Home // Archive by category "Física"

# Piloto de Podcast

##### Conversamos das 11h às 21h, Ufa! Mas só gravamos duas horas e meia. Vou colocar alguns pedaços para degustação. Se alguém tiver ideia para o nome do Podcast, deixe no comentário por favor!

Nova versão do paper, possivelmente a ser publicado na Revista da Tulha – USP

# A precursor of the sciences of complexity in the XIX century

The sciences of complexity present some recurrent themes: the emergence of qualitatively new behaviors in dissipative systems out of equilibrium, the aparent tendency of complex system to lie at the border of phase transitions and bifurcation points, a historical dynamics which present punctuated equilibrium, a tentative of complementing Darwinian evolution with certain ideas of progress (understood as increase of computational power) etc. Such themes, indeed, belong to a long scientific and philosophical tradiction and, curiously, appear already in the work of Frederick Engels at the 70’s of the XIX century. So, the apparent novelity of the sciences of complexity seems to be not situated in its fundamental ideas, but in the use of mathematical and computational models for illustrate, test and develop such ideas. Since politicians as the candidate Al Gore recently declared that the sciences of complexity have influenced strongly their worldview, perhaps it could be interesting to know better the ideas and the ideology related to the notion of complex adaptive systems.

 Comments: 29 pages, no figures, in Portuguese Subjects: Popular Physics (physics.pop-ph); Physics and Society (physics.soc-ph) Cite as: arXiv:physics/0110041 [physics.pop-ph] (or arXiv:physics/0110041v2 [physics.pop-ph] for this version)

# Tarde de autógrafos- Projeto mulah de Tróia

 Sábado | 03 | dezembro Tarde de autógrafos- Projeto mulah de TróiaTítulo: PROJETO MULAH DE TROIA Autores: Osame Kinouchi / B. B. Jenitez Editora: DRAGO EDITORIAL Jenitez nos brinda com uma pérola da Ficção Científica de humor, uma bem dosada mistura de Umberto Eco e Planeta Diário: uma estória recheada de referências internas, coerentes do início ao fim e com um estilo impecável. Com descrições claras e pouca adjetivação, além de uma ironia finíssima, o autor brinca com a física, a cultura pop e a literatura, com um texto de uma clareza e um bom gosto tão grandes que mesmo um leigo em FC pode entender e gostar. Um trabalho bem escrito não pode ser analisado a fundo, basta que apenas seja lido. E esta estória precisa ser lida. Fábio Fernandes & José S. Fernandes. Local: Ribeirão Preto Horário: 16:00

# Uma entrevista sobre divulgação científica

Entrevista concedida à Juliana Oliveira, do curso de Licenciatura em Química da FFCLRP – USP
1. Quando começou seu interesse por ciências?

Como muitos de minha geração, creio que foi com o pouso da Apolo XI na Lua em 1969. Eu tinha apenas seis anos, mas ainda me lembro das imagens na TV. No ano seguinte, apareceu o cometa Benett, muito visível nos céus brasileiros, despertando meu interesse por astronomia. Acho que minha primeira mesada, com dez anos de idade, foi gasta com um livro de Astronomia (e outro de OVNIs…). Na mesma época, meu pai começou a comprar a coleção Os Cientistas, que vinha com experimentos a serem feitos. Acho que com doze anos eu já tinha meu telescópio, e fazia observações sistemáticas de manchas solares, fases de Vênus, anéis de Saturno, posição de Marte no céu e observação dos satélites de Júpiter. Aos treze anos, eu e um colega tentávamos fazer experimentos controlados de telepatia, clarividência e telecinesia. Aprendi a traçar gráficos e séries temporais plotando a frequência de relatos de OVNIs em função do tempo. Nunca deu em nada (claro!), mas aprendemos a fazer estatísticas e testes de significância. Nessa época acho que minha biblioteca já contava com cerca de cinquenta volumes, a maior parte de pseudociências (minha geração foi muito influenciada pelo livro O Despertar dos Mágicos, de Powels e Bergier e pela revista Planeta). Aprendíamos alguma coisa de ciência nesses meios, pois não havia muitos livros de divulgação científica propriamente dita. Ou seja, tudo se definiu antes dos treze anos de idade.

1. Como começou seu interesse por divulgação científica?

Como leitor, como eu disse, primeiro foram os livros de pseudociências (que de um jeito ou outro nos estimulava como mistérios a serem solucionados cientificamente) e alguns livros de Astronomia. Mais tarde comecei a ler livros de Carl Sagan e outros. Não havia revistas de divulgação científica nem documentários, filmes ou museus de ciência. A revista Planeta, editada na época pelo escritor Ignácio de Loyola Brandão, mesmo com todo o seu pendor New Age e alternativo, trazia reportagens e notícias sobre ciência e tecnologia.

1. Como você definiria divulgação científica e qual seria a importância da mesma para a sociedade atual?

Metáforas científicas no discurso jornalístico

Rev. Bras. Ensino Fís. vol.34 no.4 São Paulo Oct./Dec. 2012

1. O jornalista brasileiro está preparado para fazer divulgação científica?

Os que se especializaram em jornalismo científico tem boa preparação. Podem aprender algo com os blogueiros de ciência (e os blogueiros de ciência tem algo a aprender com os jornalistas, por exemplo não confrontar e afastar seus leitores especialmente em temas delicados como Evolução). Dou como exemplo de ótimo jornalista científico o da FOLHA Reinaldo José Lopes, responsável pelo blog Darwin e Deus.

Muitos pesquisadores não leem livros e revistas de divulgação científica, e nem mesmo romances de ficção científica. Reclamam de falta de tempo, mas me parece ser mais uma característica pessoal (não leem livros de Literatura também, não são leitores). Daí não surge a aspiração para contribuir com essa atividade. Além disso, é muito mais fácil escrever um paper do que um artigo ou livro de divulgação científica, pois os mesmos têm que ter estilo agradável, despertar o interesse do leitor, usar uma linguagem especial, acessível e sem jargões. Isso não é fácil para o pesquisador típico.

1. Segundo as últimas pesquisas, o youtube é a quarta mídia mais acessada pelos brasileiros. Qual o potencial dessa mídia social como você explicaria o aparecimento de um grande número de vlogs que abordam ciência e tecnologia como principal temática?

Sim, parece que está é a grande onda do momento. Aqui no Laboratório de Divulgação Científica e Cientometria estamos organizando, em nossa página, um portal que redirecione para todos os vlogs de ciência em português que pudermos encontrar. Já temos um portal parecido, o Anel de Blogs Científicos, para os blogs em português.

1. Como a divulgação de ciência e tecnologia poderia contribuir para a educação formal?

É uma leitura (ou no caso dos vídeos) mais agradável e instigante que as aulas formais. Acho que ajuda na motivação dos alunos e no despertar de vocações científicas. No caso dos alunos que não se dedicarão à ciência, acho que ajuda muito na criação de um background mínimo de cultura científica (idealmente com aquele papel de empoderamento que citei). Acho também que os vídeos e em especial os livros (que se aprofundam mais) deveriam ser aproveitados pelo menos pelos professores de ensino fundamental e médio. A maior parte dos professores não conhece, por exemplo, as revistas Scientific American Brasil e Revista Mente e Cérebro, e nunca leu um livro de divulgação científica. Recomendo que, se o problema é falta de tempo, assistam os ótimos documentários de divulgação científica da BBC, NATGEO e NOVA, que podem ser encontrados no YOUTUBE, assim como os novos Vlogs de ciências tais como o Nerdologia.

# A simple impact index for scientific innovation and recognition

We introduce a new scientometric index, inspired by the Lobby index from complex networks literature, that we call K-index. The K-index grows with the impact of the citing papers and can be thought of as a measure of scientific creativity and innovation. We show that the K-index can be easily computed from the Web of Science platform and presents several advantages over other bibliometric indexes. The K-index is robust to self-citations, is not limited by the total number of papers published by a researcher and is able to distinguish in a consistent way researchers that have the same h index but different scientific impacts: Einstein and Hirsch, for example. The K-index successfully detects a known case of inflated numbers for papers, citations and h index due to scientific career fraud. Finally, we show that, in a sample of twenty-nine physics Nobel laureates and thirty highly cited non-Nobel-laureate physicists, the K-index correlates better to the achievement of scientific prizes than the number of papers, citations, citations per paper, citing articles and the h index. Clustering researchers in a K versus h plot reveals interesting patterns that can be interpreted in terms of innovation and recognition.

 Comments: 3 figures, 1 table Subjects: Digital Libraries (cs.DL); Physics and Society (physics.soc-ph) Cite as: arXiv:1609.05273 [cs.DL] (or arXiv:1609.05273v1 [cs.DL] for this version) submetido ao Journal of Informetrics

# B. B. Jenitez

Osame Kinouchi  é professor associado (livre-docente) da Universidade de São Paulo no Departamento de Física da FFCLRP. Tem experiência na área de Física Estatística e Sistemas Dinâmicos, atuando principalmente nos seguintes temas: neurociência computacional, meios excitáveis, redes neurais, automata celulares e criticalidade auto-organizada. Coordenador do Laboratório de Física Estatística e Biologia Computacional no Departamento de Física da FFCLRP-USP. Coordenador do Laboratório de Divulgação Científica e Cientometria do DF-FFCLRP-USP, é responsável pelo Anel de Blogs Científicos, com links para 400 blogs de ciência e pelo blog pessoal  SEMCIÊNCIA. Têm vários contos publicados na revista SOMNIUM do Clube de Leitores de Ficção Científica.

O conto Projeto Mulah de Tróia I ganhou o prêmio NOVA de ficção científica na categoria conto amador. Seu conto

Demiurgo foi publicado no livro FC do B – Panorama 2010-2011, Tarja editorial, após seleção entre mais de 230 contos concorrentes. Publicou também O Beijo de Juliana – Quatro físicos teóricos conversam sobre crianças, ciências da complexidade, biologia, política, religião e futebol, pela Editora Multifoco.

# Por que você acredita que a Terra é uma esfera?

They may have been disproved by science or dismissed as ridiculous, but some foolish beliefs endure. In theory they should wither away – but it’s not that simple

by Steven Poole

In January 2016, the rapper BoB took to Twitter to tell his fans that theEarth is really flat. “A lot of people are turned off by the phrase ‘flat earth’,” he acknowledged, “but there’s no way u can see all the evidence and not know … grow up.” At length the astrophysicist Neil deGrasse Tyson joined in the conversation, offering friendly corrections to BoB’s zany proofs of non-globism, and finishing with a sarcastic compliment: “Being five centuries regressed in your reasoning doesn’t mean we all can’t still like your music.”

Actually, it’s a lot more than five centuries regressed. Contrary to what we often hear, people didn’t think the Earth was flat right up until Columbus sailed to the Americas. In ancient Greece, the philosophers Pythagoras and Parmenides had already recognised that the Earth was spherical. Aristotle pointed out that you could see some stars in Egypt and Cyprus that were not visible at more northerly latitudes, and also that the Earth casts a curved shadow on the moon during a lunar eclipse. The Earth, he concluded with impeccable logic, must be round.

The flat-Earth view was dismissed as simply ridiculous – until very recently, with the resurgence of apparently serious flat-Earthism on the internet. An American named Mark Sargent, formerly a professional videogamer and software consultant, has had millions of views on YouTube for his Flat Earth Clues video series. (“You are living inside a giant enclosed system,” his website warns.) The Flat Earth Society is alive and well, with a thriving website. What is going on?

# A Secular Case for Intentional Creation

By Clay Farris Naff | November 18, 2011 |  21

“Does aught befall you? It is good. It is part of the destiny of the Universe ordained for you from the beginning.”

– Marcus Aurelius, Stoic Philosopher and Emperor of Rome, in Meditations, circa 170 CE

“’He said that, did he? … Well, you can tell him from me, he’s an ass!”

– Bertie Wooster, fictional P.G. Wodehouse character, in The Mating Season, 1949

People have been arguing about the fundamental nature of existence since, well, since people existed. Having lost exclusive claim to tools, culture, and self, one of the few remaining distinctions of our species is that we can argue about the fundamental nature of existence.

There are, however, two sets of people who want to shut the argument down. One is the drearily familiar set of religious fundamentalists. The other is the shiny new set of atheists who claim that science demonstrates beyond reasonable doubt that our existence is accidental, purposeless, and doomed. My intent is to show that both are wrong.

# Explosões cósmicas, vida no Universo e a constante cosmológica

### Cosmic Explosions, Life in the Universe, and the Cosmological Constant

##### ABSTRACT

Gamma-ray bursts (GRBs) are copious sources of gamma rays whose interaction with a planetary atmosphere can pose a threat to complex life. Using recent determinations of their rate and probability of causing massive extinction, we explore what types of universes are most likely to harbor advanced forms of life. We use cosmological -body simulations to determine at what time and for what value of the cosmological constant () the chances of life being unaffected by cosmic explosions are maximized. Life survival to GRBs favors Lambda-dominated universes. Within a cold dark matter model with a cosmological constant, the likelihood of life survival to GRBs is governed by the value of and the age of the Universe. We find that we seem to live in a favorable point in this parameter space that minimizes the exposure to cosmic explosions, yet maximizes the number of main sequence (hydrogen-burning) stars around which advanced life forms can exist.

# A TEORIA QUE NÃO MORRERIA

SINOPSE

Esta é a história de como uma lei da matemática teve seu destino entrelaçado com os sigilos da Segunda Guerra Mundial e da Guerra Fria. De um teorema em busca de um computador e de um software. De um método que – atualizado por outsiders da física, da ciência da computação e da inteligência artificial – foi adotado quase do dia para a noite porque, de repente, funcionou. O teorema que um dia foi considerado “a pedra de crack da estatística… sedutora, viciante e basicamente destrutiva”, hoje, em um novo tipo de paradigma deslocado para um mundo pragmático, propicia o recrutamento de bayesianos para as mais inovadoras companhias.

título: A TEORIA QUE NAO MORRERIA
isbn: 9788527310345
idioma: Português
formato: 14 x 21
páginas: 480
ano de edição: 2015
edição:

# Spectral Variations of the Sky: Constraints on Alternate Universes

We analyze the spectral properties of masked, foreground-cleaned Planck maps between 100 and 545 GHz. We find convincing evidence for residual excess emission in the 143 GHz band in the direction of CMB cold spots which is well correlated with corresponding emission at 100 GHz. The median residual 100 to 143 GHz intensity ratio is consistent with Galactic synchrotron emission with a Iνν0.69 spectrum. In addition, we find a small set of ~2-4 degree regions which show anomalously strong 143 GHz emission but no correspondingly strong emission at either 100 or 217 GHz. The signal to noise of this 143 GHz residual emission is at the 6σ level. We assess different mechanisms for this residual emission and conclude that although there is a 30\% probability that noise fluctuations may cause foregrounds to fall within 3σ of the excess, it could also possibly be due to the collision of our Universe with an alternate Universe whose baryon to photon ratio is a factor of 65 larger than ours. The dominant systematic source of uncertainty in the conclusion remains residual foreground emission from the Galaxy which can be mitigated through narrow band spectral mapping in the millimeter bands by future missions and through deeper observations at 100 and 217 GHz.

 Comments: 25 pages, 8 figures (6 color, 2 B&W), Submitted to ApJ, comments welcome Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO) Cite as: arXiv:1510.00126 [astro-ph.CO] (or arXiv:1510.00126v1 [astro-ph.CO] for this version)

# Livro Projeto Mulah de Tróia levou 25 anos para ser publicado

Sim, se a qualidade literária se mede pelos anos que o autor levou para burilar o texto, então este é um candidato ao Prêmio Argos…  Para comprar, clique aqui.

• Jenitez nos brinda com uma pérola da Ficção Científica de humor, uma bem dosada mistura de Umberto Eco e Planeta Diário: uma estória recheada de referências internas, coerentes do início ao fim e com um estilo impecável. Com descrições claras e pouca adjetivação, além de uma ironia finíssima, o autor brinca com a física, a cultura pop e a literatura, com um texto de uma clareza e um bom gosto tão grandes que mesmo um leigo em FC pode entender e gostar. Um trabalho bem escrito não pode ser analisado a fundo, basta que apenas seja lido. E esta estória precisa ser lida. Fábio Fernandes

# The exoplanets analogy to the Multiverse

The idea of a Mutiverse is controversial, although it is a natural possible solution to particle physics and cosmological fine-tuning problems (FTPs). Here I explore the analogy between the Multiverse proposal and the proposal that there exist an infinite number of stellar systems with planets in a flat Universe, the Multiplanetverse. Although the measure problem is present in this scenario, the idea of a Multiplanetverse has predictive power, even in the absence of direct evidence for exoplanets that appeared since the 90s. We argue that the fine-tuning of Earth to life (and not only the fine-tuning of life to Earth) could predict with certainty the existence of exoplanets decades or even centuries before that direct evidence. Several other predictions can be made by studying only the Earth and the Sun, without any information about stars. The analogy also shows that theories that defend that the Earth is the unique existing planet and that, at the same time, is fine-tuned to life by pure chance (or pure physical necessity from a parameter free Theory of Everything) are misguided, and alike opinions about our Universe are similarly delusional.

 Comments: 9 pages, 1 figure Subjects: General Physics (physics.gen-ph); History and Philosophy of Physics (physics.hist-ph) Cite as: arXiv:1506.08060 [physics.gen-ph] (or arXiv:1506.08060v1 [physics.gen-ph] for this version)

## Submission history

From: Osame Kinouchi [view email]
[v1] Tue, 16 Jun 2015 22:42:12 GMT (566kb)

# Artigo aceito pelo PRE

Aceito pelo Physical Review E.

# Nonsynchronous updating in the multiverse of cellular automata

In this paper we study updating effects on cellular automata rule space. We consider a subset of 6144 order-3 automata from the space of 262144 bi-dimensional outer-totalistic rules. We compare synchronous to asynchronous and sequential updatings. Focusing on two automata, we discuss how update changes destroy typical structures of these rules. Besides, we show that the first-order phase-transition in the multiverse of synchronous cellular automata, revealed with the use of a recently introduced control parameter, seems to be robust not only to changes in update schema but also to different initial densities.

 Subjects: Cellular Automata and Lattice Gases (nlin.CG); Statistical Mechanics (cond-mat.stat-mech) Cite as: arXiv:1503.01350 [nlin.CG] (or arXiv:1503.01350v1 [nlin.CG] for this version)

# Multiverso com ferramenta matemática preditiva

Me parece que a ideia de Multiverso está ficando cada vez mais relevante e preditiva. Já a ideia de explicar fine tuning no universo usando ideias físicas convencionais (simetrias etc) parece estar num beco sem saída, nenhum avanço foi obtido há décadas.

# Radiative PQ Breaking and the Higgs Boson Mass

The small and negative value of the Standard Model Higgs quartic coupling at high scales can be understood in terms of anthropic selection on a landscape where large and negative values are favored: most universes have a very short-lived electroweak vacuum and typical observers are in universes close to the corresponding metastability boundary. We provide a simple example of such a landscape with a Peccei-Quinn symmetry breaking scale generated through dimensional transmutation and supersymmetry softly broken at an intermediate scale. Large and negative contributions to the Higgs quartic are typically generated on integrating out the saxion field. Cancellations among these contributions are forced by the anthropic requirement of a sufficiently long-lived electroweak vacuum, determining the multiverse distribution for the Higgs quartic in a similar way to that of the cosmological constant. This leads to a statistical prediction of the Higgs boson mass that, for a wide range of parameters, yields the observed value within the 1σ statistical uncertainty of 5 GeV originating from the multiverse distribution. The strong CP problem is solved and single-component axion dark matter is predicted, with an abundance that can be understood from environmental selection. A more general setting for the Higgs mass prediction is discussed.

 Comments: 30 pages, 10 figures Subjects: High Energy Physics – Phenomenology (hep-ph) Cite as: arXiv:1502.06963 [hep-ph] (or arXiv:1502.06963v1 [hep-ph] for this version)

# Exponential Economist Meets Finite Physicist

Some while back, I found myself sitting next to an accomplished economics professor at a dinner event. Shortly after pleasantries, I said to him, “economic growth cannot continue indefinitely,” just to see where things would go. It was a lively and informative conversation. I was somewhat alarmed by the disconnect between economic theory and physical constraints—not for the first time, but here it was up-close and personal. Though my memory is not keen enough to recount our conversation verbatim, I thought I would at least try to capture the key points and convey the essence of the tennis match—with some entertainment value thrown in.

Cast of characters: Physicist, played by me; Economist, played by an established economics professor from a prestigious institution. Scene: banquet dinner, played in four acts (courses).

Note: because I have a better retention of my own thoughts than those of my conversational companion, this recreation is lopsided to represent my own points/words. So while it may look like a physicist-dominated conversation, this is more an artifact of my own recall capabilities. I also should say that the other people at our table were not paying attention to our conversation, so I don’t know what makes me think this will be interesting to readers if it wasn’t even interesting enough to others at the table! But here goes…

## Act One: Bread and Butter

Physicist: Hi, I’m Tom. I’m a physicist.

Economist: Hi Tom, I’m [ahem..cough]. I’m an economist.

Physicist: Hey, that’s great. I’ve been thinking a bit about growth and want to run an idea by you. I claim that economic growth cannot continue indefinitely.

Economist: [chokes on bread crumb] Did I hear you right? Did you say that growth can not continue forever?

Physicist: That’s right. I think physical limits assert themselves.

Economist: Well sure, nothing truly lasts forever. The sun, for instance, will not burn forever. On the billions-of-years timescale, things come to an end.

Physicist: Granted, but I’m talking about a more immediate timescale, here on Earth. Earth’s physical resources—particularly energy—are limited and may prohibit continued growth within centuries, or possibly much shorter depending on the choices we make. There are thermodynamic issues as well.

Economist: I don’t think energy will ever be a limiting factor to economic growth. Sure, conventional fossil fuels are finite. But we can substitute non-conventional resources like tar sands, oil shale, shale gas, etc. By the time these run out, we’ll likely have built up a renewable infrastructure of wind, solar, and geothermal energy—plus next-generation nuclear fission and potentially nuclear fusion. And there are likely energy technologies we cannot yet fathom in the farther future.

Physicist: Sure, those things could happen, and I hope they do at some non-trivial scale. But let’s look at the physical implications of the energy scale expanding into the future. So what’s a typical rate of annual energy growth over the last few centuries?

Economist: I would guess a few percent. Less than 5%, but at least 2%, I should think.

Physicist: Right, if you plot the U.S. energy consumption in all forms from 1650 until now, you see a phenomenally faithful exponential at about 3% per year over that whole span. The situation for the whole world is similar. So how long do you think we might be able to continue this trend?

Economist: Well, let’s see. A 3% growth rate means a doubling time of something like 23 years. So each century might see something like a 15–20× increase. I see where you’re going. A few more centuries like that would perhaps be absurd. But don’t forget that population was increasing during centuries past—the period on which you base your growth rate. Population will stop growing before more centuries roll by.

Physicist: True enough. So we would likely agree that energy growth will not continue indefinitely. But two points before we continue: First, I’ll just mention that energy growth has far outstripped population growth, so that per-capita energy use has surged dramatically over time—our energy lives today are far richer than those of our great-great-grandparents a century ago [economist nods]. So even if population stabilizes, we are accustomed to per-capita energy growth: total energy would have to continue growing to maintain such a trend [another nod].

Second, thermodynamic limits impose a cap to energy growth lest we cook ourselves. I’m not talking about global warming, CO2 build-up, etc. I’m talking about radiating the spent energy into space. I assume you’re happy to confine our conversation to Earth, foregoing the spectre of an exodus to space, colonizing planets, living the Star Trek life, etc.

Economist: More than happy to keep our discussion grounded to Earth.

Physicist: [sigh of relief: not a space cadet] Alright, the Earth has only one mechanism for releasing heat to space, and that’s via (infrared) radiation. We understand the phenomenon perfectly well, and can predict the surface temperature of the planet as a function of how much energy the human race produces. The upshot is that at a 2.3% growth rate (conveniently chosen to represent a 10× increase every century), we would reach boiling temperature in about 400 years. [Pained expression from economist.] And this statement is independent of technology. Even if we don’t have a name for the energy source yet, as long as it obeys thermodynamics, we cook ourselves with perpetual energy increase.

Economist: That’s a striking result. Could not technology pipe or beam the heat elsewhere, rather than relying on thermal radiation?

Physicist: Well, we could (and do, somewhat) beam non-thermal radiation into space, like light, lasers, radio waves, etc. But the problem is that these “sources” are forms of high-grade, low-entropy energy. Instead, we’re talking about getting rid of the waste heat from all the processes by which we use energy. This energy is thermal in nature. We might be able to scoop up some of this to do useful “work,” but at very low thermodynamic efficiency. If you want to use high-grade energy in the first place, having high-entropy waste heat is pretty inescapable.

Economist: [furrowed brow] Okay, but I still think our path can easily accommodate at least a steady energy profile. We’ll use it more efficiently and for new pursuits that continue to support growth.

Physicist: Before we tackle that, we’re too close to an astounding point for me to leave it unspoken. At that 2.3% growth rate, we would be using energy at a rate corresponding to the total solar input striking Earth in a little over 400 years. We would consume something comparable to the entire sun in 1400 years from now. By 2500 years, we would use energy at the rate of the entire Milky Way galaxy—100 billion stars! I think you can see the absurdity of continued energy growth. 2500 years is not that long, from a historical perspective. We know what we were doing 2500 years ago. I think I know what we’re not going to be doing 2500 years hence.

Economist: That’s really remarkable—I appreciate the detour. You said about 1400 years to reach parity with solar output?

Physicist: Right. And you can see the thermodynamic point in this scenario as well. If we tried to generate energy at a rate commensurate with that of the Sun in 1400 years, and did this on Earth, physics demands that the surface of the Earth must be hotter than the (much larger) surface of the Sun. Just like 100 W from a light bulb results in a much hotter surface than the same 100 W you and I generate via metabolism, spread out across a much larger surface area.

Economist: I see. That does make sense.

Economist: So I’m as convinced as I need to be that growth in raw energy use is a limited proposition—that we must one day at the very least stabilize to a roughly constant yearly expenditure. At least I’m willing to accept that as a starting point for discussing the long term prospects for economic growth. But coming back to your first statement, I don’t see that this threatens the indefinite continuance of economic growth.

For one thing, we can keep energy use fixed and still do more with it in each passing year via efficiency improvements. Innovations bring new ideas to the market, spurring investment, market demand, etc. These are things that will not run dry. We have plenty of examples of fundamentally important resources in decline, only to be substituted or rendered obsolete by innovations in another direction.

Physicist: Yes, all these things happen, and will continue at some level. But I am not convinced that they represent limitless resources.

Economist: Do you think ingenuity has a limit—that the human mind itself is only so capable? That could be true, but we can’t credibly predict how close we might be to such a limit.

Physicist: That’s not really what I have in mind. Let’s take efficiency first. It is true that, over time, cars get better mileage, refrigerators use less energy, buildings are built more smartly to conserve energy, etc. The best examples tend to see factor-of-two improvements on a 35 year timeframe, translating to 2% per year. But many things are already as efficient as we can expect them to be. Electric motors are a good example, at 90% efficiency. It will always take 4184 Joules to heat a liter of water one degree Celsius. In the middle range, we have giant consumers of energy—like power plants—improving much more slowly, at 1% per year or less. And these middling things tend to be something like 30% efficient. How many more “doublings” are possible? If many of our devices were 0.01% efficient, I would be more enthusiastic about centuries of efficiency-based growth ahead of us. But we may only have one more doubling in us, taking less than a century to realize.

Economist: Okay, point taken. But there is more to efficiency than incremental improvement. There are also game-changers. Tele-conferencing instead of air travel. Laptop replaces desktop; iPhone replaces laptop, etc.—each far more energy frugal than the last. The internet is an example of an enabling innovation that changes the way we use energy.

Physicist: These are important examples, and I do expect some continuation along this line, but we still need to eat, and no activity can get away from energy use entirely. [semi-reluctant nod/bobble] Sure, there are lower-intensity activities, but nothing of economic value is completely free of energy.

Economist: Some things can get awfully close. Consider virtualization. Imagine that in the future, we could all own virtual mansions and have our every need satisfied: all by stimulative neurological trickery. We would stil need nutrition, but the energy required to experience a high-energy lifestyle would be relatively minor. This is an example of enabling technology that obviates the need to engage in energy-intensive activities. Want to spend the weekend in Paris? You can do it without getting out of your chair. [More like an IV-drip-equipped toilet than a chair, the physicist thinks.]

Physicist: I see. But this is still a finite expenditure of energy per person. Not only does it take energy to feed the person (today at a rate of 10 kilocalories of energy input per kilocalorie eaten, no less), but the virtual environment probably also requires a supercomputer—by today’s standards—for every virtual voyager. The supercomputer at UCSD consumes something like 5 MW of power. Granted, we can expect improvement on this end, but today’s supercomputer eats 50,000 times as much as a person does, so there is a big gulf to cross. I’ll take some convincing. Plus, not everyone will want to live this virtual existence.

Economist: Really? Who could refuse it? All your needs met and an extravagant lifestyle—what’s not to like? I hope I can live like that myself someday.

Physicist: Not me. I suspect many would prefer the smell of real flowers—complete with aphids and sneezing; the feel of real wind messing up their hair; even real rain, real bee-stings, and all the rest. You might be able to simulate all these things, but not everyone will want to live an artificial life. And as long as there are any holdouts, the plan of squeezing energy requirements to some arbitrarily low level fails. Not to mention meeting fixed bio-energy needs.

## Act Three: Main Course

Physicist: But let’s leave the Matrix, and cut to the chase. Let’s imagine a world of steady population and steady energy use. I think we’ve both agreed on these physically-imposed parameters. If the flow of energy is fixed, but we posit continued economic growth, then GDP continues to grow while energy remains at a fixed scale. This means that energy—a physically-constrained resource, mind—must become arbitrarily cheap as GDP continues to grow and leave energy in the dust.

Economist: Yes, I think energy plays a diminishing role in the economy and becomes too cheap to worry about.

Physicist: Wow. Do you really believe that? A physically limited resource (read scarcity) that is fundamental to every economic activity becomes arbitrarily cheap? [turns attention to food on the plate, somewhat stunned]

Economist: [after pause to consider] Yes, I do believe that.

Physicist: Okay, so let’s be clear that we’re talking about the same thing. Energy today is roughly 10% of GDP. Let’s say we cap the physical amount available each year at some level, but allow GDP to keep growing. We need to ignore inflation as a nuisance in this case: if my 10 units of energy this year costs $10,000 out of my$100,000 income; then next year that same amount of energy costs $11,000 and I make$110,000—I want to ignore such an effect as “meaningless” inflation: the GDP “growth” in this sense is not real growth, but just a re-scaling of the value of money.

Economist: Agreed.

Physicist: Then in order to have real GDP growth on top of flat energy, the fractional cost of energy goes down relative to the GDP as a whole.

Economist: Correct.

Physicist: How far do you imagine this can go? Will energy get to 1% of GDP? 0.1%? Is there a limit?

Economist: There does not need to be. Energy may become of secondary importance in the economy of the future—like in the virtual world I illustrated.

Physicist: But if energy became arbitrarily cheap, someone could buy all of it, and suddenly the activities that comprise the economy would grind to a halt. Food would stop arriving at the plate without energy for purchase, so people would pay attention to this. Someone would be willing to pay more for it. Everyone would. There will be a floor to how low energy prices can go as a fraction of GDP.

Economist: That floor may be very low: much lower than the 5–10% we pay today.

Physicist: But is there a floor? How low are you willing to take it? 5%? 2%? 1%?

Economist: Let’s say 1%.

Physicist: So once our fixed annual energy costs 1% of GDP, the 99% remaining will find itself stuck. If it tries to grow, energy prices must grow in proportion and we have monetary inflation, but no real growth.

Economist: Well, I wouldn’t go that far. You can still have growth without increasing GDP.

Physicist: But it seems that you are now sold on the notion that the cost of energy would not naturally sink to arbitrarily low levels.

Economist: Yes, I have to retract that statement. If energy is indeed capped at a steady annual amount, then it is important enough to other economic activities that it would not be allowed to slip into economic obscurity.

Physicist: Even early economists like Adam Smith foresaw economic growth as a temporary phase lasting maybe a few hundred years, ultimately limited by land (which is where energy was obtained in that day). If humans are successful in the long term, it is clear that a steady-state economic theory will far outlive the transient growth-based economic frameworks of today. Forget Smith, Keynes, Friedman, and that lot. The economists who devise a functioning steady-state economic system stand to be remembered for a longer eternity than the growth dudes. [Economist stares into the distance as he contemplates this alluring thought.]

## Act Four: Dessert

Economist: But I have to object to the statement that growth must stop once energy amount/price saturates. There will always be innovations that people are willing to purchase that do not require additional energy.

Physicist: Things will certainly change. By “steady-state,” I don’t mean static. Fads and fashions will always be part of what we do—we’re not about to stop being human. But I’m thinking more of a zero-sum game here. Fads come and go. Some fraction of GDP will always go toward the fad/innovation/gizmo of the day, but while one fad grows, another fades and withers. Innovation therefore will maintain a certain flow in the economy, but not necessarily growth.

Economist: Ah, but the key question is whether life 400 years from now is undeniably of higher quality than life today. Even if energy is fixed, and GDP is fixed once the cost of energy saturates at the lower bound, will quality of life continue to improve in objectively agreed-upon ways?

Physicist: I don’t know how objective such an assessment can be. Many today yearn for days past. Maybe this is borne of ignorance or romanticism over the past (1950′s often comes up). It may be really exciting to imagine living in Renaissance Europe, until a bucket of nightsoil hurled from a window splatters off the cobblestone and onto your breeches. In any case, what kind of universal, objective improvements might you imagine?

Economist: Well, for instance, look at this dessert, with its decorative syrup swirls on the plate. It is marvelous to behold.

Physicist: And tasty.

Economist: We value such desserts more than plain, unadorned varieties. In fact, we can imagine an equivalent dessert with equivalent ingredients, but the decorative syrup unceremoniously pooled off to one side. We value the decorated version more. And the chefs will continue to innovate. Imagine a preparation/presentation 400 years from now that would blow your mind—you never thought dessert could be made to look so amazing and taste so delectably good. People would line the streets to get hold of such a creation. No more energy, no more ingredients, yet of increased value to society. That’s a form of quality of life improvement, requiring no additional resources, and perhaps costing the same fraction of GDP, or income.

Physicist: I’m smiling because this reminds me of a related story. I was observing at Palomar Observatory with an amazing instrumentation guru named Keith who taught me much. Keith’s night lunch—prepared in the evening by the observatory kitchen and placed in a brown bag—was a tuna-fish sandwich in two parts: bread slices in a plastic baggie, and the tuna salad in a small plastic container (so the tuna would not make the bread soggy after hours in the bag). Keith plopped the tuna onto the bread in an inverted container-shaped lump, then put the other piece of bread on top without first spreading the tuna. It looked like a snake had just eaten a rat. Perplexed, I asked if he intended to spread the tuna before eating it. He looked at me quizzically (like Morpheus in the Matrix: “You think that’s air you’re breathing? Hmm.”), and said—memorably, “It all goes in the same place.”

My point is that the stunning presentation of desserts will not have universal value to society. It all goes in the same place, after all. [I’ll share a little-known secret. It’s hard to beat a Hostess Ding Dong for dessert. At 5% the cost of fancy desserts, it’s not clear how much value the fancy things add.]

## After-Dinner Contemplations

The evening’s after-dinner keynote speech began, so we had to shelve the conversation. Reflecting on it, I kept thinking, “This should not have happened. A prominent economist should not have to walk back statements about the fundamental nature of growth when talking to a scientist with no formal economics training.” But as the evening progressed, the original space in which the economist roamed got painted smaller and smaller.

First, he had to acknowledge that energy may see physical limits. I don’t think that was part of his initial virtual mansion.

Next, the efficiency argument had to shift away from straight-up improvements to transformational technologies. Virtual reality played a prominent role in this line of argument.

Finally, even having accepted the limits to energy growth, he initially believed this would prove to be of little consequence to the greater economy. But he had to ultimately admit to a floor on energy price and therefore an end to traditional growth in GDP—against a backdrop fixed energy.

I got the sense that this economist’s view on growth met some serious challenges during the course of the meal. Maybe he was not putting forth the most coherent arguments that he could have made. But he was very sharp and by all measures seemed to be at the top of his game. I choose to interpret the episode as illuminating a blind spot in traditional economic thinking. There is too little acknowledgement of physical limits, and even the non-compliant nature of humans, who may make choices we might think to be irrational—just to remain independent and unencumbered.

I recently was motivated to read a real economics textbook: one written by people who understand and respect physical limitations. The book, called Ecological Economics, by Herman Daly and Joshua Farley, states in its Note to Instructors:

…we do not share the view of many of our economics colleagues that growth will solve the economic problem, that narrow self-interest is the only dependable human motive, that technology will always find a substitute for any depleted resource, that the market can efficiently allocate all types of goods, that free markets always lead to an equilibrium balancing supply and demand, or that the laws of thermodynamics are irrelevant to economics.

This is a book for me!

## Epilogue

The conversation recreated here did challenge my own understanding as well. I spent the rest of the evening pondering the question: “Under a model in which GDP is fixed—under conditions of stable energy, stable population, steady-state economy: if we accumulate knowledge, improve the quality of life, and thus create an unambiguously more desirable world within which to live, doesn’t this constitute a form of economic growth?”

I had to concede that yes—it does. This often falls under the title of “development” rather than “growth.” I ran into the economist the next day and we continued the conversation, wrapping up loose ends that were cut short by the keynote speech. I related to him my still-forming position that yes, we can continue tweaking quality of life under a steady regime. I don’t think I ever would have explicitly thought otherwise, but I did not consider this to be a form of economic growth. One way to frame it is by asking if future people living in a steady-state economy—yet separated by 400 years—would always make the same, obvious trades? Would the future life be objectively better, even for the same energy, same GDP, same income, etc.? If the answer is yes, then the far-future person gets more for their money: more for their energy outlay. Can this continue indefinitely (thousands of years)? Perhaps. Will it be at the 2% per year level (factor of ten better every 100 years)? I doubt that.

So I can twist my head into thinking of quality of life development in an otherwise steady-state as being a form of indefinite growth. But it’s not your father’s growth. It’s not growing GDP, growing energy use, interest on bank accounts, loans, fractional reserve money, investment. It’s a whole different ballgame, folks. Of that, I am convinced. Big changes await us. An unrecognizable economy. The main lesson for me is that growth is not a “good quantum number,” as physicists will say: it’s not an invariant of our world. Cling to it at your own peril.

Note: This conversation is my contribution to a series at www.growthbusters.org honoring the 40th anniversary of the Limits to Growth study. You can explore the series here. Also see my previous reflection on the Limits to Growth work. You may also be interested in checking out and signing the Pledge to Think Small and consider organizing an Earth Day weekend house party screening of the GrowthBusters movie.

# Livro ensina física por meio do absurdo

Cinco anos atrás, quando estava dando uma palestra sobre física a estudantes do Ensino Médio no Massachusetts Institute of Technology, Randall Munroe percebeu que a plateia não estava muito interessada.

Ele estava tentando explicar o que são energia potencial e potência -conceitos que não são complexos, mas difíceis de entender.

Assim, no meio da palestra de três horas, Munroe, mais conhecido por ser o criador da HQ on-line xkcd, resolveu apelar para “Star Wars”.

“Pensei na cena de ‘O Império Contra-ataca’ em que Yoda tira a asa-X do pântano”, comentou.

“A ideia me ocorreu quando eu estava dando a aula.”

No lugar de definições abstratas (um objeto erguido ganha energia potencial porque vai se acelerar quando cair; a potência é o índice de mudança na energia), Munroe fez uma pergunta: quanta energia da Força seria Yoda capaz de produzir?

“Fiz uma versão aproximada do cálculo ali mesmo, na sala de aula, procurando as dimensões da nave na internet e medindo as coisas na cena no projetor, diante dos alunos”, contou. “Todos começaram a prestar atenção.”

Para a maioria das pessoas, a física não é interessante por si só. “As ferramentas só são divertidas quando a coisa com a qual você as utiliza é interessante.”

Os alunos começaram a fazer outras perguntas. “E o final de ‘O Senhor dos Anéis’, quando o olho de Sauron explode, quanta energia há nisso?”

A experiência inspirou Munroe a começar a pedir perguntas semelhantes dos leitores do xkcd.

Ele reuniu esse trabalho, incluindo uma versão dos cálculos que fez sobre Yoda e outros materiais novos, no livro “E se?”, lançado em setembro e que desde então está na lista dos livros de não ficção mais vendidos.

Como afirma sua capa, “E se?” é repleto de “respostas científicas sérias a perguntas hipotéticas absurdas”.

“O livro exercita a imaginação do leitor, e o humor espirituoso de Munroe é encantador”, comentou William Sanford Nye, mais conhecido como “Billy Nye, the Science Guy”. “Ele cria cenários que, por falta de um termo melhor, precisamos descrever como absurdos, mas que são muito instrutivos.”

O que aconteceria se você tentasse rebater uma bola de beisebol lançada a 90% da velocidade da luz? “A resposta é ‘muitas coisas’, e todas acontecem muito rapidamente. Não termina bem para o batedor (nem para o lançador).”

Se todo o mundo mirasse a Lua ao mesmo tempo com um ponteiro de laser, a Lua mudaria de cor? “Não se usássemos ponteiros de laser normais.”

Por quanto tempo um submarino nuclear poderia permanecer em órbita? “O submarino ficaria ótimo, mas seus tripulantes teriam problemas.”

As explicações são acompanhadas pelos mesmos desenhos e o mesmo humor nerd que garantiram a popularidade do xkcd. (O que significa xkcd? “É simplesmente uma palavra para a qual não existe pronúncia fonética”, explica o site do seriado on-line.)

Na época em que era estudante de física na Universidade Christopher Newport, na Virginia, Munroe começou a trabalhar como técnico independente em um projeto de robótica no Centro Langley de Pesquisas, da Nasa, e continuou depois de se formar.

Foi nessa época que ele começou a scanear seus desenhos rabiscados e colocá-los na web.

O contrato com a Nasa terminou em 2006, por decisão mútua das duas partes.

Munroe tornou-se cartunista em tempo integral e se mudou para a região de Boston porque, explicou, queria viver numa cidade maior, com mais coisas de geek para fazer. Em 2012 ele incluiu a parte de “E se?” no site.

Hoje ele recebe milhares de perguntas por semana. Muitas são evidentemente de estudantes à procura de ajuda com sua lição de casa. Outras podem ser respondidas com uma só palavra: “Não”.

“Uma das perguntas que recebi foi: ‘Existe algum equipamento comercial de mergulho que permita a sobrevivência debaixo de lava incandescente?'”, Munroe contou. “Não. Não existe.”

Munroe também gostava de fazer perguntas quando era criança. Na introdução do livro, ele conta que se perguntava se havia mais coisas duras ou moles no mundo. Essa conversa causou impressão tão forte à sua mãe que ela a anotou e guardou.

“Dizem que não existem perguntas estúpidas”, escreve Munroe, 30. “Isso não é verdade, obviamente. Acho que minha pergunta sobre as coisas duras e moles foi bastante estúpida. Mas tentar responder uma pergunta estúpida de modo completo pode levar você a alguns lugares muito interessantes.”

# Self-Organized Criticality and Neuronal Avalanches in SIRS Networks with Depressing Synapses

Neuronal networks can present activity described by power-law distributed avalanches presumed to be a signature of a critical state. Here we study a random-neighbor network of excitable (SIRS) cellular automata coupled by dynamical (depressing) synapses that exhibits bona ?de self-organized criticality (SOC) even with dissipative bulk dynamics. This occurs because in the stationary regime the model is conservative on average and in the thermodynamic limit the probability distribution for the global branching ratio converges to a delta-function centered at its critical value. Analytical results show perfect agreement with annealed simulations of the model and enable us to study the emergence of SOC as a function of the parametric derivatives of the stationary branching ratio.

 Comments: 4 pages, 5 figures Subjects: Adaptation and Self-Organizing Systems (nlin.AO); Statistical Mechanics (cond-mat.stat-mech) Cite as: arXiv:1405.7740 [nlin.AO] (or arXiv:1405.7740v1 [nlin.AO] for this version)

# Obtiuário: Robert Lee Zimmerman

Bob foi meu primeiro orientador (de Iniciação Cientítica) e foi muito importante na minha formação e estímulo para continuar na Física.
De Sergio Mascarenhas: