The enigma of cosmic rays — 1

Cosmic rays are energetic particles that zoom through space and occasionally enter our atmosphere. They are believed to be produced by violent astronomical events in and outside our Galaxy. Study of these particles provides a glimpse into the fascinating world of high energy physics. Biman Nath is an astrophysicist at the Raman Research Institute, Bangalore.     

Dark matter

In Part I¹ of this article we learnt that there are compelling evidences from dynamics of spiral galaxies, like our own, that there must be non-luminous matter in them. In this second part we will see that even clusters of galaxies must harbour dark matter. As if this was not enough, it turns out that if our knowledge of the universe is not completely wrong, then the universe as a whole has to contain dark matter and that it must be of some exotic type.     

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.     

Homi Bhabha and cosmic ray research in India

Cosmic rays are very high energy particles arriving from the depths of space and incident on the earth’s atmosphere at all places and at all times. The energy of these particles extends over 12 decades from around 10⁹ ev to 10²¹ ev and mercifully for the survival of life, the intensity falls by atleast 22 decades from about 100 particles/cm²/s to 1 particle/1000 km² year. Cosmic ray research led to the discovery of many of the fundamental particles of nature in the 30’s, 40’s and 50’s of this century and ushered in the era of ‘elementary particle physics’ at man-made accelerators. Even 86 years after the discovery, the sources of these particles and the mechanism of acceleration continue to remain a mystery. Homi Bhabha who became famous for his ‘cascade theory of the electron’ in the 30′s did pioneering theoretical and experimental research in this field during his post doctoral fellowship in Cambridge and later at the Indian Institute of Science in Bangalore. The Tata Institute of Fundamental Research, which he founded in 1945, became under his leadership, a major centre of cosmic ray research covering practically all aspects of the radiation and continues to be active in this field.     

Bhabha’s contributions to elementary particle physics and cosmic rays research

Bhabha’s scientific research contributions are descibed in the context of his life and contemporary science. During the Cambridge period (1927–1939), he worked in positron theory (Bhabha scattering), cosmic rays (Bhabha-Heitler theory of cosmic ray showers, prediction of heavier electrons) and meson theory. In Bangalore during 1939–1945, he worked on classical relativistic spinning particles (Bhabha-Corben equations), meson theory and initiated experimental work in cosmic rays in India. He then founded Tata Institute of Fundamental Research in 1945 at Bombay and moved there. Here he started work on relativistic wave equations (Bhabha equations.). He also initiated India’s nuclear energy programme in 1948 and this was his main preoccupation later.     

The Rhythm of the University: Part Two - Whitehead's Break with the Mechanistic Materialism of 17th Century Science

In this second article on the rhythm of the university, I concentrate on Alfred North Whitehead's theory of a distinctive rhythm of research. The narrow assumptions of 17^th century science, which still comprise the dominant paradigm for a good deal of university research, emanate from "the Fallacy of Misplaced Concreteness" and result in "quite unbelievable" abstractions that continue to hold sway over the university as a whole. What is needed is an aesthetic appreciation, grounded in our concrete experience of nature, that enables researchers to recognize our organic connections with the world. In particular, the bodily feelings at the base and forefront of our experience constitute a "vectoral" energetic flow from the universe to our bodies that must be recognized in all research. Fortunately, prominent researchers in diverse disciplines - physics, chemistry, philosophy, theology, economics, and the philosophy of economics - are now using this Whiteheadian paradigm and demonstrating its value to the research community as a whole. In conclusion, Whitehead's theory of the university knits together teaching, learning, administering, and research into a seamless web capable of restoring balance to the postmodern university.     

Homi Bhabha and Cosmic Ray research in India

Cosmic rays are very high energy particles arriving from the depths of space and incident on the earth’s atmosphere at all places and at all times. The energy of these particles extends over 12 decades from around 10⁹ ev to 10²¹ ev and mercifully for the survival of life, the intensity falls by atleast 22 decades from about 100 particles/cm²/s to 1 particle/1000 km² year. Cosmic ray research led to the discovery of many of the fundamental particles of nature in the 30’s, 40’s and 50’s of this century and ushered in the era of ‘elementary particle physics’ at man-made accelerators. Even 86 years after the discovery, the sources of these particles and the mechanism of acceleration continue to remain a mystery.     

The myth of the martians and the golden age of Hungarian science

Enrico Fermi was a man with outstanding talents, he had many interests outside his own particular field. He was credited with asking famous questions. There are long preambles to Fermi's questions like this: — ‘The universe is vast, containing myriads of stars, many of them not unlike our Sun. Many of these stars are likely to have planets circling around them. A fair fraction of these planets will have liquid water on their surface and a gaseous atmosphere. The energy pouring down from a star will cause the synthesis of organic compounds, turning the ocean into a thin, warm soup. These chemicals will join each other to produce a self-reproducing system. The simplest living things will multiply, and evolve by natural selection and become more complicated. And eventually active, thinking creatures will emerge. Civilization, science and technology will follow. Then, yearning for fresh worlds, they will travel to neighboring planets, and later to planets of nearby stars. Eventually they should spread out all over the Galaxy. These highly exceptional and talented people could hardly overlook such a beautiful place as our Earth’. And so Fermi came to his overwhelming question, — ‘If all this has been happening, they should have arrived here by now, so where are they?’ It was Leo Szilard, a man with an impish sense of humor who supplied the perfect reply to Fermi's rhetoric: ‘They are among us’, he said, ‘but they call themselves Hungarians’.     

Sunyaev-zeldovich effect

Soon after the discovery of the cosmic background radiation, Zeldovich and Sunyaev proposed that hot gas in galaxy clusters should cast a faint shadow because of the interaction between energetic electrons and the radiation photons. Sunayev-Zeldovich effect is now routinely observed, and it has become an important tool for studying the history of the universe.     

Dark matter

In Part I of this article we learnt that there are compelling evidences from dynamics of spiral galaxies, like our own, that there must be non-luminous matter in them. In this second part we will see that even clusters of galaxies must harbour dark matter. As if this was not enough, it turns out that if our knowledge of the universe is not completely wrong, then the universe as a whole has to contain dark matter and that it must be of some exotic type.     

Nobel Prize in Physics 2006

The discovery of the cosmic microwave background radiation in 1965 was a defining moment in the history of cosmology — the science that deals with the universe as a whole, its origin, evolution and future. This discovery was recognized with Nobel Prizes to Penzias and Wilson in 1978. The Nobel Prize in Physics for 2006 further acknowledged the importance of the study of this background radiation. The precise measurement of the spectrum of this radiation and its variation across the sky have helped our understanding of the evolution of structures in the universe. This article explains these discoveries and their importance. T Padmanabhan is a professor at IUCAA, Pune. He is interested in all aspects of theoretical physics, and especially in those in which gravity plays a role.     

Our particle universe

Ever since the discovery of the electron more than 100 years ago, scientists have asked the questions –“what is our universe made of?” and “why is the universe the way it is?” Not long before, it was found that these two questions are related to each other. The interactions of particles in the universe determines its evolution, its very form, and existence. In this article, we will trace the discovery of some of these particles, learn about their interactions, and try to understand their properties such as electric charge and mass.     

Anisotropic Open Cosmological Models of Spin Matter with Magnetic Moment

We have derived a set of field equations for a Weyssenhoff spin fluid including magnetic interacton among the spinning particles prevailling in spatially homogeneous,but anisotropically cosmological models of Bianchi type V based on Einstein-Cartan theory.We analyze the field equations in three different equations of states specified by p=1(1/3)ρand p=0,The analytical solutions found are non-singular provided that the combined energy arising from matter spin and magnetic interaction among particles overcomes the anisotropy energy in the Universe,We have also deduced that the minimum particle numers for the radiation(p=(1/3)ρ) and matter(p=0) epochs are 10^88 and 10^108 respectively.the minimum particle number for the state p=ρ is 10^96,leading to the conclusion that we must consider the existence of neutrinos and other creation of particles and anti-particles under torsion and strong gravitational field in the early Universe.     

Space Scale: Models in the History of Science and Students Mental Models

This paper deals with the problem of relating distance and scale by way of alternative models of perception taken from the history of science.The intuitive patterns of modern school children in evaluating the Solar System are then compared with those in the history of science. Immediate experience and intuition by children often contradict scientific understanding. The children in this study, for example, do not see the rays of the Sun as being parallel and ignore the curvature of the Earth. The authors argue that children's understanding of the rays of the Sun as not being parallel as well as their ignoring the curvature of the Earth is due to the limitation resulting from the students' `actual activity zone', and not to their insufficient knowledge. This study makes specific suggestions to broaden the scientifically based `actual activity zone' of students. We suggest that laboratory work based on historical experiments using elementary geometry – as, for example, the determination of the radiusof the Earth by Eratosthenes – promotes a scientific understanding of astronomicalmeasurements....The scale of space and time, which we customarily observe on Earth, and which is part of time, we become aware of the vastness of our universe, we are awed and humbled. But if astronomers spent all their time speculating about the immensity of the cosmos and the prodigious interval of time necessary for the evolution of the stars, their accomplishments would be few. The primary concerns of the astronomer when studying the cosmos are physical and mathematical interpretations of observations, predictions of future observations, and the development and refinement of his instruments for such interpretation and prediction. To help him in the conceptualization of his problem, astronomer may, consciously or unconsciously, visualize a small model representing the cosmic system under investigation. Using this method, we can arrive at an understanding of the relative dimensions of the system and an understanding of the time intervals involved.Shklovskii I.S. and Carl Sagan (1966)Intelligent Life in the Universe     

关于构建社会主义和谐社会价值导向的思考

正确的价值导向是构建社会主义和谐社会的灵魂,文章对其价值导向所面临的问题和必须把握的几个关系进行了思考。要解决我国价值导向的现状所反映出来的理论和现实问题,树立正确的价值导向,其关键是要处理好核心价值体系和多样化社会思想的关系、个人利益和集体利益的关系、物质需求和精神需求的关系、道德规范和人格操守的关系,使我们的价值导向发挥其应有实效性,为构建社会主义和谐社会提供精神动力和信念支持。     

平坦ΛCDM宇宙学模型下的光度距离级数解(英文)

宇宙学观测表明,目前宇宙的时空结构为平坦的且以暗能量(DE)为主要成分.光度距离对于研究宇宙的结构和演化具有重要意义,然而它在实际应用时需要进行繁重的数值求积过程.本文得到一个平坦ΛCDM宇宙学模型下的光度距离级数解.经过计算发现,在多项式阶数n=100,相对参数β∈[0,4](即0.2<ΩΛ<1,红移z>0.1)时,其相对误差低于0.36%.     

Nature watch

In our previous article ‘On observing the night sky’¹ we had introduced the reader to the stars and constellations and suggested how they may be observed. In this article we will provide a few technical details, which we had deliberately left out earlier and also introduce the reader to a number of the other remarkable objects that may be seen in the sky.     

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 .     

WOMEN EDUCATORS: LEADERSHIP IN THE 1990s

Institutions of higher learning have been places where men have ruled supreme, but in the past 20 years women have come into the sphere of academia with strong academic backgrounds and an energetic desire to establish a place for themselves equal to their male counterparts in the profession. Women administrators, teachers, lecturers, research scholars, and counselors are moving into career positions and are sharing with distinction the responsibilities and duties of education. To maintain this academic impetus, women educators in junior colleges, in community colleges, and in universities must continue to strive for the highest goals. In a world of change and of much discord, educators will be called on to contribute knowledge and solutions that will lead to a more peaceful universe. Women educators must have a role in world affairs as well as in the educational institutions of the world.     

古印度的天文思想

古印度的天文思想与当时的宗教哲学有着千丝万缕的联系,吠陀时代的天文学已经以大梵天不断再生宇宙的神话认识到宇宙的永恒循环,并提出了类似中国二十八宿的27或28月站的星座体系;耆那教对于构成宇宙的元素作出了精细的宗教哲学思辨,佛教立足于生命的永恒轮回,建立了以须弥山为中心的地心世界模型,推测无边无际的永恒循环宇宙具有高度的自相似结构,但不太符合现代科学揭示的宇宙演化模型。