Is Energy Truly Conserved in an Expanding Universe?

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Discussion Overview

The discussion centers around the concept of energy conservation in the context of an expanding universe, particularly within the framework of General Relativity and the Friedmann-Lemaître-Robertson-Walker (FLRW) metric. Participants explore the implications of cosmic expansion on energy, including the potential for energy to be "lost" and the idea of negative energy during inflation.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • One participant suggests that energy may be lost forever as it travels beyond the observable universe due to the expansion of space, proposing that this could imply a non-zero total energy in the universe.
  • Another participant questions the relevance of creating multiple threads on similar topics, indicating a perceived overlap in the discussions.
  • A third participant clarifies that the threads address different aspects of energy conservation, with one focusing on the role of expansion in energy conservation and the other on the implications of negative energy during the universe's creation.
  • A later reply asserts that both threads fundamentally address energy conservation in the FLRW metric, noting that while energy is conserved locally in General Relativity, it is not well-defined globally in a non-static metric.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between the threads, with some asserting they are distinct while others see them as fundamentally similar. The discussion on energy conservation remains unresolved, with multiple perspectives on how it applies in an expanding universe.

Contextual Notes

The discussion highlights limitations in defining energy conservation globally in non-static metrics and the assumptions underlying the concept of negative energy during cosmic inflation.

zeromodz
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I realized that if right now, energy is being lost forever by traveling across our Hubble volume. That energy will never reach us because no information can travel faster than c except the expansion of space. So in that sense, that energy is truly lost forever from our perspective. Maybe the zero energy universe was never really zero. Maybe it started off with negative energy expanding faster than c so it could never cancel out with the positive energy. Therefore, we have a universe with a positive amount of energy only because the negative energy traveled faster than c during inflation. What do you think?
 
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Why are you making two threads with almost the same topic at the same time?
 
DaleSpam said:
Why are you making two threads with almost the same topic at the same time?

They are not on the same topic, one is about how the expansion of space can support the contribute the conservation of energy and the other is about the creation of the universe idea of negative energy not being able to cancel out.
 
They are both questions on conservation of energy in the FLRW metric. They are essentially the same question and the answer is essentially the same: energy is conserved locally in GR, but in a non-static metric it is not even well defined globally.
 

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