A day on the planet Mercury is twice as long as its year.

水星上的一天比它的一年要长一倍。

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One day, a little boy was walking on the planet.

有一天，一个小男孩在这个星球上行走。

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Maybe the story is telling us if we don't look after the planet, a day will come when flowers can only grow on the moon.

也许这个故事告诉我们，如果我们不爱护这个星球，总有一天，花就只能在月球上生长。

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Borders and boundaries have ceased to exist as people tweet, blog and chat online in real-time, 24 hours a day, seven days a week with just about every country on the planet.

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What a "day" or "year" means clearly depends on the planet!

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In fact, the wealthiest man on the planet, Carlos Slim, had himself a billion dollar day.

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