【１３个最伟大的天文发现（中）】世界上最伟大的天文家

　　为纪念伽利略首次使用望远镜进行天文观测400周年,在国际天文学联合会和联合国教科文组织的共同倡议下,联合国大会将2009年正式定为国际天文年,并将其主题定为“探索我们的宇宙”。上期“专题”,小编为大家带来了天文史早期的六个最伟大发现,由于后七个发现篇幅较长,原定分上下两期的节目不得不延长至三期。本期将带来四个新发现,最新发现请关注下期“专题”。
　　
　　General Relativity
　　Discover: Albert Einstein
　　Thanks to the musings[沉思] of an obscure[无名的]
　　clerk working in a Swiss patent[专利权] office, our next great discovery revealed that the universe is a strange mysterious place. That clerk was Albert Einstein.
　　In the early 1900s, he was puzzled, along with the rest of the scientific community, by the orbit of the planet Mercury. Despite the ability of Newton’s laws of gravity to precisely predict the motion of the planets, the laws failed when it came to correctly predicting Mercury’s orbit. The puzzle had to do with Mercury’s perihelion[近日点], that point in its orbit where it’s closest to the sun. Every century Mercury’s perihelion advanced slightly, a change that Newton’s equations[方程] could not account for.
　　In a bold and startling move, young Einstein proposed his own theory to explain the puzzle of Mercury’s orbit and in the process developed a theory that refined Newton’s laws of gravity. Einstein believed that his concept of “curved space” was responsible for shifting Mercury’s orbit.
　　Einstein called his idea, “the theory of general relativity.” The idea that space itself was warped[扭曲] by mass was too strange for many to accept. An approaching solar eclipse[日蚀] gave scientists the perfect opportunity to put Einstein’s new theory to the test. Photographs were taken of the background stars before the eclipse, and then afterwards. These pictures were then compared with photos taken during the eclipse. The photos showed that the positions of the stars in the eclipse photo shifted slightly inward, bending as the light from the stars passed the sun’s gravitational field. Einstein’s theory of general relativity was right. His great discovery rocked the world.
　　
　　The Universe Is Expanding
　　Discover: Edwin Hubble
　　General relativity had shown that space was weirder than anyone could imagine; anyone but Einstein, that is. To gain a clearer understanding of this strange universe, astronomers needed more observational data, and that required larger, more powerful telescopes, like the one that lead to our next great discovery.
　　When the Herschels注 had finished their survey of the heavens in the 1830s, they had catalogued thousands of these beautiful but hazy[朦胧的] objects, then called “white nebulae[星云].” At the time, no one knew whether they were part of our galaxy or distant island universes like the Milky Way.
　　In 1924, astronomer Edwin Hubble was studying the stars in several of these nebulae using a 100-inch reflector telescope at the Mount Wilson Observatory in California. The telescope enabled Hubble to estimate that the galaxies were routinely many hundreds of thousands, even millions, of light years away. Here were objects as huge and as populated with stars as our very own Milky Way galaxy, which is why we today call white nebulae “galaxies.” The more Hubble studied these galaxies, the more he became intrigued[激起好奇心].
　　At the time, scientists knew that a beam of light from a star appears as a different color on the spectrum[光谱]. The color changed according to the motion of the star. A shift toward the blue end of the spectrum meant the star was moving closer to earth. A red shift meant it was moving away. The amount of the color shift also revealed the speed of that movement. Hubble found that when he measured the distance of a galaxy, its spectrum almost always was shifting to the red. And something else � the farther the distance, the greater the red shift. In other words, the universe was expanding. It was an astonishing discovery with profound implications. Measuring backwards from the expansion, scientists found that the universe appeared to have a cataclysmic[洪水的] beginning, what one astronomer labeled, “the Big Bang.”
　　
　　Milky Way Emits Radio Waves
　　Discover: Karl Jansky
　　Just three years after Hubble discovered the expanding universe, our next great discovery revealed a mysterious object hidden behind the dust at the center of the Milky Way, and gave birth to a whole new branch of astronomy using wave lengths invisible to the human eye.
　　In 1930, Karl Jansky was a 25-year-old physicist working for the Bell Laboratories in Homedale, New Jersey. Jansky’s job was to identify the kinds of interference[干扰] occurring at the 15-meter wave length then used for ship-to-shore and transatlantic communication. After spending more than a year recording data, Jansky decided there were three forms of static[静电干扰] at this
　　frequency. The first was clearly produced in the earth’s ionosphere[电离层]. The second was caused by local thunderstorms. And the third signal was mysterious, continuous. It was coming from what appeared at first to be the sun. Each morning this signal slowly rose with the sun. During the day it rotated[旋转] across the sky, and then it set when the sun did. But as time passed, Jansky found that the mysterious radio signal slowly drifted[偏离] away from the sun, as if it were coming from a point outside the solar system. Eventually Jansky pinpointed[精确定位] its location as somewhere in the region of the constellation[星座] Sagittarius[人马座]. He believed he had discovered an unknown interstellar[星际的] object at the center of the galaxy, and he was right. Later astronomers confirmed that Jansky had discovered a super-massive “black hole,” equal in mass to three million suns. Perhaps even more significant, he was the first human to look at the universe using radio astronomy, a whole new way to study the sky.
　　It was a landmark discovery. Jansky had proved that the sky does not merely sparkle with the gentle glow of starlight. Hidden out there are many strange objects, many light years away, that actually radiate more energy than whole galaxies, like quasars[类星体] and pulsars[脉冲星], dead stars spinning madly with masses so dense that a single teaspoon would weigh millions of tons.
　　Before astronomers could even begin to understand the life and death of stars, new telescopes would have to be built that could look at the sky in many different wavelengths. Before that could happen, though, radio astronomy produced another great discovery that, although predicted, was as unexpected by its discoverers as Jansky had been. And once again it happened at Bell labs in Homedale, New Jersey.
　　
　　Cosmic Microwave Background Radiation
　　Discover: Arno Penzias and Robert Wilson
　　In 1964, Bell labs had this spare 20-foot microwave antenna[天线] sitting dormant[未用的]. Rather than destroy it, the lab decided to let astronomers use it for research. Two physicists, 31-year old Arno Penzias and 28-year old Robert Wilson, decided to use the antenna for measuring the temperature of the gas halo[(日月周围的)晕轮] surrounding the Milky Way galaxy. What happened next is one of the most exciting discoveries in modern astronomy.
　　At the time that Penzias and Wilson detected the radio static, there were two competing theories about the origin of the universe. There was the Big Bang Theory, which Hubble’s expanding universe supported. Then there was the Steady State Theory, which proposed that the universe is timeless, with no beginning or end, expanding forever. When a friend heard what Penzias and Wilson had found, he suggested they get in touch with some cosmologists[宇宙学家] at Princeton University, who were advocates[拥护者] of the Big Bang Theory. They believed that a Big Bang would have left a faint thermal[热的] afterglow[残光] in the universe, traces of heat from the roar of the bang itself, detectable across the entire sky, and they were about to conduct research in hopes of measuring that afterglow.
　　Nye: So what does your discovery mean?
　　Wilson: Well, it means that we live in a Big Bang universe and that we’re seeing the radiation from 300,000 years after the Big Bang. In many cases, when there’s a paradigm[范例] shift in science, it takes a generation before people really accept it, but in this case I think the world was ready for it. Human societies have always worried about where they came from. There’re religious stories in every civilization that’s ever been found, and I think we have a definitive answer that we came out of a Big Bang.
　　
　　广义相对论
　　发现者:艾伯特・爱因斯坦
　　多亏了一位无名小职员在瑞士专利局沉思研究,我们的下一个伟大发现(才得以)揭示出宇宙是一个奇特而又神秘的地方。那位职员就是艾伯特・爱因斯坦。
　　在20世纪初期,爱因斯坦与所有科学家一样,对水星绕太阳运转的轨道感到十分困惑。虽然牛顿的万有引力定律能够精确预测行星的运转,却无法正确预测水星的绕行轨道。问题出在水星的近日点上――即水星运行时最靠近太阳的位置。每100年,水星的近日点都会略微前移,而牛顿的力学公式却无法解释这个变化。
　　年轻的爱因斯坦提出了大胆惊人的假设,用自己的一套理论来解释水星轨道运行之谜,同时也完善了牛顿的万有引力定律。爱因斯坦相信,正是“空间弯曲”使水星的轨道发生移动。他将自己的想法称为“广义相对论”。很多人难以接受“空间被质量所扭曲”这个概念。一次将至的日蚀给了科学家一个绝佳的机会来验证爱因斯坦的新理论。他们在日蚀前后拍摄下背景群星的照片,随后将这些照片与日蚀期间拍摄的进行对比。照片显示,日蚀期间群星位置略向内移,星光经过太阳的重力场的时候产生了弯曲。爱因斯坦的广义相对论是正确的。他的伟大发现震撼了全世界。
　　
　　宇宙在膨胀
　　发现者:埃德温・哈勃
　　广义相对论让我们知道,太空比人们所想象的还要玄妙,大概只有爱因斯坦能想到这一点。为了进一步了解这个奇妙的宇宙,天文学家需要更多观测数据,而那就意味着需要更强大的高倍望远镜,例如这具带领我们迈向下一个伟大发现的望远镜。
　　19世纪30年代,当赫歇尔一家完成了星象观测的时候,他们记录下了数千个当时被称为“白星云”的美丽的朦胧星体。当时,没有人知道它们是隶属我们的银河系,还是更遥远且类似于银河的独立星系。
　　1924年,天文学家埃德温・哈勃在(美国)加利福尼亚州威尔逊山天文台使用一具100英寸(25.4米)的光学反射式望远镜研究数个白星云里的星体。这具望远镜让哈勃能估算出这些星系与我们有着数十万,甚至数百万光年的固定距离。它们也如同我们的银河系一般庞大且满布繁星。这也是为什么我们今天把白星云改称为“星系”。哈勃对星系的研究越深,他的兴趣就越大。
　　那时,科学家们已经知道恒星的光线在光谱上可能出现不同的颜色,并且颜色随恒星的运行而改变。光谱上朝向蓝端的位移代表该恒星正向地球靠近,越向红端则代表它正远离地球。位移量也可以显示该恒星的运动速度。在测量星系的距离时,哈勃发现光谱总是出现红移(即远离地球)。不仅如此,距离越远的星系红移量越大。换句话说,宇宙正在扩张。这项惊人发现具有深远意义。从扩张推算回来,科学家发现宇宙的起源似乎异常剧烈。其中一位天文学家将之称为“大爆炸”。
　　
　　银河系发射无线电波
　　发现者:卡尔・詹斯基
　　就在哈勃发现宇宙扩张现象之后三年,另一个伟大发现揭示出在银河中心的星尘背后隐藏着一个神秘的星系,由此诞生了全新的天文学分支,促使人们使用肉眼看不见的无线电波来研究星体。
　　1930年,25岁的物理学家卡尔・詹斯基在(美国)新泽西州赫姆戴尔市的贝尔实验室工作。詹斯基的工作是识别影响15米波长的各种干扰。该波长的电波当时被用于船对海岸及横跨大西洋的通讯。经过一年多的记录,詹斯基发现有三种静电会干扰这种频率的电波。第一种很明显产生自地球的电离层,第二种是当地雷电造成的,第三种则是神秘又稳定的杂讯,刚开始,这种干扰看似来自太阳。每天清晨,这种讯号随着太阳一起缓缓上升,白天时持续通过天空,日落时也随之静止。但是后来,詹斯基发现这种神秘的电波缓慢地偏离太阳,似乎是来自太阳系以外的某一点。最后,詹斯基终于确切指出它来自人马座。他相信自己发现了存在于银河系中心的某个不知名的星体。他是对的。不久后,天文学家确认詹斯基发现了一个超重黑洞,其质量相当于三百万个太阳。或许更重要的是,他是以电波天文学观测宇宙的第一人。这是研究天空的全新方法。
　　这是划时代的新发现。詹斯基的发现证明天空中不只有温柔的闪闪星光,还有许多奇怪的星体隐藏在外太空。在许多光年之外,它们所放射的巨大能量远远超出整个银河系的总和,比如类星体、脉冲星以及疯狂旋转的死星――其产生的物质密度之高,可能一小茶匙(这样的物质)就重达数百万吨。
　　在天文学家开始了解恒星的诞生和死亡之前,他们必须建造新型的望远镜以利用各种不同波长的电波观测星空。而在建造好这些望远镜之前,电波天文学又有一个新的发现。虽然可以预期到,其发现者仍和詹斯基一样颇感意外,发现地点也是在新泽西州赫姆戴尔市的贝尔实验室。
　　
　　宇宙微波背景辐射
　　发现者:阿诺・彭齐亚斯和罗伯特・威尔森
　　1964年,贝尔实验室有一具闲置不用的20英尺(6.6米)微波天线。与其销毁,实验室决定给天文学家用于研究。两位物理学家――31岁的阿诺・彭齐亚斯和28岁的罗伯特・威尔森决定用此天线测量银河系外围光晕的温度,从而引出了近代天文学史中最激动人心的发现。
　　在彭齐亚斯和威尔森探测电波干扰的时期,科学界有两种关于宇宙起源的理论争执不下。一种是大爆炸理论,由哈勃的宇宙膨胀理论作为支持;另一种是稳态学说理论,它假设宇宙是无穷的,根本没有起点或终点,永远在扩张。当一个朋友听说彭齐亚斯和威尔森的发现时,他建议两人联络普林斯顿大学主张大爆炸理论的宇宙学家。这些科学家相信,大爆炸之后会有微弱的热余光残留在宇宙中,那是大爆炸本身留下的余温踪迹,在整个天空都可以探测到。他们正准备着手研究,希望测量到余光。
　　纳尔:那么,你们的发现意味着什么?
　　彭齐亚斯:它表明我们身处于宇宙大爆炸中。我们看到了大爆炸30万年后的辐射。很多时候,当科学有典型转变时,往往要经过一代人才能被广为接受。但就这个案例来说,我想全世界都已经作好接受它的准备了。人类一直在思考自己的起源,每一个已知的文明都有与此相关的宗教故事。我相信我们找到了明确的解答,那就是我们起源于宇宙大爆炸。
　　
　　注:这里的赫歇尔一家指的是威廉・赫歇尔及其妹妹卡罗琳、儿子约翰。卡罗琳一直作为哥哥的研究助手(现认为是合作者),共同制作星云和星团表。而威廉的儿子约翰也是当时一位伟大的科学家,在父亲无法视事时扩充和修订了其研究计划,亲赴南非制作了南天的星云星团表。他写的科普书《天文学概要》于1849年出版,堪称当时的《时间简史》。他在1837年的维多利亚女王加冕典礼上被封为准男爵。赫歇尔一家的努力,开辟了观测天文学时代,为20世纪的天文学发展建筑了舞台。关于威廉・赫歇尔的伟大发现请查看上期“专题”。