Added to this that a tunnel would have to be about 50 km long and that the removal of earth would require a fleet of trucks etc it is liable to detection.

此外，一条长达50公里的隧道必然要挖出大量的土方，需要大量的卡车装载运出，诸如此类的事件都使得隧道很容易被发现。

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Trimming lead times on sunspot detection would allow for better forecasts of space weather—bursts of radiation and charged particles from the sun that can cause real problems on and around Earth.

黑子探测可用于预报空间天气---即源于太阳的辐射爆发和带电粒子等引起的各种空间活动现象。

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But as detection methods improved, astronomers began to find planets closer in size to Earth and planetary systems that contain nearly as many planets as our solar system.

但随着观测手段的提高，天文学家们开始找到与地球的大小相近的行星，以及与我们的太阳系拥有大致相同数目行星的行星系统。

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NASA's slice of the pie includes a plan that would improve detection of near-Earth asteroids, send a solar-powered robot ship (like the NASA concept above) to capture one of the space rocks and tow it back to a stable orbit near Earth, where researchers could study it up close.

ENGADGET

The newfound world, dubbed Kepler-22b, is much bigger than our planet - but, even so, it's also the smallest world yet discovered outside our Solar System, and finding it does bode well for the eventual detection of a true twin, a planet that really is a second Earth.

BBC: Viewpoint: The obsession with a 'twin Earth'

Rare earth elements are also used for military applications, such as advanced optics technologies, radar and radiation detection equipment, and advanced communications systems, according to a 2011 research report by the US Government Accountability Office.

BBC: US to build $120m rare earth research institute