Discussion Overview
The discussion revolves around the conservation of energy in the context of an expanding universe, particularly focusing on the implications of redshift on photon energy. Participants explore the relationship between photon wavelength, frequency, and energy as it pertains to cosmological expansion.
Discussion Character
- Debate/contested
- Conceptual clarification
Main Points Raised
- One participant posits that as a photon travels through expanding space, its wavelength increases (redshift), leading to a decrease in frequency and energy, raising the question of where this energy goes in light of conservation laws.
- Another participant argues that energy conservation applies only within inertial frames, suggesting that in non-inertial frames, such as those involving galactic redshift, energy is defined locally and global conservation does not hold.
- A third participant agrees with the previous point and references a blog post by cosmologist Sean Carroll, which discusses the non-conservation of energy in general relativity, noting that this concept can be counterintuitive.
- One participant emphasizes that the issue with energy conservation lies in how energy is defined rather than energy itself.
- A participant provides a link to a FAQ that discusses the total mass-energy of the universe, indicating that this topic has been addressed in other discussions.
Areas of Agreement / Disagreement
Participants express differing views on the conservation of energy in an expanding universe, with some asserting that global energy conservation does not apply, while others raise questions about the implications of energy loss and its definition. The discussion remains unresolved with multiple competing perspectives.
Contextual Notes
The discussion highlights limitations in defining energy in non-inertial frames and the implications of general relativity on energy conservation, without reaching a consensus on these complex issues.