What is the role of elasticity in space-time according to Sakharov's theory?

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Discussion Overview

The discussion revolves around the role of elasticity in space-time as proposed by Sakharov's theory, particularly in the context of gravity's effects on space-time and the implications of its potential elasticity. Participants explore theoretical implications, conceptual understandings, and the nature of space-time in relation to gravity.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants question whether space-time returns to equilibrium after the removal of a gravitational mass, pondering the fate of other masses in the same gravitational well.
  • One participant asserts that space-time would revert to a flat configuration when mass is removed, but notes that gravitational waves can leave a lasting imprint on space-time geometry.
  • Another participant claims that space is elastic and flexible, suggesting that without such properties, the universe would have fragmented long ago.
  • Conversely, some argue that space is not a substance and lacks properties like elasticity, positing that gravity affects matter and photons by altering their paths rather than being a property of space itself.
  • A participant raises a question about the origin of virtual particles if space-time is not considered a substance.
  • Reference is made to Sakharov's 1967 concept of "elasticity of space," which is likened to the curvature of space-time in general relativity.

Areas of Agreement / Disagreement

Participants express differing views on the nature of space-time, its elasticity, and the implications of gravity's effects, indicating that multiple competing perspectives remain without consensus.

Contextual Notes

Participants reference various interpretations of gravity's relationship with space-time, highlighting the complexity and nuance of the discussion. There are unresolved questions regarding the definitions of space and its properties, as well as the implications of gravitational phenomena.

Fuzzy Logic
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If gravity distorts space-time, does space-time return to equilibrium when the gravity mass is gone (let's say it vanished instantly)? If so, what happens to other satellite masses that are caught in the same gravity well?

Does space-time just instantly slip out from under them? Or do the satellites get dragged along with it?
 
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Fuzzy Logic said:
If gravity distorts space-time, does space-time return to equilibrium when the gravity mass is gone (let's say it vanished instantly)? If so, what happens to other satellite masses that are caught in the same gravity well?

Does space-time just instantly slip out from under them? Or do the satellites get dragged along with it?

In general, yes the spacetime will return to the background minkowski (read: flat) configuration when the mass is gone. However, gravitational waves can leave an 'imprint' on spacetime even after they have passed through a region, permanently altering the spacetime geometry. Look up gravitational wave memory.
 
Space is definitely elastic and flexible. If it wasn't the universe would have shattered into an infinite amount pieces a long time ago.
 
Space is not a 'substance', so it has no properties such as elasticity. Gravity affects 'things' that pass through the gravitational field - like matter and photons - altering their path. Some would say the gravitational field IS the fabric of space. Some would even say that if gravity suddenly disappeared, so would space.
re: http://www.astronomycafe.net/gravity/gravity.html

"Perhaps the most unusual thing about gravity we know about is that, unlike the other forces of nature, gravity is intimately related to space and time. In fact, space and time are viewed by physicists, and the mathematics of relativity theory, as qualities of the gravitational field of the cosmos that have no independent existence. Gravity does not exist like the frosting on a cake, embedded in some larger arena of space and time. Instead, the 'frosting' is everything, and matter is embedded and intimately and indivisibly connected to it. If you could turn off gravity, it is mathematically predicted that space and time would also vanish!"
 
If spacetime is not a substance, where do virtual particles come from?
 
Sakharov ( 1967 ) suggested accounting for the effects of general relativity by introducing the concept of an "elasticity of space," analogous to the well-known curvature of space-time.
 

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