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

Heavy nuclei/mass defect

  1. Jan 28, 2009 #1
    how sure are we that heavy nuclei are less massive than the sum of their constituent particles? the masses of atoms are determined by sending their ions through magnetic fields and measuring how much they are deflected. how do we know that heavy nuclei dont simply produce, at any given velocity, slightly stronger magnetic fields than lighter nuclei?
    Last edited: Jan 28, 2009
  2. jcsd
  3. Jan 28, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    The nuclei bend in Magnetic fields due to their own charge. The magnetic field is external, the only thing you are measuring of the nuclei is their charge vs. mass ratio.

    So there is not a magnetic field beeing produced by the nucleus.. only electric charge, which electric field is additative.

    There was a crackpot here almost a year ago who claimed that the other protons in the nuclei whould sheild the charge from the protons inside, hence resulting in a smaller net charge than the sum of the constituent protons... but as he didn't know, equal charges do not screen...
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook