Gravity at its maximum range question.

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    Gravity Maximum Range
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Discussion Overview

The discussion revolves around the nature of gravity, its range, and the relationship between gravity and the curvature of space-time. Participants explore whether gravity has a finite or infinite range and how this relates to the bending of space and time, particularly in a hypothetical universe with only two massive bodies at opposite ends.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions whether two massive bodies in a vast universe would exert gravitational influence on each other and whether gravity has a finite range or infinite range that weakens with distance.
  • Another participant asserts that the Newtonian gravitational field extends to infinity and only approaches zero at infinity, suggesting that space-time can become asymptotically flat in certain conditions.
  • A participant expresses confusion about the relationship between gravity, space-time curvature, and the implications of gravity's infinite range on the bending of space and time.
  • Another reply clarifies that the space-time curvature produced by an isolated body approaches flatness at spatial infinity, similar to how the gravitational field approaches zero, emphasizing that this does not imply gravity is non-zero everywhere.

Areas of Agreement / Disagreement

Participants exhibit some agreement on the concept of gravity extending to infinity but express differing views on the implications of this for space-time curvature and the nature of gravity's influence over vast distances. The discussion remains unresolved regarding the relationship between gravity's range and the bending of space-time.

Contextual Notes

Participants discuss the concepts of asymptotic flatness and the behavior of gravitational fields at large distances, but there are unresolved assumptions about the nature of space-time and the conditions under which these principles apply.

solar71
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Hey guys. I have an unusual question.

Lets say the universe is 100,000,000,000 Light years across. (100 billion I think)

Lets say there are only 2 bodies that have mass in said universe.
One body is at one end of this universe and the other body is at the opposite end.

Do these 2 bodies pull on each other? Does gravity have a finite range?
Or does gravity have infinite range but only gets infinitely weaker with distance?

Does space/time eventually flatten out?

Thanks
 
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The Newtonian gravitational field extends out to infinity in all directions and only goes to zero at infinity. As for space-time eventually flattening out, if you have a system consisting of isolated bodies (bodies that are always localized to some fixed region of space) then yes space-time will eventually flatten out (such space-times are called asymptotically flat).
 
Ok thanks for your well informed reply. Much appreciated.

One more question. I was under the impression that the bending of space and therefor time is what caused gravity to act on objects. So how is it possible for gravity to have infinite range but space/time not to?

Doesn't space have to be slightly bent for gravity to be present? And if gravity has infinite range doesn't that mean that the bending of space also has infinite range as well? And if so doesn't that mean that time is also slightly bent/stretched as well?

I'm a little confused. Please enlighten me.

Thanks
 
Consider for example an isolated stationary star. The space-time curvature produced by the star asymptotically becomes flat meaning it approaches flat space-time as you approach spatial infinity. So in this sense it is exactly like the Newtonian gravitational field which itself approaches zero as you approach spatial infinity. Sorry if that wasn't clear before; I wasn't implying that the Newtonian gravitational field is non-zero everywhere, I was implying that it asymptotically approached zero as you approach spatial infinity.
 

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