Define Red-Shift: Explaining BH Event Horizon

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Discussion Overview

The discussion centers on the concept of redshift in relation to the event horizon of a black hole, exploring its implications and the underlying physics involved. Participants seek to clarify the meaning of redshift in this specific context, touching on gravitational effects and observational phenomena.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant requests an explanation of redshift as it pertains to the event horizon of a black hole.
  • Another participant mentions that redshift for moving bodies is caused by the Doppler Effect, suggesting a connection to motion.
  • A subsequent reply clarifies that "EH" stands for "event horizon" and "BH" for "black hole."
  • It is proposed that observers in stronger gravitational fields appear time dilated to those in weaker fields, leading to the perception that an observer falling into a black hole slows down and never crosses the event horizon, which contributes to the observed redshift of light waves emitted by them.

Areas of Agreement / Disagreement

Participants express different aspects of the phenomenon, but there is no consensus on a singular understanding of redshift in this context. The discussion remains open with multiple viewpoints presented.

Contextual Notes

Some assumptions regarding the nature of gravitational effects and time dilation are present, but these are not fully explored or resolved within the discussion.

Aurora-Sky
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Could some one explain what red-shift really means when we're talking about the EH of a BH?

Thank you.
 
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EH of a BH? Remind me what that stands for.

Redshift for moving bodies is caused by the Doppler Effect.
 
Whovian said:
EH of a BH? Remind me what that stands for.


Event horizon
Black hole
 
Aurora-Sky said:
Event horizon
Black hole

Oh! In which case you have to understand that observers under higher gravitation appear time dilated to observers under lower gravitation. So those of us watching an observer falling into a black hole will see that observer slow down (and, in fact, if I understand correctly, never cross the event horizon), and any sort of waves they send back will have more infrequent peaks due to the time dilation. And so we see redshift in light waves.
 

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