成都少年牙齿矫正费用美乐园
时间:2018年12月12日 06:51:08

Science and technology科学技术Searching for aliens寻找外星人The wow factor防止再次意外A new citizen-science project will improve the chances of finding ET一个新的平民科学项目可以增大找到地外智慧的机会EVER since 1993, when funding from Americas space agency, NASA, was cut, the Search for Extraterrestrial Intelligence, which scans the sky looking for radio signals from intelligent aliens, has been inventive in its methods.自从1993年,寻找地外智慧在失去了美国航天局的资助后,开辟了一个新的的研究途径。In particular, it was one of the pioneers of the field of citizen science, in which interested amateurs are recruited to help professionals crunch data.具体来说,这个新途径是平民科学的先驱之一,它邀请感兴趣的外行人来帮助专家处理海量数据。In 1999 it started SETIhome, an application that uses spare processing power on volunteers computers to sift the information generated by its radio telescopes.1999年,在家寻找地外智慧项目启动了,它通过一个应用程序利用志愿者的电脑上闲置的计算资源来筛选来自射频望远镜的信息。These days, SETIhome boasts more than 1m users.今天,在家寻找地外智慧已经号称拥有超过100万的用户。On February 29th the SETI Institute launched another citizen-science project.2月29号,寻找地外智慧协会启动了一个新的平民科学项目。This time, though, its researchers are less interested in the digital computers on volunteers desks than in the biological ones between their ears.这次,研究人员们更加感兴趣的是志愿者的双眼,而不是他们桌上的计算机。实时寻找地外智慧,SETILive, as the project is called, hopes to use the pattern-recognition capabilities of brains to distinguish interesting signals from the cacophony of interference generated by the denizens of planet Earth—and to do so in real time.就像它的名称所说,它希望利用我们大脑的模式识别能力来辨认出夹杂在由地球原住民产生的信号中的有趣信号,实时地。The basic idea behind SETI is to look for distinctive radio-frequency emissions that might come from advanced aliens rather than natural sources like stars.寻找地外智慧的基本想法是寻找来自高级地外生命而不是其他自然来源如恒星的射频信号。To do this, the SETI Institute uses an instrument called the Allen Telescope Array—a group of 42 small radio-telescope dishes in California, partly paid for by the eponymous co-founder of Microsoft.其协会依靠的工具是坐落在加州的艾伦望远镜阵列,它由42个小的射频望远镜组成,因为微软的共同创始人提供了部分资金而得名。Unfortunately, some parts of the radio spectrum are full of signals created by Earthlings, rather than aliens.不幸的是,来自地球居民而不是外星人的信号挤满了射频频谱的一部分。Everything from passing satellites and tumbling space junk to ground-based radar and even the ignition systems of nearby cars can generate spurious radio waves that confuse the software.各种各样的来源产生了欺骗性的信号迷惑了相关软件,这些来源包括划过天空的卫星和翻滚的太空垃圾,地面上的雷达甚至是附近汽车的点火系统。Until now, the project has dealt with that by ignoring the more crowded bits of the spectrum.目前,项目只能避开这些拥挤的频段。But SETILive will bring them into play.但是实时寻找地外智慧就可以把这些被迫忽略的频段拿来一起分析。It will do so by feeding pictorial representations of data from these noisy chunks of the spectrum to its users in the hope that they will be able to filter out the noise and spot potentially interesting signals buried behind the radio clutter from Earth.它把在这些充满噪声的拥挤频段内的信息转换成图像发送给用户,希望他们能够在这些噪音中发现潜在特别的信号。Those interesting signals will not necessarily have come from alien civilisations, says Chris Lintott,这些特别的信号不一定就来自外星文明。Chris Lintott说。an astrophysicist at Oxford University who helps to run Zooniverse, a citizen-science website that manages several projects, including SETILive.他是牛津大学的天文物理学家,But even if they do not, some new astronomical phenomena may be discovered by the project. And as the various sources of interference become better characterised, the results will be fed back into the automated-search algorithms, improving their ability to deal with Earth-generated noise.帮助运作一个管理了包括实时寻找地外智慧在内的一些项目的平民科学网站-宇宙动物园。Other citizen-science projects aly use the superior pattern-recognition capabilities of human wetware, but SETILive is different from these in one important way.其他一些平民科学项目已经在利用人类自身湿件的模式识别能力了,但是实时寻找地外智慧在一个重要方面与它们都不同。Rather than having its users pore at leisure over stored data, aliens are hunted on the fly.外星人是被即时捕捉到的,而不是用户从容地凝视那些储存好了的数据。Users logging on to the projects website view information that is hot from the Allen Array.用户登录项目网站后看到的信息是刚刚从艾伦望远镜阵列传来的。They have to work quickly, though.他们还必须看得快些,Every 90 seconds, the array switches to looking at a different star, or a different frequency range, and a new image is generated.因为每隔90秒望远镜阵列就会切换观测另外一个星体或者一个不同的频段,一幅新的信息转换成的图像就会显示出来。If, however, the humans do spot something interesting, the array can be told within three minutes to switch back to observing the star or range in question, to see if the signal is still there.如果万一有人确实看到了一些特别的信息,望远镜阵列会在3分钟之内切换回那个特定的星体或者频段,看看信号还是否在那。That is a big advantage, says Dr Lintott.Lintott士说这是一个很大的优势。Volunteers working on SETIhome have found plenty of interesting signals,在家寻找地外智慧的志愿者们就发现过很多有趣的信号,but because the data they analyse are often months old, those signals have usually vanished by the time anyone gets around to checking up on them.但是因为那些数据大多是几个月之前的,当研究人员有机会回头查看时通常它们都已经消失了。The most famous example of such delayed discovery, though it long predates the start of SETIhome, is the so-called Wow! signal.这类延迟事件最出名的一次,尽管早在在家寻找地外智慧启动之前,是一个被称为Wow!的信号。This signal, which looked exactly like the sort of thing astronomers had theorised aliens might use to get in touch was spotted in telescope printouts in 1977.1977年,这个信号在一个望远镜输出文件中被发现了,它完全符合天文学家理论预测的外星人用来和外界联系的特征。It was a powerful, finely tuned broadcast at the most important natural frequency for radio astronomers—the one generated by the flipping spin of the electron in a hydrogen atom.这个信号不仅强烈,而且精确地在射频天文学中最重要的自然频率上发射出来。But by the time astronomers had noticed it and set their instruments up to double-check, the signal had vanished.但是等到天文学家发现并且使用仪器进行二次确认的时候它已经消失了。If a second Wow! signal were discovered by SETILive, astronomers could focus on it almost immediately.如果第二个Wow!信号被实时寻找地外智慧发现,天文学家就可以几乎立即对准它。First contact with aliens, then, might take place not in a lab full of computers but late one night in a suburban bedroom. There could be a film in that.第一次与外星人的接触,说不定就不是发生在满是电脑的实验室里,而是深夜在一个城郊住宅区的卧室中。果真如此就可以拍一部电影了。 点击此处下载本期经济学人讲解PDF与音频字幕 /201307/246413

Higher education更烧钱的教育Why textbooks cost so much课本这么贵为啥哩Its Economics 101经济学主要章节STUDENTS can learn a lot about economics when they buy Greg Mankiws “Principles of Economics”—even if they dont it. Like many popular textbooks, it is horribly expensive: 292.17 on Amazon. Indeed, the nominal price of textbooks has risen more than fifteenfold since 1970, three times the rate of inflation.当学生们购买Greg Mankiw写的《经济学原理》,他们可以学习很多经济学知识—即使他们只买不读。如同众多流行教材,它贵的离谱:在亚马逊上要花费292.17美元。确实,课本的虚价从1970年开始疯涨了15倍,是通货膨胀率的三倍。Like doctors prescribing drugs, professors assigning textbooks do not pay for the products themselves, so they have little incentive to pick cheap ones. Some assign books they have written themselves. The 20m post-secondary students inAmericaoften have little choice in the matter. Small wonder textbooks generate megabucks.正像医生们开的药物那样,教授们布置的这些教材并不用他们自己付钱,因此他们对于挑选廉价教材没有太多动力。一些人吩咐学生买他们自己写的书籍。美国两千万的高年级学生经常在这件事上没多少选择。课本产生巨大效益也就不足为奇。But hope is not lost for poor scholars. Foreign editions are easy to find online and often cheaper—sometimes by over 90%. Publishers can be litigious about this, but in 2013 the Supreme Court ruled that Americans have the right to buy and resell copyrighted material obtained legally. Many university bookstores now let students rent books and return them. Publishers have begun to offer digital textbooks, which are cheaper but cant be resold. And if all else fails, there is always the library.但是贫穷的学者们不会丧失希望。网上很容易找到国外版本,而且往往更便宜,有时候价格能低到将近一折。出版商们对此怨念不已,但是2013年最高法院裁决美国人有权购买或重卖合法占有的合法出版物。许多大学书店现在准许学生租借书籍并到时返还。出版商们开始提供电子版教科书,这种更便宜但是不可出售。而且如果所有方法都失败了,图书馆永远对你开放。 /201408/321640


文章编辑: 39优惠
>>图片新闻