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Matter Creation.

  1. May 29, 2014 #1
    How does matter be created from light? When a photon strikes a heavy nucleus, it disintegrates and produces a pair of an electron and a positron.

    Or

    Two photons are collided and an electron positron pair is produced.

    Which is true?
     
  2. jcsd
  3. May 29, 2014 #2

    Dale

    Staff: Mentor

    Both processes happen, but the first is much more common.
     
  4. May 29, 2014 #3
    I didn't understand the meaning of collision used here. If we search the meaning of the word collide, we get the following results:

    hit by accident when moving.
    "she collided with someone"
    synonyms: crash (into), come into collision (with), bang (into), slam (into), impact (with); hit, strike, run into, meet head-on, smash into, smack into, cannon into, plough into, bump into, crack into/against, knock into, dash against; informalbarrel into
    "she collided with someone"

    I seems that the word collision is related to the things which have physical existence. I think there is no significance in speaking about the collision of photons (tiny packets of energy).
     
  5. May 29, 2014 #4

    Nugatory

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    In particle physics, "collision" has a specific technical meaning that you won't find in non-specialist sources. The best layman-friendly synonym (which many of us prefer) is "interaction", and you wont go too far wrong if you mentally substitute "interaction" for "collision" throughout this thread.

    (And I do feel compelled to point out that "Large Hadron Interactor" and "Superconducting Superinteractor" don't sound quite as cool as "Large Hadron Collider" and "Superconducting Supercollider" :smile:).
     
  6. May 29, 2014 #5

    phyzguy

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    I don't understand this comment. Photons certainly have physical existence. How do you think you are reading this post? They can collide (i.e interact). As you said, they are "tiny packets of energy". Why does this make you think they don't have physical existence?
     
  7. May 29, 2014 #6
    Uhhhh....??? Photons have physical existence, you know that, right?
     
  8. May 29, 2014 #7
    I did't know that photons have physical existence (Having substance or material existence). Has it been proved that they have material existence?
     
  9. May 29, 2014 #8

    phyzguy

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    You would need to define what you mean by having material existence. I think any reasonable definition would conclude that they do. They carry energy and momentum, for example. Light striking an object exerts a force on the object. How can it exert a force unless the light has physical existence? How can you see things if light doesn't have physical existence?
     
  10. May 29, 2014 #9

    Nugatory

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    That question cannot be answered without an agreed-upon definition of "material existence", and that cannot be found through the methods of empirical science. Physics can tell us about the measurable properties and behaviors of various things, from supernovae to subatomic particles and photons, but "material existence" is not one of these properties/behaviors.

    If we cannot pull this thread back to the original question, I expect that a moderator will (rightly) lock it as out-of-scope for PF.
     
  11. May 29, 2014 #10

    micromass

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    Yes. Let us please focus on the original question and let us stop discussing things like "material existence".
     
  12. May 29, 2014 #11

    phyzguy

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    The original question was answered in post #2. It looks to me like we are done.
     
  13. May 29, 2014 #12

    micromass

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    Right. So let us wait for the OP to post again. Maybe he has more questions or something is still unclear.
     
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