how far do our electromagnetic (EM) signals reach in to outer space? lets estimate that we started transmitting EM signals with the first radios about 100 years ago... which means we have been sending weak signals in every direction for 100 years, and the first signals have reached a maximal distance of 100 light years away from earth! there are about 130 stars within a radius of 20 light years from us and probably several thousand stars within 100 light years.
a recent abstruse goose cartoon puts this into perspective for us earthlings, by showing what TV shows are currently being broadcast to stars at various distances from earth! (click image for larger view)
there are ~400 billion stars in our galaxy alone, and hundreds of billions of galaxies in our universe... just remember that our synthetic radiation hasnt really traveled very far! (aka. to know who yoda is, closer than pollux a civilization must be!)