Conservation of Matter/Energy

  1. I learned that matter could not be created nor destroyed. I also learned that energy could not be created nor destroyed.

    But now I'm confused so I figure I would ask the experts to clarify so I can figure this out.

    Someobody told me, (and I'm not sure if it's true or not so please advise) that we have particle accelerators capable of creating tiny ammounts of antimatter. In this process a tiny and comparable ammount of matter is created?

    I don't know maybe that's baloney. But nevertheless the red flag for me is when I learned about how nuclear weapons work.

    Apparently they take matter, and convert it to its equivelent in energy. So isn't this both destroying matter and creating energy?

    Are these laws out of date or do I just have a misunderstanding? I'm just highly confused is all.
     
  2. jcsd
  3. ZapperZ

    ZapperZ 29,644
    Staff Emeritus
    Science Advisor
    Gold Member

    The more generalized conservation principle is the conservation of energy + mass, not energy alone, nor mass alone.

    In many cases, each one is conserved separately. However, when you start including processes in which matter and mass can be converted into each other, you have to use the more generalized conservation law.

    Zz.
     
  4. Hey Zapper, this might be a stupid question, but did you intend to say, "However, when you start including processes in which matter and mass can be converted into each other" or did you mean "energy and mass"? No disrepect intended - either it's a typo, or I'm misunderstanding something.
     
  5. ranger

    ranger 1,684
    Gold Member

    Zz meant to say "energy and mass".
     
  6. Another way of looking at it is to keep in mind that energy itself has mass (inertia and weight). You can't create energy, but you can sometimes change its form. You mentioned the example of converting a little bit of the nuclear potential energy of uranium, ie. of the mass of uranium, into heat and violence... and then if you cool down the left over matter, you find it weighs a little less, because that much mass-energy escaped in the form of heat, etc.
     
  7. ZapperZ

    ZapperZ 29,644
    Staff Emeritus
    Science Advisor
    Gold Member

    Yup. It was a typo. My brain and my fingers weren't working.

    Zz.
     
  8. Hey cesiumfrog,i agree with u.Mass according to my understanding is just a FORM of energy(or energy itself but with different energy density)
     
  9. The way that's worded, I'm not even certain what it means, but just to further differentiate/clarify what I'm saying: a wound spring (or a hot potato) is heavier than a relaxed spring (or cold potato), because the former contains more energy.
     
  10. BINGO.The energy density in both is different
     
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