文章来源:未知 文章作者:meng 发布时间:2010-08-20 00:02 字体: [ ]  进入论坛

Normal matter like that found in stars, planets and dust clouds only makes up a tiny fraction(分数,部分) of the mass–energy content of the Universe. It is dwarfed1(变矮小) by the amount of dark matter — which is invisible, but can be detected by its gravitational pull(引力) . In turn, the amount of dark matter in the Universe is itself overwhelmed by the diffuse2(弥漫的,散开的) dark energy that permeates3(弥漫) the entire Universe. Scientists believe that the pressure exerted by this dark energy is what pushes the Universe to expand at an ever-increasing rate. Probing the nature of dark energy is, therefore, one of the key challenges in modern cosmology(宇宙论) . Since its discovery in 1998, the quest has been to characterise and understand it better. This work presents an entirely4 new way to do so.

Eric Jullo, lead author of a new paper in the journal Science explains: "Dark energy is characterised by the relationship between its pressure and its density5: this is known as its equation(方程式,等式) of state. Our goal was to try to quantify this relationship. It teaches us about the properties of dark energy and how it has affected6 the development of the Universe."

The team measured the properties of the gravitational lensing in the galaxy7 cluster Abell 1689. Gravitational lensing is a phenomenon predicted by Einstein's theory of general relativity, and was here used by the team to probe how the cosmological distances (and thus the shape of space-time) are modified by dark energy. At cosmic distances, a huge cluster of galaxies8 in the foreground has so much mass that its gravitational pull bends beams of light from very distant galaxies, producing distorted images of the faraway objects. The distortion(变形,失真) induced by the lens depends in part on the distances to the objects, which have been precisely9 measured with large ground-based telescopes such as ESO's Very Large Telescope and the Keck Telescopes.

"The precise effects of lensing depend on the mass of the lens, the structure of space-time, and the relative distance between us, the lens and the distant object behind it," explains Priyamvada Natarajan, a co-author of the paper. "It's like a magnifying glass, where the image you get depends on the shape of the lens and how far you hold it from the object you're looking at. If you know the shape of the lens and the image you get, you can work out the path that light followed between the object and your eye."

Looking at the distorted images allows astronomers10 to reconstruct the path that light from distant galaxies takes to make its long journey to Earth. It also lets them study the effect of dark energy on the geometry(几何学) of space in the light path from the distant objects to the lensing cluster and then from the cluster to us. As dark energy pushes the Universe to expand ever faster, the precise path that the light beams follow as they travel through space and are bent11 by the lens is subtly altered. This means that the distorted images from the lens encapsulate information about the underlying12 cosmology, as well as about the lens itself.

So why is the geometry of the Universe such a big issue?

"The geometry, the content and the fate of the Universe are all intricately(杂乱地) linked," says Natarajan. "If you know two, you can deduce the third. We already have a pretty good knowledge of the Universe's mass-energy content, so if we can get a handle on its geometry then we will be able to work out exactly what the fate of the Universe will be."

The real strength of this new result is that it devises a totally new way to extract information about the elusive13 dark energy. It is a unique and powerful one, and offers great promise for future applications.

According to the scientists, their method required multiple, meticulous14(一丝不苟的,小心翼翼的) steps to develop. They spent several years developing specialised mathematical models and precise maps of the matter — both dark and "normal" — that together constitute the Abell 1689 cluster.

Co-author Jean-Paul Kneib explains: "Using our unique method in conjunction(互相协调) with others, we were able to come up with(提出,赶上) results that were far more precise than any achieved before."


1 dwarfed cf071ea166e87f1dffbae9401a9e8953     
  • The old houses were dwarfed by the huge new tower blocks. 这些旧房子在新建的高楼大厦的映衬下显得十分矮小。
  • The elephant dwarfed the tortoise. 那只乌龟跟那头象相比就显得很小。 来自《简明英汉词典》
2 diffuse Al0zo     
  • Direct light is better for reading than diffuse light.直射光比漫射光更有利于阅读。
  • His talk was so diffuse that I missed his point.他的谈话漫无边际,我抓不住他的要点。
3 permeates 290eb451e7da5dcf5bb4b8041c3d79fa     
弥漫( permeate的第三人称单数 ); 遍布; 渗入; 渗透
  • Studies show that water vapor quickly permeates plastic packaging material. 研究证明水蒸汽能迅速渗入塑料封装材料。
  • Democracy permeates the whole country. 民主主义(的思想)普及全国。
4 entirely entirely     
  • The fire was entirely caused by their neglect of duty. 那场火灾完全是由于他们失职而引起的。
  • His life was entirely given up to the educational work. 他的一生统统献给了教育工作。
5 density rOdzZ     
  • The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。
  • The region has a very high population density.该地区的人口密度很高。
6 affected TzUzg0     
  • She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
  • His manners are affected.他的态度不自然。
7 galaxy OhoxB     
  • The earth is one of the planets in the Galaxy.地球是银河系中的星球之一。
  • The company has a galaxy of talent.该公司拥有一批优秀的人才。
8 galaxies fa8833b92b82bcb88ee3b3d7644caf77     
星系( galaxy的名词复数 ); 银河系; 一群(杰出或著名的人物)
  • Quasars are the highly energetic cores of distant galaxies. 类星体是遥远星系的极为活跃的核心体。
  • We still don't know how many galaxies there are in the universe. 我们还不知道宇宙中有多少个星系。
9 precisely zlWzUb     
  • It's precisely that sort of slick sales-talk that I mistrust.我不相信的正是那种油腔滑调的推销宣传。
  • The man adjusted very precisely.那个人调得很准。
10 astronomers 569155f16962e086bd7de77deceefcbd     
n.天文学者,天文学家( astronomer的名词复数 )
  • Astronomers can accurately foretell the date,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
  • Astronomers used to ask why only Saturn has rings. 天文学家们过去一直感到奇怪,为什么只有土星有光环。 来自《简明英汉词典》
11 bent QQ8yD     
  • He was fully bent upon the project.他一心扑在这项计划上。
  • We bent over backward to help them.我们尽了最大努力帮助他们。
12 underlying 5fyz8c     
  • The underlying theme of the novel is very serious.小说隐含的主题是十分严肃的。
  • This word has its underlying meaning.这个单词有它潜在的含义。
13 elusive d8vyH     
  • Try to catch the elusive charm of the original in translation.翻译时设法把握住原文中难以捉摸的风韵。
  • Interpol have searched all the corners of the earth for the elusive hijackers.国际刑警组织已在世界各地搜查在逃的飞机劫持者。
14 meticulous A7TzJ     
  • We'll have to handle the matter with meticulous care.这事一点不能含糊。
  • She is meticulous in her presentation of facts.她介绍事实十分详细。
TAG标签: energy dark matter universe