Big Freeze and Law of convervation of energy

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Discussion Overview

The discussion revolves around the implications of the Big Freeze scenario in cosmology, particularly focusing on the conservation of energy and its applicability on cosmological scales. Participants explore how matter decay in this scenario aligns with or challenges the law of conservation of energy, as well as its relevance in different contexts such as inflation and gravitational energy.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants question how matter can decay in the Big Freeze scenario without violating the conservation of energy, referencing claims made by Kurzgesagt.
  • Others assert that conservation of energy does not apply on cosmological scales, suggesting that this principle may not hold in the context of the universe's evolution.
  • One participant raises a question about the role of conservation of energy during inflation, given the assertion that it does not apply cosmologically.
  • Another participant references a blog post arguing that energy is not conserved in certain cosmological contexts, prompting further inquiry into when conservation laws are valid.
  • Some contributions suggest that conservation of energy is valid in closed systems and in scenarios where gravitational potential energy is treated as a form of energy, highlighting the complexities involved in these considerations.
  • There is a discussion about the implications of gravitational energy and its behavior compared to other forms of energy, with a focus on the challenges of creating perpetual motion machines based on gravitational systems.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of conservation of energy in cosmological contexts, with no consensus reached regarding its validity in the Big Freeze scenario or during inflation.

Contextual Notes

Limitations include the dependence on definitions of energy conservation and the specific conditions under which these laws are considered valid, particularly in relation to gravitational effects.

Rodrigo Olivera
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(Kurzgesagt- In a Nutshell) says that in the Big Freeze scenario all the matter will decay in the end, how is this possible without breaking the law of convervation of energy?
 
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Rodrigo Olivera said:
(Kurzgesagt- In a Nutshell) says that in the Big Freeze scenario all the matter will decay in the end, how is this possible without breaking the law of convervation of energy?
There IS no "conservation of energy" on cosmological scales.
 
phinds said:
There IS no "conservation of energy" on cosmological scales.
Why?
By the way, why convervation of energy have an important rol in inflation if there is no convervation of energy in cosmological scales?. https://en.wikipedia.org/wiki/Zero-energy_universe
 
Rodrigo Olivera said:
(Kurzgesagt- In a Nutshell) says that in the Big Freeze scenario all the matter will decay in the end, how is this possible without breaking the law of convervation of energy?
phinds or someone else more advanced in the Standard Model may be able to confirm or refute this, but I believe the only thing actually required to be conserved in particle decay is the particle's charges (spin, Baryon/Lepton number, strange, electric, etc.).
 
Rodrigo Olivera said:
Okay, so when does the law of convervation is valid?

The laws of thermodynamics assume a closed system.
 
Rodrigo Olivera said:
Okay, so when does the law of convervation is valid?
It is valid in situations where you can neglect gravity, or in situations where you treat gravitation potential energy as a valid kind of energy. As Sean Carroll stated, there's nothing wrong with thinking of gravitational fields having gravitational energy. The drawback is that it behaves very differently from other forms of energy.

I think it is advantageous to use the concept of gravitational energy because it makes it clear that you can't make a (cyclic) perpetual motion machine based on gravity. The total non-gravitational energy might be different at different points of the gravitational cycle, but it should return to what it was at a previous cycle.
 

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