In this review of Milan Ćirković’s The Great Silence: Science and Philosophy of Fermi’s Paradox, we attempt to reconstruct the logic of Fermi’s paradox as understood by the author, and we critically examine the reasoning that leads to the paradox. We show that there is no plausible solution to Fermi’s paradox that can satisfy all of Ćirković’s proposed desiderata, which in turn suggests that the author’s standards for hypothesis adjudication need to be revised.
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Ćirković M (2018) The great silence: the science and philosophy of Fermi’s paradox. Oxford University Press, Oxford
Powell R (2020a) Contingency and convergence: toward a cosmic biology of body and mind. MIT Press, Cambridge
Powell R (2020b) Copernicanism and its biological discontents. Q Rev Biol 95(1):59–64
Funding was provided by Templeton World Charity Foundation (Grant No. TWCF0469).
|Hypothesis||Premise rejected||Desideratum rejected|
|Fermi’s flying saucers (ETIs are already here on Earth, engaging in covert activities that make them difficult to detect; p. 109)||1a||Realism|
|Ancient flying saucers (ETIs visited Earth in the distant past; p. 112)||1a||Realism|
|Special creation (the origin of humans had a supernatural cause, so there is no reason to expect the emergence of other intelligent civilizations; p. 113)||4b||Realism|
|Zoo hypothesis (Earth is located in a “zoo,” or a region of space that is set aside by advanced extraterrestrials to allow early civilizations to evolve without interference; p. 116)||2a||
|Interdict hypothesis (planets that are likely to evolve intelligent life forms, such as Earth, have been placed under interdicts that proscribe interference by other, more advanced intelligent civilizations; p. 116)||2a||
|Leaky interdict (although the interdict shielding intelligent life worlds from outside interference is not inviolable, violations will be extremely rare and sporadic, thereby evading our detection; p. 117)||2a||
|Planetarium hypothesis (our observations of the universe are simulated, or projected like stars in a planetarium, by an ETI that deliberately evades detection; p. 120)||2a||
|Peer hypothesis (a supercivilization has created our entire cosmological domain as an experiment, which is actually inhabited not just by us but by “peers,” who we cannot detect only because they are not sufficiently more advanced than we are; p. 121)||2a||Realism|
|Simulation hypothesis (we are living in a simulation in which there are no ETIs; p. 122)||2a||Realism|
|The paranoid style in galactic politics (we have unknowingly detected ETIs in the form of highly sophisticated encrypted signals that are undistinguishable from background radiation; p. 124)||1a||
|Directed panspermia (the Earth’s entire biosphere, including ourselves, is extraterrestrial in origin; p. 127)||1a||Realism|
|Bit-string invaders (ETIs exist or travel as compact bit strings that are present on Earth without our having detected them; p. 132)||1a||
|New cosmogony (highly advanced ETIs are indistinguishable from the natural processes that we perceive as physical laws; p. 134)||1a||Realism|
|Early great filter (at least one of the early steps required for the evolution of ETI is highly unlikely to occur; p. 153)||1b||Copernicanism|
|Horizon to the rescue (the probability of any of the steps required for the evolution of ETI is so small as to make detection within our event horizon nearly impossible; p. 155)||1b||Copernicanism|
|Gaian window (the planetary conditions necessary for life to emerge are extremely unlikely or insufficiently stable to prevent the regular emergence of ETI; p. 156)||1b||Copernicanism|
|Permanence (intelligence is an inefficient trait from an evolutionary perspective, and hence it will tend to be replaced by other traits, such that at any given time the existence of detectable ETI is unlikely; p. 159)||1b||Copernicanism|
|Thoughtfood exhaustion (intelligence is useful only so long as there is new information to be processed—once new content runs out, intelligence will disappear before we will have detected it; p. 164)||1b||Copernicanism|
|The gigayear of living dangerously (due to some random catastrophe, the universe is nearly uninhabitable; p. 172)||3b||Gradualism|
|Astrobiological phase transition (galactic regulation mechanisms make the emergence of early ETI much less likely than later ETI; p. 174)||3b||Gradualism|
|Stop worrying and love the bomb (all intelligent civilizations self-destruct before we are able to detect them; p. 179)||3b||
|Self-destruction, advanced version (intelligent civilizations self-destruct shortly after the discovery of post-nuclear technologies; and hence we are unable to detect them; p. 180)||3b||
|Hermit hypothesis (intelligent civilizations choose to never expand beyond their home planetary system or communicate across interstellar distances, and hence we cannot detect them; p. 27).||3b||Non-exclusivity|
|Introvert Big Brother (almost all advanced civilizations become totalitarian, drastically reducing the possibility of their contact with the rest of the universe; p. 182)||3b||
|Resource exhaustion (ETIs inevitably exhaust their natural resources, leading to their extinction; p. 185)||3b||
|Deadly probes (self-replicating machines released by an early ETI are programmed to destroy all sources of intelligence—although they have not reached us yet, they have destroyed all other detectable ETIs; p. 188)||3b||Gradualism|
|Interstellar containment (advanced ETIs are coordinating to prevent less advanced ETIs from detecting one another; p. 195)||3b||
|Transcendence (advanced ETIs have transformed themselves into some unrecognizable form; p. 196)||1a||
|Transcension (advanced ETIs have transformed themselves into more advanced space/time/energy/matter substrates, and hence we cannot detect them; p. 198)||1a||
|Red empire (ETIs tend to migrate towards dimmer, red-dwarf stars, and they have therefore avoided our solar system; p. 210)||2b||
|Brown empire (ETIs tend to gravitate toward brown dwarf stars or free-floating planets, and have therefore avoided our solar system; p. 211)||2b||
|Persistence (we happen to reside in a part of the universe that is unlikely to be colonized by ETIs for a long time; p. 213)||2b||Non-exclusivity|
|Living on the rim (advanced ETIs are likely to migrate to the outskirts of the universe where we are coincidentally unable to detect them; p. 217)||2b||Non-exclusivity|
|Eternal wanderers (advanced ETIs have no use for planets or planetary systems because they have built their own world-ships, so they are uninterested in visiting our solar system; p. 219)||2b||Non-exclusivity|
|Great old ones (advanced ETIs have put themselves into a state of estivation, waiting until conditions in the universe are more conducive to information processing; p. 219)||2b||Non-exclusivity|
|Sustainability (fast colonization is not sustainable, so any colonization attempts currently occurring are very slow and therefore have gone undetected by us; p. 221)||2b||Non-exclusivity|
|Galactic stomach ache (all ETIs eventually degenerate due to an increase in dangerous medical conditions; p. 223)||2b||Non-exclusivity|
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Hepçağlayan, C., Watkins, A. & Powell, R. What is Paradoxical About ‘Fermi’s Paradox’?. Acta Biotheor 68, 469–477 (2020). https://doi.org/10.1007/s10441-020-09376-x
- Extraterrestrial intelligence
- Fermi’s paradox
- Technological civilizations