悖论中的爆炸

以一种的的视角对大爆炸宇宙提出质疑从空间膨胀特性的分析入手而导出大爆炸理论与其赖以存在的基本证据之间深刻而又难以克服的矛盾性，基于提出了几条定理和结论，推导出几科遍及大爆炸理论与其基础证据中的悖论，诸如可测空间膨胀渤论，星系红移与宇宙起源论，哈毂定律与大爆炸悖论，此力与哈勃定律悖论等等。通过对上述悖论的分析，提出星系红移产生于一种非多普勒效应的新机制的可能性。并对其他的理论要点作了简要的分析。     

凸多面体之间的伪最小平移距离：I.定义及其性质

定义了凸多面体之间的伪最小平移距离，分析了它与Euclid度量意义下最小平移距离的上、下界关系及其关于多面体钢体运动的Lipschitz连续性、可微性等性质，给出了伪最小平移距离及其导数的计算方法，研究结果可应用于机器人无碰撞运动规划等领域。     

从宇宙看地球

从可观测宇宙来看，地球只是银河系内一颗普通恒星（太阳）周围的一个几乎微不足道的行星。但地球作为一个富有生命的世界，却又展示着宇宙向复杂而高级阶段演化的重要成果。这个我们赖以生存的家园的环境确实不可多得，人类应当倍加珍惜和保护。     

俄科学家获国际宇宙学最高奖项

国际天文学联合会决定将 2 0 0 3年度格鲁伯基金宇宙学奖授予俄科学院院士拉希德·休尼亚耶夫 ,以表彰他在研究宇宙微波背景辐射及其与周围物质相互作用的方面所作出的“开创性贡献”。格鲁伯基金宇宙学奖由格鲁伯基金会和国际天文学联合会共同设立 ,奖励在宇宙学领域有杰出贡献的科学家。它被认为是宇宙学领域最重要的国际奖项之一 ,此前有 3名美国科学家和 1名英国科学家获此殊荣。今年的奖项将于 7月 15日在澳大利亚悉尼举行的国际天文学联合会第 2 5届大会开幕式上颁发。休尼亚耶夫 194 3年生在原苏联乌兹别克苏维埃社会主义共和国 ,就…     

凸多面体之间的伪最小平移距离——Ⅰ.定义及其性质

定义了凸多面体之间的伪最小平移距离,分析了它与Euclid度量意义下最小平移距离的上、下界关系及其关于多面体刚体运动的Lipschitz连续性、可微性等性质. 给出了伪最小平移距离及其导数的计算方法. 研究结果可应用于机器人无碰撞运动规划等领域.     

日本提出20年宇宙开发长期计划

日本宇宙航空研究开发机构前些时候向宇宙开发委员会提交了20年宇宙开发长期计划，内容包括日本宇航员在月球表面进行资源调查、用观测卫星网及早了解地震受灾情况等。     

"哈勃"望远镜拍到宇宙最深处景观照片

美国宇航局前些时候说,“哈勃”太空望远镜新拍到了迄今可见宇宙最深处景观的照片,这张具有历史意义的照片中可能包含着宇宙诞生后不久产生的最早的星系。科学界普遍认为,宇宙诞生于距今约137亿年前的“大爆炸”。在“大爆炸”后的3亿年间,宇宙处于黑暗和冷寂状态,随后第一批恒星以及星系开始产生。“哈勃”新拍下的照片捕获到的正是宇宙中首批星系所发出的光芒。美国宇航局在公布新照片时称,该照片是根据“哈勃”望远镜两台相机的拍摄结果合成的,共包含约1万个星系。从照片上看,这些星系仿佛散落在黑天鹅绒上的宝石。照片覆盖的太空区域相…     

欧洲制定宇宙防灾研究计划

为了避免宇宙灾难给人类造成巨大损失 ,欧洲航天局新近制定了 6项宇宙防灾研究计划。据欧洲航天局发表的新闻公报 ,这 6项计划是欧洲航天局从众多计划中挑选出来的 ,它们将解答有关小行星与地球安全的最基本问题 ,将为人类制定宇宙灾难预防措施提供不可或缺的重要数据。欧洲航天局解释说 ,虽然小行星撞地球是小概率事件 ,如直径 5 0米的小行星撞击地球的概率是每 10 0至 30 0年一次 ,直径 1公里的撞击概率是数十万年一次 ,然而此类灾难一旦发生 ,其后果将不堪设想。为此 ,世界许多国家开展了小行星研究计划 ,但现有计划大多是在地面观测 ,而…     

基于表面间距离度量的多视点距离图像的对准算法

现有的距离图像对准算法，一般是采用最近点之间的距离和作为评价函数来估计运动参数．这种基于点对间距离的评价函数的缺点是，不同距离图像之间的最近点不一定是物体表面同一点的采样，而且不同采样点所代表的物体表面面积也不同．这些问题使得基于点对间距离度量的对准算法存在不精确对应的问题，因而对准精度不高，对初始运动参数敏感．提出一种基于表面间距离度量的对准算法．通过构造三角网格来近似表示物体的表面，采用三角网格间最近距离的均值作为评价函数来估计运动参数．推导并简化了表面间距离计算的积分公式．实验结果表明，该算法有较高的对准精度，而且收敛速度较快，抗噪声能力较强．     

以色列暗物质研究取得进展

“暗物质”是一种不可见的物质，是构成宇宙绝大多数物体的原素，它非常神秘，因为目前不仅没人知道它的构成，而且在有些星系中还难觅其踪。在今天的英国《自然》杂志上，以色列希伯来大学的研究人员公布了他们的最新研究发现，即在那些看起来似乎不含”暗物质”的星系中，“暗物质”其实也依然存在。     

Preludes to dark energy: zero-point energy and vacuum speculations

According to modern physics and cosmology, the universe expands at an increasing rate as the result of a “dark energy” that characterizes empty space. Although dark energy is a modern concept, some elements in it can be traced back to the early part of the twentieth century. I examine the origin of the idea of zero-point energy, and in particular how it appeared in a cosmological context in a hypothesis proposed by Walther Nernst in 1916. The hypothesis of a zero-point vacuum energy attracted some attention in the 1920s, but without attempts to relate it to the cosmological constant that was discussed by Georges Lemaître in particular. Only in the late 1960s, was it recognized that there is a connection between the cosmological constant and the quantum vacuum. As seen in retrospect, many of the steps that eventually led to the insight of a kind of dark energy occurred isolated and uncoordinated.     

The quantum vacuum and the cosmological constant problem

The cosmological constant problem arises at the intersection between general relativity and quantum field theory, and is regarded as a fundamental problem in modern physics. In this paper, we describe the historical and conceptual origin of the cosmological constant problem which is intimately connected to the vacuum concept in quantum field theory. We critically discuss how the problem rests on the notion of physically real vacuum energy, and which relations between general relativity and quantum field theory are assumed in order to make the problem well-defined.     

The cosmological constant, the fate of the universe, unimodular gravity, and all that

The cosmological constant is back. Several lines of evidence point to the conclusion that either there is a positive cosmological constant or else the universe is filled with a strange form of matter (“quintessence”) that mimics some of the effects of a positive lambda. This paper investigates the implications of the former possibility. Two senses in which the cosmological constant can be a constant are distinguished: the capital Λ sense in which lambda is a universal constant on a par with the charge of the electron, and the lower case λ sense in which lambda is a humble constant of integration. The latter interpretation has been touted as the means to a solution to various problems in physics. These claims are critically examined with an eye to discerning the implications for philosophy of science and foundations of physics.     

Interpreting cosmic no hair theorems: Is fatalism about the far future of expanding cosmological models unavoidable?

It may be tempting to interpret cosmic no hair theorems (establishing that, under certain conditions, a cosmological model with accelerating expansion approaches de Sitter metric in the future) as implying a form of fatalism about a future state of the universe. In this note I explore (rather general) philosophical and (more concrete) physical reasons to resist such temptation. There are good reasons to think that (even locally) futures of expanding cosmological models may be unlike de Sitter.     

Spacetime Models for the World

In this paper I take a sceptical view of the standard cosmological model and its variants, mainly on the following grounds: (i) The method of mathematical modelling that characterises modern natural philosophy—as opposed to Aristotle's—goes well with the analytic, piecemeal approach to physical phenomena adopted by Galileo, Newton and their followers, but it is hardly suited for application to the whole world. (ii) Einstein's first cosmological model (1917) was not prompted by the intimations of experience but by a desire to satisfy Mach's Principle. (iii) The standard cosmological model—a Friedmann–Lemaı̂tre–Robertson–Walker spacetime expanding with or without end from an initial singularity—is supported by the phenomena of redshifted light from distant sources and very nearly isotropic thermal background radiation provided that two mutually inconsistent physical theories are jointly brought to bear on these phenomena, viz the quantum theory of elementary particles and Einstein's theory of gravity. (iv) While the former is certainly corroborated by high-energy experiments conducted under conditions allegedly similar to those prevailing in the early world, precise tests of the latter involve applications of the Schwarzschild solution or the PPN formalism for which there is no room in a Friedmann–Lemaı̂tre–Robertson–Walker spacetime.     

Cosmological realism

I discuss the relevance of the current predicament in cosmology to the debate over scientific realism. I argue that the existence of two, empirically successful but ontologically inconsistent cosmological theories presents difficulties for the realist position.     

The unfolding of the historical style in modern cosmology: Emergence,evolution, entrenchment

This paper traces the emergence, evolution and subsequent entrenchment of the historical style in the shifting scene of modern cosmological inquiry. It argues that the historical style in cosmology was forged in the early decades of the 20^th century and continued to evolve in the century that followed. Over time, the scene of cosmological inquiry has gradually become dominated and entirely constituted by historicist explanations. Practices such as forwards and backwards temporal extrapolation (thinking about the past evolutionary history of the universe with different initial conditions and other parameters) are now commonplace. The non-static geometrization of the cosmos in the early 20th century led to inquires thinking about the cosmos in evolutionary terms. Drawing on the historical approach of Gamow (and contrasting this with the ahistorical approach of Bondi), the paper then argues that the historical style became a major force as inquirers began scouring the universe for fossils and other relics as a new form of scientific practice—cosmic palaeontology. By the 1970s the historical style became the bedrock of the discipline and the presupposition of new lines of inquiry. By the end of the 20th century, the historical style was pushed to its very limits as temporal reasoning began to occur beyond a linear historical narrative. With the atemporal ‘ensemble’ type multiverse proposals, a certain type of ahistorical reasoning has been reintroduced to cosmological discourse, which, in a sense, represents a radical de-historicization of the historical style in cosmology. Some are now even attempting to explain the laws of physics in terms of their historicity.     

Would two dimensions be world enough for spacetime?

We consider various curious features of general relativity, and relativistic field theory, in two spacetime dimensions. In particular, we discuss: the vanishing of the Einstein tensor; the failure of an initial-value formulation for vacuum spacetimes; the status of singularity theorems; the non-existence of a Newtonian limit; the status of the cosmological constant; and the character of matter fields, including perfect fluids and electromagnetic fields. We conclude with a discussion of what constrains our understanding of physics in different dimensions.     

Ψ-epistemic quantum cosmology?

This paper provides a prospectus for a new way of thinking about the wavefunction of the universe: a Ψ-epistemic quantum cosmology. We present a proposal that, if successfully implemented, would resolve the cosmological measurement problem and simultaneously allow us to think sensibly about probability and evolution in quantum cosmology. Our analysis draws upon recent work on the problem of time in quantum gravity and causally symmetric local hidden variable theories. Our conclusion weighs the strengths and weaknesses of the approach and points towards paths for future development.     

Edward Milne's influence on modern cosmology

During the 1930 and 1940s, the small world of cosmologists was buzzing with philosophical and methodological questions. The debate was stirred by Edward Milne's cosmological model, which was deduced from general principles that had no link with observation. Milne's approach was to have an important impact on the development of modern cosmology. But this article shows that it is an exaggeration to intimate, as some authors have done recently, that Milne's rationalism went on to infiltrate the discipline.