Observable Universe and Black Holes

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Discussion Overview

The discussion revolves around the relationship between the observable universe and black holes, particularly focusing on how gravity operates across these boundaries. Participants explore concepts related to gravitational influence, the nature of spacetime curvature, and the implications of general relativity in these contexts.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions whether galaxies outside the observable universe can exert gravitational influence on us, suggesting that if they cannot, gravity information must travel at the speed of light.
  • Another participant proposes that gravitational effects can be felt from distant matter, albeit very weakly, due to the finite speed of light and the time it takes for gravitational influence to propagate.
  • There is a discussion about the nature of spacetime curvature caused by black holes, with some participants suggesting that this curvature does not have a defined starting point and is an intrinsic aspect of spacetime.
  • Some participants assert that objects outside the observable universe are causally disconnected from it, meaning their gravitational effects do not influence bodies within our observable universe.
  • There is a query about whether there was a specific point in the past when the gravitational influence of distant galaxies ceased to affect us.

Areas of Agreement / Disagreement

Participants generally agree that objects outside the observable universe are causally disconnected from it, but there is disagreement regarding the extent and nature of gravitational influence from distant galaxies and the implications for black holes.

Contextual Notes

Participants express uncertainty about the exact nature of gravitational influence and the characteristics of spacetime curvature, indicating that these concepts may depend on specific definitions and assumptions that are not fully resolved in the discussion.

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Hi, my first post here!

Galaxies outside the observable universe (that we can't see their light) can affect us with their gravity?
If the answer is no, we can say that gravity information travels at the speed of light.
So, in a black hole how gravity information from an object inside, escapes the event horizon?
An object inside a black hole is also outside our observable universe.
I know that in general relativity mass of a black hole is responsible for the curvature of spacetime, but where this curvature begins in our universe? Does it begin from the Event Horizon limit? Can we say the event horizon itself carries all the gravity information of a black hole?

I can't figure it out, I have it, all in a mess inside my mind
 
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Thats...tough to answer properly. Consider that gravitation is, as far as we know, infinite in reach. Very early in the universe it is believed that the universe was compressed to a very high degree. The matter and energy here was very close together, so it would have easily had time for its gravity to affect our area. However, inflation and expansion have pushed some of that matter and energy outside of our view for the future. BUT, this process hasn't happened instantly, it has taken time, and the gravity, while having weakened, should still be affecting us at least a tiny amount. (REALLY tiny. So tiny that expansion overwhelmingly dominates gravitation between us)

Similarly, infalling objects do not fall in instantly, they take time. Plus, from our perspective they don't actually ever fall in thanks to time dilation! For practically all intents and purposes their gravity simply adds to the black hole.
I know that in general relativity mass of a black hole is responsible for the curvature of spacetime, but where this curvature begins in our universe? Does it begin from the Event Horizon limit? Can we say the event horizon itself carries all the gravity information of a black hole?

This curvature is not something you can say "starts" or "ends" somewhere. It simply exists. It is an intrinsic part of spacetime. I don't think I can explain it very well.
 
We are pretty confident objects, like galaxies, that are outside the observable universe are causally disconnected from the observable universe. Or, in other words their light, gravity, etc., have no effect on bodies within the observable universe. We are not causally disconnected from black holes within the observable universe. We still experience the effects of gravity and charges generated by black holes.
 
Chronos said:
We are pretty confident objects, like galaxies, that are outside the observable universe are causally disconnected from the observable universe. Or, in other words their light, gravity, etc., have no effect on bodies within the observable universe. We are not causally disconnected from black holes within the observable universe. We still experience the effects of gravity and charges generated by black holes.

Certainly we wouldn't be affected by changes in them since they moved out of our observable universe, but in the past was there ever a certain point where their influence on us through gravity simply disappeared?
 

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