We cannot repeat experiments with just one planet.

我们只有一个地球，无法重复进行实验。

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However, as one planet exists around this star, it is possible that others will be discovered — perhaps in more habitable orbits — as observations continue.

但是，既然恒星周围存在一颗行星，那随着观测的进展，很可能会发现其他的行星——也许位于更适宜居住的轨道上。

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Earth is just one planet in the universe.

地球只是宇宙中的一颗行星。

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The movie is about a man who travels to a distant planet about one hundred fifty years in the future.

VOA: special.2010.01.01

You bring iron ore from one part of the planet, carbon, limestone, you put it into this reactor and you ship this all over the world.

你得到钢铁从地球的一个地方，还有碳，石灰岩，将它们放入这个反应器,你将它运送到世界各地。

麻省理工公开课 - 固态化学导论课程节选

But smallpox was, at one time, one of the most frightening diseases on the planet.

但是天花曾经,是这个星球上最令人恐惧的疾病之一

耶鲁公开课 - 生物医学工程探索课程节选

The human race shouldn't have all its eggs in one basket, or on one planet.

CNN: Hawking: If we survive the next 200 years, we should be OK

But when more than one planet is tugging at a star, deciphering the meaning of the wobble is complicated.

ECONOMIST: Extrasolar planets

Either it's going to become multiplanetary, or it's going to be confined to one planet until some eventual extinction event.

WSJ: An Electric Car and a Trip to Mars