Hubble’s menagerie of galaxies

Soon after the discovery that we live in a separate galaxy and that there are many other galaxies in the universe, Hubble designed a classification scheme of galaxies based on their appearances. It was such a robust scheme that it continues to be one of the basic tools of modern astronomy, and motivates astronomers to look for connections between different types of galaxies.     

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

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.     

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.     

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。     

Hubble, Hubble’s law and the expanding universe

Hubble’s name is associated closely with the idea of an expanding universe as he discovered the relation between the recession velocity and the distances of galaxies. Hubble also did a lot of pioneering work on the distribution of galaxies in the universe. In this article we take a look at Hubble’s law and discuss how it relates with models of the universe. We also give a historical perspective of the discoveries that led to the Hubble’s law.     

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.     

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.     

宇宙中温度最低点

To an Eskimo(爱斯基摩人), the saying goes, hell is a very cold place, not a hot one. Now NASA and European astronomers have pictures of Eskimo hell: the coldest spot in the known universe. The place is 5, 000 light-years from Earth in the constellation Centaurus(人马座). It' s the Boomerang Nebula: a cloud of gases that are being expelled from a dying star.     

Dark matter

The study of gas clouds orbiting in the outer regions of spiral galaxies has revealed that their gravitational attraction is much larger than the stars alone can provide. Over the last twenty years, astronomers have been forced to postulate the presence of large quantities of ‘dark matter’ to explain their observations. They are still in the ‘dark’ as to its true nature.     

宇宙的核式结构模型

根据原子核式结构模型和量子力学理论提出和论述宇宙核式结构的模型,利用宇宙核式结构模型解释了宇宙膨胀现象、哈勃定律、宇宙的产生和演化、奇点等几个重大问题,并进一步说明负(反)质量物质的存在.     

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.     

我们将发现外星生命么?

Alien-hunting scientists have had an eventful1 year, and they're about to get busier. In just the past few months, life-friendly soil and ice turned up on Mars, astronomers bagged a trio of2 Earth-like planets in a distant star system, and scientists looking closer to home reported that certain hardy microbes3 thrive4 below Earth's ocean floor-a big clue that life may exist on planets that at first glance appear inhospitable5.……     

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.     

物理学熵的哲学思考

熵的基本理论不仅适用于简单的热力学系统,而且也适用于有生命活动的物质系统,还可以拓展到从对构成宇宙的星系和银河系这种巨大世界的研究中.熵奠定了一种新的世界观,它为人类重新规范了行为界线.     

空间概念的探讨

空间概念是物理学的最基础概念之一,对空间性质的认识随科学发展逐渐清晰,而对空间内在本质的认识却一直是争论与模糊的。对宇宙膨胀、卡西米尔效应、量子场论的真空能量,以及星系的核聚变等进行了综合分析：空间是由物质转化而来,空间与物质是同质的;物质与空间之间存在相互转换关系,物质可转化成空间,空间可转化为物质;空间不是物质的属性,而是物质的另一种特殊形态;空间是客观实在、独立存在的,但其性质不是牛顿绝对空间的几何不变,而是与物质或运动相互作用,与广义相对论的空间几何特性一致。同时又结合宇宙背景辐射光子数密度、核聚变反应的光子产生比率,计算出了物质与空间转换关系的转换系数。     

Cosmology, Mach’s principle and relativity

The significance of Mach’s principle (and the implicit relativity principle) for field theory is discussed, also the significance of zero-mass boson fields for the geometry of the physical space. The significance of such fields for Mach’s principle within the framework of cosmology is also discussed. It is suggested that the distant matter of the universe generates one or two zero-mass boson fields, very likely a tensor field and perhaps a scalar, and that each of these fields propagates, carrying into the laboratory a quasistatic influence having its origin primarily in the distant matter of the universe. The observable effects of these “Machian fields” are described.     

论萧红小说中的生死观

萧红小说中描写了东北农民原生态的生活方式，糊糊涂涂的“生”，浑浑噩噩的“死”，无休止地在岁月的年轮中划过一个又一个相同的圆圈，这是顺应大自然的周而复始的过程，属于圆型循环的时间观。萧红站在宏观的宇宙变化领悟到生命的真义，“生”的从无到有，“死”的从有到无，生死犹如环状相接，是自然造化的过程，萧红对生命真谛的感悟受的是道家思想的影响。     

The search for another Earth

Is there life anywhere else in the vast cosmos? Are there planets similar to the Earth? For centuries, these questions baffled curious minds. Either a positive or negative answer, if found one day, would carry a deep philosophical significance for our very existence in the universe. Although the search for extra-terrestrial intelligence was initiated decades ago, a systematic scientific and global quest towards achieving a convincing answer began in 1995 with the discovery of the first confirmed planet orbiting around the solar-type star 51 Pegasi. Since then, astronomers have discovered many exoplanets using two main techniques, radial velocity and transit measurements. In the first part of this article, we shall describe the different astronomical methods through which the extrasolar planets of various kinds are discovered. In the second part of the article we shall discuss the various kinds of exoplanets, in particular about the habitable planets discovered till date and the present status of our search for a habitable planet similar to the Earth.     

Axisymmetric solutions of the Chaplygin gas for initial negative radial velocity

In this paper, a three-parameter family of self-similar and weak solutions are constructed rigorously in two space dimensions for all positive time to the Euler equations with axisymmetric and radial negative initial velocity for the Chaplygin gas. Under the axisymmetry and self-similar assumptions, the equations are reduced to a system of three ordinary differential equations, from which we obtain structures of solutions besides their existence. The solutions exhibit some phenomena, such as formation and evolution of black hole, expansion and explosive expansion, in the evolution of universe.