And that suggests understanding of cosmology is wrong
May 17th 2018
ONE of the most basic facts about the universe is that it is expanding. This observation, made by Edwin Hubble (pictured) in 1929, leads to all sorts of mind-stretching ideas. That the universe is growing implies it was smaller in the past—possibly a lot smaller. Which leads to the thought that a “Big Bang” kicked everything off. It also opens the question of whether the universe will expand for ever, or will eventually see its expansion halted and reversed by gravity, thus ending in a Big Crunch.
关于宇宙最基本的事实之一是它正在膨胀，这个由埃德温·哈勃(如图)在1929年所做的观察，引发了众多思维延伸的想法。宇宙的增长意味着它在过去更小——可能小得多，这也导出一种思想，即“大爆炸”开启一切。这也引出了一个问题：宇宙是否会永远膨胀，或者最终膨胀会被重力阻止和逆转，一切在大坍塌中结束。
Things got stranger in 1998, when a group of astrophysicists discovered that the rate of expansion is increasing, for this finding raised another question in turn. The acceleration of the expansion was so great that it seemed something was actively pushing the universe apart. Thus was born the notion of “dark energy”—a new component of the cosmos, invoked to balance the equations.
1998年，当一群天体物理学家发现扩张的速度在增加时，事情变得更奇怪了，因为这一发现反过来又提出了另一个问题。膨胀的加速度如此之大，以至于似乎有什么东西在主动地把宇宙撕开。由此诞生了“暗能量”这个概念——宇宙的一个新组成部分，用来平衡方程式。
Trying to work out what dark energy really is (or if it even exists) requires accurate measurements, particularly of the rate at which the universe is expanding. This rate is known as the Hubble constant, and there are two ways of measuring it. Unfortunately, the answers these methods come up with disagree. That is not necessarily a problem. Previous observational conflicts (for example, that the oldest stars in the universe were older than the universe itself) have gone away as measurements improved. But in this case a new set of measurements has confirmed the discrepancy. And that has got those who study astrophysics flummoxed.
想要知道暗能量到底是什么(或者它是否存在)需要精确的测量，特别是宇宙膨胀的速度。这个速率被称为哈勃常数，有两种测量方法。不幸的是，这两种方法给出的答案并不一致。这不一定是个问题。以前的观测冲突(例如，宇宙中最古老的恒星比宇宙本身更古老)随着测量的改进而消失了。但针对这种情况，一组新的测量结果证实了这种差异，这让那些研究天体物理学的人感到困惑。
The new measurements were made by a team led by Adam Riess, one of the researchers who discovered the accelerating expansion. Dr Riess works at the Space Telescope Science Institute in Baltimore. In a study just uploaded to the arXiv, a repository of papers awaiting formal approval for publication, he and his colleagues offer a new set of measurements of 50 stars of a type known as Cepheid variables.
这项新的测量是由研究人员亚当·里斯领导的一个小组进行的，正是他发现了加速膨胀。里斯博士在巴尔的摩的太空望远镜科学研究所工作。在刚刚上传到arXiv，等待正式获准出版的一叠文件的研究中，他和他的同事们提供了一套新的对50颗名为“造父变星”的恒星的测量方法。
Cepheids are important to astronomers because they are a rung on what is known as the cosmic distance ladder. A Cepheid pulsates at a frequency related to its intrinsic brightness. This makes it possible, by comparing the intrinsic brightness of such a star with its apparent brightness, as seen from Earth, to work out how far away it is relative to other Cepheids. Then, if the actual distances to some nearby Cepheids can be measured directly, those relative distances can be turned into absolute ones.
造父变星对天文学家来说很重要，因为它们是被称为宇宙距离阶梯的台阶。造父变星的频率与它的固有亮度有关。通过比较这颗恒星的固有亮度和从地球上观察到的亮度，可以知道它与其他造父变星的距离有多远。然后，如果能直接测量到附近一些造父变星的距离，那么这些相对距离可以变成绝对距离。
This is done by observing their parallax. As Earth orbits the sun, the positions of nearby stars will seem to shift relative to those farther away, in the same way that, to a passenger on a train, trees in the middle distance appear to move with respect to far-off mountains. This means their distances can be worked out by triangulation. The result is a method that has been used since Hubble’s day to work out the distances to nearby galaxies in which individual Cepheids, which are extremely bright stars, can be detected. Then, with this rung in place, other objects, such as certain sorts of supernovae that have predictable energy outputs, can be observed in galaxies of known distance and used to extend the ladder.
这是通过观察它们的视差来完成的。当地球绕太阳运行时，附近恒星的位置似乎会向相对更远的地方移动，就像在火车上的乘客所感受到的一样，中距离的树木似乎在远处的山脉上移动。这意味着它们的距离可以通过三角测量得到。这一结果是自哈勃望远镜观测到附近星系的距离后使用的一种方法，用这种方法，非常明亮的单个造父变星可以被发现。在这些星系中，可以探测到单个的仙王座，它们是非常明亮的恒星。然后，通过适当位置的台阶，其他的物体，例如某些具有可预测的能量输出的超新星，可以在已知距离的星系中观察到，并以此扩展阶梯。
The accuracy of the ladder, though, depends on the measurement of each rung. With this in mind, Dr Riess and his colleagues combined data from two space telescopes—Hubble, which has been in orbit since 1990, and Gaia, launched in 2013—to measure with unprecedented accuracy the distances to nearby Cepheids in the hope that this might make the cosmic-ladder-based estimate of the Hubble constant converge with one derived from observations of the Cosmic Microwave Background (CMB), a thin soup of radiation suffusing the universe that is left over from its earliest moments. It did not. Rather, it confirmed the previous estimate.
然而，梯子的精度取决于每一个台阶的测量。鉴于此,里斯博士和他的同事们结合两个太空望远镜的数据，它们分别是自1990年以来一直在轨道上的哈勃望远镜，和2013年推出的盖亚系统，它以前所未有的精度测量附近造父变星之间的距离，希望这可以使基于宇宙梯度估计的哈勃常数能与来自宇宙微波背景(CMB)的观察一直（宙微波背景是弥漫在宇宙中的微弱的辐射，是最开始的那一刻遗留下来的）。然而，事实并非如此，它证实了之前的估计。
According to the cosmic ladder, the universe is expanding at a rate of 73.24km per second per megaparsec. (In English, this means that for each additional megaparsec of distance—about 3.3m light years—the speed at which galaxies are moving away from each other rises by 73km per second.) According to the CMB method the rate is 67km per second. That suggests there really is something wrong with current understanding of the universe. Perhaps this is no more than a mismeasurement of one of the other steps on the cosmic distance ladder. But it could be quite profound. Which is good news for the employment prospects of astrophysicists.
根据宇宙阶梯，宇宙以每百万秒73.24公里的速度膨胀。(在英语中，这意味着每增加百万秒的距离——大约330万光年——星系之间的移动速度每秒增加73千米。)根据CMB的方法，速率是每秒67公里。这表明，目前对宇宙的认识确实存在一些错误。也许这只不过是对宇宙距离阶梯上的另一个梯度的错误测量。但这可能意义深远。这对天体物理学家的就业前景来说是个好消息。
英文部分来自《经济学人》杂志
联系客服
