You have to believe the astrophysicists. According to them, there was a pure fire ball (Energy 0f light) some millions of years ago. Due to some instability, it blew apart and converted partly in to hydrogen similar to high energy gamma rays (energy) get converted in to electron and positron pair (Particle which have finite rest mass). The hydrogen created is undergoing fusion to create helium and the other heavy elements. The Sun and the stars are factories which are responsible for creating heavy elements. It may take a lot of time but the universe is very old. Here we have elements that we know. This theory seems to help in the advancement of science.