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2019年07月19日 06:21:14 | 作者:健康资讯 | 来源:新华社
Astronomers said on Wednesday that they had discovered a lost generation of monster stars that ushered light into the universe after the Big Bang and jump-started the creation of the elements needed for planets and life before disappearing forever.天文学家在周三表示,他们发现了失踪的一代巨型恒星,是它们在宇宙大爆炸之后将光照入宇宙,并在永远消失之前,瞬间启动了星球及生命所需要的所有元素的创造。Modern-day stars like our sun have a healthy mix of heavy elements, known as metals, but in the aftermath of the Big Bang only hydrogen, helium and small traces of lithium were available to make the first stars.太阳等现代恒星拥有大量重元素,也就是金属元素,但在宇宙大爆炸之后,构成第一代恒星的元素只有氢、氦和少量锂。Such stars could have been hundreds or thousands of times as massive as the sun, according to calculations, burning brightly and dying quickly, only 200 million years after the universe began. Their explosions would have spewed into space the elements that started the chain of thermonuclear reactions by which subsequent generations of stars have gradually enriched the cosmos with elements like oxygen, carbon and iron.根据计算,此类恒星的质量可能是太阳质量的数百或数千倍,这些形成于宇宙大爆炸后2亿年的恒星猛烈燃烧,迅速消失。它们的爆炸应该向太空喷射了开启一系列热核反应的元素,后续的几代恒星通过热核反应逐渐为宇宙增添氧、碳、铁等元素。Spotting the older stars in action is one of the prime missions of the James Webb Space Telescope, to be launched by NASA in 2018. The discovery of such stars “would be wonderful,” James Peebles, a Princeton professor and one of the fathers of modern cosmology, said recently.寻找有活动的古老恒星是美国国家航空航天局(NASA)詹姆斯·韦伯太空望远镜的主要任务之一,该望远镜将于2018年发射。普林斯顿大学(Princeton)教授詹姆斯·佩布莱斯(James Peebles)最近表示,发现此类恒星“会是一件非常美妙的事情”,他是现代宇宙学奠基人之一。Now, in a paper to be published in The Astrophysical Journal, an international crew of astronomers led by David Sobral of the University of Lisbon, in Portugal, and the Leiden Observatory, in the Netherlands, said they had spotted the signature of these first-generation stars in a recently discovered galaxy that existed when the universe was only about 800 million years old. Its light has been traveling to us for 12.9 billion years, while succeeding generations of stars have worked their magic to make the universe interesting.在《天文物理期刊》(The Astrophysical Journal)即将刊登的一篇论文中,由葡萄牙里斯本大学(University of Lisbon)的戴维·索夫拉尔(David Sobral)、荷兰莱顿天文台(Leiden Observatory)带领的国际天文学家小组表示,他们在最近发现的星系中找到了第一代恒星的识别标志,该星系在宇宙只有大约8亿年历史的时候就出现了。该星系发出的光用了129亿年才到达地球,在此期间,后续的几代恒星施展魔法,让宇宙变得有趣。The galaxy, known as CR7, is three times as luminous as any previously found from that time, the authors said. Within it is a bright blue cloud that seems to contain only hydrogen and helium.作者表示,这个被称为CR7的星系的亮度是之前发现的同期星系的亮度的三倍。该星系里面是一个似乎只包含氢和氦的亮蓝色星云。In an email, Dr. Sobral called this the first direct evidence of the stars “that ultimately allowed us all to be here by fabricating heavy elements and changing the composition of the universe.”索夫拉尔在邮件中称,这是第一个直接明这些恒星“通过创造重元素,改变宇宙的构成,最终使得我们得以存在”的据。In a statement from the European Southern Observatory, he said, “It doesn’t really get any more exciting than this.”在欧洲南方天文台(European Southern Observatory)发表的声明中,他表示,“没有什么比这个更令人激动的了。”Garth Illingworth, an astronomer at the University of California, Santa Cruz, and a veteran of the search for early galaxies, pointed out, however, that these stars were appearing far later in cosmic history than theory had predicted.但加州大学圣克鲁斯分校(University of California, Santa Cruz)天文学家加思·伊林沃思(Garth Illingworth)指出,这些恒星在宇宙历史中出现的时间比理论预测的时间要晚得多。伊林沃思在寻找早期星系方面有丰富的经验。Dr. Sobral and his colleagues were using the Very Large Telescope of the Southern Observatory in Chile and the W. M. Keck Observatory in Hawaii, among other big telescopes, to build on an earlier search for glowing clouds of hydrogen that might represent very early galaxies. Galaxy CR7 — short for Cosmos Redshift 7, after the method by which distant objects in the universe are dated — stood out.索夫拉尔和他的同事利用南方天文台在智利设置的甚大望远镜(Very Large Telescope)、夏威夷的W·M·凯克天文台(W. M. Keck Observatory)及其他大型望远镜,继续之前寻找由氢组成的发光星云的工作,这些星云可能代表着早期的星系。他们发现了GR7星系——宇宙红移7号(Cosmos Redshift 7)的缩写,得名于追溯宇宙中遥远物体所使用的方法。In an expanding universe, the farther away or back in time an object is, the faster it is receding, which causes the wavelength of light from it to lengthen, the way the pitch of a siren sounds lower after it passes. In astronomy, this lengthening is known as redshifting.在不断膨胀的宇宙中,一个物体越久远,消失的速度就越快,这导致物体发出的光的波长变长,就像救护车呼啸经过后,警报器的音高会逐渐降低。在天文学上,这种延长被称为红移。The galaxy’s name, Dr. Sobral said, was also inspired by the great Portuguese soccer player Cristiano Ronaldo, a.k.a. CR7.索夫拉尔表示,该星系的名称——CR7还受到葡萄牙优秀的足球运动员克里斯蒂亚诺·罗纳尔多(Cristiano Ronaldo)的启发。As in much of astronomy, the nomenclature of these star generations is awkwardly rooted in history and Earth-centered. Modern stars like the sun, with healthy abundances of so-called metals (anything heavier than helium), are now called Population I, mainly because they were the first known. They mostly inhabit the spiral arms and younger parts of galaxies like the Milky Way.在天文学的主要领域,各代恒星的命名都尴尬地遵从历史,是以地球为中心的。太阳等现代恒星拥有充裕的金属元素(比氦重的物质),它们现在被称为第一星族(Population I),主要是因为它们是首批被发现的恒星。它们主要位于系(Milky Way)等星系的旋臂和年轻星团中。In the middle of the 20th century, however, the astronomer Walter Baade noticed that the stars in older parts of the galaxy, like its core or globular clusters, are older and have fewer metals. He called them Population II.但在20世纪中叶,天文学家瓦尔特·巴德(Walter Baade)注意到,该星系的古老星团——比如它的核心星团或球状星团——中的恒星年代更为久远,金属元素更少。他称之为第二星族(Population II)。The advent of the Big Bang theory of the origin of the universe forced astronomers to realize that the first stars must have had no metals at all; those are known as Population III.有关宇宙起源的大爆炸理论的出现,迫使天文学家认识到,第一代恒星肯定不包含金属元素;它们被称为第三星族(Population III)。Stars of both Population II and Population III are probably present in CR7, Dr. Sobral and his team report. While the blue cloud is metal-free, according to spectral measurements, the color of the rest of the galaxy is consistent with more evolved stars making up most of its mass. This suggests, they write, that the Population III stars there are late bloomers of a sort, forming from leftover clouds of pristine material as the galaxy was sending out its light 12.9 billion years ago.索夫拉尔和他的团队报告称,CR7星系中可能存在第二星族和第三星族的恒星。虽然根据光谱测量,这个蓝色星云不包含金属元素,但该星系剩余部分的颜色与演化程度较高的、构成其大部分质量的恒星一致。他们写道,这说明该星系中的第三星族恒星形成较晚,由该星系129亿年前发出光线时的崭新物质的残余星云发展而成。The only alternative explanation, Dr. Sobral said, is something so spectacular and unlikely that astronomers do not know if it has ever happened, namely a primordial cloud bypassing the star stage and collapsing directly into a black hole. That, he noted, is impossible to rule out because nobody really knows what it should look like.索夫拉尔表示,除此之外的唯一解释是,发生了一些惊人的、意想不到的事,天文学家还不知道这种事是否发生过,那就是原始星云越过恒星阶段,直接坍缩为黑洞。他指出,不能排除这种可能性,因为没人真的知道它看上去是什么样子。Further observations with the Hubble Space Telescope and the James Webb could help resolve the issue.利用哈勃太空望远镜和詹姆斯·韦伯太空望远镜进一步观察或许有助于这个问题的解决。 /201506/382016

The Gnomon圭表A simple and important astronomic instrument, the gnomon(an instru-ment used to calculate the time,season,and so on ) is composed of a vertical gnomon(about eight phi,or 2. 6 meters high ) and a horizontal ruler. It is designed to determine the length of a tropical year and the 24 Solar Terms. The rul-er has lines to indicate the months of the year.圭表是一种既简单又重要的测天仪器,它由垂直的表(一般高八尺)和水平的圭组成。圭表的主要功能是测定冬至日所在,并进而确定回归年长度,此外,通过观测表影的变化可确定方向和节气。A long time ago,the ancient people found that things,like houses and woods under the sun-shine,would cast shadows on the earth,the changes of which followed a certain rule. In order to observe the shadovVs changes,the people erected on the flat ground a straight pole or stone column,which was called a “gnomon”,and used a ruler to measure the length and direction of the gnomon’s shadow, hence calculating the time(like a sundial ).很早以前,人们发现房屋、树木等物在太阳光照射下会投出影子,这些影子的变化有一定的规律。于是便在平地上直立一根竿子或石柱来观察影子的变化,这根立竿或立柱就叫做“表”;用一把尺子测量表影的长度和方向,则可知道时辰(如日暑)。Later, after noticing the gnomon’s shadow always pointed north at midday,the ancient people laid a ruler made of stone plate on the ground,vertical to the gnomon and pointing to the north. In the midday,when the gnomon’s shadow was cast over the stone plate,they could the length of the shadow directly from the ruler.后来,发现正午时的表影总是投向正北方向,就把石板制成的尺子平铺在地面上,与立表垂直,尺子的一头连着表基,另一头则伸向正北方向。正午时,表影投在石板上,古人就能直接读出表影的长度值。After a long-time observation,the ancient people not only figured out that at mid-noon the length of the gnomon’s shadow was the shortest within a day,but also that at mid-noon of the summer solstice and the winter solstice the gnomon’s shadow was the shortest and longest respectively within a year. Therefore,the used the midday length of the shadow to measure the solar terms and the length of a year.经过长期观测,古人不仅了解到一天中表影在正午最短,而且得出一年内夏至日的正午,表影最短;冬至日的正午,表影则最长。于是,古人就以正午时的表影长度来确定节气和一年的长度。 /201511/409376

Computers are no longer just something we use every day but an integral part of our daily lives. Unfortunately, their omnipresence in our society doesn#39;t mean everyone has a full understanding of them. Many people have misconceptions about their computers and how to protect themselves from those who would target their systems maliciously.如今,电脑不再仅仅是我们每天使用的工具,而是日常生活中不可或缺的一部分。不幸的是,虽然它随处可见但并不意味着每个人都十分了解。许多人对电脑和如何保护电脑系统不受恶意攻击有误解。10.Password Length And Complexity10.密码长度和复杂性One of the most enduring nuggets of computer-related wisdom is to make your password as long, complex, and cryptic as humanly possible. As a result, incredibly easy-to-guess passwords like ;password; are becoming a thing of the past. However, that doesn#39;t mean that people have learned their lesson. Some people make passwords so long that they have trouble remembering them, so they write them down somewhere. This makes it very easy for someone else to find their way in. Many people also choose passwords related to something they like, which makes it easy for someone who knows them to guess.对电脑进行保护时,最常用的方法之一是设置又长又复杂,且神秘的密码。因此,像;password;这样很容易猜到的密码已成为过去。但并不意味着人们就得到了教训。一些人的密码设置太长,到后来很难记住,所以将密码写下来。这使得别人很容易找到密码的所在之处。许多人选择将密码设为他们喜欢的东西,所以很容易被认识的人猜到。While your password shouldn#39;t be easily guessed, it doesn#39;t really need to be that complex. What#39;s more important is not reusing it across different sites. With so many different sites to log into and passwords to remember, many people have chosen to use the same password everywhere. The problem is that if a hacker manages to break into a site and snatch their database, they can now use your password across multiple sites. The best thing you can do to keep your passwords in your head, something mildly complex but easy to remember, and vary them over multiple sites.然而,你的密码不会那么容易被猜到,所以不需要太复杂。更重要的是不要在不同的网站重复使用一个密码。因为登录不同的网站要记住不同的密码,很多人选择在每个网站上用相同的密码。问题是,如果黑客成功破解一个网站,盗取数据,他们就能使用密码登录不同的网站。所以最好的办法是用脑记住密码,稍微复杂一点但容易记住,并且不同网站使用不同密码。9.The Blue Screen Of Death9.蓝屏死机Many people assume when they have a blue screen of death that either their computer is about to die forever or that they have a virus. But while blue screens used to be a sign of much more serious trouble, they are rarely fatal errors anymore and rarely have anything to do with a virus. A blue screen nearly always occurs because a new program or a driver update caused a problem, and the computer responded by shutting itself down to prevent damage.许多人认为当电脑蓝屏死机时,电脑是会永远死机,或者因为电脑有病毒。在以前,蓝屏是有严重问题的迹象,但不是致命的错误或病毒所造成的。蓝屏往往是因为新程序或新驱动的升级造成的问题,是电脑自动关闭以防损坏。More recent versions of Windows deal with blue screen errors much better than in the past, so it isn#39;t usually much of a problem to worry about anymore. Of course, it can still occasionally be a serious hardware problem, but it won#39;t be because you have a virus. The best thing to do is plug the error message into Google and go from there.近几代Windows系统相比前几代更好地解决了蓝屏错误,所以它不再是一个值得担心的问题。当然,它也可能是出现了硬件问题,但不会因为有病毒而蓝屏。所以最好的办法是在谷歌中搜索这个错误信息,再找到解决办法。8.Random Access Memory8.随机存取存储器RAM, or Random Access Memory, is often just referred to as ;memory.; For this reason, many people think that when they are running low on space, they need more RAM. However, the long-term storage device is the hard drive, which can be confusing, because it doesn#39;t have the word ;memory; in its name.随机存取存储器(RAM: Random Access Memory)通常被认作为;内存;。因此,当电脑运行空间不足时,许多人认为需要更多内存。但是,长期存储器是硬件,会让人混淆是因为名字中没有;内存;的意思。Memory in a computer works similarly to memory in the human brain. The human brain has long-term storage, where we keep memories, and a working memory where you can keep a running conversation and do arithmetic in your head. While we are performing these tasks with our working memory, we also have the ability to retrieve memories from deep storage.电脑内存和人脑记忆工作很相似。人脑有长期存储,使我们保持工作记忆,你可以在进行对话时调动记忆,在大脑内计算。当我们用工作记忆处理这些任务,同时也能搜索深沉记忆。A computer runs in much the same way. The hard drive contains the computer#39;s long-term memories—s, pictures, and other files. The RAM is your working memory and performs immediate tasks, such as running Facebook, playing Candy Crush, and loading email while chatting on Skype. If your computer starts to perform slowly when you are trying to do all of these tasks, you probably need more RAM. If you find you don#39;t have enough room for all of your files, you need a bigger hard drive.电脑是用同样的方法运行。硬盘驱动包含电脑的长期储存--视频,电脑和其他文件。随机存储器是工作记忆,处理及时任务,如运行Facebook,玩糖果粉碎,Skype聊天时下载电子邮件。如果你的电脑在同时处理所有任务时开始运行缓慢,就可能需要更多的内存,如果你的电脑没有足够的空间储存所有文件,就需要一个更大的硬盘驱动。翻译:文思捷 来源:前十网 /201507/388603

Shenzhou I Experimental Spacecraft“神舟一号”飞船Nov. 20, 1999, China successfully launched Shenzhou I experimental spaceship on a LM-2F launch vehicle in Jiuquan Satellite Launch Center, which laid solid foundation for realizing the strategic target for manned space flight. Four orbital test flights of the Shenzhou spacecraft were conducted without crews. Remained in orbit for 21 hours, it made 14 0rbits around the Earth carrying a dummy astronaut, experimental seeds, national flags and a banner with signatures of participating engineers and scientists and after that the descent module lands in central Inner Mongolia Autonomous Region the next day.神舟一号飞船是中华人民共和国载人航天计划中发射的4艘无人飞船的第一艘实验飞船。飞船于1999年1 1月20日在酒泉航天发射场成功发射,承担发射任务的是在“长征2号”捆绑式火箭的基础上改进研制的“长征2号”F载人航天火箭。飞船携带一个飞行员模型、一些实验种子,国旗和一面带有航天工程师和科学家签名的横幅绕地球飞行14圈后,顺利降落在内蒙古中部地区的着陆场,飞船在太空中共飞行了21个小时。The unmanned spacecraft consists of orbit, descent and propulsion modules. The orbit module is the place where astronauts live and work. The descent cabin lies in the middle of the spaceship, and is the astronauts cabin and the command and control center. It is a airtight structure with a hatch on the top for astronaut to get in and out of the descent cabin and enter the orbital module, and it is the only landing part of the spaceship to return into the air and to land on the earth. In advancement spacecraft has two solar cell wings, attached to the outside of the instrument propulsion module below the descent cabin. The two solar cell wing total area of 24.48 m2, which are deployed after launch and supply the power distribution. Shenzhou I experimental spaceship is the important milestone in China#39;s spaceflight history.飞船由轨道舱、返回舱和推进舱组成。轨道舱位于飞船的前段,通过舱口与后面的返回舱相通,轨道舱是宇航员在轨飞行期间的生活舱、试验舱和货舱。飞船中部的返回舱是飞船的指挥控制中心,航天员乘坐其上天和返回地面。推进舱位于飞船的后部,主要用于飞船的姿态控制、变轨和制动。除此之外,推进舱两侧装有20多平方米的主太阳能电池阵。飞船发射后两侧太阳能电池阵机翼打开为前进中的飞船提供电力。“神舟一号”无人试验飞船是中国载人航天工程的首次飞行,标志着中国在载人航天飞行技术上有了重大突破,是中国航天史上的重要里程碑。 /201603/430084

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