M: Guess what? I know something you don't know.
F: What's that?
M: How many planets are there in the (Solar System)?
F: That's easy. Everyone knows that there are nine.
M: Not anymore. Can you believe it? They decided that Pluto is not a (planet) anymore.
F: Nice try. I wasn't born yesterday you know.
M: I am 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.
F: That sounds crazy. But they can't just change their mind about things like that.
M: Yes, they can. If you remember (correctly) people used to believe the world is flat.
F: I suppose you are right. They also used to think that they were so important that the sun (revolved) around them, not the other way around.
M: We actually know relatively little about space and (cosmos).
F: Do you that one day we are able to travel to another planet for a vacation?
M: I suppose we could actually live on a planet outside the Milky Way.
F: Do you think we will get to meet (an Alien) from outer space?
M: I hope not. I think it would be a threat to those of us that live in the earth.
F: You are so old fashioned. That's what people used to think about people from another country.
M: Point taking. Hopefully one day we are living in an (inter-planet) society.
