|
|
发表于 2006-4-2 12:29:25
|
显示全部楼层
http://www.planetary.org/program ... stathome_story.html
本人的E文比较烂 ，哪里译的不对头请务必指出，多谢！
红色的部分不知道意思对不对
+++++++++++++++++++++++++++++++++
We all know SETI@home, the wildly successful distributed computing program that brought together millions in a search for extraterrestrial intelligence. Now, just as SETI@home is transitioning to its new BOINC platform, it has spawned a new and no less remarkable scientific venture: Stardust@home, a project that will draw together users from around the world to search for tiny grains of interstellar dust. The particles are the first samples of distant stars ever brought to Earth from space, and you can help find them!
我们都知道SETI@HOME，成功的将数以百万的人聚集在一起寻找地外智慧的分布式计算项目。如今SETI@HOME已经转到了BOINC平台，并且产生了一个新的值得关注的科学冒险：Stardust@home，将来自世界各地的我们团结在一起去寻找微小的星际尘埃的项目。这些遥远星辰的微粒是第一次从太空带回地球，你将帮助发现它们！
The Long Journey
漫长的旅途
The tiny interstellar dust particles were collected by the spacecraft Stardust, which on January 15, 2006, completed its 7-year Odyssey in space by returning its samples to Earth. Two years before, on January 2, 2004, Stardust flew through the hail of rocks and dust that make up comet Wild 2's coma, collecting invaluable samples of cometary particles that will help scientists decipher the history of our solar system. But during its long voyage Stardustalso picked up a different type of sample -- miniscule particles of interstellar dust that arrived at our solar system from distant stars, lightyears away.
这些星际尘埃由“星尘”飞船收集，于2006年一月十五日完成了7年史诗般的空间飞行将样品带回地球。在两年前，2004年1月2日，“星尘”飞越了由冰、石块和尘埃构成的“怀尔特2”彗星的彗发，收集无价的彗星微粒样本，这些样品将帮助科学家解读太阳系的历史。然而在“星尘”漫长的航行中还收集了另一种的样品——极微小的星际尘埃，那是来自遥远恒星（数光年外）的微粒。
Stardust collected these particles between February and May 2000, and again between August and December 2002, while passing through a stream of dust that flows into our solar system from interstellar space. The stream was discovered quite recently -- in 1993 by the spacecraft Galileo, which passed through that region of space on its way to Jupiter. When Stardustflew through the stream,it extended its tennis-racquet shaped aerogel collector, picking up and storing the interstellar particles. No such pristine particles from distant stars have ever been collected before.
“星尘”在2000年二月和五月以及2002年8月至12月穿越一股流入太阳系的星际气体流时收集这些微粒。这股气流是1993年“伽利略”飞船在飞向木星的途中新发现的。当“星尘”穿越这股气流时，张开它的网球拍形状的气凝胶收集器，收集并存储捕获的星际颗粒。以前还从未收集到来自遥远恒星的如此古老颗粒。
On January 15, 2006, Stardust swung by the Earth once more and released a sample return capsule, which parachuted safely down onto the Utah desert. Nestled within the capsule's science canister were two sets of samples: cometary particles on one side of the aerogel collector, and interstellar dust on the other. Within days of arrival, mission scientists began extracting the dust grains from Wild 2and preparing them for shipment to scientists around the world.
在2006年1月15日，“星尘”再一次转回地球并释放了样品返回舱，安全的降落在犹他州的沙漠。安置在返回舱的科学罐里装载着两种样品：在气凝胶收集器的一面是彗星颗粒，另一面是星际尘埃。在抵达后的数天里，任务科学家开始提取“怀尔特2”的尘埃颗粒，为世界各地的科学家准备研究材料。
Few and Tiny: Searching for the Interstellar Dust Grains
寻找稀有且微小的星际尘埃
Whereas the cometary samples are relatively easy to extract from the collector plates, that is not the case for the interstellar dust samples. For one thing, there will be very few of them, probably around 40, compared to the thousands of cometary particles. For another, the interstellar grains are miniscule -- only a few microns in size. These particles, furthermore, are embedded in about 1,000 square centimeters (more than a square foot) of aerogel, which after years in space is likely to be crisscrossed with cracks and flaws. All in all, a very small number of very small particles are scattered in a very messy neighborhood. Before scientists can think about extracting them, they first have to find them.
与从收集盘相对容易的提取出彗星样品不同，星际尘埃要困难得多。其中一个原因：同上千个彗星颗粒相比它们太少，可能只有大约40个。另一个原因：星际尘埃太微小了——只有几个微米大小。此外、这些颗粒深植在1000平方厘米的气凝胶中，经过数年的太空飞行气凝胶很可能布满交错的裂痕和缺陷。所有这些使得非常少而又微小的颗粒散布在这些数量巨大的“邻居”中。在科学家想办法提取出它们以前，首先要找到它们。
Andrew Westphal, an associate director of the Space Sciences Laboratory at the University of California at Berkeley, has spent a great deal of time thinking about how to locate these proverbial needles in the haystack. His first idea was to try an automatic scan: an automated microscope would image and record every tiny portion of the aerogel interstellar dust collector, focusing on varying depths beneath the surface of the collector. The images would then be stored, creating a digital archive of the collector. This in turn would be run through a computer program, designed to detect the tell-tale signs of an impact from an interstellar dust particle. The program would register the locations, and they would then be examined manually by scientists in person.
加州大学伯克利的空间科学实验室副主管Andrew Westphal花了很多时间思考如何定位这些“大海中的针”。他的第一个想法是尝试进行自动的扫描：一台自动的显微镜将成像并记录气溶胶每一块微小的部分，对收集器表面下不同的深度聚焦。图象将被存储，建立一个收集器的数字档案。这些图象将顺序进入一个计算程序，该程序将探测泄露星际尘埃颗粒位置的那些冲击迹象。
A similar approach had worked well for Westphal in the past, when he and his team developed a method for detecting particle tracks in high-energy astrophysics experiments. In that system the microscope scanned the collector twice, focusing on two different depths. A computer program would then match the two scans and register the locations where both revealed a possible track. This way, local flaws in the collector were excluded, and only "tunnels" deep enough to pass through both levels of the scan would become candidates for actual tracks. In the last stage, Westphal and his team would visually observe the candidates to determine whether they were indeed true tracks.
Westphal和他的小组改进了一种用在高能天体物理实验中探测粒子轨迹的方法，模拟实验很成功。在那套系统中显微镜扫描收集器两次，对不同的深度聚焦。计算机程序将比较两次扫描并记录下两次扫描中都出现的可能轨迹的位置。通过这种方法排除收集器中的局部裂隙，只有那些深的足以穿过两个扫描层的“通道”才能作为真正轨迹的候选者。在最后阶段，Westphal和他的小组将亲自观察这些候选者以确定是否为真正轨迹。
The Stardust interstellar dust collector, however, posed a far more difficult challenge. This is because the miniscule particles are expected to penetrate only the very top layer of the aerogel plates, to a depth of no more than 100 microns. At that depth, it is likely that the aerogel from Stardust, returning from 7 years in space, will be filled with cracks and flaws. As a result, the automated scans will likely be flooded with false identifications, and the 40 or so actual interstellar dust grains may never be found.
然而“星尘”的星际尘埃收集器却是一个巨大的挑战。这是因为预计这些微小的颗粒只能穿透气溶胶顶部不超过100微米的深度。在这个深度上“星尘”上的气凝胶在7年的空间飞行中很可能充满了众多裂缝和瑕疵。所以自动扫描将被洪水般的虚假判别所吞没，而这大约40个真正的微粒恐怕根本发现不了。
To get around this problem, Westphal and his teams considered using sophisticated pattern recognition software that would be able to distinguish between cracks in the aerogel and actual particle tracks. They consulted with Professor Jitendra Malik, a U.C. Berkeley computer scientist, who suggested that such a finely discriminating program was, in principle, possible. In order for it to work, however, they would have to "train" the computer with real images of aerogel containing grains of interstellar dust. But here's the rub: no such particles had ever been collected! Scientists can only approximate what real grains embedded in aerogel would look like. For a computer program, this was simply not good enough, and the plan to automatically scan the aerogel collector seemed to lead to a dead end.
为了绕过这个问题，Westphal和他的小组考虑使用精密的模式识别软件来区别裂纹和真正的微粒轨迹。他们请教U.C.伯克利的计算机学家Jitendra Malik教授，Jitendra Malik认为这在理论上是可行的。为了能让软件起作用，必须用包含真正星际尘埃微粒的气凝胶图片“训练”计算机。但问题在于：以前从未收集到此类样品！科学家只是近似的知道深入气凝胶中的微粒大概会是什么样子。对计算机来说这完全行不通，自动扫描的计划走到了尽头。
How, then, can these precious grains from faraway stars be located?
那么、该如何定位这些来自遥远星辰的无价之宝呢？
Stardust@home
“在家中的星尘”
Although sophisticated computer programs could not tell interstellar particles from cracks and dirt, there was yet one instrument available that could do the job: the human eye. From his experience with high-energy physics particles, Westphal knew that unlike computers, humans using microscopes could recognize true tracks quite easily, with only a limited amount of training. If humans could scan the entire surface of the aerogel, then detecting the interstellar dust particles would be easy.
虽然先进的计算机程序无法告发那些裂隙与污垢中的星际尘埃，但是还有一种工具可用来完成这项工作：人眼。高能粒子实验的经验告诉Westphal，与计算机不同，只需要很少量的训练人们就能借助显微镜轻易的认出真正的轨迹。如果人们能查看整个气凝胶的表面，鉴定星际尘埃将变得容易起来。
This, however, raised a different problem: microscopically covering the entire collector at the required magnification would require millions of separate images. The human eye might be a good tool for identifying particle tracks, but who are the humans who can be expected to scan that many images? And if they do, how long would it take, and can they be expected to stay alert for the chance discovery of a single particle among hundreds of thousands of empty images?
但是新的问题来了：显微镜以必要的放大倍数扫描整个气凝胶表面会产生数百万张单独的图像。肉眼在识别微粒轨迹上是很好的工具，但是能期望什么人来审视这么多图片呢？即使有人来做，要用多久呢？并且能期望他们始终保持在成千上万张图片中发现一个微粒的警觉么？
It was at this point that Westphal remembered another project that was being conducted from the very same building where he has his office and laboratory. Only a few doors down the hall at the Space Sciences Laboratory, David Anderson, Dan Wertheimer, and their crew, were running SETI@home -- the largest and most successful distributed computing project in history. With SETI@home, millions of computer users worldwide could join together in the search for extraterrestrial intelligence. Would it be possible to apply a similar approach and have people from around the world join in the search for interstellar dust?
此时Westphal想起了与他的办公室和实验室同在一栋大楼运行的另一个项目。在走廊里仅仅隔几个门的空间科学实验室，David Anderson、Dan Wertheimer和他们的团队正在进行SETI@home——史上最大、最成功的分布式计算项目。世界各地数百万的计算机用户通过SETI@home联合在一起寻找地外文明。是否能以相似的途径使全世界参加到寻找星际尘埃中来呢？
It was possible, and with help from the SETI@home veterans, Westphal set out to figure how it could be done. Unlike SETI@home, the new project will be based on actual human observation rather than automated computer processing of data. But like SETI@home, it would rely on the participation of a multitude of users, who would divide a seemingly intractable job into small and manageable parcels. In tribute to the project that inspired it, the new program would be called Stardust@home.
这是可行的，基于SETI@home的经验，Westphal开始考虑项目该如何运作。与SETI@home不同，新的项目建立在人们亲自观察之上而不是计算机自动的处理数据。同SETI@home一样项目依赖众多的参与者，他们将把看似艰难的工作分割成较小且已处理的小块。鉴于此灵感的来源，新的项目就命名为Stardust@home。
Here's how it will work: as in the original plan, the automated microscope will scan the entire surface of the collector, recording digital images of each miniscule portion of the aerogel. Since each image will cover an area of 260 x 340 microns, and since each image will include a 10% overlap with its neighbor, the microscope will need to focus on 1.6 million different locations to cover the entire surface of the collector.
它是这样工作的：与先前的计划一样，自动显微镜将扫描收集器的整个表面，记录下气凝胶每一细微局部的数字影像。由于每一张图片覆盖260*340微米的区域，并且每张图片会与它相临的有10%的重叠，显微镜需要在收集器的不同地方聚焦一百六十万次才能覆盖到整个表面。
For the automated scan of the high-energy particles, the microscope took two images of each location, focusing on two different depths within the detector. This, however, will not be enough to detect the tiny interstellar dust particles, which lie very close to the surface of the collector, among cracks and flaws. The microscope will therefore take 40 separate images of each location, each focusing on a different depth, between 20 microns above the surface to more than 100 microns within the aerogel. Only a track that is visible continuously through a large portion of these images can be considered a serious candidate for the "real thing." For each location, the 40 separate images will be packaged into a "movie,"representing a continuous in-depth look at each location through different depths.
在自动扫描高能粒子的时候，显微镜在探测器上同一位置的两个不同深度上各聚焦一次。然而这样做对探测微小的星际尘埃还不够，因为它们太靠近收集器那布满裂痕的表面。因此显微镜会在同一位置采集从气凝胶表面下20微米至不超过100微米深度上的40张图象。只有一条轨迹顺序的穿过这40张图片中的大多数，才能被当作“真正星尘”重要的候选者。每个位置的上的这40张图片按照深度顺序作成一部“电影”，代替逐层的查找。
Up to this point, Stardust@home seems like a normal scientific project, though its subject matter is definitely unique. But here's where things get really interesting: thousands of users around the world will now log on to the Stardust@home website and use a simple web-based program called a "virtual microscope." The program will contact the Stardust@home server, and download a movie of a single tiny portion of the Stardust collector. Using the virtual microscope, the user will then view the movie and scan it for actual interstellar dust particles. Once the scan is complete, the program will send the results back to the server. The user will then be free to search the next movie, which was downloaded in the meantime. Overall, each user will only view a tiny portion of the collector; but together, thousands of users around the world will be able to survey the entire collector in just a few months.
此刻，Stardust@home看起来和其他的科学项目没什么两样，尽管它有一个独特的标题。但真正让事情变得有趣的是：全球数以千计的用户将登陆Stardust@home网站并使用一个称作“虚拟显微镜”的简单网页程序。程序将链接到Stardust@home的服务器，下载星尘收集器微小局部的一个影片，用户将使用虚拟显微镜观察影片找出真正的星际尘埃。然后，程序将把察看结果返回服务器，之后用户可以继续下载新的影片或者作其他的事情（同样在下载期间用户也不必一直在电脑前发呆）。总的来说每个用户只会看到收集器得很小一部分；但是联合起世界上数以千计的用户，那么要不了几个月就能纵览整个收集器。
Unlike SETI@home, which only requires users to install the program and let their computers do the work, Stardust@home relies on users' dedication and competence. It is the users themselves, not the computer, which will identify suspected particles. And since it is hard for Westphal and his team to evaluate the competence of each individual user, they will rely on majority opinion to decide whether a particular location deserves a second look: each movie will be sent out to four users, and only if at least two of them report a detection will it be considered a candidate. In that case, it will be sent out again to several more users, who will not know that it has already been flagged by others. If a majority of users in this "second round" also report detections, then professional scientists will observe the location to determine whether is does indeed contain an interstellar dust particle.
With Stardust@home and the power of distributed computing, a task beyond the endurance of any scientist and beyond the capacity of even the most sophisticated computer programs will be accomplished in short order by human volunteers. "It's simply the only way we know how to do it" said Westphal.
不像SETI@home只要用户安装并让计算机来干活，Stardust@home依赖于用户的奉献和能力。是用户而不是计算机在鉴别可疑的颗粒。既然Westphal和他的小组无法评价每个用户的能力，他们将采取多数制来决定一个特定的区域是否要进行第二轮检查（每个影片将会分发给四个用户，至少两人报告有发现它才能被看成是候选者）。在这种情况下，该影片将再次发给更多的人，但他们并不知道这个影片已经被别人插了小旗儿。如果第二轮的多数人将它作为发现报告，那么专家会对该区域进行观察以确定那里是否存在真正的尘埃颗粒。
依靠Stardust@home和分布式计算的力量，一个超越众多科学家甚至是先进计算程序耐力的任务将由志愿者像吃快餐一样在短时间内完成。Westphal认为这简直是他所知道的完成这项工作的唯一途径了。
========================
终于完成了！
[ Last edited by Rojer on 2006-5-28 at 11:13 ] |
|
发表于 2006-2-5 12:13:10
