Today I'm going to try something a little different — at first, anyway. First, let me tell you a bit about my job.

Around the world every day, lots of important things happen. Some of the most interesting and exciting things are about humans, the world we live in and how everything works — things such as why stars burn, why people get sick, what is space made of, how the brain works and how babies grow?

My job is to decide which of these things you really need to know and understand: to decide which stuff matters.