I am no Einstein but I would like to expand my knowledge and share it. When two deuterium atoms fuse together they become a helium nuclei. Now deuterium nuclei contains 1 proton and 1 neutron. When the deuterium nuclei fuses to form a helium nuclei. Helium nuclei contains 2 protons, and 2 neutrons. Now the mass of the proton in the deuterium nuclei is reduced. This means that the individual mass of the proton when it was in deuterium nuclei is greater than the mass of the proton in helium nuclei. So here you may say that the mass difference of the proton would have caused a proportional increase in energy in the helium nuclei. If you believe in E= MC2. But in reality it is the opposite. What actually happens is that when deuterium nuclei fuse the energy in the atom decreases and so there is a corresponding decrease in proton mass. This means that the strong nuclear force and the electrostatic force are less stronger in the fused nuclei. (Not the other way round). Is this correct?