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Pure energy

  1. Feb 9, 2012 #1
    Hi. I'm new around here, and from Norway so please excuse my english/any other mistake I make.

    I have read several articles concerning fusion/fission, and they all say that the "lost mass" is turned into "pure energy". What is meant by pure energy? Is it the new nuclear particles increased kinetic energy they refer to?
  2. jcsd
  3. Feb 9, 2012 #2


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    Welcome to PF!

    Hi KristianBF! Welcome to PF! :wink:
    I've no idea! :biggrin:

    Maybe the so-called dark energy the cosmologists are looking for is "pure energy"? :rolleyes:

    The "lost mass" in fusion and fission either goes to make massive particles, or goes to make electronmagnetic radiation, which is another name for (zero-rest-mass) photons.

    Maybe the books mean photons? :confused:

    (Or maybe the books mean that the "pure energy" exists for a short time as a sort-of intermediate stage?)
  4. Feb 9, 2012 #3
    Ok, thanks for the answer! :)
  5. Feb 9, 2012 #4
    I believe "pure energy" refers to non-rest-mass energy.
  6. Feb 9, 2012 #5
    it is interesting and i also want to know its meaning. My dictionary says energy is "the capacity for a physical system to do work", "its units are joule or erg" and "energy can take a wide variety of forms" (from wordnet dict). hmmm.. seems to direct to a thought of what forms can energy takes?
  7. Feb 9, 2012 #6
    You should check a physics dictionary if you want a proper definition (I believe yours isn't - I apologize if I'm wrong)
  8. Feb 9, 2012 #7
    Wikipedia is also a great source, as long as you are not looking for controversial topics :uhh:
  9. Feb 9, 2012 #8
    And as long as you aren't writing a paper.
  10. Feb 9, 2012 #9
    If you look at in on an atomic level when a U236 atom (that is a U235 atom with an added neutron) splits there will be two daughter products and several neutrons whose rest mass total less than that of the U235 and the neutron before the fission occurred, I don't think anyone has ever managed to weight a U236 atom. So obviously there is a loss of mass. That mass is changed into energy by the formula E = mc^2 where m is the mass lost and c is the speed of light. So the question is what form of energy does it turn into? And the answer is two forms. First the daughter products split off a very high rate of speed. So part of the answer is kinetic energy. The rest is released as a gamma ray. Or light energy.

    I may be wrong, but I do not think there are any neutrinos emitted in a fission reaction. It is a bit inane for someone to claim that something is "pure energy" when there are two different forms that energy takes.
  11. Feb 9, 2012 #10


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    There is no such thing as "Pure Energy" unless you want to make up a definition for it. It is usually talked about because most people don't understand what energy is and it makes it seem "mystical" and more interesting. It's like calling work "Pure Work".
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