【１３个最伟大的天文发现（上）】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年正式确定为国际天文年,并将其主题定为“探索我们的宇宙”。即使你一点都不喜欢让人费解的天文学,也会偶尔仰望星空吧,毕竟那里有太多的神秘、太多的遐想。本次专题分上下两辑,为大家带来13个天文史上最伟大的发现。噢,别太担心,主持人很擅长以简单的语句解释深奥的天文理论,保证所有小盆友都能看得明白哦!快来参加这次发现之旅吧!By the way,记得关注下期发现哦!
　　
　　For most of human history, the only light we knew came from the sky, by day the sun, by night an uncountable
　　number of stars. From the beginning, our ancestors
　　believed that the sun and the stars were heavenly[神圣的],
　　out of this world. And they were right. We’ve been watching the sky for thousands of years, but until
　　recently, we couldn’t see well enough to understand our connection to the cosmos. But now our astronomical
　　vision has sharpened. We can see farther and clearer. We can observe objects that are invisible to human eyes. Our increasingly improving vision has allowed us to make great discoveries, revealing an astonishing
　　and wonderful universe. What follows are 13 of the greatest discoveries in astronomy.
　　
　　The Planets Move
　　Discoverer: Greeks
　　Our first great discovery happened over centuries as the first humans looked carefully at the sky in places like this, the empty cloudless deserts of the American southwest, the Middle East, Africa and South America. Of these ancient astronomers the most important were the
　　Mesopotamians注1. They considered the objects in the sky gods, and built giant towers so they could record the rising and setting of the sun, the moon and the stars. For more than 1,000 years, they used clay tablets[小平板] to
　　record what they saw.
　　After the Mesopotamians made the first records, it was the Greeks who took the next step.
　　Owen Gingerich (Astronomy professor): Some of the Greek astronomers made a field trip[实际考察旅行] out to Mesopotamia to find out what had been going on there. And they seem to have brought back some systematic records, so that ultimately, it gave the basis for making a mathematical theory of the motion of the planets.
　　From their observations, the Greeks developed a
　　vision of the solar system that would stand for some 2,000 years � that the planets move, revolving[绕转] around the Earth. It would take our next great discovery to set the
　　record straight[澄清问题].
　　
　　The Earth Moves
　　Discoverer: Nicolaus Copernicus
　　As a young man, Copernicus had studied the heavens and found that the Greek’s earth-centered system failed when it came to predicting planetary[行星的] motion. He
　　began to wonder if the Earth itself moved.
　　Copernicus realized that the movements of the
　　planets were better explained if the sun were at the centre of the solar system and the Earth circled it like an ordinary planet. It was a revolutionary insight.
　　Nye: This idea, this…this book注2, changed the world.
　　Gingerich: Yes, because it made the Earth a planet and it fixed the sun in the centre. If you don’t have that
　　blueprint, you don’t march ahead to the physics…the physics of the cosmos.
　　
　　Planetary Orbits Are Elliptical [椭圆的]
　　Discoverer: Johannes Kepler
　　Everyone from the Greeks to Copernicus assumed the orbits of the planets had to be circular[圆形的], but in 1571 German mathematician Johannes Kepler shattered[使粉碎] that assumption with our next great discovery.
　　Lacking calculus[微积分], Kepler improvised[即席创作]
　　ways to compute[计算] the circular orbit of Mars. The work was tedious[冗长乏味的]. Kepler wrote that he was, “almost
　　driven to madness considering and calculating the
　　matter.” His calculations began to reveal that the
　　accepted notion of planets moving in circles simply did not work. Then a new idea came to him.
　　Gingerich: Kepler
　　realized somehow the sun had to be driving the planets in some way that he didn’t fully understand, and to get a
　　self-consistent[首尾一致的]
　　picture, he found that an ellipse was the path rather than a circle.
　　With this breakthrough, Kepler had devised the first method for accurately predicting the movement of the planets and stars across the sky.
　　Gingerich: When his tables predicted the planet Mercury to pass across the front of the Sun, and nobody else’s tables were close, that was dramatic proof of the accuracy of his astronomy that linked the motions of the planets solidly to the sun. This was a very important point to help stress the idea that the Copernican sun-centered system really had physical significance.
　　Despite the success of Kepler’s theory, many
　　remained skeptical[怀疑的] that the sun could be the center of the solar system. But the final nail in that
　　coffin[一锤定音的证据] was about to be driven home[把……讲透彻] by a man who, like Kepler, preferred to use observational evidence to form his theories. And that man was Galileo Galilei.
　　
　　Jupiter Has Moons
　　Discoverer: Galileo Galilei
　　The year is 1609, and Galileo is fascinated with a new invention called a telescope. Galileo turned his
　　telescope skyward[朝天空] and was the first to see the mountains on the moon and the star clusters[星团] of the Milky Way. Then an extraordinary sight, a group of four small, bright stars arranged around the planet Jupiter. This was the moment of discovery. Galileo realized that the stars were actually four moons orbiting Jupiter.
　　Here was proof that Copernicus was right about the structure of the solar system. If moons could orbit Jupiter, then the Earth could orbit the sun. And Galileo’s discovery demonstrated[证明] that knowledge in astronomy can only be advanced by actual observation. A theory can only be viable[可行的] when it’s supported by the facts, just like our next great discovery.
　　
　　Halley’s Comet
　　Discoverer: Edmund Halley
　　For centuries, comets had been considered
　　harbingers[前兆] of evil. By the end of the Middle Ages, a comet’s appearance invoked[引起] fear and terror. But
　　Renaissance[文艺复兴(的)]
　　scientist Edmund Halley, like Galileo, was interested in facts not superstition[迷信].
　　In 1695, he began searching for records of ancient and recent comet sightings. He found 24 comets whose passage across the sky had been recorded with enough
　　detail to allow him to roughly plot their orbits. To his surprise, he found that three of the comets seemed to follow the same approximate[近似的]
　　orbit, circling the sun every 76 years. Halley was so certain of the comet’s orbit that he made a bold prediction. He said the comet would return in the year 1758.
　　Gingerich: And guess what, the comet came
　　back.
　　Unfortunately Halley was no longer alive to savor[品尝] his discovery. Since then Halley’s Comet, as it’s known, has been greeted three more times by excited sky watchers across the globe.
　　No longer a harbinger of evil, Halley’s Comet became a milestone discovery in the history of astronomy,
　　replacing a superstitious belief with a rational[理性的]
　　scientific understanding of the physical universe.
　　
　　Milky Way Is a Disk of Stars
　　Discoverer: William Herschel
　　In the 18th century, William Herschel was a classically-trained musician, whose love of astronomy led him to give up music and turn his attention to the heavens, thus setting the stage for our next great discovery.
　　Gingerich: When he discovered the price of a
　　refracting telescope[折射望远镜], which was beyond his means[超出某人的财力], he decided to make his own, and he became the most fabulous and successful telescope builder of that period.
　　He used his telescopes to methodically[有条理地]
　　survey the sky, cataloguing[为……编目] what he saw.
　　Gingerich: As he was searching the sky, he came across an object that looked a little bit different � turned out to be a new planet. That was the next planet
　　beyond Saturn, the planet Uranus.
　　Uranus was the first new planet to be identified in more than 3500 years.
　　But finding a new planet was nothing compared to Herschel’s larger goal. He built a powerful 20-foot telescope, then divided the sky into equal sections and began to systematically count the stars in each field. It was a painstaking[不辞劳苦的], monumental[重要的] task. Slowly Herschel’s star count[恒星计数] began to reveal something extraordinary. The Milky Way was much larger than anyone knew. It was a gigantic[巨大的] disk of stars. Some of its fields were jam-packed[挤的]. One showed more than a quarter of a million stars alone. Other fields farther away were practically empty. Herschel’s discovery was a revelation[启示].
　　Gingerich: What Herschel was seeing was, oh, a small range[区域] like this注3, maybe that big…So it was really a small part of the entire Milky Way.
　　But even that small part significantly changed the study of astronomy. Herschel’s discovery
　　revealed that our solar system was just an island in a deep and expansive universe.
　　
　　在人类史的很长一段时间,我们仅知的光亮来自天空。白天是太阳,夜晚则是不计其数的繁星。从一开始,我们的祖先便笃信太阳星辰都是神圣的,不属于凡尘世界。的确如此。人类观察星空持续千年,然而直至近代,我们的观察并不足以让我们很好地了解人类自身与宇宙之间的联系。如今,随着天文视野变得更为敏锐,我们能观察得更远、更清晰,也能观察到肉眼无法辨识的星体。不断扩大的视野使我们取得众多重大发现,揭开了宇宙奥妙神奇的面纱。接下来,我将为大家带来13个天文史上最伟大的
　　发现。
　　
　　地心天动说
　　发现者:希腊人
　　(天文史上)第一个伟大的发现历时数百年。当时,人类在一些空旷无云的地方――美国西南、中东、非洲及南美等地的沙漠首次仔细观察星空。在这些古代天文学家中,最为重要的是美索不达米亚人。他们将天空的星体视为神明,建造高塔以观察记录日月星辰的升降运行。一千多年来,他们使用泥板记录观察结果。
　　美索不达米亚人写下第一批天文记录之后,希腊人对其予以继承
　　发展。
　　欧文・金格里兹(天文学教授):一些希腊天文学家到美索不达米亚做实地考察,想知道当地人在研究什么。他们带回来一些系统的记录,这些记录最终为他们提出行星运动的数学理论奠定了
　　基础。
　　希腊人从观察中发展出一套两千多年来屹立不倒的太阳系理论。这个理论就是“地心天动说”――星体围绕地球运转。直到我们得出下一个伟大发现,这个理论才得到更正。
　　
　　日心地动说
　　发现者:尼古拉斯・哥白尼
　　年纪尚轻时,哥白尼就已经开始研究星空。他发现古希腊的地心天动说无法正确预测星体的运行。他开始怀疑地球本身是否也在运转。
　　哥白尼发现,只有当太阳成为太阳系中心,而地球作为普通行星围绕其运行,这个理论才能更好地解释星体的运转。这是一项革命性的见解。
　　尼尔:这个观点……这本书改变了世界。
　　金格里兹:是的,因为它将地球视为一个行星,太阳则为(太阳系的)中心。如果你没有这样的远见,就无法发展出物理学……宇宙物理学的理论。
　　
　　椭圆轨道定律
　　发现者:约翰尼斯・开普勒
　　从古希腊人到哥白尼,所有人都认为行星轨道是正圆形。但是在1571年,德国数学家约翰尼斯・开普勒以我们的下一个伟大新发现推翻了这个猜想。
　　在没有微积分的情况下,开普勒灵机一动,用新的方法变换着计算火星的运行轨道。这是一项相当枯燥的工作。开普勒曾写道,自己“尝试过无数不同的推理和计算,几近疯狂”。他的计算结果显示,我们一直习以为然的“行星依照正圆轨道运行”这个观点根本不成立。于是他产生了一个新的想法。
　　金格里兹:开普勒认为太阳以某种他不太理解的方式驱使行星绕其运行。为了让自己的推论前后一致,他发现(火星绕行轨道)是一个椭圆而不是正圆。
　　在这个突破性理论的帮助下,开普勒制定出第一个能准确预测星体在天空中运行的轨迹的方法。
　　金格里兹:当时,他的法则准确预测到“水星凌日”,其他人的法则无一能及,这有力地证明了其天文学理论的精确性,也证明了行星运行与太阳有密切关系。同时,它进一步证明哥白尼日心说确实具有重大意义。
　　尽管开普勒的理论验证成功,但仍有许多人对“太阳是太阳系的中心”一说存有怀疑。最后的铁证来自一个人,他与开普勒一样,更喜欢通过实际观测证据得出理论,这个人就是伽利略・
　　伽利莱伊。
　　
　　木星有卫星
　　发现者:伽利略・伽利莱伊
　　时间来到1609年,伽利略沉迷于一种叫“望远镜”的新发明之中。伽利略用自制的望远镜观测天体,并且首次观察到月球表面的山丘以及银河中的无数星团。随后,他发现了一个很不寻常的景象:木星的四周围绕着四颗闪亮的小星星。这是历史性的发现。伽利略发现,那四颗星星其实是绕行木星的卫星。
　　这个发现也证明了哥白尼太阳系架构理论的正确性。如果卫星能围绕木星运行,那么地球也可以围绕太阳运行。伽利略的发现还证明了一点:只有实际观测才能让天文新知得到进一步发展;只有得到事实作证,理论才得以生存。下一个伟大发现亦是如此。
　　
　　哈雷彗星
　　发现者:埃德蒙・哈雷
　　数百年来,彗星被视为不祥之兆。中世纪末期,彗星的每次出现都会引发极大的恐慌。但是,文艺复兴时期科学家埃德蒙・哈雷跟伽利略一样,相信事实而非迷信。
　　1695年,他开始寻找古今有关彗星的观测记录。他发现,记载中有24颗彗星的资料足以供其粗略地绘出运行轨迹图。令他惊讶的是,其中三颗彗星似乎遵循着相似的运行轨迹,每隔76年绕行太阳一周。哈雷对这颗彗星的轨道信心十足,于是做出大胆预测。他断言,这颗彗星将于1758年再次出现。
　　金格里兹:猜猜结果如何?彗星真的
　　回来了。
　　可惜哈雷未能亲眼见证自己的预测成真。此后,这颗彗星被称为“哈雷彗星”,全球兴奋至极的观星迷后来三次目睹了它的造访。
　　哈雷彗星不再是不祥之兆的象征,它的发现成为天文史上一个重要的里程碑――传统迷信被对真实宇宙的理性科学研究所取代。
　　
　　银河是盘状星系
　　发现者:威廉・赫歇尔
　　威廉・赫歇尔是18世纪一位专业的古典音乐家。因为热爱天文学,他放弃了音乐转而研究起星象来,从而引出了下一个伟大的发现。
　　金格里兹:当他发现自己买不起一具折射望远镜时,赫歇尔决定自己动手制作。后来,他成了当时最杰出、最成功的望远镜制作专家。
　　他用自制的望远镜系统地观测星空,并(将星象)进行分类记录。
　　金格里兹:在他观测星空时,他发现了一颗不同寻常的星体,那是一颗新行星。它就是比土星更遥远的行星――
　　天王星。
　　天王星是3500多年间被发现的第一颗行星。
　　然而,与赫歇尔所追求的、更伟大的目标相比,发现一颗新行星简直不值一提。他建造了一座高达20英尺(6米)的高倍望远镜,将星空平均分为多个区域,系统性地记录每一个星区里的星星。这是一项煞费苦心,但也意义非凡的工程。慢慢地,赫歇尔的恒星计数显示出一些不寻常的现象。银河远比任何人想象的海要大。它是一个巨大的盘状星云。某些区域挤满了星星,其中一块竟包含了25万颗星星。但一些遥远的星区却空空如也。赫歇尔的发现是一个新的启示。
　　金格里兹:赫歇尔当时观测新的星空只有,呃,只有这么一点大的星区,大概只有这么大……那实际上只占了整个银河系很小的一部分。
　　但是,即便是这么小的一部分,已经给天文研究带来重大影响。赫歇尔的发现证明,我们的太阳系只是宽广且深远的宇宙中的一个小岛。
　　
　　注1:美索不达米亚平原的绝大部分位于今天的伊拉克境内和叙利亚东北部,原为波斯湾的一部分,是位于底格里斯河及幼发拉底河之间的一片冲积平原。平原北部是亚述,南部则是古代四大文明的发源地之一――有高度发达的文明的巴比伦。
　　注2:“这本书”指的是哥白尼的著作《天体运行论》(On the Revolutions of the Heavenly Spheres)。
　　注3:当时金格里兹教授正拿着一个银河的模型给主持人进行解说。