussions about UFOs, astrobiology, and imagining the physical manifestation of these beings instantly ignite my curiosity. How can we even begin to wrap our heads around the incredible number of potentially habitable planets in our galaxy – a staggering 300 million – and still hold on to the belief that there is no possibility of any other form of life out there? (pretty arrogant take in my opinion.)

Dark Forest Theory, as presented by Liu Cixin in his titular book, explores this idea further. He writes, "The universe is a dark forest. Every civilization is an armed hunter stalking through the trees like a ghost, gently pushing aside branches that block the path and trying to tread without sound. Even breathing is done with care. The hunter has to be careful, because everywhere in the forest are stealthy hunters like him. If he finds other life—another hunter, an angel or a demon, a delicate infant or a tottering old man, a fairy or a demigod—there’s only one thing he can do: open fire and eliminate them."

Cixin invites us to understand that our universe, much like a dark forest, harbors potential threats that we are unaware of. Cixin argues that although these 'hunters' may not be an immediate threat, their silent and hostile nature makes it uncertain whether they will destroy us if given the opportunity, since all life desires to survive. I guess in some ways...we should be thankful for this?

Well... How many potential hidden alien civilizations are we talking about?!

The question was addressed by astrophysicist Dr. Frank Drake through the creation of an equation intended to answer whether humanity is alone in the universe, also known as The Drake Equation:

N = R∗ × fₚ × nₑ × fₗ × fᵢ × f꜀ × L

• N is the number of detectable communicative civilizations in our galaxy. 
• R∗ is the rate at which stars form in our galaxy. 
• fₚ is the fraction of those stars with planets. 
• nₑ is the number of planets that can potentially host life, per star that has planets. 
• fₗ is the fraction of those suitable planets on which life actually appears.
• fᵢ is the fraction of those life-bearing planets that develop intelligent life. 
• f꜀ is the fraction of those planets with intelligent life that develop the capacity for interstellar communication.  
• L is the length of time that such communicative civilizations are active. 

Although this video suggests that Drake was enthusiastic about the potential existence of 10,000 alien civilizations in our Milky Way,  it's important to note that the Drake equation is not firmly grounded in hard science and has faced significant criticism from the scientific community due to its speculative nature. 

Through my exploration of articles and research online, I've encountered alien civilization estimates spanning from 36 all the way to 12,500. Regardless of whether there is only one, 36, or thousands of these civilizations, isn't it strange that we haven't encountered at least one in our lifetime? The contrast between the seemingly high probability of the existence of aliens and the absence of conclusive evidence is commonly referred to as the Fermi Paradox.

Named after Nobel-prize winning physicist, Enrico Fermi, he wondered why no one had come to visit us by now. According to Herbert York, who was at lunch with Fermi when he posed this question, "... he went on to conclude that the reason that we hadn’t been visited might be that interstellar flight is impossible, or, if it is possible, always judged to be not worth the effort, or technological civilization doesn’t last long enough for it to happen.” Unfortunately, Fermi died just a few short years after introducing this idea, leaving the exploration and elaboration of it to others. However, his thought-provoking question continued to ignite curiosity and spark further discussions among scholars in the field. One such individual was Michael Hart, who in 1975 authored a paper titled "An Explanation for the Absence of Extraterrestrials on Earth."

Hart argues, "they are not here, so they do not exist" due to his claims that if extraterrestrial life were real, and interstellar travel was possible, then the colonization of the galaxy would be inevitable, and we should accept their absence as evidence they do not exist. In his paper, he discusses other factors to consider, like assuming that extraterrestrial life would have a similar lifespan to ours, or how relativistic time-dilation effects would be used.

A few years later, physicist Frank Tipler extended this argument by asking the clarifying question: how could any civilization acquire the resources necessary to colonize billions of stars? Tipler suggested “a self-replicating universal constructor with intelligence comparable to the human level.” As written in his paper, "Extraterrestrial Intelligent Beings do not Exist." Tipler argued that the absence of such devices on Earth implies that our intelligence is unique to the entire universe, not just our galaxy. (Which is quite the assumption TBH.)

Regardless, It's so cool to see how there are different perspectives on the existence of alien life. The Dark Forest Theory, Drake Equation, and Fermi Paradox all demonstrate the complexity and fascination of this topic. Each viewpoint offers insights and challenges, but none provide a definitive answer. Instead, they emphasize the need for continued research and discussion to unravel the mysteries surrounding extraterrestrial life.

Given all of this, some argue that the 'Fermi Paradox' is misnamed and should instead be attributed to Hart and Tipler, as they were the driving force behind the discussions and attention given to this subject. You can read more about the Hart-Tipler conjecture here.

What do you think? Are alien civilizations cautious of our potential hostility? Should we prepare for their arrival? Are we wasting our time and money exploring these ideas? Let me know below!!!

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Here are some additional resources to answer all of your alien-related questions!

➢ Neil deGrasse Tyson Explains Alien Visits, UFOs, and Other Conspiracies (YT Video)

➢ Where all all the aliens? w/ Stephen Webb (TED Talk)

Thank you for reading!🪐