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Energy and matter

  1. Mar 18, 2010 #1
    If matter is the result of the transformation of energy. Is there a way to create matter from energy, as well energy is generated from matter (nuclear fussion and/or nuclear fission)?
    If there's a way, is it just theorical?
     
  2. jcsd
  3. Mar 18, 2010 #2
    As far as I can tell isn't the universe energy, creating matter? After all E=MC(squared)
     
  4. Mar 18, 2010 #3
    I mean that energy can be obtained from matter, but does it exist the same process in reverse?
     
  5. Mar 18, 2010 #4
    If the physical universe all around us is the result of E=MC squared, then is not all matter the living breathing example of energy vibrating (string theory) therefore creating matter from energy in the form of everything, including you and me.
    Therefore matter is constantly being created from energy right in front of our eyes, nano second to nano second.
    My math sucks, but I'm talking big picture here. :)
     
  6. Mar 18, 2010 #5

    bapowell

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    Graybass, your comments are pretty speculative. String theory is not 'energy vibrating' and 'creating matter from energy'. Einstein's equation [tex]E=mc^2[/tex] of course tells us the 'currency' conversion between mass (what is usually referred to as matter) and energy. Good examples of how this conversion actually manifests itself in nature are electron/positron pair production and annihilation. Processes exist in which photons (energy) are converted to electron/positron pairs (matter). The reverse of this process also occurs in nature: electrons and positrons can annihilate to form photons. Of course, as alvarogs mentions, nuclear reactions are also a nice place to find examples of the conversion of matter to energy.
     
  7. Mar 18, 2010 #6
    Thank you. Excellent post!
     
  8. Mar 18, 2010 #7
    I took an example of how energy can be converted in matter and I tought in photosyntesis... I don't know exactly if it's a good example of the reverse process of nuclear reactions, because this process suposse some chemical reactions and requires more complex conditions like habitable environments.

    E/c^(2) = m

    My doubt is related with the process where matter is formed
     
  9. Mar 19, 2010 #8

    Chalnoth

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    I honestly don't like the language of conversion between energy and matter. Energy does not exist independent of matter as a separate entity. Energy is a property of matter.

    What [tex]E = mc^2[/tex] means is that the mass of an object is the energy that object has when it has no motion in whatever reference frame you're using. One way of understanding this is that the mass of an object is the energy in that object's internal degrees of freedom. For instance, if I have a potato, and I heat it up, its mass increases. We understand the increase in energy as being due to the increased kinetic energy of the atoms that make up the potato. Measuring its mass externally will reflect this increase in its internal energy.

    The situations where you have what people call "conversion" between energy and matter are really conversion between kinetic energy and rest-mass energy. You still have matter before and after, it's just that the amount of energy in mass is different. For example, if I take two electrons and slam them together with enough rest mass energy, then they'll produce an electron-positron pair, with all four particles moving off with less kinetic energy than they had before (because some of the kinetic energy was soaked up in the rest mass energy of the new electron-positron pair).

    Similarly, if I have an electron and a positron come together, they will annihilate and produce a pair of photons. That pair of photons has no rest mass, and so we end up with all of the rest mass energy converted into the kinetic energy of the photons.
     
  10. Mar 19, 2010 #9
    Have we ever "dissolved" mass to convert to energy for practical uses so far? What we get is in reality the binding energy released by breaking a big atom on one side of periodic table or by "gluing" four nucleons (so to say) together on the other side.
     
  11. Mar 19, 2010 #10

    Chalnoth

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    That doesn't work. Conservation laws prevent doing anything more drastic than rearranging protons and electrons, as those are the lowest-mass particles with their atomic numbers.
     
  12. Mar 19, 2010 #11

    bapowell

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    So do you consider photons matter?
     
  13. Mar 19, 2010 #12

    Chalnoth

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    Yes. They are not fundamentally different from electrons or quarks. They just have different quantum numbers.
     
  14. Mar 20, 2010 #13

    bapowell

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    OK. It sounds like this is largely a discussion of semantics. Has anyone in this thread defined what they mean by the term matter? I don't find it to be an overly helpful concept if virtually anything of substance is matter. Traditionally, matter was contrasted with other forms of energy in that it had mass. Chalnoth, you seem to disagree with this view.
     
  15. Mar 20, 2010 #14

    Chalnoth

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    Very much so, because mass doesn't appear to be a fundamental property of any matter: if you attempt to give particles mass as a fundamental property in quantum field theory, it quickly leads to a contradiction. So in the standard model of quantum physics, mass arises due to interactions.

    The largest distinction between photons (and other force carriers) and normal matter (e.g. protons, neutrons, electrons) is that normal matter is made up of fermions, while force carriers are made up of bosons. But even that's a bit tenuous of a distinction, as normal matter can also pair up to behave in a bosonic manner.
     
  16. Mar 20, 2010 #15

    bapowell

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    Right, I agree with this. I agree that mass is certainly an 'emergent' quantity in gauge theory -- spontaneous symmetry breaking merely 'dresses' massless excitations. So, I guess the original question still remains. What is the point of talking about 'matter' if it is really not (operationally) any different from energy.
     
  17. Mar 20, 2010 #16

    Chalnoth

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    Matter is a description of a quantum field, whereas energy is a property of that field.
     
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