Apparently top physicists haven't figured out the difference between "how" and "why." In a review of The Grand Design by Stephen Hawking and Leonard Mlodinow, this article says they answer "why we are here." Then it goes on to explain that Hawking and Mlodinow provide an easy-to-understand explanation of how the universe (and others) came into being out of nothing.
Unfortunately, they have confused How a thing happens, which science is very good at explaining, with Why a thing happens, which science is unequipped to answer. "Why are we here?" is not answered with references to particles and such. Science doesn't have any facts or measurements that can quantify the meaning of life.
The idea that science can provide an answer to why we are here is a fallacy, and it can lead to people thinking that because science has no answer, there is no reason. Don't fall into the trap.
I have my theories about why I'm here, based on my experiences and research. I don't claim to have the answer for everyone, but I've found meaning in my life, and I'm happy with that.
If you can't find meaning in your life, at least make up something that's fun.