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1 Expansion of the Universe 宇宙的膨胀 1 Ricardo Moreno, Susana Destua, Rosa M. Ros, Beatriz García Colegio Retamar de Madrid, España Space Telescope Science Institute, Estados Unidos Universidad Politécnica de Cataluña, España Instituto en Tecnologías y Detección de Astropartículas, Argentina 国际天文联合会, 蕾塔唛氏学院 ( 西班牙马德里 ) 空间望远镜科学研究所 ( 美国巴尔的摩 )

2 Goals 目标 Understand what is the expansion of the Universe 理解宇宙的膨胀 Understand that there is no center of the Universe 理解宇宙没有中心 2

3 Goals 目标 Understand Hubble's Law 理解哈勃定律 Analyze how to detect dark matter 分析探测暗物质的方法 3

4 Presentation 介绍 This workshop is about: 本章节的主要内容有 : 4 The Origin of the Universe: Big Bang 宇宙的起源 : 大爆炸理论 Galaxies: do not "move" through space, the space is the one that expands. 并不是星系在空间中运动, 而是空间本身在膨胀

5 Presentation 介绍 5 The Hubble Constant : v = H d 哈勃常数 : v = H d There is no center of the universe, as there is no a central country 宇宙并没有中心, 就好比没有那座城市是地球的中心一样 The microwave background 微波背景辐射 Gravitational Lens. 引力透镜

6 Models, predictions, verification: Tablecloth Experiment 模型预测与验证 : 桌布实验 Prediction: if you pull quick a tablecloth on a table spread nothing on the table will fall out. If we verify, prediction is fulfilled. 预测 : 如果你快速抽出桌上的桌布, 那桌上的物品并不会掉落如果我们验证了, 就证明预测应验了 6

7 Models, predictions, verification: Tablecloth Experiment 模型预测与验证 : 桌布实验 The experiment works because the Physics is a discipline which permits predict what will happen: if one pull quick a tablecloth, there is no time for the action of the friction forces to act on the objects on the tablecloth and this explains why they do not fall. 这个实验会奏效是因为物理这个学科能够预测将会发生的情况 : 如果足够快速抽出桌布, 那么摩擦力将来不及影响桌布上的物体, 这就解释了物品为什么没有掉落 The Physics developed on Earth is the same than those which Astronomers apply to all the Universe. 地球上的物理学家所做的与天文学家应用于宇宙中 7 的是一样的

8 Movement towards red 1/3 红移 1/3 The scattered light of each element shows the lines: it is the spectrum, characteristic of each element. 各种元素的散射光线中有着如右图所示的线条 : 这就是光谱, 是每种元素的特征 8

9 Movement towards red 1/3 红移 1/3 Observing the light from galaxies, we see that the lines are shifted toward the red, and that the farther is the galaxy, the shift is greater. 通过观察星系的光谱, 我们发现谱线向红端发生了移动, 而且越是遥远的星系, 移动幅度越大 9 It is interpreted as a result of its movement away from us. 这是星系在远离我们而带来的现象

10 Movement towards red 2/3 红移 2/3 Nearby galaxies have relative small and irregular movements: the Large Magellanic Cloud +13 km/s, the Small - 30 km/s, Andromeda -60 km/s, M km/s. 临近的星系相对运动幅度较小, 且为不规则运动 : 10 大麦哲伦云为 +13 km/s, 小麦哲伦云为 -30 km/s, 仙女座为 -60 km/s, M 32 为 +21 km/s

11 Movement towards red 2/3 红移 2/3 In the Virgo cluster, (50 million l.y.), all galaxies are moving away from us at speeds between 1,000 and 2,000 km/s. 在室女座星系团 ( 五千万光年外 ), 所有的星系都在以 1000~2000 km/s 的速度远离我们 In the Coma Berenice supercluster, (300 million l.y.) the speeds are between 7,000 and 8,500 km/s. 在后发座超星系团中 ( 三亿光年外 ), 星系的退行速度达到了 7000~8500 km/s 11

12 Movement towards red 3/3 红移 3/3 In the opposite direction, M 74 moves away at 800 km/s and M 77 at km/s. 在另一侧,M74 的退行速度为 800 km/s,m 77 为 km/s If we observe distant and faint galaxies, the recession velocity is even greater: NGC 375 moves away at 6200 km/s, NGC 562 at km/s and NGC 326 at km/s. 如果我们观察那些遥远而且暗弱的星系就会发现, 它们的退行速度更大 : NGC 375 为 6200 km/s, NGC 562 为 km/s,ngc 326 为 km/s 12

13 Movement towards red 3/3 红移 3/3 Independently of the direction in which we observe, all, except the very close galaxies, move away from us. 通过我们的观测发现, 除了那些临近的星系, 其他各个方向上的所有星系都在离我们而去 13

14 Doppler effect 多普勒效应 An ambulance, a motorcycle, an approaching train we heard a high-pitched sound when moving away from us 当行驶中的救护车摩托车或者火车从身边经过时, 我们总能听见尖利的声音 High the wave is shortened 高音声波被压缩 Grave the wave is stretched 低音声波被拉伸 14

15 Activity 1: Doppler Effect 活动 1: 多普勒效应 The Doppler effect can be heard by rotating in a horizontal plane an alarm clock. 利用一个在水平面上绕转的闹钟, 我们就能听到多普勒效应 When it approaches the viewer, is shortened and the sound is higher pitched. 当闹钟靠近观众时, 波长就被压缩, 音调变高 15

16 Activity 1: Doppler Effect 活动 1: 多普勒效应 When it goes away from us, is stretched and the sound is lower pitched. 当闹钟远离观众, 波长就被拉伸, 音调变低 Happens the same as the sound of a motorcycle race, an ambulance, a train... 上面的现象和摩托车救护车火车经过我们身边产生的声音变化是同样的原理 This Doppler effect is due to the displacement. But this is not the Doppler effect that galaxies have with the expansion. 上述现象是由于位移引起了多普勒效应但是星系扩张形成的多普勒效应 16, 和上述并不一样

17 Activity 2. Stretch of photons 活动 2: 光子的拉伸 The Universe, when it expands, "stretches" the photons in it. 当宇宙膨胀时, 其中的光子会被拉伸 17

18 Activity 2. Stretch of photons 活动 2: 光子的拉伸 You can make a model of that stretch using a semi-rigid cable, which is used in electrical installations of houses. 你可以利用家用电器里的半刚性的电缆来做一个拉伸模型 The longer is the photon s path, they are more stretched. 光子运动的时间越长, 它的形变越明显 18

19 Hubble Law 哈勃定律 In 1930, Edwin Hubble realized that the most distant galaxies are moving away faster 年, 爱德温哈勃发现距离越远的星系退行速度越快 Hubble Law : v = H d 哈勃定律 : v = H d 19

20 Hubble Law 哈勃定律 They don't move through space: it is the space which expands, dragging the galaxies 星系并没在空间中移动, 而是空间发生了膨胀, 并把星系间的距离也拉大了 20

21 21 Activity 3: The Universe in a rubber 活动 3: 橡皮筋宇宙模型

22 Activity 4: The Universe in a balloon 活动 4: 气球宇宙模型 The distance between the "galaxies" increases with the expansion. 随着气球的膨胀, 星系间的距离也随之变大 The galaxies are not moving through the balloon 22 星系本身并未在气球上发生移动

23 Expansion of the Universe 宇宙的膨胀 23 1 The distance to the nearest Galaxies is obtained mainly from the period-luminosity relation of the Cepheid variable stars 1 我们与近邻星系间的距离主要是通过造父变星的周光关系得到的 : From the light curve is possible to obtain the period P 利用光变曲线可以得到周期 P

宇宙的膨胀 24 Universe Expansion of the From the relation period-luminosity the absolute magnitude M 利用周光关系可以得到绝对星等 M With these quantities, is possible to calculate the distance d=10

24 宇宙的膨胀 24 Universe Expansion of the From the relation period-luminosity the absolute magnitude M 利用周光关系可以得到绝对星等 M With these quantities, is possible to calculate the distance d=10 (m-m+5)/5 pc 利用以上参量可以计算出距离 d=10 (m-m+5)/5 pc To determine distances of the most distant galaxies the astronomers use one type of supernova with similar luminosities. 天文学家利用一类具有接近光度的超新星来确定最遥远星系的距离

25 Expansion of the Universe 宇宙的膨胀 25 2 The velocity of recession is measured in the spectrum: v ( / )*c 2 退行速度可根据光谱测得 : v ( / )*c

26 Expansion of the Universe 宇宙的膨胀 26 3 The Hubble constant is the slope of the line: v = H 0 d, where H 0 is the rate of expansion of the Universe: H 0 = 72 km/s/mpc 3 该直线的斜率即为哈勃常数 : v = H 0 d, 其中 H 0 是宇宙的膨胀速率 : H 0 = 72 km/s/mpc Fig. 1 from Freedman et al, 2001, ApJ, vol 553, p47.

27 Activity 5: Calculation of the Hubble constant 活动 5: 计算哈勃常数 Blue = Universe before expanding 蓝色是宇宙开始膨胀前的星系位置 Red = Universe after expanding 红色是宇宙膨胀后的星系所在位置 27

28 28 Activity 5: Calculation of the Hubble constant 活动 5: 计算哈勃常数

29 29

30 Big Bang 大爆炸 If we go back, there was a time when everything was united: Universe in expansion. 如果时光倒流, 我们会发现在某一刻宇宙万物都集中于一体 : 宇宙在不断膨胀 30

31 Big Bang 大爆炸 Georges Lemaître, solving the equations of relativity, came to the idea of an expanding universe that began as a cosmic egg. 乔治勒梅特解出了相对论方程的结果, 并萌生了正在膨胀的宇宙是源于宇宙蛋的想法 31

32 Big Bang 32 大爆炸 Name of the Big Bang: big explosion. 大爆炸理论, 顾名思义就是大规模的膨胀 Fred Hoyle, with certain antireligious prejudices, thought it seemed too consistent with the idea of a Creator 这个名字本来是天文学弗雷德霍伊尔出于偏见想出来的, 他认为这个名字就像造物主这个词一样可笑

33 Big Bang 大爆炸 S & T made a competition to rename it. 12,000 proposals. None was better. 美国的天空望远镜杂志针对大爆炸发起了一次更名活动活动共收到份建议, 但却无一能够撼动原本的大爆炸这个名字 33

34 Big Bang 大爆炸 Before the Big Bang? We know nothing. 对于大爆炸开始之前的事情, 我们一无所知 What was the cause? Why it happened? And why it has these physical laws? 发生的起因是什么? 为什么会发生呢? 为什么会遵循这些物理规律? Physics is about how the existing things work, not about why do they exist. 物理学家关心的是这些存在的物质是如何相互作用的, 他们并不研究这些存在的理由 34

35 Big Bang 大爆炸 Physics studies the matter from its origins (since the Big Bang), not before, nor it studies the reason or purpose of why it exists. These are philosophical, religious, but not scientific questions. 物理学家会研究这些物质自产生之时 ( 大爆炸时期 ) 起的种种, 但并不会研究这之前的情况, 也不会研究这些存在的理由和目的这些属于哲学宗教范畴, 并不是科学的问题 2 errors: make religion from science and doing the science from religion. They have their own field of study, method, and way of seeing the complex reality. 两个错误 : 从科学来获得信仰与根据信仰做科学这两者有着自己的研究领域和看待这个复杂世界的不同方式 35

36 Big Bang 大爆炸 Fluctuation of the quantum vacuum? 空间的量子涨落? Emptiness is not nothing, it exists. 量子真空不是一无所有, 而是存在的 Multiple Universes? Indemonstrable by definition. Non-Scientific theory 多重宇宙? 它的定义无法核实属于非科学的理论 36

37 Evolution of the Universe 宇宙的演化 37

38 Development of the Universe 宇宙的发展历史 38

39 Activity 6: There is not a spreading center 活动 6: 无中心的膨胀 100% 105% 39

40 Activity 6: There is not a spreading center 活动 6: 无中心的膨胀 40

41 Radiation 辐射 Radiation which became free at 380,000 years after the Big Bang. 在大爆炸发生后的 38 万年, 产生了微波背景辐射 41

42 Radiation 辐射 Over time as space expands, the photons expanded in wavelength. 随着时间流逝, 空间发生膨胀, 光子波长也变大了 It is now in the microwave region. 它目前处于微波波段 42

Microwave Background Radiation The COBE, WMAP and

radiation, each time more detailed, detecting small

galaxies began to form 微波背景辐射 COBE, WMAP 和 PLANCK

43 Microwave Background Radiation The COBE, WMAP and PLANCK missions made a map of the sky of that radiation, each time more detailed, detecting small fluctuations: imprints of lumps of matter from which galaxies began to form 微波背景辐射 COBE, WMAP 和 PLANCK 都对天空中的辐射给出了分布示意图, 并且越来越细节, 连微小的涨落也都探测到了 : 图中块状的物质分布的印记就是星系开始形成的地方 43

44 Activity 7: Cosmic background radiation 活动 7: 宇宙微波背景辐射 300,000 years after the Big Bang, the photons were separated from matter and began to travel freely through the universe. 在大爆炸过后的三十万年, 光子从物质中分离出来, 开始在宇宙间自由穿梭 44

45 Activity 7: Cosmic background radiation 活动 7: 宇宙微波背景辐射 By expanding the space, photons extended their wavelength, currently = 2 mm, equivalent to T = 2.7 K = -270 C. 随着空间的膨胀, 光子的波长也被拉大了目前 = 2 mm, 相当于温度为 2.7 K( 即 -270 C) 45

46 Activity 7: Cosmic background radiation 活动 7: 宇宙微波背景辐射 We can detect it with an analogue TV. In an empty channel, one out of ten points comes from microwave background radiation. 我们可以利用一台普通的电视来探测微波背景辐射把电视转到一个空台, 其中,10% 的雪花就来自于宇宙微波背景辐射 46

47 Dark Matter: Spin table which compensates the terrestrial gravity atraction 暗物质 : 旋转的台面抵消了地心引力 Black Holes are not visible, but we know that they exist because their gravitational attraction on that revolved around them. 黑洞是观测不到的, 但我们始终知道它的确存在, 因为在其周围绕转的物体都会受到其引力的作用 47

matter is invisible, one way to detect it is observing

48 Dark Matter: Spin table which compensates the terrestrial gravity atraction 暗物质 : 旋转的台面抵消了地心引力 Dark matter is invisible, one way to detect it is observing the behavior of the near objects. 暗物质也是不可见的, 探测其的方法之一就是观察其附近天体的运动轨迹 48

49 Other way to detect dark matter: gravitational lens 探测暗物质的其他方法 : 引力透镜 The mass of a gravitational lens acts like an optical lens distorting the surrounding space and deflecting the light of a distant object. 与光学透镜类似, 大质量的引力透镜体会使周围的空间和遥远天体发出的光线出现偏折 49

50 Gravitational lenses 引力透镜 Light always follows the shortest possible path 光线总是沿着两点间的最短路径传递 If the surface is curved, the line is curved 如果空间是弯曲的, 那么两点间的最短路径也是弯的 50

51 Why light bends when passing near a body? 当光线经过某个天体附近时为何会发生偏折? If a mass is present, space is curved and the shortest path between two points is a curve. 如果空间中某处存在一定质量, 那么空间就会弯曲, 那么两点间的最短路径也是弯的 A similar situation can be seen using the Earth globe. 这种情况在地球仪上也同样存在 51

52 How do gravitational lenses work? 引力透镜的原理是什么? For a convex optical lens, the lens focuses the parallel rays of light onto one point: the focus. 凸透镜会把多路平行光聚焦到一点焦点 52

53 How do gravitational lenses work? 引力透镜的原理是什么? For a gravitational lens, the lens focuses light rays on a line instead of a point; this can introduce several distortions in the image. 引力透镜体不会将光线聚焦到一点, 而是聚焦在一条线上, 这会造成图像的多种扭曲 53

54 Position changes and multiplication 位移和多重成像 54 The deflection produces the apparent position of star, galaxy, or quasar 恒星星系和类星体会出现明显的视位置偏离 Gravitational lenses are not perfect, the largest ones can produce multiple images. 引力透镜也非完美, 最大的透镜体甚至可形成多重成像

55 Deformation 形变 If the deflected body is an extended astronomical source, the resulting images produce a set of bright arcs. 如果背景天体是展源, 图像会被拉伸成光弧状 55

如果透镜系统是完美对称的, 那么光线会汇合, 并形成一个完整的光环 If the deflected body is

56 Deformation 形变 56 if the lens system is perfectly symmetrical, the rays converge and the result is a ring. 如果透镜系统是完美对称的, 那么光线会汇合, 并形成一个完整的光环 If the deflected body is a star or a quasar, the image is a point. 如果背景天体是恒星或者类星体, 那么图像将仍是点状

white wine on graph paper and look through the wine, you

57 Activity 8: Simulation of the space deformation with a glass of wine 活动 8: 利用一杯酒模拟空间形变 57 If you put the glass of white wine on graph paper and look through the wine, you can see this deformation. 把玻璃杯放在一张坐标纸上, 加入白葡萄酒, 透过液体观察坐标纸, 你会看到坐标线变形了

58 Activity 8: Fix a flashlight and move slowly while looking through the glass of wine 活动 8: 固定手电后, 透过装有红酒的酒杯观测, 并缓慢移动 58 This simple model shows that "matter" can reproduce distortions observed in the images to "through" it. 这个简单的模型说明, 透过物质看到的图像是会由于物质的影响而发生扭曲的

59 Activity 8: Fix a flashlight and move slowly while looking through the glass of wine 活动 8: 固定手电后, 透过装有红酒的酒杯观测, 并缓慢移动 Fragment of arc Amorphous figure Einstein cross. 光弧不规则图像爱因斯坦十字 59

60 Activity 8: Simulation of the deformation with the foot of a glass 活动 8: 利用玻璃杯底座模拟形变 60 if we place the base of a bowl on graph paper we can see the deformation. 把酒杯底座放在坐标纸上, 就能看到网格线的弯折

61 Activity 8: Looking through the bottom of a glass 活动 8: 透过酒杯底座看物体 Just cut the bottom of the glass. 截取酒杯的底座 61

62 Activity 8: Looking through the "bottom of a glass 活动 8: 透过酒杯底座看物体 Arc fragment Einstein Cross Einstein ring 弧形爱因斯坦十字爱因斯坦环 62

63 Why is it dark at night? 63 为什么夜晚是黑色的? Olbers suggested that if: 奥伯斯结论的前提假设为 : The universe is infinite in extent. 宇宙的面积是无穷大的 The number of stars is uniformly distributed throughout the universe. 恒星大体上均匀地分布在宇宙中 All stars have a similar luminosity throughout the Universe 全宇宙中恒星的亮度是相似的

64 Dark Night 黑夜 64 An infinite Universe will have an infinite number of objects and must be brilliant in the night 无穷大的宇宙中将有无穷多的天体, 所以夜空应该是亮如白昼的

65 Why is it dark at night? 为什么夜晚是黑色的? Then : 然后 : Any point on the sky would be bright, not black, since there would be always a distant star shining. 由于在任何方向上都应该有遥远的恒星在闪烁, 所以夜空在各个方向上都应该是明亮如昼的, 而非黑色的 65

66 Why is it dark at night? 为什么夜晚是黑色的? The number of stars in each "onion layer" of the sky is proportional to r 2, and their light is inversely proportional to r 2, where each layer provide the same amount of light at the Earth. If there are infinite layers, the sky should appear bright at night. 夜空中, 每一层中星星的数目正比于 r 2, 它们的亮度与 r 2 成反比, 所以在地球上接收到的每一层的光线总量应该是相同的如果有无数个这样的壳层, 夜空就应该看起来亮如白昼 66

由于宇宙膨胀, 越遥远的恒星看起来越红 ( 越暗 ) But above all, the sky doesn t have an infinite

67 Mistakes: 错误 : Why is it dark at night? 为什么夜晚是黑色的? Due to expansion, more distant stars look more reddish (less bright). 由于宇宙膨胀, 越遥远的恒星看起来越红 ( 越暗 ) But above all, the sky doesn t have an infinite age. There are no infinite layers of stars. 更重要的是, 宇宙的年龄也不是无限的, 所以也没有无穷多的恒星分布壳层 The night can be dark! 夜晚是黑色的! 67

68 Thank you very much for your attention! 谢谢! 68

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<4D6963726F736F667420576F7264202D2032303130C4EAC0EDB9A4C0E04142BCB6D4C4B6C1C5D0B6CFC0FDCCE2BEABD1A15F325F2E646F63> 2010 年理工类 AB 级阅读判断例题精选 (2) Computer mouse How does the mouse work? We have to start at the bottom, so think upside down for now. It all starts with mouse ball. As the mouse ball in the bottom