Non-carbon based lifeforms

[flyingpig]

1. The problem statement, all variables and given/known data

I have no real experience in biology, so forgive me.

Why exactly are all life carbon based? What's so special about carbon?

Are there lifeforms where they don't need water to live?

I've heard about lifeforms on asteroid that are silicon based, is that true?

[Borek]

We have never seen life form that is not carbon based, that would be a huge discovery.

Why is life carbon based? Check out http://en.wikipedia.org/wiki/Carbon#Organic_compounds