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Light and Gravity

  1. Jan 8, 2007 #1
    Light is energy.Also light has photons as energy carriers.So,if large amount of light is concentrated on a small area to an extent that the energy has effect of significantly large mass,would it create gravity as energy also warps space-time?:rolleyes:
     
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  3. Jan 8, 2007 #2

    Hootenanny

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    Yes, photons do produce curvature in space-time. As you correctly say, energy curves space-time. However, as I have said in previous threads I strongly disagree that photons have 'mass' so much in as I strongly disagree with the use of 'relativistic mass' which is not real. So I would prefer if we do not discuss that photons 'in effect' have mass.
     
    Last edited: Jan 8, 2007
  4. Jan 8, 2007 #3

    disregardthat

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    No, at least not the way I see it. The photon have 0 mass, and there is no number you can muliply it with to get more than 0.
    Anyway, the 'evidense' that the photon has zero mass, is because it moves at einsteins constant 'c', I think.
     
  5. Jan 8, 2007 #4
    Hmm.Mass and energy have the same effects if im not mistaken!
     
  6. Jan 8, 2007 #5

    disregardthat

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    This makes me confused, if energy equals mass, how can zero mass be energy at all :S. the photon have energy all right, but I thought it was in a 'preserved medium' that it didn't have any mass. Guess it was wrong...
     
  7. Jan 8, 2007 #6
    Sorry.Mass is a form of energy.When mass energy is converted to any other form of energy E=mc^2 can be useful in calculating only the AMOUNT of energy.A photon has effects of mass as it caries energy
     
  8. Jan 8, 2007 #7
    @Hootenanny

    Why do forms of energy differ at all?
     
  9. Jan 8, 2007 #8

    Hootenanny

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    Jarle: What is a preserved medium?

    To all: This is why I dislike the use of relativistic mass, it only results in confusion.
     
  10. Jan 8, 2007 #9

    Hootenanny

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    They differ in the way they are defined. For example gravitational potential energy is defined as the potential energy per unit mass of an object in a gravitational field. Thermal energy is defined as internal energy of a system.
     
  11. Jan 8, 2007 #10

    cristo

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    I agree with Hootenanny: using the relativistic mass leads to confusion. The relativistic mass is not "real" in the sense that, with the correct choice of inertial frame, the relativisitic mass of a particle will be zero.

    However, the mass of a particle is invariant under transformations between inertial frames, and thus this is a "real" quantity.
     
  12. Jan 8, 2007 #11
    Then why are their effects different in nature?
     
  13. Jan 8, 2007 #12

    Hootenanny

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    What do you mean by 'their effects'?
     
  14. Jan 8, 2007 #13

    ranger

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    Last edited: Jan 8, 2007
  15. Jan 8, 2007 #14
    heat energy has the heating effect,electrical energy causes motion of electrons.Why isnt it say,the other way round?
     
  16. Jan 8, 2007 #15

    cristo

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    Anantchowdhary: I recall a few days ago, you asking the same question, to which russ_waters replied and gave you a link to a site describing different forms of energies. Here is the link to that thread: https://www.physicsforums.com/showthread.php?t=150002
    Did you read the webpage?
     
  17. Jan 8, 2007 #16
    Yea surely i did as the thread was made by me.But still i havent got any clear answer.Zap was wrong as what he was trying to say was lik saying if u stack up shoes ull get a house.That was not what i meant
     
  18. Jan 8, 2007 #17

    ranger

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    Electrical energy doesnt bring about the motion of electrons, rather its the energy made available by the flow of electric charge in a conductor.
     
  19. Jan 8, 2007 #18

    Hootenanny

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    Then what do you mean, because I for one am pretty confused as to what you're asking if that previous thread didn't answer your question.
     
  20. Jan 8, 2007 #19
    I read the thread as i made it.But still ive got no clear answer
     
  21. Jan 8, 2007 #20

    cristo

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    With all due respect, I suggest you read up on the fundamentals of energy. Then come back with a specific question with respect to a point that you are not clear on, since, at present, you are just waffling!
     
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