Rastreando massa e luz no universo: onde está a energia escura???

segunda-feira, julho 28, 2014

Tracing mass and light in the Universe: where is the dark matter?

How is mass distributed in the Universe? How does it compare with the distribution of light and stars? We address these questions by examining the distribution of mass, determined from weak lensing observations, and starlight, around >105 SDSS MaxBCG groups and clusters as a function of environment and scale, from deep inside clusters to large cosmic scales of 22h1 Mpc. The observed cumulative mass-to-light profile, M/L(<r), rises on small scales, reflecting the increasing M/L of the central bright galaxy of the cluster, then flattens to a nearly constant ratio on scales above 300h1 kpc, where light follows mass on all scales and in all environments. A trend of slightly decreasing M/L(r) with scale is shown to be consistent with the varying stellar population following the morphology-density relation. This suggests that stars trace mass remarkably well even though they represent only a few percent of the total mass. We determine the stellar mass fraction and find it to be nearly constant on all scales above 300h1 kpc, with M/Mtot1.0±0.4%. We further suggest that most of the dark matter in the Universe is located in the large halos of individual galaxies (300 kpc for L galaxies); we show that the entire M/L(r) profile -- from groups and clusters to large-scale structure -- can be accounted for by the aggregate masses of the individual galaxies (whose halos may be stripped off but still remain in the clusters), plus gas. We use the observed mass-to-light ratio on large scales to determine the mass density of the Universe: Ωm=0.24±0.02×b2M/L=0.26±0.02.
Comments:12 pages, 9 figures; version accepted to MNRAS
Subjects:Cosmology and Nongalactic Astrophysics (astro-ph.CO)
Journal reference:Monthly Notices of the Royal Astronomical Society, Volume 439, Issue 3, p.2505-2514 (2014)
Cite as:arXiv:1310.0022 [astro-ph.CO]
 (or arXiv:1310.0022v2 [astro-ph.CO] for this version)

Submission history

From: Andrea Kulier [view email]
[v1] Mon, 30 Sep 2013 20:00:17 GMT (924kb)
[v2] Sun, 27 Apr 2014 19:08:01 GMT (924kb)

Uma prova empírica direta da existência da energia escura???

The Astrophysical Journal Letters Volume 648 Number 2

Douglas Clowe et al. 2006 ApJ 648 L109 doi:10.1086/508162

A Direct Empirical Proof of the Existence of Dark Matter*

Douglas Clowe1, Maruša Bradač2, Anthony H. Gonzalez3, Maxim Markevitch4,5, Scott W. Randall4, Christine Jones4, and Dennis Zaritsky1


1 Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 

2 Kavli Institute for Particle Astrophysics and Cosmology, P.O. Box 20450, MS 29, Stanford, CA 94309 

3 Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611 

4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 

5 Also at the Space Research Institute, Russian Academy of Sciences, Profsoyuznaya 84/32, Moscow 117997, Russia 


We present new weak-lensing observations of 1E 0657-558 (z = 0.296), a unique cluster merger, that enable a direct detection of dark matter, independent of assumptions regarding the nature of the gravitational force law. Due to the collision of two clusters, the dissipationless stellar component and the fluid-like X-ray-emitting plasma are spatially segregated. By using both wide-field ground-based images and HST/ACS images of the cluster cores, we create gravitational lensing maps showing that the gravitational potential does not trace the plasma distribution, the dominant baryonic mass component, but rather approximately traces the distribution of galaxies. An 8 σ significance spatial offset of the center of the total mass from the center of the baryonic mass peaks cannot be explained with an alteration of the gravitational force law and thus proves that the majority of the matter in the system is unseen.

Footnote * Based on observations made with the NASA/ESA Hubble Space Telescope (HST), obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555, under program 10200, with the 6.5 m Magellan telescopes located at Las Campanas Observatory, Chile, with the ESO telescopes at the Paranal Observatory under program IDs 72.A-0511, 60.A-9203, and 64.O-0332, and with the NASA Chandra X-Ray Observatory, operated by the Smithsonian Astrophysics Observatory under contract to NASA. Subject headings

dark matter; galaxies: clusters: individual (1E 0657–558); gravitational lensing


Issue 2 (2006 September 10)

Received 2006 June 6, accepted for publication 2006 August 3

Published 2006 August 30

Epistemologia social: o futuro de uma promessa não cumprida

Fuller, Steve. “Social Epistemology: The Future of an Unfulfilled Promise.” Social Epistemology Review and Reply Collective 3, no. 7 (2014): 29-37.

Social Epistemology: The Future of an Unfulfilled Promise 1

Steve Fuller, Auguste Comte Chair in Social Epistemology, University of Warwick

How the World Has Changed Since the Eighties

I recently ran across a South African book that offered a critical survey of the various strands of thought that feed into contemporary ‘transdisciplinarity’. The text contained a brief discussion of social epistemology – in particular my version (the analytic version was not mentioned). Much to my bemusement, ‘social epistemology’ was described as a movement from the 1980s. While it certainly began then, I would hope that it continues to have relevance in a world that has consigned both the Cold War and Duran Duran to the dustbin of history. At the same time, it is clear that many of the field’s sustaining themes look different from when I founded the journal and published the book Social Epistemology (1988), now more than a quarter-century ago.

If I had to point one consistent source of ‘originality’ in my thinking, it would lie in imagining a moment in the past when things could have been different, and then tracing the consequences of the path not followed. Such moments would be chosen strategically to satisfy some normative ambition, but the import of this exercise would be to show that ‘the real’ can operate as a platform for launching ‘the ideal’. The policy problem then is determining what – if any – aspects of our current condition might produce a similar effect in the foreseeable future. Applied to Science and Technology Studies (STS), it would mean, say, reading Leviathan and the Air-Pump’s account of how Robert Boyle 
triumphed over Thomas Hobbes not as a celebration of the sheer contingency of the outcome, but as a record of failure from which one might learn when a similar circumstance arises in the future, so that the Hobbes-figure might win (assuming, as I do, his way is preferable). When I founded social epistemology, these two positions were not so clearly distinguished because they faced a common foe: the classic ‘Whig’ view according to which Boyle justifiably beat Hobbes, and the world has been a better place for it. However, that foe is largely gone, and so the differences between its two opponents now acquire salience.


FREE PDF GRATIS: Social Epistemology

Qual língua os Neandertais falavam?

domingo, julho 27, 2014


Front. Psychol., 04 July 2013 | doi: 10.3389/fpsyg.2013.00397

On the antiquity of language: the reinterpretation of Neandertal linguistic capacities and its consequences

Dan Dediu1,2*† and Stephen C. Levinson2,3†

1Language and Genetics Department, Max Planck Institute for Psycholinguistics, Nijmegen, Netherlands
2Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, Netherlands
3Language and Cognition Department, Max Planck Institute for Psycholinguistics, Nijmegen, Netherlands


It is usually assumed that modern language is a recent phenomenon, coinciding with the emergence of modern humans themselves. Many assume as well that this is the result of a single, sudden mutation giving rise to the full “modern package.” However, we argue here that recognizably modern language is likely an ancient feature of our genus pre-dating at least the common ancestor of modern humans and Neandertals about half a million years ago. To this end, we adduce a broad range of evidence from linguistics, genetics, paleontology, and archaeology clearly suggesting that Neandertals shared with us something like modern speech and language. This reassessment of the antiquity of modern language, from the usually quoted 50,000–100,000 years to half a million years, has profound consequences for our understanding of our own evolution in general and especially for the sciences of speech and language. As such, it argues against a saltationist scenario for the evolution of language, and toward a gradual process of culture-gene co-evolution extending to the present day. Another consequence is that the present-day linguistic diversity might better reflect the properties of the design space for language and not just the vagaries of history, and could also contain traces of the languages spoken by other human forms such as the Neandertals.

Origem e evolução do ribossomo

sexta-feira, julho 25, 2014

Origin and Evolution of the Ribosome

  1. George E. Fox
-Author Affiliations
  1. Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204-5001
  1. Correspondence: fox@uh.edu


The modern ribosome was largely formed at the time of the last common ancestor, LUCA. Hence its earliest origins likely lie in the RNA world. Central to its development were RNAs that spawned the modern tRNAs and a symmetrical region deep within the large ribosomal RNA, (rRNA), where the peptidyl transferase reaction occurs. To understand pre-LUCA developments, it is argued that events that are coupled in time are especially useful if one can infer a likely order in which they occurred. Using such timing events, the relative age of various proteins and individual regions within the large rRNA are inferred. An examination of the properties of modern ribosomes strongly suggests that the initial peptides made by the primitive ribosomes were likely enriched for L-amino acids, but did not completely exclude D-amino acids. This has implications for the nature of peptides made by the first ribosomes. From the perspective of ribosome origins, the immediate question regarding coding is when did it arise rather than how did the assignments evolve. The modern ribosome is very dynamic with tRNAs moving in and out and the mRNA moving relative to the ribosome. These movements may have become possible as a result of the addition of a template to hold the tRNAs. That template would subsequently become the mRNA, thereby allowing the evolution of the code and making an RNA genome useful. Finally, a highly speculative timeline of major events in ribosome history is presented and possible future directions discussed.

    Einstein - uma celebridade cognitiva

    terça-feira, julho 22, 2014

    Cognitive celebrity
    Albert Einstein was a genius, but he wasn’t the only one – why has his name come to mean something superhuman?

    by Matthew Francis 1,500 words

    Albert Einstein (1879 - 1955) at home in Princeton, New Jersey, 1944. 
    Photo by Popperfoto/Getty Images

    Before he died, Albert Einstein requested that his whole body be cremated as soon as possible after death, and his ashes scattered in an undisclosed location. He didn’t want his mortal remains to be turned into a shrine, but his request was only partially heeded. Einstein’s closest friend, the economist Otto Nathan, took possession of his ashes, but not before Thomas Harvey, the pathologist who performed the autopsy, removed his brain. Family and friends were aghast, but Harvey convinced Einstein’s son Hans Albert to give his reluctant permission after the fact. The eccentric doctor kept the brain in a glass jar of formalin inside a cider box under a cooler, until 1998, when he returned it to Princeton Hospital, and from time to time, he would send little chunks of it to interested scientists.

    Most of us will never be victims of brain-theft and ash hoarding, but Einstein’s status as the archetypical genius of modern times singled him out for special treatment. An ordinary person can live and die privately, but a genius – and his grey matter – belongs to the world. Even in his lifetime, which coincided with the first great flowering of mass media, Einstein was a celebrity, as famous for his wit and white shock of hair as he was for his science. Indeed, his life seems to have been timed perfectly to take advantage of the proliferations of newspapers and radio shows, whose reports often framed Einstein’s theories as being incomprehensible to anyone but the genius himself.

    There’s no doubt that Einstein’s contributions to science were revolutionary. Before he came along, cosmology was a part of philosophy but, thanks to him, it’s become a branch of science, tasked with no less than a mathematical history and evolution of the Universe. Einstein’s work also led to the discovery of exotic physical phenomena such as black holes, gravitational waves, quantum entanglement, the Big Bang, and the Higgs boson. But despite this formidable scientific legacy, Einstein’s fame owes something more to our culture’s obsession with celebrity. In many ways, Einstein was well-suited for celebrity. Apart from his distinctive coif, he had a way with words and, as a result, he is frequently quoted, occasionally with bon mots he didn’t actually say. More than anything, Einstein possessed the distinctive mystique of genius, a sense that he was larger than life, or different from the rest of us in some fundamental way, which is why so many people were desperate to get hold of his brain.

    Many people have wondered whether genius is a physical attribute, a special feature that could be isolated in the brain, and Einstein’s grey matter is considered a fertile experimental ground for testing this claim. Unfortunately, as the psychologist Terence Hines has argued, the published studies that were carried out on Einstein’s brain are flawed in important ways. In each case, researchers compared parts of Einstein’s brain to people assumed to be ‘normal’, but in most of these studies the scientists knew which brain sample was Einstein’s. They set about looking for differences – any differences – between Einstein and the control brains and, when you approach science in this way, it’s very easy to find differences.

    After all, there was only one Einstein, just as there’s only one ‘you’ and only one ‘me’. The only way to be sure that Einstein’s brilliance was due to his anatomy would be to analyse his brain alongside many other people like him, in contrast to people unlike him. Otherwise, it’s impossible to tell the difference between the unique physiological characteristics of his genius and random variation between individuals. But that doesn’t mean we can’t investigate his genius. For while we might not have good studies of his brain, we do have the story of his life, and the contents of his mind, in the form of his research.

    Einstein is often remembered as a harmless, other-worldly figure, detached from mundane problems. Certainly he had his eccentricities: he wore sweatshirts that grew rattier over the years, because wool sweaters made him itch. He didn’t like socks, and sometimes wore women’s shoes on vacation. But the conventional narrative of Einstein as tweedy eccentric ignores his radical politics and occasionally troubled personal life. After all, Einstein was a socialist and advocate for one-world government and, until Hitler rose to power, championed demilitarisation and pacifism. He was also passionately anti-racist, hosting the African-American contralto Marian Anderson at his house when Princeton hotels refused to serve her in 1937, and after.

    Read more here/Leia mais aqui: Aeon

    A ameaça ao método científico

    The Threat To The Scientific Method

    Patrick Michaels | Jul 21, 2014

    The legacy of Franklin Roosevelt is harming American science.
    At the end of World War II, President Roosevelt asked Vannevar Bush, who oversaw the explosively successful Manhattan Project, if there was a way that the horde of scientists recruited to produce The Bomb could somehow be kept in government employment.
    Within eight months, Bush sketched out a blueprint in which the Universities, not the government, would be the employers, but that the pay, either for faculty or for hired researchers, would actually originate from federal science agencies, cabinet departments, or the clandestines.
    The consequences were obvious. Universities charge 50 percent overhead on federal grants, using these profitable science Department monies to pay for unprofitable Art and Music Departments. The seeds of political correctness—which requires big, expensive, expansive government—were planted as the schools became addicted to federal welfare.
    Under unforgiving competition to secure funding for their institutions (and promotion for themselves) some scientists are behaving badly.
    Last week, a technical publication, Journal of Vibration and Control, retractedsixty papers, after an internal investigation revealed a fraudulent “peer review and citation process” that greased the skids for a small number of authors to have an enormous number of citations in what is a prestigious engineering specialty. At least one of the authors even managed to review his own papers under an alias.
    That’s symptomatic of a larger sickness raging in what should be our most sacrosanct of institutions. If we can no longer trust science, what do we have as the basis for knowledge?
    It is a fact that the policy world—particularly the environmental policy world—claims to base policies on “science,” such as the reports of United Nations’ Intergovernmental Panel on Climate Change, or the U.S. Global Change Research Program’s periodical “National Assessments” of the impact of climate change on our country.
    These influential documents are essentially large reviews of a voluminous scientific literature. The tragedy is that literature is being insidiously poisoned by the incentive structure for science itself.
    The evidence is increasingly compelling. University of Montreal’s Danielle Fanelli has written several comprehensive reviews of the content of published science and he found, in the last twenty years, that the number of “positive” results is increasing dramatically. That’s when the data confirm a proposed hypothesis rather than suggesting rejection or modification.
    In a real world where scientists are answering real questions, that would be impossible. People have not suddenly become smarter, except, perhaps at how to advance in academia. There, candidates for promotion in the sciences are basically asked two questions: What did you publish, and how much taxpayer money did you bring in to support your research?
    Read more here/Leia mais aqui: Townhall