Where could I download legal free e-books on quantum physics,astro physics etc.?

I'm 13 and I know this is very early to be thinking about my career but don't comment on this as I merely want to have a lot of choices of careers when it's time to look for a career.So does anyone know where I can download free physics e-books?I'm seriously thinking about becoming some sort of a physicist.I'm very open minded on what sort of physicist.So anywhere I can download free physics e-books really appreciated.