Can someone explain to me how this works in relation to the scale? Is nuclear fusion THAT INSANELY efficient? Imagine our sun being the size of a tennis ball, providing warmth and light on scale in a model of our solar system. Now if that tennis ball was made up of mostly hydrogen for the fusion reaction, how can that amount of fuel, which the star consists of and uses to emit that extremely intense radiation, last for BILLIONS of years? That's just hard for me to comprehend. I do understand the basics of atomic motion's repulsive forces vs. gravity force, so I can imagine that it's not the whole star that needs to fusion-burn to emit that amount of energy, but even if it is just a super-thin outer layer where reaction happens, it is still damn bright for its size! Is external flow of energy a factor? I read about that electrical universe theory stuff and how stars have electromagnetic energy fields that might 'fuel' them via plasma currents or such.