Discussion Overview
This thread addresses questions posed by a newcomer, Mathbrain, regarding the nature of cosmic expansion, the cosmic microwave background (CMB), and the limitations of the balloon analogy in representing curvature in space. The discussion encompasses theoretical concepts and interpretations within cosmology and geometry.
Discussion Character
- Exploratory
- Debate/contested
- Conceptual clarification
Main Points Raised
- Mathbrain questions whether the distance D between two galaxy clusters A and B can be predicted given their perpendicular motion and the expansion of space.
- Some participants suggest that the answer to Mathbrain's first question depends on the spatial geometry and the need for a specified metric to calculate future separation.
- Mathbrain seeks clarification on whether all instances of CMB originate from the Big Bang and how they can be detected constantly from all directions.
- One participant explains that the universe is filled with ancient light from the Big Bang, which is uniformly distributed, allowing for constant detection of CMB photons.
- Mathbrain expresses confusion about the balloon analogy, arguing that it cannot adequately represent curvature without an extra dimension and lacks mathematical representation.
- Another participant counters that curvature can be represented mathematically without embedding in higher dimensions, referencing historical contributions from mathematicians like Gauss and Riemann.
- Mathbrain rephrases questions about the predictability of space expansion and its relation to the Hubble constant, as well as the implications for measuring distances to galaxies.
- There is a suggestion that the ancient light may be perceived as coming from all directions due to bending around the curvature of space, but this remains a point of discussion.
Areas of Agreement / Disagreement
Participants express differing views on the balloon analogy's effectiveness in representing curvature and the nature of cosmic expansion. There is no consensus on the predictability of distance D or the implications of CMB detection.
Contextual Notes
The discussion involves complex concepts in cosmology and geometry, with limitations in assumptions about spatial geometry and the nature of light propagation in an expanding universe. The relationship between redshift and current galaxy positions remains unresolved.