Energy is mass, mass is energy. E=mc^2, remember? Mass is not in general conserved. Every second every main-sequence star in the universe converts untold milli

Energy is mass, mass is energy. E=mc^2, remember? Mass is not in general conserved. Every second every main-sequence star in the universe converts untold millions of tons of mass to energy. But in general relativity even energy is not conserved because the universe is expanding.