国家地理:送给外星人的地图(1)（在线收听）

A half century ago astronomers designed a map that would point to Earth from anywhere in the galaxy. Then they sent it into space, reasoning that any aliens smart enough to intercept a spacecraft could decode the map and uncover its origin. Many movies and TV shows have used variations on this theme as a plot point, but we didn't borrow it from science fiction. It's reality.

半个世纪前，天文学家设计了一幅可以从银河系任何地方指向地球的地图。然后他们把这幅地图发送至太空，推论任何聪明到能拦截宇宙飞船的外星人，都有能力破解这幅地图并找出它来自哪里。许多电影和电视节目都使用了这个主题的变体作为情节，但我们没有从科幻小说中借用。这是现实。

Truth is, this tale has been part of my family's lore since before I was born. Growing up, I'd heard stories about the map and seen its depiction on multiple interstellar spacecraft, and several years ago, I found the original, penciled-in pathway to Earth where my parents had stashed it.

事实上，在我出生前，这个故事就已经是我家族历史中的一页。我在成长过程中听了关于这幅地图的故事，也在多艘星际宇宙飞船上看到复制的地图，在几年前，我从父母收藏这张地图的地方挖出这张以铅笔绘制、通往地球路径的最早版本。

That was an exciting find! Then came the buzzkill: This original map won't be good for much longer, cosmically speaking. The signposts it uses will disappear within tens of millions of years, and even if they don't, the map would point toward our home for only a fraction of the 200 to 250 million years it takes the sun and other nearby stars to spin once around the Milky Way.

那真是令人兴奋！然后扫兴的事情来了：以宇宙的时间尺度来说，这幅原始地图即将失效。它所使用的路标将在千万年内消失，而就算这些路标没有消失，这幅地图能指向我们家园的时间，也只占太阳和其他邻近恒星绕行银河系一周（约需2亿至2亿5000万年）的一小段时间而已。

Sure, the chances of aliens intercepting the map are astronomically improbable -- but if that did happen, an outdated map would be useless rather than helpful. And that wasn't the goal.

当然，外星人拦截到这幅地图的机会很渺茫，但若真的发生，一幅过时的地图将派不上用场。而这并不是本来的目标。