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Metal packing structure and curved space

  1. Mar 21, 2014 #1
    In flat space the atoms in a metal have regular packing structures.

    A slight curvature of space would mean this wasn't geometrically possible. As a consequence do we expect metals to have a significantly lower density with a slight curvature of space?

    Obviously, this doesn't just apply to the atomic structures of metals, but it's an example of where the effect would be most pronounced.

    This effect seems to differ significantly between the Newtonian and Einsteinian views of gravity. Is that correct?

    Do we expect atomic structures to be under a vastly greater degree of stress when moving though varying gravitational fields than is predicted by Newtonian gravity?

    Can we use this effect to detect and measure curvature in space?

    Does it have a name?
     
    Last edited: Mar 21, 2014
  2. jcsd
  3. Mar 21, 2014 #2
    Too many questions in one OP. Regarding your first question... no. A curvature in space time doesn't deform objects like in a reflection of a curved mirror. The electromagnetic interactions in the molecules are responsible for keeping the shape of the object.A curvature in space time will be felt as gravity.
     
  4. Mar 21, 2014 #3
    Thanks for your reply I was starting to think that no one would reply at all.

    What you're saying is that the electrmagnetic force doesn't see curved space under the influence of a gravitational field. I just don't buy that at all. If it were correct, then the curvature of space described by GR would just be an apparent curvature to explain gravity.

    Let me give you an example to illustrate why I think you're wrong. Suppose in flat space we have 7 nuclei of the same element arranged with one in the middle and 6 surrounding it. The distance between any two nuclei is the same. Now if we take the same example in uniformly curved space, the distance from the cental nucleus to the adjacent nuclei differs from the other distances between nuclei. Your argument means that the central atom is in someway distinguishable with respect to the electomagnetic force. Now suppose instead of just 7 nuclei we have a large number arranged in the same packing structure, how then do we select central atoms? The only logical conclusion is such a structure is only viable in flat space.

    The thing that I find most compelling about this, is that under Newtonian gravity, your view is correct. Under Ensteinian gravity, a small change from flat space to curved space would mean that microscopic dislocations would result in large scale lattice structure changes, magnifying the influence of very small changes in the gravitational field.
     
    Last edited: Mar 21, 2014
  5. Mar 21, 2014 #4
    first of all, if you have just the nuclei, they are positively charged and will repel one another wether there is a curvature in space or not.

    I'm just saying that when you have a solid structure, it will be the same way it is, it will just move to some direction. Unless it is too soft or not too rigid. Distortions in space time is felt as gravity, pretty much
     
  6. Mar 21, 2014 #5
    Sure, but the role of the electrons in binding the lattice isn't relevant here. All we need to consider is distance between nuclei to describe our packing structure and the local geometry must determine packing structure.

    That can't be true. Space-time curvature isn't just a way to visualise gravity. It's a real prediction of GR which has been confirmed. We can't just take the conclusions from it that describe gravitation and ignore the others, we must take them all.

    There can be no conistent way to treat an non-point object, without considering the distortion effects on it, due to the curvature of space and what I describe is much more than the stretching effects of Newtonian gravity.
     
    Last edited: Mar 21, 2014
  7. Mar 21, 2014 #6
    Why did you start a thread then if you think you're right?
     
  8. Mar 21, 2014 #7
    Thinking I'm right and having confirmation or refutation of it are two very different things.

    I'm hoping someone who is further down the line with this stuff can offer some insight before I take this too much further, but there are 2 implications that seem very powerful.

    Firstly, from an experimental perpective, the only limitation on the minimum magnitude of curvature that could be detected this way would seem to be how big we can make a perfect lattice. Presuming of course, we have a method to detect the dislocations. Conversely, the curvature of space would put a limitation on how big we can make a perfect lattice.

    Also, from a theoretical perspective, something very peculiar happens when the curvature of space reaches a threshold where it's no longer possible to surround a nucleus with 2 or more other nuclei. Presumably this threshold has some other significance too.
     
    Last edited: Mar 21, 2014
  9. Mar 21, 2014 #8

    Drakkith

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    Staff: Mentor

    First, realize that it isn't the curvature itself that results in stress on the object, but a difference in curvature between two points that introduces stress. This effect is most pronounced around small, massive objects like neutron stars and black holes where the tidal effects of gravity start to become very noticeable.

    The stress introduced manifests as forces that pull atoms away from other atoms. However, chemical and metallic bounds are VERY strong and will resist the same way that a metal bar resists two people trying to pull it apart. So no, metals do not have significantly reduced density in curved space.

    No, the effect is identical. In newtonian gravity stress is introduced when you have a gradient in the field. For example, a metal sphere falling towards the Earth will feel a stronger pull on the side closest to the Earth. The side facing away from the Earth is further away and will experience a lesser force.

    Only when close to very massive objects.

    We would only be able to measure the difference between two points, not the "absolute" curvature.

    I believe it's called the tidal force.
    http://en.wikipedia.org/wiki/Tidal_force
     
  10. Mar 21, 2014 #9

    Nugatory

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    Staff: Mentor

    No. A slight curvature of space doesn't change the packing of atoms in a solid, it just means that correspondingly slight unmeasurably small stresses will be present in the solid, stresses that wouldn't be there in flat space. Take a lump of iron the size of your fist... You can move it through regions of very different spacetime curvature (for example, turn it over to reverse all the curvature effects) and the arrangement of atoms will be unaffected.
     
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