The plan put forward by Dr Laughlin，and his colleagues Don Korycansky and Fred Adams，needs carefully directing a comet or asteroid so that it passes close by our planet and sends some of its gravitational energy to Earth.

　　“Earth's orbital speed would increase as a result and we would move to a higher orbit away from the Sun，” Laughlin said.

　　Engineers would then direct their comet so that it passed close to Jupiter or Saturn.The comet would pick up energy from one of these giant planets.Later its orbit would bring it back to Earth，and the process would be repeated.

　　In the short term，the plan provides an ideal way to global warming，although the team was actually concerned with a much greater danger.The sun is certain to heat up in about a billion years and so “seriously compromise” our biosphere(生物圈)— by cooking us.

　　That's why the group decided to try to save Earth.

　　The plan has one or two worrying aspects，however.For a start，space engineers would have to be very careful about how they directed their asteroid or comet towards Earth.The smallest miscalculation(误算)in orbit could fire it straight at Earth—with deadly consequences.

　　There is also the question of the Moon.As the current issue of Scientific American以约30词概括文章大意

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