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Why do electromagnetic fields exist where there is no matter

  1. Apr 9, 2015 #1
    Wikipedia define EM field as "a physical field produced by electrically charged objects"

    But there are no electrically charged objects in between cosmic entities and yet Wiki states "The electromagnetic field extends indefinitely throughout space".

    What am I missing here?
     
  2. jcsd
  3. Apr 9, 2015 #2

    Drakkith

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    Staff: Mentor

    Consider that two electrically charged particles will experience a force due to their charges no matter what the distance is between them, with the strength of this force inversely proportional to the square of the distance between them. In other words, it scales at 1/r2. The range is infinite. So no matter where in the universe one of them is placed, an EM field will exist. So even if intergalactic space was completely empty (which it isn't) there would still be an EM field because matter exists somewhere in the universe.
     
  4. Apr 9, 2015 #3
    Can you please explain simply why that is so?
     
  5. Apr 9, 2015 #4

    Drakkith

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    Staff: Mentor

    It's an observed fact. Charged particles are observed to either repel or attract each other. The strength of the force follows the inverse square law, which I gave above. What would you like explained?
     
  6. Apr 9, 2015 #5
    Why are there EM forces linked?

    Wiki just says: an inverse-square law is any physical law stating that a specified physical quantity or intensity is inversely proportional to the square of the distance from the source of that physical quantity.

    That's just saying how the strength of the force is to be calculated? That doesn't tell me much about why the forces of each atom are linked?
     
  7. Apr 9, 2015 #6

    Drakkith

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    You won't find an absolute answer. We know how to calculate the strength of the force, but we don't know the fundamental cause of the EM force or any of the other fundamental forces.
     
  8. Apr 9, 2015 #7
    Well, that seems quite a predicament for the cosmic evolution of human beings now isn't it. If we were to know... what could we do with that knowledge?
     
  9. Apr 9, 2015 #8

    Drakkith

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    Staff: Mentor

    Who knows? Perhaps nothing, perhaps something.
     
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