A origem microscópica da termodinâmica: o papel da entropia em um sistema quântico

Entanglement and thermodynamics after a quantum quench in integrable systems

Vincenzo Alba a,1 and Pasquale Calabrese a  

Author Affiliations

a International School for Advanced Studies, Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, 34136 Trieste, Italy

Edited by Subir Sachdev, Harvard University, Cambridge, MA, and approved June 6, 2017 (received for review March 3, 2017)

Source/Fonte

Significance

Understanding how statistical ensembles arise from the out-of-equilibrium dynamics of isolated pure systems has been a fascinating question since the early days of quantum mechanics. Recently, it has been proposed that the thermodynamic entropy of the long-time statistical ensemble is the stationary entanglement of a large subsystem in an infinite system. Here, we combine this concept with the quasiparticle picture of the entanglement evolution and integrability-based knowledge of the steady state to obtain exact analytical predictions for the time evolution of the entanglement in arbitrary 1D integrable models. These results explicitly show the transformation between the entanglement and thermodynamic entropy during the time evolution. Thus, entanglement is the natural witness for the generalized microcanonical principle underlying relaxation in integrable models.

Abstract

Entanglement and entropy are key concepts standing at the foundations of quantum and statistical mechanics. Recently, the study of quantum quenches revealed that these concepts are intricately intertwined. Although the unitary time evolution ensuing from a pure state maintains the system at zero entropy, local properties at long times are captured by a statistical ensemble with nonzero thermodynamic entropy, which is the entanglement accumulated during the dynamics. Therefore, understanding the entanglement evolution unveils how thermodynamics emerges in isolated systems. Alas, an exact computation of the entanglement dynamics was available so far only for noninteracting systems, whereas it was deemed unfeasible for interacting ones. Here, we show that the standard quasiparticle picture of the entanglement evolution, complemented with integrability-based knowledge of the steady state and its excitations, leads to a complete understanding of the entanglement dynamics in the space–time scaling limit. We thoroughly check our result for the paradigmatic Heisenberg chain.

entanglement quantum quench integrability thermodynamics

Footnotes

1 To whom correspondence should be addressed. Email: valba@sissa.it.

Author contributions: V.A. and P.C. designed research, performed research, analyzed data, and wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1703516114/-/DCSupplemental.

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E os cananeus não foram totalmente destruídos conforme afirmado em texto oriental milenar

Continuity and Admixture in the Last Five Millennia of Levantine History from Ancient Canaanite and Present-Day Lebanese Genome Sequences

Marc Haber9,Claude Doumet-Serhal9, Christiana Scheib9, Yali Xue, Petr Danecek, Massimo Mezzavilla, Sonia Youhanna, Rui Martiniano, Javier Prado-Martinez, Michał Szpak, Elizabeth Matisoo-Smith, Holger Schutkowski, Richard Mikulski, Pierre Zalloua, Toomas Kivisild, Chris Tyler-Smith

9These authors contributed equally to this work

Published Online: July 27, 2017

Publication stage: In Press Corrected Proof

Open Access

DOI: http://dx.doi.org/10.1016/j.ajhg.2017.06.013

Open access funded by Wellcome Trust

Article Info

Publication History

Published: July 27, 2017 Accepted: June 27, 2017

Received: May 25, 2017

User License

Creative Commons Attribution (CC BY 4.0)

Source/Fonte: The New York Times

The Canaanites inhabited the Levant region during the Bronze Age and established a culture that became influential in the Near East and beyond. However, the Canaanites, unlike most other ancient Near Easterners of this period, left few surviving textual records and thus their origin and relationship to ancient and present-day populations remain unclear. In this study, we sequenced five whole genomes from ∼3,700-year-old individuals from the city of Sidon, a major Canaanite city-state on the Eastern Mediterranean coast. We also sequenced the genomes of 99 individuals from present-day Lebanon to catalog modern Levantine genetic diversity. We find that a Bronze Age Canaanite-related ancestry was widespread in the region, shared among urban populations inhabiting the coast (Sidon) and inland populations (Jordan) who likely lived in farming societies or were pastoral nomads. This Canaanite-related ancestry derived from mixture between local Neolithic populations and eastern migrants genetically related to Chalcolithic Iranians. We estimate, using linkage-disequilibrium decay patterns, that admixture occurred 6,600–3,550 years ago, coinciding with recorded massive population movements in Mesopotamia during the mid-Holocene. We show that present-day Lebanese derive most of their ancestry from a Canaanite-related population, which therefore implies substantial genetic continuity in the Levant since at least the Bronze Age. In addition, we find Eurasian ancestry in the Lebanese not present in Bronze Age or earlier Levantines. We estimate that this Eurasian ancestry arrived in the Levant around 3,750–2,170 years ago during a period of successive conquests by distant populations.

FREE PDF GRATIS: The American Journal of Human Genetics

Cientistas do Instituto Salk veem a estrutura 3D do DNA pela primeira vez: mero acaso, fortuita necessidade ou design inteligente?

ChromEMT: Visualizing 3D chromatin structure and compaction in interphase and mitotic cells

Horng D. Ou1, Sébastien Phan2, Thomas J. Deerinck2, Andrea Thor2, Mark H. Ellisman2,3, Clodagh C. O’Shea1,*

1Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.

2National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.

3Department of Neurosciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.

↵*Corresponding author. Email: oshea@salk.edu

+ See all authors and affiliations

Science 28 Jul 2017: Vol. 357, Issue 6349, eaag002

A close-up view inside the nucleus

The nuclei of human cells contain 2 meters of genomic DNA. How does it all fit? Compaction starts with the DNA wrapping around histone octamers to form nucleosomes, but it is unclear how these further compress into mitotic chromosomes. Ou et al. describe a DNA-labeling method that allows them to visualize chromatin organization in human cells (see the Perspective by Larson and Misteli). They show that chromatin forms flexible chains with diameters between 5 and 24 nm. In mitotic chromosomes, chains bend back on themselves to pack at high density, whereas during interphase, the chromatin chains are more extended.

Science, this issue p. eaag0025; see also p. 354

https://www.youtube.com/watch?v=aeMjECfSowo

Structured Abstract

INTRODUCTION

In human cells, 2 m of DNA are compacted in the nucleus through assembly with histones and other proteins into chromatin structures, megabase three-dimensional (3D) domains, and chromosomes that determine the activity and inheritance of our genomes. The long-standing textbook model is that primary 11-nm DNA–core nucleosome polymers assemble into 30-nm fibers that further fold into 120-nm chromonema, 300- to 700-nm chromatids, and, ultimately, mitotic chromosomes. Further extrapolating from this model, silent heterochromatin is generally depicted as 30- and 120-nm fibers. The hierarchical folding model is based on the in vitro structures formed by purified DNA and nucleosomes and on chromatin fibers observed in permeabilized cells from which other components had been extracted. Unfortunately, there has been no method that enables DNA and chromatin ultrastructure to be visualized and reconstructed unambiguously through large 3D volumes of intact cells. Thus, a remaining question is, what are the local and global 3D chromatin structures in the nucleus that determine the compaction and function of the human genome in interphase cells and mitotic chromosomes?

RATIONALE

To visualize and reconstruct chromatin ultrastructure and 3D organization across multiple scales in the nucleus, we developed ChromEMT, which combines electron microscopy tomography (EMT) with a labeling method (ChromEM) that selectivity enhances the contrast of DNA. This technique exploits a fluorescent dye that binds to DNA, and upon excitation, catalyzes the deposition of diaminobenzidine polymers on the surface, enabling chromatin to be visualized with OsO4 in EM. Advances in multitilt EMT allow us to reveal the chromatin ultrastructure and 3D packing of DNA in both human interphase cells and mitotic chromosomes.

RESULTS

ChromEMT enables the ultrastructure of individual chromatin chains, heterochromatin domains, and mitotic chromosomes to be resolved in serial slices and their 3D organization to be visualized as a continuum through large nuclear volumes in situ. ChromEMT stains and detects 30-nm fibers in nuclei purified from hypotonically lysed chicken erythrocytes and treated with MgCl2. However, we do not observe higher-order fibers in human interphase and mitotic cells in situ. Instead, we show that DNA and nucleosomes assemble into disordered chains that have diameters between 5 and 24 nm, with different particle arrangements, densities, and structural conformations. Chromatin has a more extended curvilinear structure in interphase nuclei and collapses into compact loops and interacting arrays in mitotic chromosome scaffolds. To analyze chromatin packing, we create 3D grid maps of chromatin volume concentrations (CVCs) in situ. We find that interphase nuclei have subvolumes with CVCs ranging from 12 to 52% and distinct spatial distribution patterns, whereas mitotic chromosome subvolumes have CVCs >40%.

CONCLUSION

We conclude that chromatin is a flexible and disordered 5- to 24-nm-diameter granular chain that is packed together at different concentration densities in interphase nuclei and mitotic chromosomes. The overall primary structure of chromatin polymers does not change in mitotic chromosomes, which helps to explain the rapid dynamics of chromatin condensation and how epigenetic interactions and structures can be inherited through cell division. In contrast to rigid fibers that have longer fixed persistence lengths, disordered 5- to 24-nm-diameter chromatin chains are flexible and can bend at various lengths to achieve different levels of compaction and high packing densities. The diversity of chromatin structures is exciting and provides a structural basis for how different combinations of DNA sequences, interactions, linker lengths, histone variants, and modifications can be integrated to fine-tune the function of genomic DNA in the nucleus to specify cell fate. Our data also suggest that the assembly of 3D domains in the nucleus with different chromatin concentrations, rather than higher-order folding, determines the global accessibility and activity of DNA.

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Teoria da informação, previsibilidade, e o surgimento da vida complexa: mero acaso, fortuita necessidade ou design inteligente?

Information theory, predictability, and the emergence of complex life

Luís F Seoane 1, 2, 3 and Ricard V. Solé 2, 3, 4

1 Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139.

2 ICREA-Complex Systems Lab, Universitat Pompeu Fabra (GRIB), Dr Aiguader 80, 08003 Barcelona, Spain.

3 Institut de Biologia Evolutiva, CSIC-UPF, Pg Maritim de la Barceloneta 37, 08003 Barcelona, Spain.

4 Santa Fe Institute, 1399 Hyde Park Road, Santa Fe NM 87501, USA.

Source/Fonte: Jon Lieff

Abstract

Despite the obvious advantage of simple life forms capable of fast replication, different levels of cognitive complexity have been achieved by living systems in terms of their potential to cope with environmental uncertainty. Against the inevitable cost associated to detecting environmental cues and responding to them in adaptive ways, we conjecture that the potential for predicting the environment can overcome the expenses associated to maintaining costly, complex structures. We present a minimal formal model grounded in information theory and selection, in which successive generations of agents are mapped into transmitters and receivers of a coded message. Our agents are guessing machines and their capacity to deal with environments of different complexity defines the conditions to sustain more complex agents.

Keywords: Complexity, emergence, computation, evolution, predictability

FREE PDF GRATIS: arXiv

Novos genes e inovação funcional em mamíferos

New genes and functional innovation in mammals

José Luis Villanueva-Cañas Jorge Ruiz-Orera M.Isabel Agea Maria Gallo David Andreu M.Mar Albà

Genome Biol Evol evx136. DOI: https://doi.org/10.1093/gbe/evx136

Published: 21 July 2017 

Article history

Received: 09 February 2017 Revision Received: 17 May 2017

Revision Received: 29 June 2017 Accepted: 14 July 2017

Source/Fonte: Edvotek

Abstract

The birth of genes that encode new protein sequences is a major source of evolutionary innovation. However, we still understand relatively little about how these genes come into being and which functions they are selected for. To address these questions we have obtained a large collection of mammalian-specific gene families that lack homologues in other eukaryotic groups. We have combined gene annotations and de novo transcript assemblies from 30 different mamalian species, obtaining about 6,000 gene families. In general, the proteins in mammalian-specific gene families tend to be short and depleted in aromatic and negatively charged residues. Proteins which arose early in mammalian evolution include milk and skin polypeptides, immune response components, and proteins involved in reproduction. In contrast, the functions of proteins which have a more recent origin remain largely unknown, despite the fact that these proteins also have extensive proteomics support. We identify several previously described cases of genes originated de novo from non-coding genomic regions, supporting the idea that this mechanism frequently underlies the evolution of new protein-coding genes in mammals. Finally, we show that most young mammalian genes are preferentially expressed in testis, suggesting that sexual selection plays an important role in the emergence of new functional genes.

de novo gene, species-specific gene, lineage-specific gene, evolutionary innovation, adaptive evolution, mammals

Issue Section: Research article

Author notes

# Current address: Institute of Evolutionary Biology (CSIC-Universitat Pompeu Fabra), Barcelona, Spain

© The Author(s) 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com

FREE PDF GRATIS: Genome Biol Evol Sup. Info.

Da estrutura ao mecanismo - compreendendo a iniciação da replicação do DNA

From structure to mechanism—understanding initiation of DNA replication

Alberto Riera1, Marta Barbon1,2,3, Yasunori Noguchi1,3, L. Maximilian Reuter1,3, Sarah Schneider1,3 and Christian Speck1,2

- Author Affiliations

1DNA Replication Group, Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, London W12 0NN, United Kingdom;

2Medical Research Council (MRC) London Institute of Medical Sciences (LMS), London W12 0NN, United Kingdom

Corresponding author: chris.speck@imperial.ac.uk

↵3 These authors contributed equally to this work.

Source/Fonte: ThoughtCo

Abstract

DNA replication results in the doubling of the genome prior to cell division. This process requires the assembly of 50 or more protein factors into a replication fork. Here, we review recent structural and biochemical insights that start to explain how specific proteins recognize DNA replication origins, load the replicative helicase on DNA, unwind DNA, synthesize new DNA strands, and reassemble chromatin. We focus on the minichromosome maintenance (MCM2–7) proteins, which form the core of the eukaryotic replication fork, as this complex undergoes major structural rearrangements in order to engage with DNA, regulate its DNA-unwinding activity, and maintain genome stability.

Keywords MCM2–7 DNA replication pre-RC CMG replisome cryo-EM

Footnotes

Article is online at http://www.genesdev.org/cgi/doi/10.1101/gad.298232.117.

Freely available online through the Genes & Development Open Access option.

© 2017 Riera et al.; Published by Cold Spring Harbor Laboratory Press

This article, published in Genes & Development, is available under a Creative Commons License (Attribution 4.0 International), as described at http://creativecommons.org/licenses/by/4.0/.

FREE PDF GRATIS: Genes and Development

Darwin, rir é o melhor remédio: momentos desapontadores na evolução!

Source/Fontes: WrongHands

Este blogger achou interessante este site: humor fino!

Controle hidráulico das nadadeiras de tuna: mero acaso, fortuita necessidade ou design inteligente?

Hydraulic control of tuna fins: A role for the lymphatic system in vertebrate locomotion

Vadim Pavlov1,*,†, Benyamin Rosental1,2,*, Nathaniel F. Hansen1, Jody M. Beers1, George Parish3, Ian Rowbotham3, Barbara A. Block1,†

+ See all authors and affiliations

Science 21 Jul 2017:

Vol. 357, Issue 6348, pp. 310-314

DOI: 10.1126/science.aak9607

Researchers from the lab of Barbara Block at Stanford University and the Monterey Bay Aquarium have discovered a bio-hydraulic system in fins of tunas. (Image credit: Monterey Bay Aquarium)

Source/Fonte: Stanford News

Hydraulic fins

The lymphatic system in fish has much the same function as it does in mammals—immune response and homeostasis. Pavlov et al. show, however, that in the scromboid (tuna and mackerel) family of fish, this fluid homeostasis function has been co-opted to help facilitate dorsal fin rigidity and movement (see the Perspective by Triantafyllou). In bluefin tuna, a series of lymphatic vessels are integrated with muscles that allow the fish to raise and stiffen their dorsal fin. This provides extra stability during swimming.

Science, this issue p. 310; see also p. 251

Abstract

The lymphatic system in teleost fish has genetic and developmental origins similar to those of the mammalian lymphatic system, which is involved in immune response and fluid homeostasis. Here, we show that the lymphatic system of tunas functions in swimming hydrodynamics. Specifically, a musculo-vascular complex, consisting of fin muscles, bones, and lymphatic vessels, is involved in the hydraulic control of median fins. This specialization of the lymphatic system is associated with fish in the family Scombridae and may have evolved in response to the demand for swimming and maneuvering control in these high-performance species.

Science

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Especialistas advertem: fazer campanha sobre o consenso da ciência do clima pode sair pela culatra!

Beyond Counting Climate Consensus

Warren Pearce, Reiner Grundmann ORCID Icon, Mike Hulme, Sujatha Raman, Eleanor Hadley Kershaw & Judith Tsouvalis

Pages 1-8 | Received 27 Aug 2016, Accepted 30 Apr 2017, Published online: 23 Jul 2017

Download citation http://dx.doi.org/10.1080/17524032.2017.1333965

Source/Fonte

Abstract

Several studies have been using quantified consensus within climate science as an argument to foster climate policy. Recent efforts to communicate such scientific consensus attained a high public profile but it is doubtful if they can be regarded successful. We argue that repeated efforts to shore up the scientific consensus on minimalist claims such as “humans cause global warming” are distractions from more urgent matters of knowledge, values, policy framing and public engagement. Such efforts to force policy progress through communicating scientific consensus misunderstand the relationship between scientific knowledge, publics and policymakers. More important is to focus on genuinely controversial issues within climate policy debates where expertise might play a facilitating role. Mobilizing expertise in policy debates calls for judgment, context and attention to diversity, rather than deferring to formal quantifications of narrowly scientific claims.

KEYWORDS: Climate change, climate policy, climate change communication

FREE PDF GRATIS: Environmental Communication

Os tardígrados (ursos-d'água) sobreviverão ao fim do mundo que nós conhecemos

The Resilience of Life to Astrophysical Events

David Sloan, Rafael Alves Batista & Abraham Loeb

Scientific Reports 7, Article number: 5419 (2017)

doi: 10.1038/s41598-017-05796-x  

Download Citation

Astrobiology Exoplanets

Received: 18 January 2017 Accepted: 05 June 2017 

Published online: 14 July 2017

Source/Fonte: Science News

Abstract

Much attention has been given in the literature to the effects of astrophysical events on human and land-based life. However, little has been discussed on the resilience of life itself. Here we instead explore the statistics of events that completely sterilise an Earth-like planet with planet radii in the range 0.5–1.5R⊕ and temperatures of ∼300 K, eradicating all forms of life. We consider the relative likelihood of complete global sterilisation events from three astrophysical sources – supernovae, gamma-ray bursts, large asteroid impacts, and passing-by stars. To assess such probabilities we consider what cataclysmic event could lead to the annihilation of not just human life, but also extremophiles, through the boiling of all water in Earth’s oceans. Surprisingly we find that although human life is somewhat fragile to nearby events, the resilience of Ecdysozoa such as Milnesium tardigradum renders global sterilisation an unlikely event.

Acknowledgements

D.S. and R.A.B. acknowledge the financial support from the John Templeton Foundation.

Author information

Affiliations

Department of Physics - Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, OX1 3RH, Oxford, UK

David Sloan & Rafael Alves Batista

Astronomy Department, Harvard University, 60 Garden Street, Cambridge, MA, 02138, USA

Abraham Loeb

Contributions

The idea of this work was conceived by A.L., D.S. and R.A.B. contributed equally to the analysis of results, with some input from A.L. D.S. did most of the writing, with aid of R.A.B. Figures were produced by R.A.B., A.L. was responsible for the scope and accuracy checking of the analysis.

Competing Interests

The authors declare that they have no competing interests.

Corresponding author

Correspondence to Rafael Alves Batista.

FREE PDF GRATIS: Science Reports

Sacudindo o paradigma da matéria escura

Shaking the dark matter paradigm

07/18/17 By Ali Sundermier

A theory about gravity challenges our understanding of the universe.

Illustration by Ana Kova

For millennia, humans held a beautiful belief. Our planet, Earth, was at the center of a vast universe, and all of the planets and stars and celestial bodies revolved around us. This geocentric model, though it had floated around since 6th century BCE, was written in its most elegant form by Claudius Ptolemy in 140 AD.

When this model encountered problems, such as the retrograde motions of planets, scientists reworked the data to fit the model by coming up with phenomena such as epicycles, mini orbits.

It wasn’t until 1543, 1400 years later, that Nicolaus Copernicus set in motion a paradigm shift that would give way to centuries of new discoveries. According to Copernicus’ radical theory, Earth was not the center of the universe but simply one of a long line of planets orbiting around the sun.

But even as evidence that we lived in a heliocentric system piled up and scientists such as Galileo Galilei perfected the model, society held onto the belief that the entire universe orbited around Earth until the early 19th century.

To Erik Verlinde, a theoretical physicist at the University of Amsterdam, the idea of dark matter is the geocentric model of the 21st century. 

“What people are doing now is allowing themselves free parameters to sort of fit the data,” Verlinde says. “You end up with a theory that has so many free parameters it's hard to disprove.”

Dark matter, an as-yet-undetected form of matter that scientists believe makes up more than a quarter of the mass and energy of the universe, was first theorized when scientists noticed that stars at the outer edges of galaxies and galaxy clusters were moving much faster than Newton’s theory of gravity said they should. Up until this point, scientists have assumed that the best explanation for this is that there must be missing mass in the universe holding those fast-moving stars in place in the form of dark matter. 

But Verlinde has come up with a set of equations that explains these galactic rotation curves by viewing gravity as an emergent force — a result of the quantum structure of space.

The idea is related to dark energy, which scientists think is the cause for the accelerating expansion of our universe. Verlinde thinks that what we see as dark matter is actually just interactions between galaxies and the sea of dark energy in which they’re embedded.

“Before I started working on this I never had any doubts about dark matter,” Verlinde says. “But then I started thinking about this link with quantum information and I had the idea that dark energy is carrying more of the dynamics of reality than we realize.”

Verlinde is not the first theorist to come up with an alternative to dark matter. Many feel that his theory echoes the sentiment of physicist Mordehai Milgrom’s equations of “modified Newtonian dynamics,” or MOND. Just as Einstein modified Newton’s laws of gravity to fit to the scale of planets and solar systems, MOND modifies Einstein’s laws of gravity to fit to the scale of galaxies and galaxy clusters.

Verlinde, however, makes the distinction that he’s not deriving the equations of MOND, rather he’s deriving what he calls a “scaling relation,” or a volume effect of space-time that only becomes important at large distances. 

Stacy McGaugh, an astrophysicist at Case Western Reserve University, says that while MOND is primarily the notion that the effective force of gravity changes with acceleration, Verlinde’s ideas are more of a ground-up theoretical work.

“He's trying to look at the structure of space-time and see if what we call gravity is a property that emerges from that quantum structure, hence the name emergent gravity,” McGaugh says. “In principle, it's a very different approach that doesn't necessarily know about MOND or have anything to do with it.”

One of the appealing things about Verlinde’s theory, McGaugh says, is that it naturally produces evidence of MOND in a way that “just happens.” 

“That's the sort of thing that one looks for,” McGaugh says. “There needs to be some basis of why MOND happens, and this theory might provide it.”

Verlinde’s ideas have been greeted with a fair amount of skepticism in the scientific community, in part because, according to Kathryn Zurek, a theoretical physicist at the US Department of Energy’s Lawrence Berkeley National Laboratory, his theory leaves a lot unexplained. 

“Theories of modified gravity only attempt to explain galactic rotation curves [those fast-moving planets],” Zurek says. “As evidence for dark matter, that's only one very small part of the puzzle. Dark matter explains a whole host of observations from the time of the cosmic microwave background when the universe was just a few hundred thousand years old through structure formation all the way until today.”

...

Read more here/Leia mais aqui: Symmetry

Alô ETs, disquem 0800-NASA e digam alô: a prevalência de espécies tecnológicas no universo

A New Empirical Constraint on the Prevalence of Technological Species in the Universe

To cite this article:

Frank A. and Sullivan W.T. III. Astrobiology. May 2016, 16(5): 359-362. https://doi.org/10.1089/ast.2015.1418

Source/Fonte: Revista Exame

Published in Volume: 16 Issue 5: May 13, 2016

Online Ahead of Print: April 22, 2016

A. Frank1 and W.T. Sullivan III2

1Department of Physics and Astronomy, University of Rochester, Rochester, New York.

2Department of Astronomy and Astrobiology Program, University of Washington, Seattle, Washington.

Address correspondence to:

A. Frank

Department of Physics and Astronomy

University of Rochester

Rochester, NY 14620

E-mail: afrank@pas.rochester.edu

Submitted 5 October 2015

Accepted 16 February 2016

Abstract

In this article, we address the cosmic frequency of technological species. Recent advances in exoplanet studies provide strong constraints on all astrophysical terms in the Drake equation. Using these and modifying the form and intent of the Drake equation, we set a firm lower bound on the probability that one or more technological species have evolved anywhere and at any time in the history of the observable Universe. We find that as long as the probability that a habitable zone planet develops a technological species is larger than ∼10−24, humanity is not the only time technological intelligence has evolved. This constraint has important scientific and philosophical consequences. 

Key Words: Life—Intelligence—Extraterrestrial life. 

Astrobiology 2016, 359–362.

FREE PDF GRATIS: Astrobiology