我们生活在地球上，可是我们还是对外星球有很大的好奇，来看看下面的对话吧！

Ben: Guess what! I know something you don’t know!

Layla: What’s that?

B: How many planets are there in the solar system?

L: That’s easy. Everyone knows that there are nine.

B: Not anymore! Can you believe it? They’ve decided that Pluto is not a planet anymore!

L: Nice try. I wasn’t born yesterday, you know.

B: I’m dead serious. They’ve decided that it’s too small to be a planet, but actually they haven’t yet agreed on how big something has to be in order to be a planet anymore.

L: That sounds crazy. They can’t just change their mind about things like that.

B: Yes, they can. If you remember correctly, people used to believe that the world was flat.

L: I suppose you’re right. They also used to think that they were so important that the sun revolved around them, not the other way around.

B: We actually know relatively little about space and the cosmos.

L: Do you think that we’ll one day be able to travel to another planet for a vacation?

B: I suppose we could actually live on a planet outside of the milky way.

L: Do you think we’ll ever get to meet an alien from outer space?

B: I hope not. I think they would be a threat to those of us that lived on Earth.

L: You’re so old fashioned. That’s what people used to think about people from another country!

B: Point taken. Hopefully one day, we’ll live in an interplanetary society.

B：你猜怎么着？我知道一些你不知道的事情！

L：什么事？

B：你知道太阳系有多少行星吗？

L：很简单。大家都知道有九大行星。

B：现在可不是啦！你相信吗？他们决定取消冥王星的行星资格了。

L：想得美。别哄我了，我又不是昨天才生出来（我又不是三岁的孩子）。

B：我是认真的。他们认为冥王星太小了，不够做行星的资格，不过他们尚未对行星的体积究竟该有多大而达成一致的意见。

L：这听起来简直是疯了！他们不能对这种事情随便乱改主意。

B：是的，他们可以。如果你还记得的话，以前人们曾经认为地球是平的。

L：我觉得你说的有道理。他们过去还认为人类是特别重要的，以至于太阳都是围绕着我们转的，不存在其他运行的方式。

B：可能我们对空间和宇宙的了解只是非常有限的一点点。

L：你觉得未来我们有可能去其它星球度假吗？

B：我想我们可以居住在银河系以外的其他星球上。

L：你觉得咱们会在外太空遇到外星人吗？

B：我希望不会。我觉得他们可能对生活在地球上的人类是一种威胁。

L：你的思想可太老派了。这就好像人们以前对外国人的看法一样！

B：知道啦。希望未来有一天，我们能生活在一个行星际的社会里。