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Thread: m=E/c^2 ?

  1. #1 m=E/c^2 ? 
    Forum Senior miomaz's Avatar
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    If one can create energy out of mass, can one create mass out of energy?
    how much energy would, theoretically an atom be equvalent to?
    If we where to convert energy into mass, what kind of mass would we gain?

    I've tried to answer these question based on wikipedia saying a letter weighing 1g is equvalent to 27 megatons of TNT. The answeres where so obsure that either Im claculating wrong or the numbers in wiki are too rounded-off.


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  3. #2  
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    Where in Wikipedia did you find that?


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  4. #3 Re: m=E/c^2 ? 
    . DrRocket's Avatar
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    Quote Originally Posted by miomaz
    If one can create energy out of mass, can one create mass out of energy?
    how much energy would, theoretically an atom be equvalent to?
    If we where to convert energy into mass, what kind of mass would we gain?

    I've tried to answer these question based on wikipedia saying a letter weighing 1g is equvalent to 27 megatons of TNT. The answeres where so obsure that either Im claculating wrong or the numbers in wiki are too rounded-off.
    1) Yes, you can theoretically create mass from energy, and that is what is believed to have happened in the Big Bang. Mass can come from a photon-photon collision if there is sufficient energy to create a massive particle. You won't get an atom from such a collision but rather a particle-antiparticle pair.

    2) The energy of an atom depends on the atom, and specifically on the mass of the atom

    3) You can do the calculation for the energy of 1 g of mass yourself using and the fact that a megaton of TNT is equivalent to Joules.
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  5. #4  
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    If you enter "1 gram *c^2 in joules" into Google calculator you get:

    1 gram * (c^2) = 8.98755179 10^13 joules

    And using Doctor Rocket's conversion factor that's

    (8.987 * (10^13)) / (4.184 * (10^15)) = 0.0214794455 megatons, or 21.4 kilotons.
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  6. #5 Re: m=E/c^2 ? 
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    Quote Originally Posted by DrRocket
    You won't get an atom from such a collision but rather a particle-antiparticle pair.
    Sorry, but what that mean?
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  7. #6 Re: m=E/c^2 ? 
    Forum Professor leohopkins's Avatar
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    Quote Originally Posted by AbuYusuf
    Quote Originally Posted by DrRocket
    You won't get an atom from such a collision but rather a particle-antiparticle pair.
    Sorry, but what that mean?
    Hmmmmm.......

    That seems to be incorrect. If a particle and an anti-particle collide, they usually annihalate in a glorious show of gama-rays.

    However, in simple laymans terms, yes it is possible to create mass from energy but you need a lot of it in a small enough space. Luckily the strong nuclear force (which binds quarks together inside protons and neutrons follows an inverse square law - that is the force between the particles gets STRONGER as the particles are moved further apart (unlike other forces such as magnetism and gravity) Eventually if you move quarks far enough from each other then what will happen is that the force will become so strong that the energy will collapse on itself and form another particle (another quark infact) - and thats why you wont find single quarks floating around the universe - they have to exist at least in pairs.

    And to the OP; dont take everything you find in wikipaedia as read or wholly correct; remember wikipaedia is an open-source encyclopaedia so anyone can add anything. although yes the general gist of it is correct - from a small amount of mass you get a large amount of energy.
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  8. #7 Re: m=E/c^2 ? 
    Forum Masters Degree thyristor's Avatar
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    [quote="leohopkins"]
    Quote Originally Posted by AbuYusuf
    Quote Originally Posted by DrRocket
    You won't get an atom from such a collision but rather a particle-antiparticle pair.
    Sorry, but what that mean?
    Hmmmmm.......

    That seems to be incorrect. If a particle and an anti-particle collide, they usually annihalate in a glorious show of gama-rays.

    quote]
    Well, they move away from each other.
    373 13231-mbm-13231 373
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  9. #8 Re: m=E/c^2 ? 
    Forum Professor leohopkins's Avatar
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    [quote="thyristor"]
    Quote Originally Posted by leohopkins
    Quote Originally Posted by AbuYusuf
    Quote Originally Posted by DrRocket
    You won't get an atom from such a collision but rather a particle-antiparticle pair.
    Sorry, but what that mean?
    Hmmmmm.......

    That seems to be incorrect. If a particle and an anti-particle collide, they usually annihalate in a glorious show of gama-rays.

    quote]
    Well, they move away from each other.
    No - they dont move away from each other. They have an opposite charge therefore they attract and the end result is annihalation.
    The hand of time rested on the half-hour mark, and all along that old front line of the English there came a whistling and a crying. The men of the first wave climbed up the parapets, in tumult, darkness, and the presence of death, and having done with all pleasant things, advanced across No Man's Land to begin the Battle of the Somme. - Poet John Masefield.

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  10. #9 Re: m=E/c^2 ? 
    . DrRocket's Avatar
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    Quote Originally Posted by leohopkins
    Quote Originally Posted by AbuYusuf
    Quote Originally Posted by DrRocket
    You won't get an atom from such a collision but rather a particle-antiparticle pair.
    Sorry, but what that mean?
    Hmmmmm.......

    That seems to be incorrect. If a particle and an anti-particle collide, they usually annihalate in a glorious show of gama-rays.
    Gamma rays are photons. And if you have photons with high enough energy colliding to form massive particles those particles occur in particle/anti-particle pairs.

    http://en.wikipedia.org/wiki/Pair_production
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  11. #10 Re: m=E/c^2 ? 
    Forum Masters Degree thyristor's Avatar
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    [quote="leohopkins"]
    Quote Originally Posted by thyristor
    Quote Originally Posted by leohopkins
    Quote Originally Posted by AbuYusuf
    Quote Originally Posted by DrRocket
    You won't get an atom from such a collision but rather a particle-antiparticle pair.
    Sorry, but what that mean?
    Hmmmmm.......

    That seems to be incorrect. If a particle and an anti-particle collide, they usually annihalate in a glorious show of gama-rays.

    quote]
    Well, they move away from each other.
    No - they dont move away from each other. They have an opposite charge therefore they attract and the end result is annihalation.
    After the pair production, the electron and positron move away from each other in an angle of 180 degrees.
    373 13231-mbm-13231 373
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  12. #11  
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    That's because they possess the excess energy of the initial photon that remains as kinetic energy after their formation. If this is too small, they annihilate immediately again.
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  13. #12  
    Forum Professor leohopkins's Avatar
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    Quote Originally Posted by Dishmaster
    That's because they possess the excess energy of the initial photon that remains as kinetic energy after their formation. If this is too small, they annihilate immediately again.
    Thats much better explained.
    The hand of time rested on the half-hour mark, and all along that old front line of the English there came a whistling and a crying. The men of the first wave climbed up the parapets, in tumult, darkness, and the presence of death, and having done with all pleasant things, advanced across No Man's Land to begin the Battle of the Somme. - Poet John Masefield.

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