Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Popular misconception -- When the deuterium nuclei fuses to form a helium nucleus

  1. Jul 2, 2015 #1
    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?
     
  2. jcsd
  3. Jul 2, 2015 #2
    I think the correct conclusion would be that what actually happens is that when deuterium nuclei fuse the energy in the atom increases and so there is a corresponding decrease in proton mass in the nuclei. This means that the strong nuclear force and the electrostatic force are more stronger in the fused nuclei. More energy lesser mass.

    Is this proper?
     
  4. Jul 2, 2015 #3

    DrChinese

    User Avatar
    Science Advisor
    Gold Member

    You are discussing a topic which has a substantial number of books and general summaries around it. When fusion occurs, energetic particle(s) are ejected. Naturally, there is conservation of total mass/energy through each step. E=mc^2 does apply.

    Not sure there are any general or popular misconceptions about this.
     
  5. Jul 2, 2015 #4

    Nugatory

    User Avatar

    Staff: Mentor

    No. The total mass of the nucleus is a property of the nucleus as a whole. You can't pick out the individual nucleons and assign them masses that will add to the total mass - all you can say is that one configuration of two neutrons and two protons has a different mass than another.
     
  6. Jul 2, 2015 #5

    jtbell

    User Avatar

    Staff: Mentor

    Another way to put it is that the mass of a system of particles does not generally equal the sum of the masses of the individual particles. (Here by "mass" I mean what physicists generally mean by "mass" nowadays, which is often called "rest mass" in popular literature and sometimes "invariant mass" by physicists; but not the "relativistic mass" that you often see in popular literature)
     
  7. Jul 2, 2015 #6

    Drakkith

    User Avatar

    Staff: Mentor

    No, the strength of the forces involved does not change.
     
  8. Jul 2, 2015 #7

    Nugatory

    User Avatar

    Staff: Mentor

    This thread is pushing the edge of the rule about personal theories. Now that the underlying misconception has been explained by several posters, we should close it.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Popular misconception -- When the deuterium nuclei fuses to form a helium nucleus
  1. Bubbles fusing (Replies: 2)

Loading...