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  • 一个扩张宇宙

    The big picture 

    ::A. 总体情况

    The universe started with a Big Bang. It is striking that the nearly uniform hot plasma that appeared after the Big Bang now has pockets of highly structured complexity, including creatures who are self-aware and have reconstructed the birth of the universe, a story that unraveled without witnesses.  How did we figure all of this out?

    Hubble's Law
    ::《哈勃法律》

    In 1929, Edwin Hubble published a now-famous paper in the Publications of the National Academy of Science titled, "A Relation between Distance and Radial Velocity in Extragalactic Nebulae.''  As mentioned in the previous chapter, this work showed that M31 and M33 were beyond the known boundaries of our galaxy.  In this paper he included a  showing distances, r , and radial velocities, v , to a couple of dozen "extragalactic nebulae,'' objects that we now understand to be other galaxies.
    ::1929年,Edwin Hubble在国家科学院的出版物中发表了一篇现在著名的论文,题为“外星星系距离和辐射速度之间的关系。'”正如前一章所述,这项工作表明M31和M33超出了我们银河系已知的界限。在这份文件中,他包含了一个显示距离、r和射线速度,v, 与一对夫妇的“扩展星云,'我们现在认为是其他星系的物体”。

    The "radial'' velocity is the component of velocity along our line of sight to an object. We defer a discussion of how the galactic velocities were measured to the chapter on spectroscopy, but for now, trust us... measuring radial velocities of galaxies is bread-and-butter astronomy. 
    ::“ 半径” 速度是我们视线上速度的成份。 我们把关于银河速度如何测量的讨论推迟到关于光谱学的一章, 但是现在, 相信我们... 测量星系的半径速度是面包和珠子天文学。

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    Table 1 from Edwin Hubble's 1929 paper, listing observational data for extragalactic "nebulae." The entries are sorted by distances. Can you see a relationship between distance and the radial velocity of these galaxies? Why do some galaxies have negative velocities?
    ::Edwin Hubble 1929年的论文表1列出了“ 宇宙” 外星系的观测数据。 条目按距离进行分类。 您能看到这些星系的距离和辐射速度之间的关系吗? 为什么某些星系有负速度?

    Hubble sorted the galaxies by distance and immediately noticed a correlation: the more distant galaxies generally had larger radial velocities than closer galaxies. It was also clear that most galaxies - especially those at large distances - are moving away from us (by convention, positive velocities recede from us and negative velocities approach us). A few scientists of the day had already predicted this result as a critical test for a Big Bang. 
    ::哈勃按距离对星系进行分类,并立即注意到一个相关关系:较远的星系的辐射速度通常大于较近的星系。同样明显的是,大多数星系 — — 特别是那些距离遥远的星系 — — 正在远离我们(按惯例,正速度偏离我们,负速度接近我们 ) 。 当今的几位科学家已经预测了这一结果,这是对大爆炸的关键测试。

    Hubble plotted up his data and derived the best-fit linear . There is some scatter in Hubble's diagram.  Some of this was the result of errors in the data, particularly the distances to galaxies.  However, our Milky Way is one of a few dozen galaxies in what we call the Local Group. Galaxies in clusters are gravitationally bound and have orbital velocities that are larger than velocities from the expansion of the universe. Some of the velocities of galaxies in the Local Group (like the Andromeda Galaxy) are directed toward us -- those galaxies have negative velocities. Hubble's law really applies only  to distant galaxies beyond the Local Group.
    ::哈勃绘制了他的数据, 并获得了最合适的线性。 哈勃的图表中有些散射。 其中一些是数据错误的结果, 特别是星系的距离。 然而, 我们的银河系是我们称之为本地组的几十个星系之一。 星团中的星系是引力捆绑的, 轨道速度大于宇宙扩张的速度。 本地组中星系的一些速度( 如安卓美达银河系)是针对我们的, 这些星系有负速度。 哈勃的法律实际上只适用于本地组以外的遥远星系 。

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    A copy of Hubble's 1929 diagram, showing radial velocities plotted against distance. Two solutions are calculated by treating the data in slightly different ways; both suggest a linear relationship between distance and radial velocity. What is the range of distances for the galaxies that Hubble observed? What is the range of velocities? How should we interpret the scatter in the velocities of these galaxies - is it real, or measurement error?
    ::哈勃1929年的图表副本,显示了射线速度与距离的对比图。通过以略微不同的方式处理数据,可以计算出两种解决办法;两种方法都表明距离和射线速度之间的线性关系。哈勃观察到的星系的距离范围是多少?速度的范围是多少?我们应该如何解释这些星系速度中的散射——这是真实的,还是测量错误的?

     

    The speed with which galaxies are moving apart is called the recession speed. Let's think about what this linear relation between distance and recession speed means. Imagine that Galaxy A is initially at a distance  d , and Galaxy B is initially at a distance 2d . Now, let enough time pass so that Galaxy A is at a distance 2d . If the expansion of space is constant everywhere, then Galaxy B will have moved to a distance 4d in that same time interval. Speed is distance divided by time; since Galaxy B travels twice the distance of Galaxy A in the same time interval, it must be traveling at twice the speed .  When the expansion of the universe is constant, distance is proportional to recession velocity. 
    ::星系分离的速度被称为衰退速度。 让我们想想距离和衰退速度之间的线性关系意味着什么。 想象一下银河A最初在距离 d 上, 银河B 最初在距离 2 d 。 现在, 足够长的时间间隔让银河A 在距离 2 d 上。 如果空间的扩展无处不在, 那么银河B 将会在同一时间间隔中移动到4 d 的距离。 速度会因时间间隔而异; 因为银河B 的距离是银河A 的两倍, 它必须以两倍的速度运行。 当宇宙的扩张是恒定的, 距离会与衰退的速度成正比 。

      Think about it

    ::考虑考虑一下

    Can you think of how it might be possible to deduce the age of the universe from Hubble's data?

    At first glance, it is tempting to conclude that the universe is expanding away from us - that we are the center of the universe. In fact, there is nothing special about our place in the universe. From the perspective of observers in every galaxy, most other galaxies seem to be receding. Indeed, alien astronomers in other galaxies have probably already published these same results, showing the relation between the distance and velocity of other galaxies. Like Hubble, they will know that they are not at the center of the universe.

    ::乍一看,得出宇宙正在从我们身边膨胀的结论,即我们是宇宙的中心。事实上,我们在宇宙中的位置没有什么特别之处。从每个星系观察家的角度来看,大多数其他星系似乎正在消退。事实上,其他星系的外星人天文学家可能已经公布了这些同样的结果,显示了其他星系的距离和速度之间的关系。和哈勃一样,他们也会知道自己不在宇宙的中心。

    The linear relationship between distance and recession velocity in Hubble's diagram (above) is expressed by a simple equation:
    ::哈勃图(以上)中的距离和衰退速度之间的线性关系用简单的方程式表示:

    v = H 0 d      [Eqn 1]
    ::v=H0d [Eqn 1]

    The astute reader will  immediately recognize  this as the equation of a straight line:   Here, H 0 is the slope of the line and the y-intercept is zero. This equation says that the recession velocity of a galaxy is proportional to its distance. The constant of proportionality, H 0 , is called Hubble's constant. Mathematically, it is the slope of the line in the . The units of H 0 are physically meaningful: they have units of speed per distance (typically, km/s per megaparsec, Mpc). Assuming that Hubble's constant is really constant (i.e., not changing over time), then once this value is determined, you can measure the velocity of a galaxy (with spectroscopy) to derive its distance.  Galaxies with larger velocities are farther away. So, Equation 1 is a powerful way to estimate distances to other galaxies.  But, keep in mind the chicken and egg problem - we had to measure velocities and distances for some galaxies to derive the Hubble relationship. Once that was done, we  were able to lean on the linear model to find distances to other galaxies.
    ::尾读器将立即确认这是一条直线的方程式 : 在这里, H0 是线的斜度, Y- 界面是零。 此方程式表示一个星系的衰退速度与其距离成正比。 相称性常数 H0 被称为哈勃常数 。 从数学角度讲, 这是线的斜度 。 H0 的单位具有物理意义 。 H0 的单位具有物理意义 : 它们具有每距离的速度单位( 典型的, 每兆帕塞克, Mpc 。 假设哈勃的常数是真正恒定的( 即, 不随时间变化而变化 ) 。 一旦确定这个值, 你就可以测量一个星系( 带光谱仪) 的速度以获得它的距离 。 因此, 方位 1 是估算距离到其他星系的强大方法 。 但是, 记住鸡蛋问题 - 我们必须测量某些星系的速度和距离, 以便得出哈勃关系 。 一旦完成这项工作, 我们就可以在直线模型上找到距离 。

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    The deeper Hubble looks back, the farther in time it sees. This figure illustrates galaxies that Hubble has imaged as a function of look-back time. What is the difference between objects in the Hubble Deep Field and objects in the Hubble Ultra Deep Field?
    ::更深的哈勃回过头来看, 它看到的时间越长。 这个图解显示了哈勃所描绘的星系 。 哈勃深处的天体和哈勃超深处的天体之间有什么区别?

    tells us something rather surprising. The units of 1/ H 0 , (or distance / velocity ) are time, and this "time'' is none other than the age of the universe.  It is incredible that we can calculate the slope of the line in Hubble's data and solve for the age of the universe. The only rookie mistake has to do with the units - make sure that the speed (distance per time - usually km/s) and distance (usually Mpc) are converted to the same units so that distance really cancels out. And then, you will want to convert to more useful units than seconds: years or billions of years.
    ::告诉我们一些相当令人惊讶的事情。 1/ H0 的单位( 或距离/ 速度) 是时间, 而这个“ 时间” 是宇宙的年代。 令人难以置信的是, 我们可以在哈勃的数据中计算线的斜度, 并解决宇宙的年代。 唯一的新人错误与单位有关 - 确保速度( 每时间的距离 - 通常公里/ 秒) 和距离( 通常是 Mpc) 转换为相同的单位, 这样距离就能真正取消 。 然后, 您将会想要转换为比秒( 年或数十亿年) 更有用的单位 。

    So, to recap, Edwin Hubble measured distances to the nearest galaxies, proving that they were outside of the Milky Way. He measured the velocities of other galaxies and found a correlation between distance and recession speed, providing observational evidence that the universe is expanding, and yielding an estimate for the age of the universe. This work provided a resolution to Olbers' paradox : the universe is not infinitely old (we can calculate its age), and because it is expanding, the light from stars in the most distant galaxies has been redshifted out of the optical bandpass (a concept we will discuss more in later chapters). Hubble's work changed our perspective of our place in the universe, and astronomers honored his contributions by naming a space  observatory  after him: the Hubble Space Telescope (HST) has been  a workhorse telescope for the community since the mid-1990's.
    ::因此,回顾一下,Edwin Hubble测量了与最近的星系的距离,证明它们不在银河系之外。他测量了其他星系的速度,发现了距离和衰退速度之间的关联,提供了宇宙正在扩展的观测证据,并得出了宇宙时代的估计值。这项工作为Olbers的悖论提供了一个解析:宇宙并非无限老化(我们可以计算其年代 ) , 并且由于宇宙正在扩大, 最远星系的恒星光已经从光频谱中变红(一个概念我们将在以后的章节中进行更多讨论 ) 。 哈勃的工作改变了我们对我们在宇宙中的位置的看法,天文学家通过在他之后命名一个空间观测站来完成他的贡献:哈勃空间望远镜(HST)自1990年代中期以来一直是社区的工作望远镜。

    We started with a presentation of Edwin Hubble's observations of the expanding universe because it was intuitively easy to understand. However, the Belgian priest George Lemaitre deserves a lot of credit for pioneering modern cosmology.  In 1927, two years before Hubble's famous paper, Lemaitre published a paper with the rather wordy title: "A homogeneous universe of constant mass and growing radius accounting for the radial velocity of extragalactic nebulae."  We now know Lemaitre's model as "Hubble's law" but it was Lemaitre who worked out the theory of the expanding universe with pencil and paper, based on Einstein's theory of general relativity. He proposed that the recession velocity of galaxies (extragalactic nebulae) could be explained by this expansion, and he derived the first estimate for the rate of expansion, which is now known as the Hubble constant, H 0 .  Lemaitre gets extra credit for persisting in the face of a harsh critic; Einstein himself reportedly told him: "Sir, your calculations are correct, but your physics is atrocious." In the 1930's the idea that the universe was expanding was an extraordinary claim, and it would require extraordinary evidence (to borrow a phrase from Carl Sagan) before this theory was accepted.
    ::我们首先介绍了Edwin Hubbble对宇宙扩张的观察,因为它是显而易见的容易理解的。然而,比利时牧师George Lemaitre在开创现代宇宙学方面值得高度赞扬。1927年,在哈勃著名论文发表前的两年,Lemaitre发表了一篇论文,题目相当单词,题目是:“一个质量和半径不断增长的同质宇宙,计算着超银河系的辐射速度。”我们现在知道Lemaitre的模型是“Hubbble's law”的模型,但莱玛特尔根据爱因斯坦的广义相对论用铅笔和纸张提出了宇宙扩张理论。他在1927年提出,星系的衰退速度(极端星云)可以用这种扩张来解释,他得出对扩张速度的最初估计,现在称之为Huble stand stand, H0. Lemaitre由于面对一个严酷的批评家的面而得到额外赞扬。 爱因斯坦本人告诉他:“你所作的计算是正确的,但你的计算是不断扩展的,而你的宇宙的理论则是从1930年的非常的理论需要借用。”

    The Cosmic Microwave Background Radiation
    ::宇宙微波背景辐射

    Thirty years later, a surprising observation further cemented the idea that the universe started with a Big Bang and has been expanding ever since. Bell Telephone Labs in New Jersey had built a sensitive  designed to send signals across long distances.  The antenna became obsolete when telecommunication satellites were launched in 1962. Two Bell Lab employees with backgrounds in radio astronomy, Arno Penzias and Robert Wilson, realized that the antenna would be an excellent radio telescope if it were used as a receiver instead of a transmitter. As soon as they began using the telescope, they picked up background noise, like static in a radio, with a specific wavelength of 7.35 centimeters. No matter where they pointed the antenna, they measured the same signal. The isotropy of the signal suggested that the source was extragalactic; but what was causing it?
    ::30年后,一个令人惊讶的观察进一步巩固了宇宙以大爆炸开始并自那以来一直在扩展的理念。 新泽西州的贝尔电话实验室已经建立了一个用于远距离发送信号的敏感设备。当1962年发射通信卫星时天线已经过时。两个具有射电天文学背景的贝尔实验室雇员Arno Penzias和Robert Wilson意识到,如果天线被用作接收器而不是发射机,那么天线将是一个出色的射电望远镜。一旦他们开始使用望远镜,他们就会发现背景噪音,就像无线电中静态的一样,有7.35厘米的波长。不管他们指向天线的位置,他们都测量了同样的信号。信号的方位表示该源是外星系;但是什么原因呢?

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    In 1978, Penzias and Wilson were awarded the Nobel Prize in physics for their discovery of the cosmic background radiation using the Bell Labs Holmdel Antenna. How were the radio waves detected with this antenna connected to the high energy radiation from the Big Bang?
    ::1978年,Penzias和Wilson因利用Bell Labs Holmdel Antenna发现宇宙背景辐射而获得诺贝尔物理学奖。 与大爆炸高能辐射相连的天线是如何探测到无线电波的?

    Meanwhile, just down the road from Bell Labs at Princeton University, four cosmologists (astrophysicists who study the origin of the universe) were thinking about observational tests that could support their theories about the early universe. They reasoned that if the matter-dominated universe started with a Big Bang, it must have been accompanied by a tremendous burst of high energy radiation.  As the universe expanded and cooled, that primordial energy would have stretched to longer-wavelength, lower-energy radiation. This radiation should permeate the entire universe so that today it would be a low-energy isotropic cosmic background radiation. The Princeton astrophysicists had already drafted a paper predicting that the cosmic background radiation should be detectable today at microwave energies.  The Princeton and Bell Labs scientists worked collaboratively and published side-by-side papers presenting the theory and the observations: "The Cosmic Background Radiation" by Dicke, Peebles, Roll and Wilkinson and "A Measurement of Excess Antenna Temperature at 4080 Megacycles per Second" by Penzias and Wilson. The cosmic microwave background (CMB) radiation has traveled for almost the entire history of the universe. We are immersed in the CMB today - there are about 400 photons from the CMB in every cubic centimeter of the space around us.
    ::同时,在普林斯顿大学贝尔实验室的路上,四位宇宙学家(研究宇宙起源的天体物理学家)正在思考能够支持早期宇宙理论的观测测试。他们推想,如果物质主宰的宇宙始于大爆炸,它必定伴有巨大的高能量辐射。随着宇宙的扩大和冷却,原始能量将延伸至更长的波长、低能量辐射。这种辐射应渗透到整个宇宙,以便今天它将成为低能量的异地宇宙背景辐射。普林斯顿天体物理学家已经起草了一份文件,预测宇宙背景辐射在今天的微波能中是可以检测的。普林斯顿和贝尔实验室的科学家们合作工作并出版了附带论文,介绍理论和观察结果:Dicke, Peebles, Rolle和Wilkinson的“宇宙背景辐射”和Penzias和Wilson的“4080年超度超度温度循环的测量” 。Penzias和Wilson的宇宙微波背景(CMB)的宇宙微波背景(CMB)几乎从我们40%的宇宙中得出了400号。

      A rose by any other name...
    ::玫瑰用任何其他名称...

    What is the difference between radiation with 7.35 cm wavelengths, radiation with 4080 Megacycle per second frequency, radiation with a characteristic temperature of 2.73 Kelvin, and microwave radiation?

    The discovery of the cosmic microwave background radiation by Penzias and Wilson was so transformational that it earned them a Nobel prize in physics in 1978. It also motivated the launch of not one, not two, but three space satellites to refine measurements of the CMB.  Each new mission provided higher spatial resolution and more precise information about the energy fluctuations in the CMB. The first of these satellites, the (COBE) was launched by NASA in 1989 to map the microwave background of the universe. The COBE mission measured energy of the CMB radiation and showed that it was consistent with a blackbody (more about this later, but a blackbody emits a distribution of energy that is characteristic of its temperature) radiating with a peak temperature of 2.73 Kelvin.
    ::Penzias和Wilson发现了宇宙微波背景辐射,这在1978年获得了诺贝尔物理学奖,使Penzias和Wilson的宇宙微波背景辐射变幻莫测,这促使他们发射的不是一颗,不是两颗,而是三颗空间卫星来改进对CMB的测量。每个新飞行任务都提供了更高的空间分辨率和关于CMB的能源波动的更准确的信息。这些卫星中的第一颗是美国航天局于1989年发射的(COBE)卫星,用于测绘宇宙的微波背景。COBE飞行任务测量了CMB辐射的能量,并表明它与黑体(后来更接近于此点,但黑体释放了一种具有温度特征的能量分布,以2.73开尔文为顶点)辐射。

    The fact that the universe has approximately the same temperature in all directions is profoundly important.  It implies that the entire universe was once in thermal contact - the entire universe sprang into existence from a tiny point. Importantly, there are also very subtle deviations from this uniform temperature and that fact is equally profound. This suggests that  there were small fluctuations in the temperature that are linked to slight density variations (1 part in 100,000) in the early universe.  These density variations were the seeds for the large scale structure of the "normal" matter in the universe: galaxies, galaxy clusters, and vast empty voids.  The anisotropy of the CMB is important enough to re-emphasize: if the universe had been perfectly homogenous and smooth, it would not be possible for galaxies, stars, or us to exist today.
    ::宇宙各个方向的温度大致相同这一事实非常重要。 它意味着整个宇宙曾经一度处于热接触中, 整个宇宙从一个小点开始存在。 重要的是, 与这个统一温度也存在非常微妙的偏差, 这一事实同样深刻。 这说明, 温度有小的波动, 与早期宇宙的微小密度变化( 10万分之一) 有关。 这些密度变化是宇宙“ 正常” 物质大规模结构的种子: 星系、 星系群和巨大的空隙。 CMB 的厌食性非常重要, 足以重新强调: 如果宇宙是完全同质和平稳的, 那么星系、 恒星或我们今天都不可能存在 。

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    The all-sky image of the early universe created from the NASA COBE mission (top), nine years of operation by the NASA WMAP satellite (middle) and the ESA Planck mission. The image uses a color scale to show tiny temperature fluctuations in the spectrum of the cosmic background radiation. These temperature fluctuations are the result of differences in the density of matter that seeded the cosmic web of galaxy clusters and dark matter throughout the universe. What are the differences in the data product from these three missions? What is the (profound) significance of the fact that the CMB is the same ~2.73 degrees in every direction?
    ::美国航天局COBE飞行任务(顶部)创造的早期宇宙全天空图像,美国航天局WMAP卫星(中层)和欧空局Planck飞行任务运行了九年。该图像使用彩色比例表显示宇宙背景辐射频谱的微小温度波动。这些温度波动是产生整个宇宙的星系群和暗物质宇宙网络的物质密度差异的结果。这三个飞行任务的数据产品有何不同?CMB在每个方向都相同~2.73度这一事实具有什么(明显)意义?

     

    COBE was the precursor for a second NASA mission called the (WMAP). The obviously has higher spatial resolution, but it also provided a more precise resolution of temperature variations. By fitting models of expansion to the WMAP image, astronomers were able to nail down the age of the universe as 13.77 billion years, and they quantified the composition of the universe: ordinary atoms (4.6%), dark matter (24%), and dark energy (71.4%).
    ::COBE是美国航天局第二次任务(WMAP)的先锋。 显然,COBE具有更高的空间分辨率,但它也提供了更精确的温度变化分辨率。 通过对WMAP图像进行扩展的模型,天文学家能够将宇宙的时代定在13.77亿年,并量化了宇宙的构成:普通原子(4.6%)、暗物质(24%)和暗能量(71.4%)。

    The European Space Agency (ESA) launched , the third major space probe to study the CMB.  Planck provided the ever of the distribution of matter in the universe on large and small scales. The data from the ESA Planck mission provided a more precise measurement of the age and composition of the universe and showed that the first stars formed 370,000 years after the Big Bang - later than previous estimates. Planck also derived an independent measurement of the Hubble constant, H 0 = 67, which disagrees with measurements derived from the recession velocity of galaxies. This suggests that either astronomers are .
    ::欧洲航天局(欧空局)发射的第三大空间探测器是研究CMB的第三大空间探测器。Planck提供了宇宙中物质在大尺度和小尺度上的分布情况。欧空局Planck飞行任务的数据更准确地测量了宇宙的年龄和组成情况,并表明第一颗恒星在大爆炸之后形成370,000年,比以前的估计晚。Planck还得出了哈勃常数H0=67的独立测量结果,该常数与从星系衰退速度得出的测量结果不一致。这表明天文学家中的任何一个都是。

     

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    Wendy Freedman is well known for her work refining the Hubble constant. She was the Director of the Carnegie Observatories until 2015 when she joined the faculty at the University of Chicago.
    ::温迪·弗里德曼以其精炼哈勃常数的作品而著称。 在2015年之前,她一直担任卡内基观察所主任,直到2015年她加入芝加哥大学的教职。

     

    The Hubble measurement was so important that it has been re-examined by several astronomers, including and her colleagues in 2001. Compare the range of distances and recession velocities from , reproduced below, with the . The exact value for the Hubble constant, H0, is still a topic of research and intense debate. 
    ::哈勃测量非常重要,包括2001年她的同事们在内的数位天文学家都重新审查了哈勃测量方法,将下文转载的距离和衰退速度与哈勃常数H0的确切价值相比较。 哈勃常数H0的确切价值仍然是研究和激烈辩论的主题。

     

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    Updated measurements to refine the Hubble Constant by Freedman and colleagues who used the aptly named Hubble Space Telescope in 2001. The bottom plot shows the residuals - the scatter after fitting for the Hubble constant. Why is the scatter in the Hubble constant larger for the galaxies that are closest to us? Shouldn't we have more precise data for the closest galaxies?
    ::由Freedman和2001年使用恰如其分的哈勃空间望远镜的同事对哈勃常数进行更新的测量,以完善哈勃常数。 底图显示了残留物 — — 与哈勃常数相配之后的散射量。 为什么哈勃常数中的散射量对我们最接近的星系更大? 我们是否应该拥有最接近星系的更精确的数据?

     

      Question
    ::问 问 问

    What existed before the Big Bang?  No one knows - maybe a quantum soup of energy. What triggered  a Big Bang where a matter-dominated universe emerged? No one knows. There is quite a bit about our universe that we don't understand. But we do know that the universe is expanding. We know that the background temperature of the universe is the same in all directions, supporting the idea that all of the material in the universe was in thermal contact 14 Byr ago. And we know that there were tiny deviations from that singular temperature that point to density variations that gave rise to stars, galaxies, planets, and life. 

      The Early Universe
    ::早期宇宙

    Astrophysicists have used observations of the expanding universe and the CMB radiation along with standard models of physics to extrapolate back to roughly 10 -43 seconds after the birth of the universe.  We do not yet have physical data to tell us what existed before that time, and standard models of physics cannot describe this era. But, it seems likely that the universe existed in a state of extremely high pure energy.  Quantum energy fluctuations would have transformed this pure energy into particles with mass. The problem is that those particles should have emerged in equal measures of matter and antimatter: quarks and anti-quarks, electrons and anti-electrons (or positrons).  When a matter and antimatter particle come into contact, they destroy each other, producing electromagnetic radiation with the same energy that corresponds to the mass of the particle. The universe might have existed for a very long time before the Big Bang, bubbling back and forth with some equilibrium between pure energy and particle-antiparticle constituents.  However, as far as we can tell (and luckily for us), the antimatter counterparts are missing from our universe today except when they are briefly created in particle accelerators. Indeed, understanding what happens to is one of the key research questions of physicists working now at the CERN Large Hadron Collider.
    ::天体物理学家们利用对宇宙和CMB辐射的观测以及标准的物理模型,在宇宙诞生后的大约10-43秒后,将宇宙和CMB辐射的观测结果外推回到宇宙诞生后的大约10-43秒。我们还没有物理数据来告诉我们当时存在的情况,而标准的物理模型无法描述这个时代。但是,似乎宇宙存在于一个极高的纯能量状态中。量子能量波动本可以将这种纯能量转化为质量的粒子。问题是,这些粒子本应在物质和反物质的等量中出现:夸克和反夸克、电子和反电极(或正电子 ) 。当一个物质和反物质粒子发生接触时,它们彼此摧毁对方,产生与粒子质量相匹配的电磁辐射。宇宙可能在大爆炸之前很久就存在,在纯能量和粒子-静态成分之间产生某种平衡。然而,只要我们能够知道(和我们幸运地), 反物质对应物在今天从我们的宇宙中消失了,除非它们正在短暂地研究的C号的关键。

    Immediately after the Big Bang, the cosmic clock began ticking and all of space popped into existence with a temperature of about 10 billion degrees and with unimaginable pressure. At this stage, the universe was a soup of fundamental particles: electrons, protons, neutrons, and quarks. As the seconds ticked by, protons fused together to form the nuclei of helium and lithium atoms.
    ::大爆炸发生后,宇宙时钟立即开始响起,所有空间都以约100亿度的温度和难以想象的压力出现。在现阶段,宇宙是基本粒子的汤:电子、质子、中子和二次粒子。随着时间的流逝,质子合在一起形成氦原子和锂原子的核。

    The nuclei for all of the hydrogen atoms and most of the helium and lithium atoms that exist in the universe today were formed in the first three minutes after the Big Bang. After three minutes, the universe had expanded and cooled so that the conditions for nuclear fusion no longer existed.  The cosmic web of space and time continued to expand and cool, and after 300,000 years, the temperature of the universe was about 3000 Kelvin, cool enough for electrons to pair with the atomic nuclei and form the first three elements in the Periodic Table.  As the universe expanded, the density of energy decreased. The number of photons is approximately constant, and the energy of a photon is defined by its wavelength. So in a universe where the energy density has decreased, the wavelength of light stretched from the highest energy gamma rays at the time of the Big Bang, to the low energy microwaves that make up the CMB today.  
    ::今天存在于宇宙中的所有氢原子和大部分和锂原子的核核体是在大爆炸后头3分钟形成。3分钟后,宇宙已经扩大和冷却,从而核聚变的条件不再存在。宇宙空间和时间网继续扩大和冷却,30万年后,宇宙的温度大约为3000开尔文,足够冷,电子可以与原子核结合,形成周期表的前三个元素。随着宇宙的扩展,能量密度下降。光子的数量大约保持不变,光子的能量由波长决定。因此,在一个能量密度下降的宇宙中,光的波长从大爆炸时的最高能量伽马射线延伸至今天构成光谱仪的低能量微波。

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    There are four types of "stuff" in the universe: baryonic matter (you, me and everything we see), radiation (energy), dark matter, and dark energy. Since we don't know what dark matter or dark energy are, how would you characterize our ignorance about the universe? How can energy and mass be mathematically related as "stuff" in the universe?
    ::宇宙中有四种“东西”类型:大斗物质(你、我和我们所见的一切)、辐射(能源)、暗物质和暗能量。由于我们不知道什么是暗物质或暗能量,你会如何描述我们对宇宙的无知?能源和质量如何在数学上与宇宙中的“东西”相联系?

     

    The density variations that we see in the CMB maps provided the seeds for structure. As higher density pockets began to collapse over the 300,000 years, the first stars formed, and on larger scales, over millions of years, the first galaxies formed. Our model of the CMB allows us to create a model of the earliest moments of the universe that ends with the structure of the universe as we know it today. The CMB observations also help to constrain the fractional mass and energy constituents of the universe. We are in the strange position of knowing that most of the universe is comprised of mass and energy that we can't really describe - we simply call it "dark matter" and "dark energy." 
    ::我们所看到的CMB地图中的密度变化为结构提供了种子。随着300,000年高密度地区开始崩溃,第一批恒星形成,在更大的尺度上,数以百万年的时间里,第一批星系形成。我们的CMB模型使我们得以创建宇宙最早时刻的模型,以我们今天所知道的宇宙结构结束。CMB的观测还有助于限制宇宙的分数质量和能量成分。我们处在一种奇怪的境地,知道宇宙大部分是由我们无法真正描述的质量与能量组成的,我们称之为“暗物质”和“暗能量”。

    In Caleb Scharf's well-written book "Gravity's Engines," he discusses the idea of a "fair sample of the universe." Imagine that you have a giant bag that contains a representative and proportional sample of all the mass-energy "stuff" in the universe. Shake the bag so that everything is well mixed and then scoop out some of this stuff. What would you be holding? Hydrogen? Photons? Exotic particles like neutrinos?  It's a good bet that you would have scooped out dark energy (this is a thought experiment - dark energy is not something that can actually be scooped up) with perhaps a smattering of dark matter. As the above  shows, something like 73% of the universe is comprised of dark energy, and dark matter makes up another 23%. If you study chemistry, you are studying less than 0.4% of the stuff in the universe.  It turns out that the part of the universe that we encounter in our lives is rare stuff.
    ::在Caleb Scharf的写得很好的书《重力引擎》中,他讨论了“宇宙的公平样本”的概念。想象一下,你有一个巨大的包包,里面含有宇宙中所有质量能源“部件”的代表性和成比例的样本。摇摆袋,以便所有的东西都很好地混合起来,然后拿出来。你会持有什么?氢气?光子?像中微子那样的外向粒子?这是一个好赌注,你会拿出暗能量(这是一个思想实验——暗能量不是真正可以挖掘出来的东西)来点暗物质。正如上面所显示的那样,73%的宇宙是由暗能量组成的,暗物质构成另外23 % 。如果你研究化学,你就会研究不到宇宙中微子的0.4%的东西。结果显示,我们在我们生活中遇到的宇宙的一部分是稀有的东西。

    There are cross checks for the beginning-to-end model that is derived from the : it must also agree with the cosmological models that are derived from observations that from the present time. In other words, we can start with the CMB observations and model the evolution of the universe forward in time. Or we can start with observations of the local, present-day universe and observe more distant galaxies (i.e., look backward in time) to calculate the Hubble constant and the expansion of the universe. Those two methods: "from the beginning to the present time" and "from the present time to the beginning" should have predictions and postdictions that match.  
    ::开始到结束的模型有交叉检查, 取自 : 它也必须与从现在的观测得出的宇宙模型一致。 换句话说, 我们可以从资本市场管理局的观测开始, 并模拟宇宙的进化时间。 或者我们可以从对本地的当前宇宙的观测开始, 并观察更远的星系( 即向后看时间) 来计算哈勃常数和宇宙的扩张。 这两种方法 : “ 从一开始到现在” 和“ 从现在到开始” 应该有相应的预测和后缀 。

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    The evolving universe from the Big Bang through the formation of galaxies and stars. How long did the dark ages of the universe last? When did the first stars form? Were there stars before there were galaxies?
    ::从大爆炸到星系和恒星的形成,宇宙从大爆炸演变而来。 宇宙的黑暗时代持续了多久? 最初的恒星是何时形成的? 在星系出现之前有恒星吗?

    The agreement is good to about 10%, but when we account for all of the physics that we think we understand, that agreement should be much better.  In other words, there is a cosmological . The CMB  model  predicts a universe  with  too little matter to match observations today.  The resolution to this disagreement is that the over time. Looking back to a time when the universe was half its current age, the expansion rate was slower - about 80% of the current rate. 
    ::协议占10%左右,但当我们计算了我们认为我们理解的所有物理学时,协议应该更好一些。换句话说,这是一个宇宙学模型。资本市场管理局模型预测宇宙的大小太小,无法与今天的观测相匹配。这一分歧的解决方案是随着时间的推移。回顾到宇宙目前的一半,扩张速度更慢 — — 大约是当前速度的80%。

    Dark Matter and Dark Energy
    ::黑暗物质和黑暗能量

    In discussing the Big Bang and the expansion of the universe, we focused on the formation and evolution of the stuff that we can see. But, as noted above, astronomers have learned that there is more -- so much more -- to the universe. We just don't know what it is. The existence of dark matter was first predicted by Fritz Zwicky - a Swiss physicist working at the California Institute of Technology, who was by all accounts both a prescient thinker, and quite a . Zwicky obtained photographs of the Coma galaxy cluster and calculated the gravitational mass that must be keeping the cluster bound together -- that calculation suggested that the cluster mass was 400 times greater than the luminous material.  His results were not widely accepted at the time.
    ::在讨论大爆炸和宇宙的扩张时,我们侧重于我们能够看到的东西的形成和演变。但是,如上所述,天文学家们已经认识到宇宙中有更多的 -- -- 这么多 -- -- 更多的是宇宙。我们只是不知道它是什么。暗物质的存在最初是由弗里茨·兹威基预测的,他是一个在加利福尼亚理工学院工作的瑞士物理学家,从各方面讲,他都是一位有先见之明的理论家,而且相当多的Zwicky也获得了Coma星系集的照片,并计算了必须把集群捆绑在一起的重力质量。计算表明,集体质量比发光的材料大400倍。当时,他的结果没有得到普遍接受。

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    Vera Rubin at the Lowell Observatory in Flagstaff AZ in 1965. Rubin was the first woman allowed at Caltech's Palomar Observatory in 1965. At the time, women were not allowed to use the telescope. Can you guess what reason was given to the women?
    ::1965年在Flagstaff AZ的Lowell天文台的Vera Rubin,Rubin是1965年第一个允许进入Caltech的Palomar天文台的妇女,当时不允许妇女使用望远镜。你能猜到给这些妇女什么理由吗?

    Then, in the 1960s, and Kent Ford studied the velocities of stars in spiral galaxies and found that the stars at the outer edges of the galaxy were moving as fast as the stars closer to the center. That observation does not fit with Newtonian physics unless one invents the idea that there is "dark matter" - material that cannot be seen but that exerts a gravitational effect on objects that we do see. Rubin proposed that a spherical distribution of dark matter existed in galaxies - an idea that was initially viewed with great skepticism.
    ::然后,在1960年代,肯特福特研究了星系螺旋星系中的恒星速度,发现星系外缘的恒星移动速度与接近中心中心的恒星速度一样快。这种观察与牛顿物理学不相适应,除非有人发明了“暗物质”的理念,即“暗物质”是看不见的,但对我们所看到的天体产生引力效应的材料。鲁宾建议星系中的暗物质球状分布是暗物质 — — 最初是用怀疑论论来看待的。

    The existence of dark matter was also observed in elliptical galaxies. Sandy Faber and Robert Jackson measured a correlation between the orbital speeds of stars in elliptical galaxies and the mass of the galaxy. Faber and Lin later helped to lift the curtain on the properties of dark matter, ruling out fast-moving neutrinos and concluding that dark matter could still be another type of slow-moving sub-atomic particle. Many candidates for "dark matter" have been proposed, from free-floating planets to weaking interacting massive particles (WIMPS). WIMPS are winning out as the favored candidate for dark matter, but we have not detected them yet.  If WIMPS are the answer, their discovery may await detection with a clever new instrument with higher precision.  Zwicky deserves credit for proposing the existence of dark matter.  and  obtained confirming data that convinced the astronomical community that there really was more to the universe than just the stuff that we see.
    ::在椭圆星系中也观察到暗物质的存在。 Sandy Faber和Robert Jackson测量了星系中恒星轨道速度与星系质量之间的关系。 Faber和Lin后来帮助提高了暗物质特性的窗帘,排除了快速移动的中微子,并得出结论认为暗物质仍可能是另一种移动缓慢的亚原子粒子。 已经提出了许多“暗物质”的候选物,从自由漂浮的行星到衰弱的相互作用的大规模粒子(WIMS ) 。 WIMPS正以暗物质优胜选者的身份获胜,但我们尚未发现它们。 如果WIMPS是答案, 其发现可能会以更精密的新工具等待探测。 Zwicky 提出暗物质的存在值得称赞。 并获得了证实数据, 即天文学界相信宇宙真正存在的东西不仅仅是我们所看到的东西。

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    Sandy Faber receiving the National Medal of Science from President Obama in 2013. If you believe that the laws of gravity are correct, how could you reconcile the observation that stars in the outer parts of galaxies are moving "too fast?"
    ::2013年,桑迪·法伯从奥巴马总统那里获得国家科学奖章。 如果你认为重力法则是正确的, 你怎么能调和星系外部恒星移动“太快”的观察呢?

    We know that the universe is expanding, but is the expansion constant? Was it faster in the past, and decelerating now? Or was it expanding more slowly in the beginning, but now the expansion rate is accelerating?  The second possibility, a decelerating universe, would mean that the universe is headed for a big crunch. The third possibility -- an accelerating expansion -- is only possible if there is a mysterious energy driving the expansion. A "mysterious energy source" seems the least likely; yet that is what the empirical evidence suggests. The expansion rate of the universe is increasing and we have no idea why.  Astronomers refer to the mysterious energy source that is accelerating the expansion of the universe as "dark energy."
    ::我们知道宇宙正在膨胀,但扩张是恒定的吗?过去是加速,现在却在减速吗?是过去加快,现在减速吗?还是一开始更缓慢地膨胀,但现在扩张速度正在加速?第二个可能性,一个减速的宇宙,意味着宇宙正走向一个大紧缩。第三种可能性,即加速扩张,只有在有神秘的能量驱动扩张的情况下才有可能。“神秘的能源源”似乎是最不可能的;然而,经验证据表明,这是最不可能的。宇宙的扩张速度正在上升,我们不知道为什么。天文学家们把加速宇宙扩张的神秘能源称为“暗能量 ” 。

    The Future Universe: Expanding Out of Sight
    ::未来宇宙:视觉的扩张

    The expansion of the universe is accelerating and .  We can currently  observe light that has been traveling for less than  14 billion years. However, the expansion of the universe has carried those distant galaxies away from us during this 14 billion year timespan. As a result, the universe is larger than 14 billion light years in size. Current models of the universe estimate that the universe is 90 billion light years across.
    ::宇宙的扩张正在加速 。 我们目前可以观察到的光线已经运行了不到140亿年。 然而,宇宙的扩张却让这些遥远的星系在这个140亿年的时间跨度中远离了我们。因此,宇宙的大小超过了140亿光年。目前宇宙的模型估计宇宙的光年是900亿光年。

    The expansion rate of the universe is so fast that light leaving a galaxy that is more than 14 billion light years away will never catch up to us.  Those distant galaxies have disappeared from the observable universe.   T he size of the observable universe is 14 billion light years but the  radius of the actual universe is about 45 billion light years; we have lost the ability to see 97%  of the galaxies in the universe. 
    ::宇宙的扩张速度如此之快,以至于光线离开距离140亿光年远的星系永远不会赶上我们。这些遥远的星系已经从可观测的宇宙中消失。可观测宇宙的大小是140亿光年,但实际宇宙的半径大约是450亿光年;我们已经失去了在宇宙中看到97%的星系的能力。

       The Missing Universe
    ::失踪的宇宙

    Assume that the universe is spherically shaped. If the density of galaxies is constant throughout the entire universe, then we can calculate the fraction of galaxies that reside in the "observable" universe as the ratio of a sphere with a radius of 14 billion light years to a spherical volume with a radius of 45 billion light years: 
    ::假设宇宙是球形形状的。 如果星系的密度在整个宇宙中是恒定的, 那么我们可以计算“ 可观察”宇宙中的星系分数, 即以140亿光年为半径的球体与以450亿光年为半径的球体体体体积之比 :

                         V o b s e r v a b l e V t o t a l = 4 3 π ( 14 ) 3 4 3 π ( 45 ) 3 = 0.03 = 3 %
    ::可见观测总和=43(14)343(45)3=0.03=3%

    Only 3% of the galaxies in the universe are possible to observe. The other 97% have receded from our view. 
    ::宇宙中只有3%的星系可以观测。其他97%的星系已经从我们的视野中消失。

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    The light we see from the beginning of the universe is 14.5 billion years old. However, during this time, the universe has continued to expand. A reasonable estimate for the fraction of the universe that can be observed is just the ratio of these two spherical volumes. How does the fraction of the observable universe change as time goes on?
    ::我们从宇宙的最初所看到的光线是145亿年前的14.5亿年。然而,在这个时期,宇宙在继续扩大。可以观察到的宇宙部分的一个合理估计只是这两个球体体体积的比。随着时间的流逝,可观测宇宙部分是如何变化的呢?

    The accelerating expansion of the universe means that the fraction of the universe that is unobservable  to us  in the future will continue to increase. Our local cluster of galaxies will remain gravitationally bound with the Milky Way.  However, the rest of the universe is disappearing from sight.  
    ::宇宙的加速扩张意味着未来我们无法观察的宇宙部分将继续增加。 我们本地的星系群将仍然与银河相连。 然而,宇宙的其余部分正在从眼前消失。