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发表于 2010-4-3 06:53:19
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本帖最后由 hawkwolf 于 2010-4-3 07:08 编辑
A new age for the oldest science
最古老的科学迎来了新时代
For millennia, astronomy meant looking at the night sky and sketching what you saw, making star maps by estimating the relative brightnesses of stars by eye and the routes of wandering planets traced against the celestial sphere.
Even the advent of the telescope didn’t change this much. Sure, astronomers could see fainter objects like the Galilean moons of Jupiter, and resolve point-like planets into disks with structures of color and shade. But the human visual system remained an integral component, limiting data gathering to what could be seen and sketched by human observers in real time.
The advent of the photographic plate caused a revolution. Photography allowed more precise and objective measurements of objects in the sky, and long exposures could reveal fainter and more distant objects. But extracting data still involved human effort, from developing the photographic plates to reducing data into a standard format.
几千年来, 天文学 意味着用你的双眼在夜空中搜寻并简单记录下所看到的, 凭肉眼能识别的星辰亮度来制作星图,以及记录下星辰划过苍穹那曲折的轨迹。
即使是望远镜的出现，也没有把它改变很多。 事实上，望远镜使得天文学家们能看到些比裸视所见光线更微弱的天体，像是木星的那几颗伽利略卫星，只是把肉眼看到的点状星球“放大”成带颜色和形状的盘状结构。但人类的视觉系统仍然是望远镜不可分割的重要部分，在实时观察中，观察者仅凭肉眼来记录、描述所能看到的，所得到的数据就很受限制了。
感光片的出现曾带来过一次革命。 摄影术能进行更准确、客观的测量，长时间的底片曝光能揭示一些更遥远的、光线更暗淡的天体。但是，提取到这些数据仍然离不开人力工作，无论是在底片的显影、还是在剔除无用数据来压缩成标准格式的过程里。
In recent years, all the mucking about in darkrooms has been superseded by digital photography, leading to a huge change in the practice of astronomy. Digital astronomy began as a host of small programs targeting a few individual objects. The data, manually reduced, would typically end up in the astronomer’s desk drawer. But as digital detectors became larger and cheaper they gave birth to a new kind of astronomy: Fewer surveys, but on a much larger scale, mapping vast areas of the sky at a time. Data reduction is automatic and ends up in query-able databases that astronomers worldwide can use.
Cold nights in the dome have been replaced by the warm glow of the computer screen.
These changes, driven by policy, economics and technology, are the subject of the new UK e-Science Institute research theme, “Next Generation Sky Surveys: Astronomical Opportunities and Computational Challenges.” The Theme Leader, Bob Mann, outlined the goals and ambitions of the theme to come in an eSI public lecture on 7 July.
近些年来，那些所有在暗房里的工作，已经被数码摄影术所取代，这也导致了天文学实践中的巨大变革。 数字天文学相当于众多针对带一任务的程序的运行主机。
以前靠费时的手工缩减才生成的标准数据，现在往往是直接送到了天文学家们的抽屉里。
随着数字探测器变得功能越来越强大、成本越来越廉价，这促生出了新型的天文学：更少的人能做更多的、规模更大的事，同时测绘天空中更多块广袤的区域。自动压缩生成的标准数据被直接发送到查询数据库里，全球的天文学家们都可使用这个数据库来用于其研究工作。
苍穹里那清冷的夜空，已经被电脑显示器上那艳丽、活泼的色彩所取代。
这些由经济因素、技术因素推动的众多变革，是英国电子科技研究所（UK，eSI）研究课题的主体。
An illustration of a huge star cluster in our own Milky Way galaxy. The red ones are supergiant stars and the blue ones are young stars. There are an estimated 20,000 stars in the cluster.
一个我们银河系巨大星团的例证。 红色的是超巨星，蓝色的是年轻的恒星。 估计星团里有2万颗恒星。
Entering a bright new age
走进光明的新时代
How much data would surveying the whole sky generate? Well, the atmospheric interference that makes stars seem to twinkle limits the resolution you can observe from ground-based telescopes to about half an arcsecond, or just over one ten-thousandth of a degree. (To give a sense of size, the moon is about 1800 arcseconds across, says The Planetary Society.) Dividing the whole area of the sky by half an arcsecond, and allowing 2-to-4 bytes per pixel to give an acceptable dynamic range for measurements, puts the size of a whole-sky survey at roughly 20 terabytes.
In the old days of photographic plates, producing 20 terabytes might take 60 years of observing time, and another ten years of digitization. Current digital sky surveys can produce 20 terabytes in a year. The newest generation of sky surveys will produce 20 terabytes every night for a decade. As data volumes increase dramatically, the importance of computation increases.
勘查整个天空会生成多大的数据量？ 好吧，大气干扰使星星闪烁，当你使用地面望远镜时，这干扰使得你所能得到的观察结果被限制在半角秒（刚刚超过1度的万分之一）；来一个能感受到的比较，天空中月球的尺寸大约是1800角秒。
假设用半角秒为像素单位来划分整个天空，每像素只有 2~4字节 大小的可接受动态测量范围的话，那么得到的一张全天空的测绘图，其尺寸大约是20TB。
以前的底片时代，要产生出20TB的数据可能会花60年的观测时间，还要再花费10年把它数据化。
当今的数字化天空测绘只需要1年就能得到20TB的数据，还不需要数字化过程。
最新一代的天空测绘，每晚将生成出10组20TB的数据。
当数据量在明显增大时，处理/计算也随之越来越重要了。
Because survey science is statistical in nature, trying to characterize populations by parameters such as the clustering of galaxies or the types of stars requires a large sample volume of the cosmos to produce meaningful results. Users must analyze data sets that are too large to practically download, so data analysis code must be run at data centers.
A further challenge is in real-time follow-up studies of transient events. When a star explodes, for example, telescopes can promptly swing round to examine the explosion at different wavelengths, revealing a wealth of scientific information — but only if they’re told in time. If a sky survey is to be able to issue an alert within one minute of detecting such a transient effect, its data reduction system needs to achieve a data rate of about 2 terabytes per hour.
So astronomers need to work with computing scientists. But is the reverse true?
由于测绘科学的本质是统计性的，通过数据来描述特征对象，例如：星系聚生，或恒星的种类等，这需要测量大量的宇宙样本才能得到有意义的结果。用户要是分析这些大的无法下载的数据，分析程序就只能在数据中心里运行。
另一个挑战是在对瞬态的活动进行实时跟踪的研究上。 例如：当一个恒星爆炸时，众多望远镜需要立即展开、并在不同波长上来观察这个爆发，这才能揭示出丰富的科学信息 - 只能在它们都在同时显现出的时候。 如果一套天空测绘系统能在1分钟内部署完毕，来探测这个瞬发事件，那么，它的数据压缩系统需要达到每小时刷新2TB数据的能力。
所以，天文学家们要与计算机科学家们一起协同工作才行。 那么，倒过来说呢？
Astronomical data can be very useful to computing scientists who want to develop data-handling and mining algorithms. The data has no commercial value and doesn’t refer to human beings, so there are no issues of commercial confidentiality or personal privacy.
And there is an awful lot of it.
Therefore, computational astronomy is an excellent sandbox for data-mining algorithms, and an effective way to teach both astronomy and computer science. Consequently, the new generation of sky surveys will encourage the development of new computational techniques.
天文数据对计算机科学家来说，是非常有用的，如果他们想发展数据处理或开发新算法。
天文数据是没有商业价值的，也不会涉及到某个/某些人，也就不需要申请什么商业机密的授权或者个人隐私的授权。
而且，天文数据还是海量的。
因此，对于发掘算法来说，计算天文学是一个优秀的沙盘，也是一个让人了解天文科学和计算机科学的有效方式。
最终，新一代的天空测绘将极大地推进新的计算技术的发展。
The oldest science is entering a bright new age.
最古老的科学现在正进入一个光明的新时代。
This composite of both X-ray and Infrared images shows the Coronet Australis region, one of the nearest and most active regions of ongoing star formation.
X-射线和红外图像的合成图，显示的是南冕座，这个"从人马座头上掉落的皇冠"是一个距离我们最近的、生成恒星活动最活跃的星座。 |
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发表于 2010-4-2 20:58:29