《Lecture5-Cosmology》由会员分享，可在线阅读，更多相关《Lecture5-Cosmology（228页珍藏版）》请在金锄头文库上搜索。
1、Lecture 5,Cosmology,2,宇宙何时开始、如何开始、为何开始？它将如何变化？它的最终命运又将如何？,3,How did the Universe begin? Does time have beginning & an end? Does space have edges? The questions are as old as human curiosity. But the answers have always seemed beyond the reach of science. . . until now!,The 21st Century,4,5,6,宇宙学研究历史
2、概述A brief history of cosmology ；宇宙的结构 The Structure of the Universe宇宙的一般图景 General Picture of the Universe ；牛顿的宇宙模型及其困难 Newtonian Universe and its Problems爱因斯坦的宇宙模型 Einsteins Universe 膨胀的宇宙模型 Expanding Newtonian Universe 宇宙的大尺度结构 Large Scale Structure of the Universe 宇宙的膨胀和演化 Expansion and Evolvemen
3、t of the Universe ；宇宙观测实验 Observational Experiments、宇宙微波背景辐射 Cosmic Microwave Background Radiation (CMBR)；黑洞 Black Hole；宇宙学重大前沿课题 Frontiers Problems and Recent Progress观测宇宙学的一些新进展；超弦理论与宇宙学的挑战暗能量理论研究现状概述反物质的寻找和理论研究现状,Outline,7,1. A brief history of cosmology,Basic conceptsspatial extentfinite (with e
4、dges)finite (unbounded)infiniteour locationEarth at centreSun at centresolar system near centresolar system far from centreno centre,past and futureboth finite(creation, future destruction)both infinite(no beginning, no end)finite past, infinite futuredynamicsstaticexpanding,8,Early ideas: astronomy
5、,Clearly understood concepts in Greek and Hellenistic astronomyshape and size of the Earth (Eratosthenes厄拉多塞 , BC 276-197)size and distance of the Moon (Aristarchos阿里斯塔克, BC 310-230)Sun is much larger than Earth (Aristarchos)exact value was wrong by a large factor: method sound in principle, impossi
6、ble in practice!Ideas raised but not generally acceptedEarth rotates on its axis (Heraclides赫拉克利德 , BC 387-312)Sun-centred solar system (Aristarchos),9,Early ideas: cosmology,Aristotle/PtolemyEarth-centred, finite, eternal永恒的, staticAristarchos/CopernicusSun-centred, finite, eternal, staticAt this t
7、ime, little observational evidence for Sun-centred system!,10,Newtonian Cosmology,Newtons Philosophiae Naturalis Principia Mathematica, 1687Newtonian gravity, F = GMm/r2, and second law, F = maApproximate size of solar system (Cassini, 1672)from parallax 视差 of Mars火星Finite speed of light (Ole Romer丹
8、麦天文学家罗默 , 1676)from timing of Jupiters木星moonsNo distances to starsNo galaxies,11,Resolution(s),Light is absorbed by intervening dustsuggested by Olbersdoesnt work: dust will heat up over time until it reaches the same temperature as the stars that illuminate it(Im not sure 17th century astronomers w
9、ould have realised this)Universe has finite sizesuggested by Keplerthis works (integral is truncated at finite r)but now Newtonian universe will definitely collapse,Universe has finite ageequivalent to finite size if speed of light finitelight from stars more than ct distant has not had time to reac
10、h us(currently accepted explanation)Universe is expandingeffective temperature of distant starlight is redshifted downthis effect not known until 19th century(does work, but does not dominate in current models),Olbers + Newton could have led to prediction of expanding/contracting universe,12,State i
11、n 1900,We knowspeed of lightdistance to nearby starsthe Earth is at least several million years oldOur toolkit includesNewtonian mechanicsNewtonian gravityMaxwells electromagnetism,We dont knowgalaxies existthe universe is expandingthe Earth is several billion years oldWe are worried aboutconflict b
12、etween geology and physics regarding age of Earthabout to be resolvedlack of aether drift,13,现代宇宙学的开端1916年，广义相对论正确地预言日全食时能看到掠过太阳边缘的星光发生1.75角秒的偏折，完满地解释了牛顿引力理论不能说明的水星近日点每百年前移43角秒的现象1917年，爱因斯坦率先把他的广义相对论应用于宇宙学研究，揭开了科学宇宙学的序幕1922年，弗里德曼在广义相对论的框架下，从理论上论证了宇宙要么膨胀，要么收缩，而不会保持静止1929年哈勃发现了哈勃定律，为弗里德曼的宇宙学模型提供了观测依据,
13、14,按目前测定的哈勃常数H，可估计出我们宇宙的开端“大爆炸”发生在距今137亿年宇宙中一切天体的年龄都不应超出这个“宇宙龄”上限借助卢瑟福开创的利用放射性同位素含量测定其年代的方法，人们测量了地球上最古老的岩石、“阿波罗号”的宇航员从月球上带回的岩石以及从行星际空间掉到地球上的陨石等样本，发现它们的年龄均不超过47亿年恒星的年龄可以从恒星演化理论来估计，得到银河系中最古老的恒星的年龄为100亿年150亿年用不同方法得到的天体年龄均与“宇宙龄”不矛盾,15,根据大爆炸理论算出，氦同氢的质量比应约为13观测表明，恒星、或星际物质中，氦与氢的比例大体与此相符对大爆炸模型是一个有力支持,16,2.
14、宇宙的结构,宇宙的结构宇宙的一般图景；牛顿的宇宙模型及其困难爱因斯坦的宇宙模型膨胀的宇宙模型宇宙的大尺度结构,17,1） 宇宙的一般图景,一般把宇宙与总星系同等看待，其空间范围半径约137亿光年左右。所谓宇宙结构，即指这个空间范围内的情况。宇宙由多个层次的大系统组成，其顺序为：星球、星团、星系、星系团、超星系团、总星系等。,18,宇宙总星系,星球：基元单位，包括恒星（例如太阳）、行星（例如地球）、卫星（例如月亮）、彗星（例如哈雷彗星）、流星等。 星团：由十个以上恒星组成，被引力束缚在一起的恒星群。两大类：疏散星团和球状星团。疏散星团一般包括十几个到几百个恒星，形状不规则。球状星团所包含的星球从
15、几万颗到几十万颗以上。,19,Galaxies（星系）,星系：由几十亿到几千亿颗恒星以及星际物质和尘埃物质等构成的天体系统，银河系就是一个普通的星系。可分为旋涡星系，椭圆星系及不规则星系三大类。旋涡星系一般有一个很亮的核心部份，另有两条或两条以上的旋臂从核心延伸出来，银河系属于旋涡星系。在椭圆星系中，恒星内密外疏地分布在椭球状范围内，椭圆形呈各种不同的偏心率，大多数小的星系属于这种星系。不规则星系则没有一定形状和密集核心，在全部观察到的河外星系中所占的比例不大。,20,What Are Galaxies?,Collection of billions of stars.Held togethe
16、r by gravity.,NGC 4603 and NGC 4881,21,Numbers of galaxies,There are around 41010 galaxies in the observable universe.Over 60% of galaxies are elliptical椭圆状的, fewer than 30% are spiral螺旋状的, and fewer than 10% are irregular.,22,The Andromeda galaxy (M31仙女座),离银河系最近的大星系,直径是16万光年，为银河系的2倍，距离我们大约220万光年,23,The M33 galaxy,The third largest galaxy,M33是一个中型的螺旋星系，因为它位在三角座内，所以也常被称为是三角座星系。M33的半径只有银河系的三分之一。由于M33离M31很近，所以有部份天文学家认为它是M31的一个卫星星系。,
