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Matthew Stanley
In the eighteenth and nineteenth centuries there were many attempts to justify political and social systems on the basis of physics and astronomy. By the early twentieth century such moves increasingly also integrated the life and social sciences. The physical sciences gradually became less appealing as a sole source for sociopolitical thought. The details of this transition help explain the contemporary reluctance to capitalize on an ostensibly rich opportunity for naturalistic social reasoning: the anthropic principle in cosmology, which deals with the apparent "fine-tuning" of the universe for life...
September 2014: Isis; An International Review Devoted to the History of Science and its Cultural Influences
Jonathan R Pritchard, Abraham Loeb
Imaging the Universe during the first hundreds of millions of years remains one of the exciting challenges facing modern cosmology. Observations of the redshifted 21 cm line of atomic hydrogen offer the potential of opening a new window into this epoch. This will transform our understanding of the formation of the first stars and galaxies and of the thermal history of the Universe. A new generation of radio telescopes is being constructed for this purpose with the first results starting to trickle in. In this review, we detail the physics that governs the 21 cm signal and describe what might be learnt from upcoming observations...
August 2012: Reports on Progress in Physics
Claude-André Faucher-Giguère, Adam Lidz, Lars Hernquist
The universe is permeated by a network of filaments, sheets, and knots collectively forming a "cosmic web." The discovery of the cosmic web, especially through its signature of absorption of light from distant sources by neutral hydrogen in the intervening intergalactic medium, exemplifies the interplay between theory and experiment that drives science and is one of the great examples in which numerical simulations have played a key and decisive role. We recount the milestones in our understanding of cosmic structure; summarize its impact on astronomy, cosmology, and physics; and look ahead by outlining the challenges faced as we prepare to probe the cosmic web at new wavelengths...
January 4, 2008: Science
F J Rogers, C A Iglesias
An array of problems in astronomy, cosmology, and particle physics is dependent on our understanding of the evolution and structure of stars. Stellar structure and evolution, in turn, depend on how the nuclear energy generated in the stellar center is transported to the surface. Energy transport by photons is a primary transfer mechanism. Recent improvements in the calculation of the radiative properties of stellar matter have helped resolve several long-standing discrepancies between observations and the predictions of theoretical models...
January 7, 1994: Science
R A Alpher
No abstract text is available yet for this article.
January 1973: American Scientist
Hans-Jörg Fahr, Michael Heyl
In the more recent literature on cosmological evolutions of the universe, the cosmic vacuum energy has become a nonrenouncable ingredient. The cosmological constant Lambda, first invented by Einstein, but later also rejected by him, presently experiences an astonishing revival. Interestingly enough, it acts like a constant vacuum energy density would also do. Namely, it has an accelerating action on cosmic dynamics, without which, as it appears, presently obtained cosmological data cannot be conciliated with theory...
September 2007: Die Naturwissenschaften
James Overduin, Hans-Joachim Blome, Josef Hoell
Wolfgang Priester (1924-2005) was one of Germany's most versatile and quixotic astrophysicists, reinventing himself successively as a radio astronomer, space physicist and cosmologist, and making a lasting impact on each field. We focus in this personal account on his contributions to cosmology, where he will be most remembered for his association with quasars, his promotion of the idea of a nonsingular "big bounce" at the beginning of the current expansionary phase, and his recognition of the importance of dark energy (Einstein's cosmological constant Lambda) well before this became the standard paradigm in cosmology...
June 2007: Die Naturwissenschaften
Yinggang Li, Chi-Wing Fu, Andrew J Hanson
Navigating through large-scale virtual environments such as simulations of the astrophysical Universe is difficult. The huge spatial range of astronomical models and the dominance of empty space make it hard for users to travel across cosmological scales effectively, and the problem of wayfinding further impedes the user's ability to acquire reliable spatial knowledge of astronomical contexts. We introduce a new technique called the scalable world-in-miniature (WIM) map as a unifying interface to facilitate travel and wayfinding in a virtual environment spanning gigantic spatial scales: Power-law spatial scaling enables rapid and accurate transitions among widely separated regions; logarithmically mapped miniature spaces offer a global overview mode when the full context is too large; 3D landmarks represented in the WIM are enhanced by scale, positional, and directional cues to augment spatial context awareness; a series of navigation models are incorporated into the scalable WIM to improve the performance of travel tasks posed by the unique characteristics of virtual cosmic exploration...
September 2006: IEEE Transactions on Visualization and Computer Graphics
Hans J Fahr, Jochen H Zoennchen
The famous idea of Ernst Mach concerning the non-absolute but relational character of particle inertia is taken up in this paper and is reinvestigated with respect to its cosmological implications. From Thirring's general relativistic study of the old Newtonian problem of the relativity of rotations in different reference systems, it appears that the equivalence principle with respect to rotating reference systems, if at all, can only be extended to the system of the whole universe, if the mass of the universe scales with the effective radius or extent of the universe...
December 2006: Die Naturwissenschaften
Simon Mitton
Astroparticle physics is an interdisciplinary field that explores the connections between the physics of elementary particles and the large-scale properties of the universe. Particle physicists have developed a standard model to describe the properties of matter in the quantum world. This model explains the bewildering array of particles in terms of constructs made from two or three quarks. Quarks, leptons, and three of the fundamental forces of physics are the main components of this standard model. Cosmologists have also developed a standard model to describe the bulk properties of the universe...
May 20, 2006: Lancet
Godehard Angloher, Josef Jochum
Although first hints of the existence of Dark Matter were observed by the Swiss astronomer Zwicky already in the 1930s, only in recent years has it become known that the universe, in fact, is dominated by particles whose nature is almost unknown and which have never been directly observed. Meanwhile, as the existence of these particles is postulated not only by astronomy, but also cosmology and theoretical particle physics, there is significant effort to detect them in a laboratory experiment and determine their physical properties...
March 2005: Die Naturwissenschaften
Andrea T Borchers, Paul A Davis, M Eric Gershwin
A common theme throughout biology is homochirality, including its origin and especially implications. Homochirality has also intrigued scientists because of the hypothesis that life, as it currently exists, could not have occurred without it. In this review, we discuss several hypotheses regarding homochirality and their linkage to processes that range from subatomic in scale to processes that help define the structure of the universe. More importantly, this exploration begins with the knowledge that humans inhabit the universe in which there is an excess of normal matter over antimatter...
January 2004: Experimental Biology and Medicine
C S Frenk
A timely combination of new theoretical ideas and observational discoveries has brought about significant advances in our understanding of cosmic evolution. Computer simulations have played a key role in these developments by providing the means to interpret astronomical data in the context of physical and cosmological theory. In the current paradigm, our Universe has a flat geometry, is undergoing accelerated expansion and is gravitationally dominated by elementary particles that make up cold dark matter. Within this framework, it is possible to simulate in a computer the emergence of galaxies and other structures from small quantum fluctuations imprinted during an epoch of inflationary expansion shortly after the Big Bang...
June 15, 2002: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Roger D Blandford
Recent X-ray observations have had a major impact on topics ranging from proto-stars to cosmology. They have also drawn attention to important and general physical processes that currently limit our understanding of thermal and non-thermal X-ray sources. These include unmeasured atomic astrophysics data (wavelengths, oscillator strengths, etc.), basic hydromagnetic processes (e.g. shock structure, reconnection), plasma processes (such as electron-ion equipartition and heat conduction) and radiative transfer (in discs and accretion columns)...
September 15, 2002: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
J D Barrow
We discuss some ways in which the age, size, and structure of the Universe, together with the values of its defining constants, satisfy the necessary conditions for life. The implications for teleology and the existence of other universes are also discussed.
December 2001: Annals of the New York Academy of Sciences
J L Greenstein
In this after-dinner speech, a somewhat light-hearted attempt is made to view the observational side of physical cosmology as a subdiscipline of astrophysics, still in an early stage of sophistication and in need of more theoretical understanding. The theoretical side of cosmology, in contrast, has its deep base in general relativity. A major result of observational cosmology is that an expansion of the Universe arose from a singularity some 15 billion years ago. This has had an enormous impact on the public's view of both astronomy and theology...
June 1, 1993: Proceedings of the National Academy of Sciences of the United States of America
J Overduin, W Priester
It would be hard to find a cosmologist today who does not believe that the vast bulk of the Universe (95% or more) is hidden from our eyes. We review the evidence for this remarkable consensus, and for the latest proposal, that the mysterious dark matter consists of as many as four separate ingredients: baryons, massive neutrinos, new "exotic" dark matter particles, and vacuum energy, also known as the cosmological constant (lambda). Of these, only baryons fit within standard theoretical physics; the others, if their existence is confirmed, will mean rewriting textbooks...
June 2001: Die Naturwissenschaften
T D Saini, S Raychaudhury, V Sahni, A A Starobinsky
Observations of high-redshift supernovae indicate that the Universe is accelerating. Here we present a model-independent method for estimating the form of the potential V(phi) of the scalar field driving this acceleration, and the associated equation of state w(phi). Our method is based on a versatile analytical form for the luminosity distance D(L), optimized to fit observed distances to distant supernovae and differentiated to yield V(straight phi) and w(straight phi). Our results favor w(phi) approximately -1 at the present epoch, steadily increasing with redshift...
August 7, 2000: Physical Review Letters
I E Segal
The physical validity of the hypothesis of (redshift-dependent) luminosity evolution in galaxies is tested by statistical analysis of an intensively studied complete high-redshift sample of normal galaxies. The necessity of the evolution hypothesis in the frame of big-bang cosmology is confirmed at a high level of statistical significance; however, this evolution is quantitatively just as predicted by chronometric cosmology, in which there is no such evolution. Since there is no direct observational means to establish the evolution postulated in big-bang studies of higher-redshift galaxies, and the chronometric predictions involve no adjustable parameters (in contrast to the two in big-bang cosmology), the hypothesized evolution appears from the standpoint of conservative scientific methodology as a possible theoretical artifact...
November 23, 1999: Proceedings of the National Academy of Sciences of the United States of America
K Nomoto, K Iwamoto, N Kishimoto
Spectroscopic and photometric evidence indicates that Type Ia supernovae (SNe Ia) are the thermonuclear explosions of accreting white dwarfs. However, the progenitor binary systems and hydrodynamical models for SNe Ia are still controversial. The relatively uniform light curves and spectral evolution of SNe Ia have led to their use as a standard candle for determining cosmological parameters, such as the Hubble constant, the density parameter, and the cosmological constant. Recent progress includes the calibration of the absolute maximum brightness of SNe Ia with the Hubble Space Telescope, the reduction of the dispersion in the Hubble diagram through the use of the relation between the light curve shape and the maximum brightness of SNe Ia, and the discovery of many SNe Ia with high red shifts...
May 30, 1997: Science
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