Discussion Overview
The discussion revolves around the question of why black holes are not perceived as the brightest objects in the universe, exploring concepts related to light behavior near event horizons, time dilation, and observational limitations. The scope includes theoretical reasoning and conceptual clarifications regarding black holes and their interactions with light.
Discussion Character
- Exploratory
- Technical explanation
- Conceptual clarification
- Debate/contested
Main Points Raised
- Some participants note that an observer sees an object approaching the event horizon slow down, leading to the question of why we do not see everything that crosses the horizon frozen in time.
- One participant suggests that light from objects near the event horizon gets redshifted over time, eventually moving into the radio wave spectrum.
- Another participant questions whether radio telescopes would be overwhelmed by such redshifted radiation.
- It is argued that the power observed from an object falling into a black hole approaches zero due to increasing time dilation, which affects the detectability of emitted radiation.
- A participant raises the idea that there is a constant source of energy, such as photons, entering the horizon, prompting further discussion on visibility.
- Some participants emphasize that photons must enter an observer's eye to be seen, implying that those falling into a black hole cannot be observed.
- One participant discusses the implications of time dilation on the emission of photons from a source falling into a black hole, suggesting that the time between emissions becomes infinitely long as it approaches the event horizon.
- A later reply introduces the concept of conformal time and its relevance to observing black holes, questioning its effect in the context of our galaxy.
- Another participant mentions quasars, indicating that under certain conditions, black holes can be among the brightest objects, but not for the reasons initially proposed in the thread.
Areas of Agreement / Disagreement
Participants express differing views on the visibility of objects near black holes, the effects of time dilation, and the implications of conformal time. No consensus is reached regarding the primary reasons for the perceived brightness of black holes.
Contextual Notes
Some discussions involve complex concepts like conformal time and gravitational redshift, which may depend on specific definitions and assumptions that are not fully resolved in the conversation.