What happens to the final image of a person falling into a black hole?

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Discussion Overview

The discussion revolves around the visual perception of a person falling into a black hole, particularly focusing on the concept of a 'frozen' image at the event horizon and the implications of light and information as the person approaches and crosses this boundary. The scope includes conceptual understanding and speculative reasoning about the nature of light, observation, and the behavior of spacetime near black holes.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant describes the perception of a person falling into a black hole as appearing to slow down and eventually freeze at the event horizon, likening it to a film strip with a reduced frame rate due to spacetime stretching.
  • Another participant clarifies that the 'frozen' image does not remain visible forever, as it fades due to redshifted light waves reaching observers.
  • A different participant emphasizes that the source of an image is based on past events, stating that light from a person falling into a black hole is redshifted infinitely, making it difficult to see after crossing the horizon.
  • One participant speculates that the last detectable signal from an object falling into a black hole could be long wave radio emissions.
  • A participant expresses gratitude for the clarifications provided by others, indicating a partial understanding of the concepts discussed.

Areas of Agreement / Disagreement

There is no consensus on the nature of the 'frozen' image or its visibility duration, as participants present differing views on the persistence of the image and the implications of redshift. The discussion remains unresolved regarding the specifics of how light behaves near a black hole.

Contextual Notes

The discussion includes assumptions about the behavior of light and information near black holes, as well as the implications of redshift, which may not be fully explored or agreed upon by all participants.

jBase
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Apparently, when viewed from a distance, the motions of a person approaching the event horizon of a black hole will appear to first slow down and then come to a complete stop as they pass through the horizon. Then, as I'm led to believe by what I've seen and read, that final 'frozen' image of the person remains forevermore, motionless and stuck at/on the horizon.

The 'slowing down' phase makes sense if I think about the observed motion of the person's fall as being divided into consecutive instants of time (or information) and each instant being recorded on the individual frames of a film strip. Without the black hole, the movie camera projects the film strip at a frame rate such that any motion appears fluid and 'normal', but with the black hole present, the stretching out of spacetime outside the horizon is equivalent to slowing down the frame rate, thus giving the appearance of slow-motion. Eventually, at the horizon, the camera stops at the final frame, and all motion has ceased.

What I don't get is how that final frozen image remains visible to observers long after the person has actually gone through the event horizon boundary! What is the source of that continuous image if nothing is there anymore? Wouldn't this make the black hole some kind of photo album or montage displaying a snapshot of everything that has ever fallen into it? Surely that would make the invisible black hole visible.

I'm quite sure I've misunderstood this concept, or the film strip analogy is flawed (probably both), so I'd appreciate any info or guidance on how to visualise this process without invoking any maths.

One further question: Using the same film strip analogy, would the observed fall into the black hole transition from smooth, fluid motion into jumpy, discrete steps of motion as the stretching of spacetime at the atomic scale decompresses the atomic-fluctuation information (in terms of photons) and makes it observable on our macroscopic scale? I guess this comes down to a question on the photon emission process.

Thanks
 
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jBase said:
What I don't get is how that final frozen image remains visible to observers long after the person has actually gone through the event horizon boundary! What is the source of that continuous image if nothing is there anymore?

Hi. Welcome to PF. The image doesn't remain visible forever. It fades away until you can no longer see it. The source of the image are redshifted lightwaves that are just reaching your eyes.
 
jBase said:
What is the source of that continuous image if nothing is there anymore?
The source of an image is never "what is there" it is always "what was there". You are always looking looking at light from events on your past light cone. Many of the stars you see at night you still see even though nothing is there anymore.

The black hole just redshifts the light infinitely.
 
Last edited:
I guess that the last detectable thing which could be observed of an object falling into a black hole would be a long wave radio emission.
 
Ok, that's a little clearer...Thanks for your replies.
 

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