Discussion Overview
The discussion revolves around the implications of the supernova DES16C2nm, which exploded 10.5 billion years ago, particularly concerning its distance from Earth at the time of the explosion and the effects of cosmic expansion on this distance. Participants explore theoretical aspects of cosmology, redshift, and the interpretation of distances in an expanding universe.
Discussion Character
- Exploratory
- Technical explanation
- Conceptual clarification
- Debate/contested
Main Points Raised
- Some participants question whether the supernova was 10.5 billion light-years away from Earth at the time of the explosion, suggesting that due to the expansion of the universe, it must have been closer.
- There is a discussion about how to calculate the distance of the star at the time of the explosion, with references to specific calculators and redshift values.
- Some participants assert that the proper distance to the supernova was 5.5 billion light-years at emission and 17.3 billion light-years at reception, with clarifications on what these distances represent.
- Concerns are raised about the implications of recession velocities exceeding the speed of light, with some arguing that such statements depend on the conventions used in cosmology.
- Participants discuss the nature of cosmic expansion and its effects on the observed distances and travel time of light from distant objects.
- A hypothetical analogy involving an ant on a stretching rubber band is used to illustrate the complexities of distance changes in an expanding universe.
- There is a query about the basis for concluding that the universe is expanding rather than galaxies simply moving away from each other.
Areas of Agreement / Disagreement
Participants express differing views on the implications of cosmic expansion and the interpretation of distances. There is no consensus on several points, including the nature of recession velocities and the definitions of distances in cosmological contexts.
Contextual Notes
Participants highlight the importance of understanding the assumptions and conventions used in cosmology, particularly regarding the definitions of distances and recession velocities, which may not be universally agreed upon.