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.

In their article, ‘That is not dead which can eternal lie: the aestivation hypothesis for resolving Fermi’s paradox’, Sandberg et al. try to explain the Fermi paradox by claiming that Landauer’s principle implies that a civilization can in principle perform far more times more) irreversible logical operations if it conserves its resources until the distant future when the cosmic background temperature is very low. So perhaps aliens are out there, but quietly waiting. Sandberg et al. implicitly (...) assume, however, that computer-generated entropy can only be disposed of by transferring it to the cosmological background. In fact, while this assumption may apply in the distant future, our universe today contains vast reservoirs and other physical systems in non-maximal entropy states, and computer-generated entropy can be transferred to them at the adiabatic conversion rate of one bit of negentropy to erase one bit of error. This can be done at any time, and is not improved by waiting for a low cosmic background temperature. Thus aliens need not wait to be active. As Sandberg et al. do not provide a concrete model of the effect they assert, we construct one and show where their informal argument goes wrong. (shrink)

L’esame di un passo della Vita di Platone laerziana (III 2) – e di luoghi paralleli riferibili alla medesima tradizione – permette di mettere a fuoco un motivo mitico cruciale nei racconti sulla concorrenza tra essere umano e divinità nel gamos con una mortale: il divieto, che il nume impone al ‘rivale’ di inferiore natura, di congiungersi con la donna che reca in grembo il suo seme, finché l’eroina non abbia portato a termine la gravidanza. Le storie di personaggi femminili (...) colpevoli di duplice gamos – prima con il dio e poi, a breve distanza di tempo, con il mortale – si focalizzano sulle conseguenze nefaste del secondo contaminante connubio: uno per tutti il caso di Coronide madre di Asclepio (e forse il motivo era associato anche ad altre note madri mitiche, come Arianna, Semele e Alcmena). In questi esempi, tuttavia, in genere non è esplicitato il tema della proibizione divina, come invece accade nel bios di Diogene Laerzio. Qui infatti Apollo, dopo aver concepito Platone con Perictione, appare ad Aristone per vietargli il rapporto sessuale con la parthenos. (shrink)

Developments that suggest the universe is full of life make the Fermi paradox increasingly pressing, but our search for an extraterrestrial technological civilization (“ETC”) is handicapped by our ignorance of its probable nature and behavior. This paper offers a way around this problem by drawing on information theoretical concepts, including game theory and Bayesian probability. It argues that, whatever its ultimate goals, an ETC would have the same instrumental goals as other intelligent agents. Generically, these are self-preservation and (...) the acquisition of resources. For an advanced ETC, these generic goals imply the objectives of removing existential threats and acquiring strategic and non-strategic information. Since the most problematic existential threats for any ETC would be from other civilizations and planets hosting such civilizations would also be copious sources of information, these objectives would lead it to gather information from these locations and to protect itself against them. This dual-goals hypothesis resolves the Fermi paradox, redirects the search for extraterrestrial intelligence and makes testable predictions regarding ETC’s behavior on Earth if it is here. (shrink)

According to the most common interpretation of the simulation argument, we are very likely to live in an ancestor simulation. It is interesting to ask if some families of simulations are more likely than others inside the space of all simulations. We argue that a natural probability measure is given by computational complexity: easier simulations are more likely to be run. Remarkably this allows us to extract experimental predictions from the fact that we live in a simulation. For instance we (...) show that it is very likely that humanity will not achieve interstellar travel and that humanity will not meet other intelligent species in the universe, in turn explaining the Fermi's Paradox. On the opposite side, experimental falsification of any of these predictions would constitute evidence against our reality being a simulation. (shrink)

Transmissible cancers are elusive and understudied parasitic life forms caused by malignant clonal cells (nine lineages are known so far). They emerge by completing sequential steps that include breaking cell cooperation, evade anti‐cancer defences and shedding cells to infect new hosts. Transmissible cancers impair host fitness, and their importance as selective force is likely largely underestimated. It is, therefore, crucial to determine how common they might be in the wild. Here, we draw a parallel between the steps required for a (...) transmissible cancer to emerge and the steps required for an intelligent civilisation to emerge in the Milky Way using a modified Drake equation. Using numerical analyses, we estimate the potential number of extant marine and bivalve species in which transmissible cancers might exist. Our results suggest that transmissible cancers are more common than expected, and that new lineages can be found by screening a large number of species. (shrink)

on synchronicity, the Fermi Paradox, the Turing Test, and more.

If the discovery of life elsewhere in the universe is just around the corner, what would be the consequences for religion? Would it represent another major conflict between science and religion, even leading to the death of faith? Some would suggest that the discovery of any suggestion of extraterrestrial life would have a greater impact than even the Copernican and Darwinian revolutions. It is now over 50 years since the first modern scientific papers were published on the search for extraterrestrial (...) intelligence. Yet the religious implications of this search and possible discovery have never been systematically addressed in the scientific or theological arena. SETI is now entering its most important era of scientific development. New observation techniques are leading to the discovery of extra-solar planets daily, and the Kepler mission has already collected over 1000 planetary candidates. This deluge of data is transforming the scientific and popular view of the existence of extraterrestrial intelligence. Earth-like planets outside of our solar system can now be identified and searched for signs of life. Now is a crucial time to assess the scientific and theological questions behind this search. This book sets out the scientific arguments undergirding SETI, with particular attention to the uncertainties in arguments and the strength of the data already assembled. It assesses not only the discovery of planets but other areas such as the Fermi paradox, the origin and evolution of intelligent life, and current SETI strategies. In all of this it reflects on how these questions are shaped by history and pop culture and their relationship with religion, especially Christian theology. It is argued that theologians need to take seriously SETI and to examine some central doctrines such as creation, incarnation, revelation, and salvation in the light of the possibility of extraterrestrial life. (shrink)

Lemovo dílo Dokonalá prázdnota je sbírkou recenzí fiktivních autorů na neexistující vědecké práce. Patří sem i přednáška Alfreda Testy proslovená u příležitosti udělení Nobelovy ceny za fyziku. Je to vlastně rekapitulace kosmologického konceptu postaveného na objevu pozapomenuté myšlenky Aristida Acheropoula, která má vysvětlit silentium universi. Proč vesmír mlčí? Proč nám nikdo neodpovídá na naše výzvy posílané do mezihvězdných dálek? Proč je naše pátrání po mimozemských civilizacích neúspěšné? Testa ve své přednášce před posluchače postupně vrství fundamentální otázky vztahu matematiky a fyziky, (...) intertpretaci posledních objevů moderní kosmologie, vysvětlení fyzikálních zákonitostí teorie relativity a kvantové mechaniky včetně metafyzické otázky proč jsou právě takové. Protože Lem staví před čtenáře příběh vědeckého objevu, nabízí se možnost, vzít je zcela vážně nikoli jako fiction, ale jako science a podívat se na jeho jednotlivé komponenty očima soudobé vědy. (shrink)

Lemovo dílo Dokonalá prázdnota je sbírkou recenzí fiktivních autorů na neexistující vědecké práce. Patří sem i přednáška Alfreda Testy proslovená u příležitosti udělení Nobelovy ceny za fyziku. Je to vlastně rekapitulace kosmologického konceptu postaveného na objevu pozapomenuté myšlenky Aristida Acheropoula, která má vysvětlit silentium universi. Proč vesmír mlčí? Proč nám nikdo neodpovídá na naše výzvy posílané do mezihvězdných dálek? Proč je naše pátrání po mimozemských civilizacích neúspěšné? Testa ve své přednášce před posluchače postupně vrství fundamentální otázky vztahu matematiky a fyziky, (...) intertpretaci posledních objevů moderní kosmologie, vysvětlení fyzikálních zákonitostí teorie relativity a kvantové mechaniky včetně metafyzické otázky proč jsou právě takové. Protože Lem staví před čtenáře příběh vědeckého objevu, nabízí se možnost, vzít je zcela vážně nikoli jako fiction, ale jako science a podívat se na jeho jednotlivé komponenty očima soudobé vědy. (shrink)

Just what is Einstein's Theory of Relativity? The Big Bang Theory? Curvature of Spacetime? What do astronomers mean when they talk of a 'flat universe'? This approachable and authoritative guide to the cosmos answers these questions, and more. Taking advantage of the distinctive Companion format, readers can use the extensive, cross-referenced background chapters as a fascinating and accessible introduction to the current state of cosmological knowledge - or, they can use the convenient A-Z body of entries as a quick reference (...) to a wide range of terms and concepts. Entries include topics such as: Black Hole; Doppler Effect; Fermi, Enrico; Heat Death of the Universe; Life in the Universe; Olber's Paradox; Quantum Field Theory; Supernova; and much more. (shrink)

Just what is Einstein's Theory of Relativity? The Big Bang Theory? Curvature of Spacetime? What do astronomers mean when they talk of a 'flat universe'? This approachable and authoritative guide to the cosmos answers these questions, and more. Taking advantage of the distinctive Companion format, readers can use the extensive, cross-referenced background chapters as a fascinating and accessible introduction to the current state of cosmological knowledge - or, they can use the convenient A-Z body of entries as a quick reference (...) to a wide range of terms and concepts. Entries include topics such as: Black Hole; Doppler Effect; Fermi, Enrico; Heat Death of the Universe; Life in the Universe; Olber's Paradox; Quantum Field Theory; Supernova; and much more. (shrink)

Just what is Einstein's Theory of Relativity? The Big Bang Theory? Curvature of Spacetime? What do astronomers mean when they talk of a 'flat universe'? This approachable and authoritative guide to the cosmos answers these questions, and more. Taking advantage of the distinctive Companion format, readers can use the extensive, cross-referenced background chapters as a fascinating and accessible introduction to the current state of cosmological knowledge - or, they can use the convenient A-Z body of entries as a quick reference (...) to a wide range of terms and concepts. Entries include topics such as: Black Hole; Doppler Effect; Fermi, Enrico; Heat Death of the Universe; Life in the Universe; Olber's Paradox; Quantum Field Theory; Supernova; and much more. (shrink)

An interesting consequence of the modern cosmological paradigm is the spatial infinity of the universe. When coupled with naturalistic understanding of the origin of life and intelligence, which follows the basic tenets of astrobiology, and with some fairly incontroversial assumptions in the theory of observation selection effects, this infinity leads, as Ken Olum has recently shown, to a paradoxical conclusion. Olum's paradox is related, to the famous Fermi's paradox in astrobiology and “SETI” studies. We, hereby, present an (...) evolutionary argument countering the apparent inconsistency, and show how, in the framework of a simplified model, deeper picture of the coupling between histories of intelligent/technological civilizations and astrophysical evolution of the Galaxy, can be achieved. This strategy has consequences of importance for both astrobiological studies and philosophy. (shrink)

Spin-half fermions are considered to be limited in a spherical potential well with periodic boundary conditions. The whole system is treated like a relativistic Fermi Gas. Solving the corresponding Dirac equation, the density of states, the Fermi energy, the average energy, the density of states of nucleons and the total energy of the ground-state are obtained.

We give an account of the appearance and first developments of the statistical model of atoms proposed by Thomas and Fermi, focusing on the main results achieved by Fermi and his group in Rome. Particular attention is addressed to the unknown contribution to this subject by Majorana, anticipating some important results reached later by leading physicists.

Expert reasoning combines voluminous domain‐specific knowledge with more general factual and strategic knowledge. Whereas expert system builders have recognized the need for specificity and problem‐solving researchers the need for generality, few attempts have been made to develop expert reasoning engines combining different kinds of knowledge at different levels of generality. This paper reports on the FERMI project, a computer‐implemented expert reasoner in the natural sciences that encodes factual and strategic knowledge in separate semantic hierarchies. The principled decomposition of knowledge (...) according to type and level of specificity yields both power and cross‐doman generality, as demonstrated in FERMI's ability to apply the same principles of invariance and decomposition to solve problems in fluid statics, DC‐circuits, and centroid location. Hierarchical knowledge representation and problem‐solving principles are discussed, and illustrative problem‐solving traces are presented. (shrink)

Fermi-Dirac statistics are one of two kinds of statistics exhibited by !identical quantum particles, the other being !Bose-Einstein statistics. Such particles are called fermions and bosons respectively (the terminology is due to Dirac [1902-1984] [1]). In the light of the !spin-statistics theorem, and consistent with observation, fermions are invariably spinors (of half-integral spin), whilst bosons are invariably scalar or vector particles (of integral spin). See !spin.

We present a Gedankenexperiment that leads to a violation of detailed balance if quantum mechanical transition probabilities are treated in the usual way by applying Fermi’s “golden rule”. This Gedankenexperiment introduces a collection of two-level systems that absorb and emit radiation randomly through non-reciprocal coupling to a waveguide, as realized in specific chiral quantum optical systems. The non-reciprocal coupling is modeled by a hermitean Hamiltonian and is compatible with the time-reversal invariance of unitary quantum dynamics. Surprisingly, the combination of (...) non-reciprocity with probabilistic radiation processes entails negative entropy production. Although the considered system appears to fulfill all conditions for Markovian stochastic dynamics, such a dynamics violates the Clausius inequality, a formulation of the second law of thermodynamics. Several implications concerning the interpretation of the quantum mechanical formalism are discussed. (shrink)

We consider the quantum electrodynamic problem of the velocity of transmission of an excitation from one atom to another, which was posed by Fermi in 1932 and, in an improved version, by Ferretti in 1968. The problem is solved using Heisenberg operators. The transmission velocity is shown to exceed the light velocity. We argue that this acausal result is to be explained by the inadmissibly idealized description of the signal source used by Fermi and Ferretti.

We present a reformulation of loop quantum gravity with a cosmological constant and no matter as a Fermi-liquid theory. When the topological sector is deformed and large gauge symmetry is broken, we show that the Chern–Simons state reduces to Jacobson’s degenerate sector describing 1+1 dimensional propagating fermions with nonlocal interactions. The Hamiltonian admits a dual description which we realize in the simple BCS model of superconductivity. On one hand, Cooper pairs are interpreted as wormhole correlations at the de Sitter (...) horizon; their number yields the de Sitter entropy. On the other hand, BCS is mapped into a deformed conformal field theory reproducing the structure of quantum spin networks. When area measurements are performed, Cooper-pair insertions are activated on those edges of the spin network intersecting the given area, thus providing a description of quantum measurements in terms of excitations of a Fermi sea to superconducting levels. The cosmological constant problem is naturally addressed as a nonperturbative mass-gap effect of the true Fermi-liquid vacuum. (shrink)

The Fermi energy at 0°K is evaluated for electrons confined to cubical and spherical rigid-walled boxes of equal volume, respectively, in the Sommerfeld approximation. Due primarily to large differences in single-particle degeneracies, Fermi energies compared for equal numbers of particles in these two configurations are found to be unequal. Approximate expressions of the Fermi energy in the large particle-number limit for the spherical case reveal that it agrees in form with the Fermi energy for the cubical (...) configuration. The finite cylindrical box is also examined and it is found that for fixed number of particles and fixed volume, the Fermi energy varies as the two characteristic lengths of the box are changed. Experimental corroboration of the theory is suggested through measurement of the work function for equal-volume micrometallic samples in the different geometries. (shrink)

_Paradoxes from A to Z, Third edition_ is the essential guide to paradoxes, and takes the reader on a lively tour of puzzles that have taxed thinkers from Zeno to Galileo, and Lewis Carroll to Bertrand Russell. Michael Clark uncovers an array of conundrums, such as Achilles and the Tortoise, Theseus’ Ship, and the Prisoner’s Dilemma, taking in subjects as diverse as knowledge, science, art and politics. Clark discusses each paradox in non-technical terms, considering its significance and looking at (...) likely solutions. This third edition is revised throughout, and adds nine new paradoxes that have important bearings in areas such as law, logic, ethics and probability. Paradoxes from A to Z, Third edition is an ideal starting point for those interested not just in philosophical puzzles and conundrums, but anyone seeking to hone their thinking skills. (shrink)