The moon's gravity is a sixth as strong as the earth's, so Chang'e-4's experiment was a test: would the earth plants know which way was up on the moon?

月球的引力是地球引力的六分之一，所以嫦娥四号的实验是一个测试：地球上的植物能知道月球上哪个是向上的方向吗？

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The mission was planned as a low-Earth orbit to test the Lunar Module, the lander later used by Apollo 11 and subsequent missions to land on the moon's surface.

他们的使命只是做地球低轨道飞行，以测试月球舱和阿波罗11号以及以后的登月任务所使用的登月舱。

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Yet the destruction of the Chinese Fengyun-1C in an anti-satellite missile test in 2007 accounts for more than a quarter of all catalogued objects in low-Earth orbit.

中国在2007年进行了反卫星导弹试验，风云一号卫星被摧毁。由此产生的太空碎片使记录在册的近地轨道物体增加了四分之一强。

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Back on Earth, space scientists and engineers worked around the clock to design and test new ideas to help the astronauts survive.

VOA: special.2009.07.22

But it could launch Apollo spacecraft on test flights around the Earth.

VOA: special.2009.07.08

It would test flight conditions at the edge of Earth's atmosphere.

VOA: special.2010.07.07

The satellite launched by Seoul is designed to analyze weather data, measure radiation in space, gauges distances on earth and test how effectively South Korean-made devices installed on the satellite operate in space.

NPR: SKorea: Satellite Working Normally, Sending Data

It'll also find time for its studies, beaming VGA images snapped with an onboard camera back to Earth, to test a high-speed data transmitter.

ENGADGET: Japan's LED-stacked cubesat will burn Morse code into the heavens

An analogous test on Earth, Rayman said, would be a scenario in which an automobile found its own way from Los Angeles to Washington, D.

CNN: Spacecraft set for risky asteroid flyby