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G. D. Brin | Quarterly journal of the Royal Astronomical Society | (1983)
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Abstract

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Plain English Takeaway

People have wondered for a long time why we have not found signs of intelligent life beyond Earth, and this paper explores the reasons and debates around that mystery.

Study Aim

The paper aims to explore and analyze the ongoing debate about why, despite the vastness of the universe, humans have not yet detected any evidence of intelligent life beyond Earth. The author seeks to clarify the main arguments and theories that try to explain this puzzling lack of contact, often called the 'Great Silence.' Simply put: The paper tries to figure out why we have not found any aliens yet.

Study Design

This work is a scholarly review and discussion of existing scientific literature, theories, and arguments about the search for extraterrestrial intelligence (SETI, which stands for Search for Extraterrestrial Intelligence). The author examines historical perspectives, scientific reasoning, and philosophical viewpoints, comparing different explanations for the absence of detected signals or visits from intelligent alien civilizations. Simply put: The author looks at many ideas and past research to understand why we have not heard from aliens.

Findings

The paper highlights that there are many possible explanations for the 'Great Silence,' ranging from the rarity of life, the short lifespan of technological civilizations, to the possibility that advanced civilizations choose not to communicate. The author notes that each explanation has strengths and weaknesses, and no single theory fully resolves the mystery. The discussion suggests that continued scientific investigation and open-mindedness are needed to address this profound question. Simply put: The paper says there are many reasons we might not have found aliens, and we still do not know the answer.

Referenced In

StarTalk

Season 17, Episode 25: The “Dark Forest” and Scary Solutions to the Fermi Paradox

Hey StarTalkians! Season 17, episode 25 saw Neil, Paul and astrophysicist Charles Liu answer a whole bunch of alien-themed cosmic queries, inspired by Neil’s upcoming book Take Me to Your Leader. Among many interesting queries, the end of the show discussed the Fermi paradox:

Cosmic Queries – Take Me To Your Leader

(from 51:36)

In particular, they cover a relativity well-known idea, the “dark forest” hypothesis. But is it realistic? Should we be worried?

The Fermi Paradox: Light-Speed Summary

The Fermi paradox is simple: Since we have billions of stars in the Milky Way, there are billions of planets too, and there probably will be tons of intelligent extraterrestrial life forms in the galaxy. So where are they? Why haven’t we met them yet?

This is the Fermi paradox.

The Dark Forest Hypothesis

The “dark forest” hypothesis is named after Liu Cixin’s novel, which posits that the reason for the Fermi paradox is the same as the reason that you would stay quiet in a dark forest frequented by hunters. If you make a noise, they will come and snuff you out.

In the context of the galaxy, the “noise” would be a transmission, such as a radio transmission, and the “hunters” could be alien life forms or violent autonomous probes. So far, our signals reach out 200 light years, which is huge by our standards but pretty small on cosmic scales.

The Beserker Hypothesis

The even scarier “Beserker” hypothesis posits that some such autonomous probes could be created by a xenophobic extra-terrestrial species, loaded up with bombs and tasked to replicate and attack any signs of life they encounter.

In a famous paper David Brin writes, “It need only happen once for the results of this scenario to become the equilibrium condition in the Galaxy.”

How Likely Are These Scenarios?

These and other “scary solutions” to the Fermi hypothesis are gripping, but seem unlikely. As Brin points out in the paper, Beserker-style self-replicating probes may eventually become a threat to the creator species, so even xenophobic species may be wary of ever creating them.

We can also invert the above quote from Brin to tackle the dark forest: it only takes one species to ignore this risk – or not know about it – for signals to exist anyway. We are one example of such a species.

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