Why are USA, Britain, France attacking on Libya?

i have seen the recent news, but i couldn't find the reason behind it.We have this Japan earthquake on the other hand, by which there are billions of losses to the world and even environment and at this movement we must maintain peace and help each other on that. instead why are we fighting. We are causing a large wide spread humanitarian loss . why can we stop this and restore peace and make this world better by uniting our hands together.