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The strong force and the weak force

  1. Aug 13, 2012 #1
    I'm still highly confused about the weak force. Every time I read about it I get something along the lines of it is responsible for beta decay which to my understanding is when a proton or a neutron exits from the atom's nucleus. One thing I have trouble understanding is that if the strong force is pulling protons and neutrons together what stops them from being totally next to each other unable to move closer together due to the Pauli Exclusion Principle? Is it because the strong force pulls protons and neutrons together, while the weak force pulls them apart, creating an equilibrium? I sort of doubt that given that the strong force is 40 orders of magnitude stronger than gravity and the weak force is only 25 order of magnitude stronger than gravity. So getting back to the weak force, what would happen if it did not exist? It doesn't seem to be that important. I'm pretty sure the Sun's energy is caused by the weak force but I'm not exactly sure how. I've also heard that magma bursting up through the Earth's fault lines has something to do with the weak force.
  2. jcsd
  3. Aug 13, 2012 #2


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    georges, The strong force, in terms of its effect on protons and neutrons, is attractive at larger distances and repulsive at shorter distances. The net result is that nucleons prefer to stay a fixed distance apart, about one fermi. Because of this, the size of the nucleus gets larger as the number of nucleons is increased. The weak force plays no part.

    The weak force is responsible for beta decay, in which a neutron turns into a proton, emitting an electron, a neutrino and an antineutrino. The opposite can also happen, in which a proton turns into a neutron.

    Of course on a more fundamental level, this can all be expressed in terms of quarks.

    The weak force is actually not all that weak, it only appears weak because the intermediate particle that must be created and absorbed during a weak process, the W boson, has a rather large mass.
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