经济学人下载:阻止小行星撞击地球 地球的守护者

Science and technology
科学技术

Stopping asteroid strikes
阻止小行星撞击地球

Defenders of the Earth
地球的守护者

The cosmic near-miss in February has boosted research on space rocks
二月一颗小行星掠过地球，促进了对太空岩石的研究

ON JUNE 24th NASA, America's space agency, announced it had discovered the 10,000th Near Earth Object,
6月24日，美国宇航局NASA宣布已发现第10000颗近地天体。

the rather dry name given to asteroids and comets that orbit the sun in the vicinity of Earth and which might, therefore, one day smash into it.
这个颇为平淡的名称指的是在地球邻近区域围绕太阳运动的小行星和彗星，它们可能说不定哪天就撞向地球。

Ten thousand potentially dangerous objects sounds a lot, but NASA reckons there could be ten times as many still waiting to be found.
一万颗潜在危险物体听起来很多，但NASA认为尚待发现的NEO数量，可能是这个数字的10倍。

A week earlier, on June 18th, the agency therefore launched a Grand Challenge intended to recruit and co-ordinate help from industry, academia and anyone else who is interested for a project to detect any asteroid that could threaten Earth.
一星期前的6月18日，NASA因此发布了一项大挑战，为一个探测可能威胁地球的小行星的工程，向企业界和学术界求助，意图从中招募人才和协调力量，任何对此有兴趣的个人也可以参与进来。

All ideas are welcome.
NASA对各方建议一概欢迎。

NASA's bosses are also thinking of allocating extra time on the ground-based telescopes they control to the search for such threats.
NASA的领导们也在考虑将旗下的地面望远镜更多地用于搜索此类威胁。

They have plans, too, to revive a mothballed space telescope called the Wide-field Infrared Survey Explorer to aid in the hunt.
同时，他们还打算唤醒一台休眠中的太空望远镜—广域红外巡天探测者—来协助搜寻工作。

And Lori Garver, the agency's deputy administrator, has asked for the budget of a programme to find 90% of NEOs with a diameter above 140 metres to be doubled.
NASA还有一个项目，旨在找出90%的直径在140米以上的NEO，NASA副署长洛瑞-伽尔瓦已申请将该项目的预算加倍。

So far, NASA reckons it has a quarter of these in the bag, but finishing the job at the present rate of discovery will take decades.
目前，NASA估算自己已确认了这些NEO中的四分之一，但按照目前的探测进度计算，完成这项工作还需要几十年时间。

Nor is this renewed effort all NASA's.
在这股NEO探测复兴中努力的不只有NASA一家。

The European Space Agency is chipping in, too.
欧洲航天局也参与其中，

In May it opened a NEO Co-ordination Centre, to help scientists organise their work and share data.
5月开放了一个NEO协调中心，该中心能帮助众科学家组织工作和分享数据。

And the B612 Foundation, a charity which hopes to build and launch an asteroid-hunting space telescope called Sentinel, has also reported a substantial rise in donations.
此外还有一个叫做B612基金会的慈善组织，希望建造和发射一台名为哨兵的太空望远镜，用于小行星搜寻。该基金会报告称其获得捐款数显著上升。

The reason for all this activity is the events of February 15th, when an asteroid a mere 15-20 metres across exploded with the force of a medium-sized atom bomb over Chelyabinsk, in Russia, and another, much larger one buzzed Earth a few hours later.
上述所有行动，都是因为2月15日发生了一些事情，一颗半径只有15-20米的小行星在俄罗斯车里亚宾斯克州上空爆炸，威力相当于中等大小的原子弹；就在数小时之后，又有一颗比这大得多的小行星掠过地球。

What had been regarded as the stuff of science-fiction novels suddenly became a clear and present danger—but one that, unlike earthquakes, volcanic eruptions, tsunamis and hurricanes, might actually be prevented by timely human action.
原先认为是科幻小说里的情节，突然变成了实实在在的危险—但与地震、火山喷发、海啸和飓风等灾难不同的是，人类可以采取及时的行动阻止小行星撞击地球。

NEOShield, a research project involving several European Union countries, as well as Russia and the United States, is looking at three main ways of diverting incoming asteroids.
近地轨道防护盾是几个欧盟国家与俄罗斯美国合作开展的研究项目，研究让来袭的小行星改变方向的三个主要办法。

One is to use a kinetic impactor—in effect employing a heavy, fast-moving spacecraft as the cue ball in a game of interplanetary billiards.
一种办法是使用动能冲击飞船—就好像把一种重型快速移动的飞船当做白球，在太空打台球一样。

The second is a gravity tractor.
第二种是重力牵引飞船，

This is a spacecraft parked near an asteroid, so that its minute gravitational pull will slowly tug the rock into a safer orbit.
这种航天器会靠在小行星旁边，利用微小的引力效应，慢慢把岩石牵引到安全的轨道。

And if an incoming object is particularly large, or is detected particularly late, the third course of action would be to blast it into a new orbit with nuclear weapons.
如果来袭的物体特别大，或者侦测得特别晚，就轮到第三种应对措施了—使用核武器把它炸到新的轨道上。

If all else fails, or if a threat is spotted too late to deflect, there is also the option of evacuation.
如果所有手段失败的话，或者威胁发现得太晚以至于无法让它转向，我们还有疏散的选择。

In 2008, for example, a small asteroid was detected 20 hours before it hit Earth. The world's astronomers scrambled, and its likely point of impact was calculated with what turned out to be reasonable accuracy.
举例来说，2008年，一颗小行星在撞击地球前的20小时才侦测到。全世界的天文学家急忙开始行动，结果证明，计算撞击点的精确度还是不错的。

It blew up over the Nubian Desert, in Sudan, and no one was injured.
这颗小行星在苏丹的努比亚沙漠上空爆炸，无人受伤。

But this incident showed that a properly organised early-warning system might pay dividends if ground zero turned out to be a populated area.
但这个事件说明，如果地面零点是居住区域的话，组织恰当的预警系统就能显示出它的价值了。

John Tonry, of the University of Hawaii, hopes to provide one.
夏威夷大学的约翰-通瑞希望自己能提供一个预警系统。

He is working on an eight-telescope system called ATLAS.
他正在开发一个8台望远镜组成的系统，名为ATLAS。

It is designed to scan the whole sky twice a night, looking for fast-moving objects.
根据设计，该系统每晚会对天空全面扫描两次，搜寻快速移动的物体。

Unlike most astronomers, Dr Tonry presumably hopes he will not find what he is looking for.
与大多数天文学家不同的是，通瑞博士可能不太希望找到他要找的东西。

But if he does, many people who would not otherwise have lived to tell the tale may thank him.
但如果他找到了，会有许多人感谢他的—否则他们都无法幸存下来，向他人诉说这次惨遇。