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Thread: Where do neutrons come from?

  1. #1 Where do neutrons come from? 
    Forum Freshman PA Ed's Avatar
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    Hi. I'm new here. I'm trying to understand some basic concepts on the sub-atomic level and I hope that the good folks here will be able to help me out.

    The sun is composed mostly of Hydrogen which is made up of one proton and one electron. Via nuclear fusion, the sun turns hydrogen into helium. Helium is composed of two electrons, two protons and two neutrons. Where did the neutrons come from? If you combine two hydrogens, I can understand the two electrons and the two protons but I don't understand where the two neutrons came from.

    Thanks in advance for your replies.


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  3. #2  
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    The pp chain reaction
    The first step involves the fusion of two hydrogen nuclei 1H (protons) into deuterium, releasing a positron and a neutrino as one proton changes into a neutron.
    http://en.wikipedia.org/wiki/Proton-...chain_reaction


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  4. #3  
    Forum Freshman NADH dehydrogenase's Avatar
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    Yes, that link will help. However it involves Positron Emissions.

    ~Nav
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  5. #4  
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    Quote Originally Posted by Harold14370
    The pp chain reaction
    The first step involves the fusion of two hydrogen nuclei 1H (protons) into deuterium, releasing a positron and a neutrino as one proton changes into a neutron.
    http://en.wikipedia.org/wiki/Proton-...chain_reaction
    Thank you for your reply. It was very helpful.
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  6. #5  
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    Quote Originally Posted by NADH dehydrogenase
    it involves Positron Emissions.
    Is "Positron Emissions" an issue? Wouldn't the extra electron just collide with it's anti-self and destroy each other?
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    Yes, it does. If you read on from the sentence I quoted above in the Wikipedia article, the positron annihilates with an electron and their mass is carried off by two gamma ray photons.
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  8. #7  
    Forum Freshman PA Ed's Avatar
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    I though photons had no at-rest mass?
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  9. #8  
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    Try and get one to sit still.
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  10. #9  
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    That's my point.
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  11. #10  
    Reptile Dysfunction drowsy turtle's Avatar
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    http://en.wikipedia.org/wiki/Photon#...ss_of_a_system

    Photons have energy, therefore they have mass. When they are stationary, they have no energy, and so have no mass.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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