Discussion Overview
The discussion revolves around the implications of the Hubble law in relation to special relativity (SR) and whether the velocity of receding galaxies affects their mass as perceived from a different reference frame. It touches on theoretical concepts and interpretations within the framework of cosmology and relativity.
Discussion Character
- Exploratory, Technical explanation, Conceptual clarification
Main Points Raised
- One participant questions whether a galaxy with a recessional velocity gains mass relative to an observer, suggesting that the velocity might be low enough to avoid relativistic effects.
- Another participant asserts that velocities can indeed be high, implying that relativistic considerations may be more relevant than initially suggested.
- A third participant clarifies that the concept of relativistic mass is deprecated and that "mass" typically refers to invariant mass unless specified otherwise. They argue that in a zero-mass density FLRW universe, distant objects appear to recede without the need for relativistic mass, and that curved spacetime complicates the applicability of this concept.
- A later reply expresses understanding of the clarification provided.
Areas of Agreement / Disagreement
Participants express differing views on the relevance of relativistic mass in the context of the discussion. There is no consensus on whether the concept applies or how it should be interpreted in relation to the Hubble law and receding galaxies.
Contextual Notes
The discussion highlights limitations in the application of relativistic mass, particularly in curved spacetime and non-Einstein coordinate systems, but does not resolve the implications of these factors on the original question posed.