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O Paradoxo de Fermi e Caminhadas do Turista

International Journal of Astrobiology

Research Article

Slingshot dynamics for self-replicating probes and the effect on exploration timescales

Arwen Nicholsona1 c1 and Duncan Forgana1

 

a1 Scottish Universities Physics Alliance (SUPA), Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK

 

Abstract

 

Interstellar probes can carry out slingshot manoeuvres around the stars they visit, gaining a boost in velocity by extracting energy from the star’s motion around the Galactic Centre. These manoeuvres carry little to no extra energy cost, and in previous work it has been shown that a single Voyager-like probe exploring the Galaxy does so 100 times faster when carrying out these slingshots than when navigating purely by powered flight (Forgan et al.2012). We expand on these results by repeating the experiment with self-replicating probes. The probes explore a box of stars representative of the local Solar neighbourhood, to investigate how self-replication affects exploration timescales when compared with a single non-replicating probe. We explore three different scenarios of probe behaviour: (i) standard powered flight to the nearest unvisited star (no slingshot techniques used), (ii) flight to the nearest unvisited star using slingshot techniques and (iii) flight to the next unvisited star that will give the maximum velocity boost under a slingshot trajectory. In all three scenarios, we find that as expected, using self-replicating probes greatly reduces the exploration time, by up to three orders of magnitude for scenarios (i) and (iii) and two orders of magnitude for (ii). The second case (i.e. nearest-star slingshots) remains the most time effective way to explore a population of stars. As the decision-making algorithms for the fleet are simple, unanticipated ‘race conditions’ among probes are set up, causing the exploration time of the final stars to become much longer than necessary. From the scaling of the probes’ performance with star number, we conclude that a fleet of self-replicating probes can indeed explore the Galaxy in a sufficiently short time to warrant the existence of the Fermi Paradox.

(Received April 02 2013)  (Accepted May 24 2013)

 

Planetas extra-solares, Kepler 62 e o Paradoxo de Fermi local

Conforme aumentam o número de planetas extra-solares descobertos, também aumentamos vínculos sobre as previsões do modelo de percolação galática (Paradoxo de Fermi Local).
A previsão é que, se assumirmos que Biosferas Meméticas (Biosferas culturais ou Tecnosferas) são um resultado provável de Biosferas Genéticas, então devemos estar dentro de uma região com pucos planetas habitáveis. Pois se existirem planetas habitados (por seres inteligentes) por perto, com grande probabilidade eles são bem mais avançados do que nós, e já teriam nos colonizado.
Como isso ainda não ocorreu (a menos que se acredite nas teorias de conspiração dos ufólogos e nas teorias de Jesus ET, deuses astronautas etc.), segue que quanto mais os astronomos obtiverem dados, mais ficará evidente que nosso sistema solar é uma anomalia dentro de nossa vizinhança cósmica (1000 anos-luz?), ou seja, não podemos assumir o Princípio Copernicano em relação ao sistema solar: nosso sistema solar não é tipico em nossa vizinhança.  Bom, pelo menos, essa conclusão está batendo com os dados coletados até hoje…
Assim, é possível fazer a previsão de que uma maior análise dos planetas Kepler 62-e e Kepler 62-f revelará que eles não possuem uma atmosfera com oxigênio ou metano, sinais de um planeta com biosfera.

Persistence solves Fermi Paradox but challenges SETI projects

Osame Kinouchi (DFM-FFCLRP-Usp)
(Submitted on 8 Dec 2001)

Persistence phenomena in colonization processes could explain the negative results of SETI search preserving the possibility of a galactic civilization. However, persistence phenomena also indicates that search of technological civilizations in stars in the neighbourhood of Sun is a misdirected SETI strategy. This last conclusion is also suggested by a weaker form of the Fermi paradox. A simple model of a branching colonization which includes emergence, decay and branching of civilizations is proposed. The model could also be used in the context of ant nests diffusion.

03/05/2013 – 03h10

Possibilidade de vida não se resume a planetas similares à Terra, diz estudo

SALVADOR NOGUEIRA
COLABORAÇÃO PARA A FOLHA

Com as diferentes composições, massas e órbitas possíveis para os planetas fora do Sistema Solar, a vida talvez não esteja limitada a mundos similares à Terra em órbitas equivalentes à terrestre.

Editoria de arte/Folhapress

Essa é uma das conclusões apresentada por Sara Seager, do MIT (Instituto de Tecnologia de Massachusetts), nos EUA, em artigo de revisão publicado no periódico “Science“, com base na análise estatística dos cerca de 900 mundos já detectados ao redor de mais de 400 estrelas.

Seager destaca a possível existência de planetas cuja atmosfera seria tão densa a ponto de preservar água líquida na superfície mesmo a temperaturas bem mais baixas que a terrestre. Read more [+]

Seleção Artificial Cosmológica: primeiras referências

Tive a mesma ideia em 1995, mas não publiquei. Sexta feira passada, achei numa pasta abandonada os escritos que estão digitalizados aqui.  Por um erro de memória, confundi Lee Smolin (em inglês e mais completo aqui) com Sidney Coleman.

Meduso-anthropic principle

The meduso-anthropic principle is a quasi-organic universe theory originally proposed by mathematician and quantum gravity scholar Louis Crane in 1994.

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Universes and black holes as potential life cycle partners

Crane’s MAP is a variant of the hypothesis of cosmological natural selection (fecund universes), originally proposed by cosmologist Lee Smolin (1992). It is perhaps the first published hypothesis of cosmological natural selection with intelligence (CNS-I), where intelligence plays some proposed functional role in universe reproduction. It is also an interpretation of the anthropic principle (fine-tuning problem). The MAP suggests the development and life cycle of the universe is similar to that of Corals and Jellyfish, in which dynamic Medusa are analogs for universal intelligence, in co-evolution and co-development with sessile Polyp generations, which are analogs for both black-holes and universes. In the proposed life cycle, the Universe develops intelligent life and intelligent life produces new baby universes. Crane further speculates that our universe may also exist as a black hole in a parallel universe, and extraterrestrial life there may have created that black hole.

Crane’s work was published in 1994 as a preprint on arXiv.org. In 1995, in an an article in QJRAS, emeritus cosmologist Edward Harrison (1919-2007) independently proposed that the purpose of intelligent life is to produce successor universes, in a process driven by natural selection at the universal scale. Harrison’s work was apparently the first CNS-I hypothesis to be published in a peer-reviewed journal.

Why future civilizations might create black holes

Crane speculates that successful industrial civilizations will eventually create black holes, perhaps for scientific research, for energy production, or for waste disposal. After the hydrogen of the universe is exhausted civilizations may need to create black holes in order to survive and give their descendants the chance to survive. He proposes that Hawking radiation from very small, carefully engineered black holes would provide the energy enabling civilizations to continue living when other sources are exhausted.

Philosophical implications

According to Crane, Harrison, and other proponents of CNS-I, mind and matter are linked in an organic-like paradigm applied at the universe scale. Natural selection in living systems has given organisms the imperative to survive and reproduce, and directed their intelligence to that purpose. Crane’s MAP proposes a functional purpose for intelligence with respect to universe maintenance and reproduction. Universes of matter produce intelligence, and intelligent entities are ultimately driven to produce new universes.

See also

References

O melhor livro de divulgação científica que encontrei em quarenta anos de leituras

Depois escrevo minha resenha…

A REALIDADE OCULTA – Universos paralelos e as leis profundas do cosmo
Brian Greene
R$ 59,00 Comprar
R$ 39,00 E-Book
Indique Comente
É necessário estar logado para utilizar este recurso. Acompanhe

Meio século atrás, os cientistas encaravam com ironia a possibilidade de existirem outros universos além deste que habitamos. Tal hipótese não passava de um delírio digno de Alice no País das Maravilhas – e que, de todo modo, jamais poderia ser comprovada experimentalmente. Os desafios propostos pela Teoria da Relatividade e pela física quântica para o entendimento de nosso próprio universo já eram suficientemente complexos para ocupar gerações e gerações de pesquisadores. Entretanto, diversos estudos independentes entre si, conduzidos por cientistas respeitados em suas áreas de atuação – teoria das cordas, eletrodinâmica quântica, teoria da informação -, começaram a convergir para o mesmo ponto: a existência de universos paralelos – o multiverso – não só é provável como passou a ser a explicação mais plausível para diversos enigmas cosmológicos.
Em A realidade oculta, Brian Greene – um dos maiores especialistas mundiais em cosmologia e física de partículas – expõe o fantástico desenvolvimento da física do multiverso ao longo das últimas décadas. O autor de O universo elegante passa em revista as diferentes teorias sobre os universos paralelos a partir dos fundamentos da relatividade e da mecânica quântica. Por meio de uma linguagem acessível e valendo-se de numerosas figuras explicativas, Greene orienta o leitor pelos labirintos da realidade mais profunda da matéria e do pensamento.

“Se extraterrestres aparecessem amanhã e pedissem para conhecer as capacidades da mente humana, não poderíamos fazer nada melhor que lhes oferecer um exemplar deste livro.” – Timothy Ferris, New York Times Book Review

Aliens e Sondas Extraterrestres: cadê todo mundo?

Mais referências para o meu paper sobre Paradoxo de Fermi:

Galactic exploration by directed Self-Replicating Probes, and its implications for the Fermi paradox

Martin T. Barlow
(Submitted on 5 Jun 2012 (v1), last revised 20 Aug 2012 (this version, v2))

This paper proposes a long term scheme for robotic exploration of the galaxy,and then considers the implications in terms of the `Fermi paradox’ and our search for ETI. We discuss the parameter space of the `galactic ecology’ of civilizations in terms of the parameters T (time between ET civilizations arising) and L, the lifetime of these civilizations. Six different regions are described.

Comments: 1 figure
Subjects: Popular Physics (physics.pop-ph)
Cite as: arXiv:1206.0953 [physics.pop-ph]
(or arXiv:1206.0953v2 [physics.pop-ph] for this version)

Fermi Paradox Points to Fewer Than 10 Extraterrestrial Civilizations

 

The absence of alien probes visiting the solar system places severe limits on the number of advanced civilizations that could be exploring the galaxy.

 

Aliens on Earth. Are reports of close encounters correct?

(Submitted on 26 Mar 2012 (v1), last revised 12 Jul 2012 (this version, v2))

Popular culture (movies, SF literature) and witness accounts of close encounters with extraterrestrials provide a rather bizarre image of Aliens behavior on Earth. It is far from stereotypes of human space exploration. The reported Aliens are not missions of diplomats, scientists nor even invasion fleets; typical encounters are with lone ETs (or small groups), and involve curious behavior: abductions and experiments (often of sexual nature), cattle mutilations, localized killing and mixing in human society using various methods. Standard scientific explanations of these social memes point to influence of cultural artifacts (movies, literature) on social imagination, projection of our fears and observations of human society, and, in severe cases, psychic disorder of the involved individuals. In this work we propose an alternate explanation, claiming that the memes might be the result of observations of actual behavior of true Aliens, who, visiting Earth behave in a way that is then reproduced by such memes. The proposal would solve, in natural way, the Fermi paradox.

Comments: Revised version, taking into account the British Ministry of Defence unclassified UFO related documents
Subjects: Popular Physics (physics.pop-ph); Physics and Society (physics.soc-ph)
Cite as: arXiv:1203.6805 [physics.pop-ph]
(or arXiv:1203.6805v2 [physics.pop-ph] for this version)

Novo artigo sobre automata celulares e Paradoxo de Fermi

Saiu um novo artigo sobre a hipótese de percolação para o Paradoxo de Fermi, onde simulações de automata celulares em três dimensões são usadas.  Dessa vez, a conclusão dos autores é a de que as simulações não suportam a hipótese.

Bom, acho que isso não é o fim da história. Eu já sabia que, para a hipótese dar certo, a difusão deveria ser critica (ou seja, formando um cluster crítico ou levemente supercrítico de planetas ocupados).

Ou seja, a hipótese precisa ser complementada com algum argumento de porque a difusão deveria ser crítica. Bom, como sistemas críticos são abundantes nos processos sociais e biológicos, eu acho que basta encontrar esse fator de criticalidade para justificar o modelo. Minha heurística seria: Read more [+]

Landis e a abordagem de percolação para o Paradoxo de Fermi

Published in Journal of the British Interplanetary Society, London, Volume 51, page 163-166 (1998).
Originally presented at the NASA Symposium “Vision-21: Interdisciplinary Science and Engineering in the Era of Cyberspace” (NASA CP-10129), Mar. 30-31, 1993, Westlake, OH U.S.A.


The Fermi Paradox: An Approach Based on Percolation Theory

Geoffrey A. Landis

NASA Lewis Research Center, 302-1
Cleveland, OH 44135 U.S.A.


Abstract

If even a very small fraction of the hundred billion stars in the galaxy are home to technological civilizations which colonize over interstellar distances, the entire galaxy could be completely colonized in a few million years. The absence of such extraterrestrial civilizations visiting Earth is the Fermi paradox.

A model for interstellar colonization is proposed using the assumption that there is a maximum distance over which direct interstellar colonization is feasable. Due to the time lag involved in interstellar communications, it is assumed that an interstellar colony will rapidly develop a culture independent of the civilization that originally settled it.

Any given colony will have a probability P of developing a colonizing civilization, and a probability (1-P) that it will develop a non-colonizing civilization. These assumptions lead to the colonization of the galaxy occuring as a percolation problem. In a percolation problem, there will be a critical value of the percolation probability, Pc. For P<Pc, colonization will always terminate after a finite number of colonies. Growth will occur in “clusters,” with the outside of each cluster consisting of non-colonizing civilizations. For P>Pc, small uncolonized voids will exist, bounded by non-colonizing civilizations. When P is on the order of Pc, arbitrarily large filled regions exist, and also arbitrarily large empty regions.

Marina Silva e a colonização galática


Bom, uma alternativa é uma expansão em forma de lei de potência: N(t) = c t^\theta. Talveza se possa demonstrar que tal expansão seria economicamente sustentável. Interessante que isso corresponderia a um processo de ramificação crítico, que criaria uma expansão fractal, de modo que haveria bolhas não colonizadas de todos os tamanhos dentro da galáxia. E a minha solução para o Paradoxo de Fermi (que estamos dentro de uma dessas bolhas, e portanto não adianta fazer pesquisa SETI nas estrelas vizinhas) seria compativel com esse vínculo de expansão economicamente sustentável… Quem sabe os ETs (e nós no futuro) têm a mesma opinião da Marina Silva?

The Sustainability Solution to the Fermi Paradox

Jacob D. Haqq-Misra, Seth D. Baum
(Submitted on 2 Jun 2009)

No present observations suggest a technologically advanced extraterrestrial intelligence (ETI) has spread through the galaxy. However, under commonplace assumptions about galactic civilization formation and expansion, this absence of observation is highly unlikely. This improbability is the heart of the Fermi Paradox. The Fermi Paradox leads some to conclude that humans have the only advanced civilization in this galaxy, either because civilization formation is very rare or because intelligent civilizations inevitably destroy themselves. In this paper, we argue that this conclusion is premature by introducing the “Sustainability Solution” to the Fermi Paradox, which questions the Paradox’s assumption of faster (e.g. exponential) civilization growth. Drawing on insights from the sustainability of human civilization on Earth, we propose that faster-growth may not be sustainable on the galactic scale. If this is the case, then there may exist ETI that have not expanded throughout the galaxy or have done so but collapsed. These possibilities have implications for both searches for ETI and for human civilization management.

Comments: 14 pages, PDF file
Subjects: Popular Physics (physics.pop-ph); Earth and Planetary Astrophysics (astro-ph.EP)
Journal reference: J.Br.Interplanet.Soc.62:47-51, 2009
Cite as: arXiv:0906.0568v1 [physics.pop-ph]

Persistence solves Fermi Paradox but challenges SETI projects

Osame Kinouchi (DFM-FFCLRP-Usp)
(Submitted on 8 Dec 2001)

Persistence phenomena in colonization processes could explain the negative results of SETI search preserving the possibility of a galactic civilization. However, persistence phenomena also indicates that search of technological civilizations in stars in the neighbourhood of Sun is a misdirected SETI strategy. This last conclusion is also suggested by a weaker form of the Fermi paradox. A simple model of a branching colonization which includes emergence, decay and branching of civilizations is proposed. The model could also be used in the context of ant nests diffusion.

Comments: 2 pages, no figures, v2 with corrected definition of branching ratio
Subjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech)
Cite as: arXiv:cond-mat/0112137v1 [cond-mat.dis-nn]

Cadê os monolitos negros?

Arthur C. Clark defende uma tese de Desígnio Inteligente na série 2001-2010-2061-3001. Mas é uma questão sem sentido perguntar se ele acreditava no DI. Afinal, a ficção científica hard tipo Clark brinca com “especulação científica”. Acho que a especulação científica, ou seja, a formulação de hipóteses (não necessariamente testáveis) compatíveis com a ciência é uma atividade normal de todo cientista. Como me respondeu uma vez o prof. Roland Koberle quando lhe perguntei se ele gostava de ficção científica:

– Mas eu faço ficção científica!

Roland trabalhava na época em Termodinâmica de Buracos Negros…

Fermi Paradox Points To Fewer Than Ten ET Civilisations

Posted: 29 Jul 2009 09:10 PM PDT

The absence of alien probes visiting the Solar System places severe limits on the number of advanced civlisations that could be exploring the galaxy.

The Fermi Paradox focuses on the existence of advanced civilisations elsewhere in the galaxy. If these civilisations are out there–and many analyses suggest the galaxy should be teaming with life–why haven’t we seen them?

Today Carlos Cotta and Álvaro Morales from the University of Malaga in Spain add an another angle to the discussion. One line of thought is the speed at which a sufficiently advanced civilisation could colonise the galaxy. Various analyses suggest that using spacecraft that travel at a tenth of the speed of light, the colonisation wavefront could take some 50 million years to sweep the galaxy. Others have calculated that it may be closer to 13 billion years, which may explain ET’s absence.

Cotta and Morales take a different tack by studying how automated probes sent ahead of the colonisation could explore the galaxy. Obviously, this could advance much faster than the colonisation wavefront. The scenario involves a civilisation sending out 8 probes, each equipped with smaller subprobes for studying regions that the host probe visits.

This is not a new scenario. One previous calculation suggests that in about 300 millions years these 8 probes could explore just 4 per cent of the galaxy. The question that Cotta and Morales ask is: what if several advanced civilisations were exploring the galaxy at the same time? Surely, if enough advanced civilisations were exploring simultaneously, one of their probes would end up visiting the solar system. So that fact we haven’t seen one places a limit on how many civilisations can be out there.

The numbers that Cotta and Morales come up with depend crucially on the lifetime of the probes doing the exploring (and obviously on the number of probes each civilisations ends out). They say that if each probe has a lifetime of 50 million years and that evidence of them visiting the solar system lasts for about a million years, there can be no more than about 1000 advanced civilisations out there now.

But if these probes can leave evidence of a visit that lasts for 100 million years, then there can be no more than about 10 civilisations out there.

Of course, we may not have discovered the evidence yet. And when we finally find the black obelisk on the Moon, the paradox will be resolved.

Ref: arxiv.org/abs/0907.0345: A Computational Analysis of Galactic Exploration with Space Probes: Implications for the Fermi Paradox

Paradoxo de Fermi: onde está todo mundo?

Figure 1. A slice from a percolation simulation on a simple cubic lattice in three dimensions. Here N=6 and P=1/3. Filled circles denote “colonizing” sites, open circles “non-colonizing” sites, and the absence of circles represents sites not visited. The irregular shape of the boundary and large voids in the percolation structure are clearly visible.


A Computational Analysis of Galactic Exploration with Space Probes: Implications for the Fermi Paradox

Carlos Cotta, Álvaro Morales
(Submitted on 2 Jul 2009)

Temporal explanations to the Fermi paradox state that the vast scale of the galaxy diminishes the chances of establishing contact with an extraterrestrial technological civilization (ETC) within a certain time window. This argument is tackled in this work in the context of exploration probes, whose propagation can be faster than that of a colonization wavefront. Extensive computational simulations have been done to build a numerical model of the dynamics of the exploration. A probabilistic analysis is subsequently conducted in order to obtain bounds on the number of ETCs that may be exploring the galaxy without establishing contact with Earth, depending on factors such as the number of probes they use, their lifetime and whether they leave some long-term imprint on explored systems or not. The results indicate that it is unlikely that more than ~10^2-10^3 ETCs are exploring the galaxy in a given Myr, if their probes have a lifetime of 50 Myr and contact evidence lasts for 1 Myr. This bound goes down to ~10 if contact evidence lasts for 100 Myr, and is also shown to be inversely proportional to the lifetime of probes. These results are interpreted in light of the Fermi paradox and are compatible with non-stationary astrobiological models in which a few ETCs have gradually appeared in the Fermi-Hart timescale.

Comments: 14 pages, 6 figures
Subjects: Popular Physics (physics.pop-ph); Earth and Planetary Astrophysics (astro-ph.EP)
Journal reference: J.Br.Interplanet.Soc.62(3):82-88,2009
Cite as: arXiv:0907.0345v1 [physics.pop-ph]