Origin (?) of the universe

The first part of this series covers the historical background to the subject of cosmology-the study of the structure and evolution of the whole universe. Ancient ideas, such as those of the Greeks, already show the beginnings of attempts to account for observations by natural laws, and to prove or disprove these by other observations. It needed the invention of the telescope and studies by scientists like Herschel and Hubble to reach the current understanding of our place in our galaxy, and its place as only one member of a far larger collection of galaxies which fill the observable universe.     

Black holes in our universe

Current technologies have enabled glimpses at the many facets of black holes, which we know to be plentiful in our cosmos. A panoramic view of the evidence for them is presented here across the large range of masses that they span.     

Origin(?) of the universe

In this part of the series we discuss the standard cosmological model valid close to the big bang epoch. The origin of light nuclei is believed to have taken place within the first three minutes or so when the universe was very hot and dominated by radiation. Subsequently, it cooled down and today we should see radiation decoupled from matter but spread almost homogeneously all over the universe with a black body spectrum. This expectation has been realized by the discovery of the microwave background in 1965. Jayant V Narlikar Director, Inter-University Centre for Astronomy and Astrophysics, works on action at a distance in physics, new theories of gravitation and new models of the universe. He has made strong efforts to promete taaching and research in astronomy in the universities and also writes extensively in English and Marathi for a wider audience on science and other topics.     

Origin (?) of the universe

In this part of the series we look at the simplest cosmological models based on the simplifying assumptions of the Weyl postulate and the cosmological principle. These models were discovered independently by Friedmann, Lemaitre and Robertson in the 1920s. They led to the striking conclusion that the universe started in an enormous explosion often called the Big Bang.     

Origin(?) of the universe

The final article in the series reviews the strengths and weaknesses of the big bang cosmology, conceptual as well as observational. It is argued that despite its many successes there are enough question marks against this cosmology to keep the issue open. In particular, an alternative view-point developed by the author and his colleagues is described. In this the universe has always been in existence. Known as the Quasi-Steady State Cosmology it combines some good features of the big bang cosmology with new ideas which may help resolve some of the outstanding questions of today.     

Origin (?) of the universe

The expansion of the universe was established based on observations made in the 1920’s, of the Doppler shift of light from galaxies. The proportionality between velocity and distance is the famous Hubble Law. Simplified mathematical models of the universe are based on the idea, which is supported by observations, that there are no preferred locations or directions in space.     

Origin (?) of the universe

In this part of the series we look at the present astronomical evidence both from distant parts of the universe as well as from our local region to test cosmological predictions. Included in this discussion are Hubble’s law, source counts, angular diameters, the age of the universe, abundances of light nuclei and the microwave background. The significance of the findings for big bang models is discussed. An erratum to this article is available at .     

The biggest explosions in the universe

Gamma ray bursts — which are first detected in energetic gamma rays and which then glow in X-ray, visible and radio wavelengths — are the result of the biggest explosions in the universe. Astronomers wonder what causes these violent events, and some of their ideas are discussed in this article.     

广义测不准关系与de Sitter宇宙的熵

利用经广义测不准关系改进的薄层brick-wall方法计算了de Sitter时空背景下宇宙的熵．结果表明。用这种方法得到的宇宙熵与视界面积成正比，与人们预期的结果相符．从中揭示了宇宙的熵与视界面积之间的内在联系。也进一步表明了宇宙的熵是视界面上量于态的熵，是一种量子效应．     

Violence and the changing universe of disabilities

The field of special education has primary responsibility for providing specialized services to young children with disabilities in the schools. Increasingly, it is recognized that many disabilities identified among young children may be attributable to environmental variables, such as violence, poverty, toxic materials exposure, and family dysfunction. Issues of violence hold particular relevance for special education professionals. Recent studies report that young children with disabilities are 1.7 times more likely to be victims of maltreatment than children without disabilities. For children with disabilities living with the effects of violence, the infrastructure of special education as it is now developing may be the most promising approach to individual and systems intervention. Comprehensive community-based initiatives are replacing fragmented practices. The new collaborations can multiply the results of intervention or support programs beyond those attainable through any single approach. Views expressed in this article are solely those of the author and do not reflect policies of the U.S. Department of Education.     

Pentadic cartography: Mapping the universe of discourse

Expressions of time have increasingly infused the rhetorical experience of post-industrial war, especially since 9/11. This essay demonstrates how these “signs of time” operate as one of three tropes: deadline/countdown, infinite/infinitesimal war, and the ticking clock. The persistence of such signs of time in public discourse can be seen as an expression of what Paul Virilio has called the “chronopolis,” a political universe textured by real-time communication technologies. The chronopolitical will exhibits certain autocratic traits at odds with democratic ideals, primarily the refashioning of citizen identity into that of the “contemporary.” The analysis here charts the autocratic rhetoric of the chronopolis as a critical democratic project.     

Radiation: The key to understanding the universe

The only source of information about the universe is the radiation that we receive from various astronomical sources. This article describes some of the methods used by astronomers to analyze this radiation to unveil the mysteries of the universe.     

General relativity and the accelerated expansion of the universe

The 2011 Nobel Prize in Physics has been awarded to S Perlmutter, A Riess and B Schmidt for their path-breaking discovery that the rate of expansion of the universe is increasing with time. The trio used Type Ia supernovae (SNe Ia) as standard candles to estimate their luminositydistances. To appreciate some of the far-reaching implications of their work, I have provided an elementary exposition of the general theory of relativity, accelerated expansion of the universe, luminosity-distance, SNe Ia and the cosmological constant problem.     

宇宙速度及其简明计算

第三宇宙速度的计算是个繁杂的多体问题，利用系统逃逸动能的可叠加性，将多体问题化为二体问题的叠加给出了一个可以计算第三宇宙速度数值的主项。