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B Is the universe an object?

  1. May 8, 2017 #1
    What I don't understand about the universe is empty space must be made of some kind of material or substance because stars and other large bodies, in fact anything with mass can bend space then it must be made of something which has the capability to bend and be distorted.

    How can space bend if space is not a thing? I don't understand.
  2. jcsd
  3. May 8, 2017 #2
    It does not necessarily need to be made of anything. Light can be bent as a result of strong gravitational fields, which is what happens in the case of black holes.
  4. May 8, 2017 #3


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    You are having a very common misunderstanding, based on pop-sci presentations. Space is not a thing and does not actually bend or warp or do any of those things. What DOES happen is that things travel on what are called "geodesics", which are straight lines in Riemann Geometry, which is the geometry that describes space-time. When looked at from the point of view of Euclidean Geometry, those same lines are "bent" or "curved". So we SAY that heavy objects like planets "bend" spacetime but that's just shorthand for what I just said.
  5. May 8, 2017 #4


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    As phinds said, Space isn't bending. That's just a common way to describe it because the effect is somewhat similar to what happens if you bend the surface of an object. What happens is that the geometry of spacetime changes in the presence of mass or energy.

    Still, your question has merit and the question of whether space (or spacetime) is a "thing" depends upon your definition of what a "thing" is. This gets into metaphysics and there's no consensus that I know of at this time.
  6. May 8, 2017 #5


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    Space is like a force. Is a force made of some kind of material? I don't know the fact is that it is a measurable quantity that has effects on things in the nature. We cannot see a force but only its effect ad we cannot see the space but the extension of the space ...
    I don't know if this clarify, sometimes speaking on these thin interpretations I get confused ...

  7. May 8, 2017 #6


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    This may be too philosophical a question for PF, because you can't resolve it to one way or the other with any experimental data... Ernst Mach said something along the lines "Space is a mental abstraction that we construct to describe relationships between objects", which clearly implies a view that without objects like planets, stars, dust clouds, etc. there is no space. Then again, an "empty" space can contain energy in the form of gravitational waves, but you can't measure that energy without also having matter present (because any measuring instrument, not to mention a person using it, must necessarily be made of matter).
  8. May 8, 2017 #7


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    I think that's certainly a valid point.

    AishaGirl, I don't mean to shut down your question, but the fact is that this falls more into philosophy than science and we don't usually allow philosophy here at PF. If you'd like to understand how science models spacetime and all the rules we use to predict things within it, feel free to ask. But the question of "is space an object" just cannot be answered at this time.

    Thread locked.
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