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Matter In A VeryLarge Box

  1. Dec 12, 2004 #1
    This is my first post here and I am not quite sure if this is the right place to put this post but here it goes anyway...

    It is said that space only exists in the presence of matter. IF this is true what would happen in the following situation...

    Let us say we have a box with incredibly large dimensions and infinitely strong sides. Inside this box there is a perfectly uniform vacuum, in which there are no atoms or any other particles are inside the box. Is it possible to say that since there is no matter inside the enormous box that there is no space inside the box? (Not sure if there would be "no Space" in the middle area or uniformly throughout???) And if there is space could we consider those units to be the standard units of space, if there is such thing?

    And Finally... If we were to run an electric current through the box would electrons and positrons appear? IF so were do they come from?

    Thanks Alot.

    Derek Mohammed
     
  2. jcsd
  3. Dec 12, 2004 #2

    Ivan Seeking

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    The short answer to your question is no. We exist in the spacetime of our universe and as far as we know there is no escaping it.

    Who says that space only exists in the presence of matter?

    Ernst Mach once commented that we only experience centrifugal [I think he said fugal and not petal] forces because the rest of the universe exists [which is another discussion], but your quote is new to me.
     
    Last edited: Dec 12, 2004
  4. Dec 12, 2004 #3
    The way I thought of it was if space does not have some standerdized units then it must depend on the presence of matter. But what would happen with the electric field, would electrons and positrons appear in the vacuum?
     
  5. Dec 12, 2004 #4

    DaveC426913

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    "If we were to run an electric current through the box would electrons and positrons appear? IF so were do they come from? "

    By what mechanism do you propose to run current through the box *without* injecting electrons?
     
  6. Dec 12, 2004 #5
    Ahh I see, I meant to say pass an electric field through the box, not current... (please note I am in my second year of university (physics/mathematics) and my knowledge of eltricricity is limited...
     
  7. Dec 13, 2004 #6

    DaveC426913

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    If the box does not allow electrons to pass though it, then it is an insulator. There will be no field within it. And yes, vacuum is an excellent insulator.

    BTW, note that, vacuum or no, and very large size or no, the box is still made from atoms and molecules that contain electrons - all of which are capable of providing electrons or electron holes as much as any other material. There is no reason why the box would not behave exactly as any old box (or vacuum tube) filled with vacuum would behave.


    However my overriding point would be aimed at the original premise. Who says you can only have space in the presence of matter?
     
  8. Dec 13, 2004 #7

    Integral

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    You have done nothing to exclude Electromagnetic fields from existing inside of your box. Numerous phenomena associated with space/time will occur inside the box. It will be at some temperature so there is thermal electromagnetic energy. The fundamental electrical properties of free space will be unchanged therefore Electromagnetic fields which do not require the existence of matter to propagate, will be able to pass through the space in the box. In addition virtual particles will continue to pop into and out of existence inside the box. There is more to space time then the presence or absence of massive bodies. Evacuating a box does nothing to alter space.
     
  9. Dec 16, 2004 #8
    I recommend reading Brian Green's Fabric of the Cosmos, he covers that very topic very well.
     
  10. Dec 17, 2004 #9

    DaveC426913

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    Want for Christmas please!

    If it's half as good as The Elegant Universe, it'll be fantastic.
     
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