I'm just trying to get a few things straight as I delve into the world of quantum physics and string theory. First of all, what does it mean when someone says two forces combine, such as the electromagnetic and weak force as the electroweak force? Does that mean that the particles are the same or what? Second of all, why does gravity not fit with quantum mechanics? Is it because the concepts of time and distance are strange when discussing electrons and other subatomic particles? Thanks.