Black Hole Time Dilation: What Would an Astronaut See?

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Discussion Overview

The discussion revolves around the experience of an astronaut approaching a black hole, particularly focusing on time dilation effects and the perception of time relative to an outside observer. Participants explore the implications of black hole physics, including Hawking radiation and the event horizon, in a theoretical context.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that an astronaut falling into a black hole would perceive time normally while observing the universe outside speeding up due to time dilation effects.
  • Others suggest that the astronaut would witness the black hole evaporating before reaching it, raising questions about the astronaut's experience of time relative to the black hole's life span.
  • One participant introduces the idea of an indestructible observer who could theoretically view the singularity and the future of the universe shortly after crossing the event horizon.
  • Another viewpoint emphasizes that to observe the distant future of the universe, one would need to remain stationary near the event horizon, which is deemed impossible for a free-falling observer.
  • Concerns are raised about the relativistic effects experienced by the astronaut, including redshift of external light as they approach the singularity.

Areas of Agreement / Disagreement

Participants express differing views on the astronaut's experience and the mechanics of time perception near a black hole. No consensus is reached regarding the specifics of what the astronaut would observe or the implications of Hawking radiation.

Contextual Notes

Limitations include the dependence on hypothetical scenarios and the complexities of relativistic physics, which may not be fully resolved in the discussion.

Will K
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So let's say an astronaut was being sucked into a black hole and was able to escape spaghettification and all the death a black hole brings. Since black holes bend space-time itself, the astronaut would experience a differen't time zone than an outside observer (time is relative). The astronaut would see time moving normally, but would see the rest of the universe in a fast forward. Black holes evaporate due to Hawking Radiation, so would the astronaut see the black hole evaporate before he even reaches it? Or would the astronaut experience the black hole in his own time frame, while the rest of the universe sees the black hole evaporate away?
 
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A hypothetical indestructable observer gets to meet the singularity shortly after they cross the event horizon.
A few minutes at most, but the view of the entire future of the Universe might be worth the thrills.
 
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rootone said:
A hypothetical indestructable observer gets to meet the singularity shortly after they cross the event horizon.
A few minutes at most, but the view of the entire future of the Universe might be worth the thrills.
Yes it would definatly be worth it : ) But in order to reach the singularity of a black hole you must pass the event horizon. The event horizon puts the external universe on an infinite speed to the astronaut. But due to Hawking radiation and dimming cosmic background radiation, the black hole is going to evaporate. This means that the black hole has a life span (as long as the universe is around for it). So the astronaut would see the outside universe speed up infinitely. So as soon as the astronaut passes the event horizon, they will be immediately "transported" to the evaporation of the black hole (final moments). So does the astronaut ever have time to hit the singularity, and see the observable universe?
 
No, it doesn't work that way. The only way to view the distant future of the universe is to remain stationary near the EH, which is impossible. You must choose your coordinate system carefully to understand what a free falling observer sees during his brief journey into the spaghetti factory. Keep in mind you achieve relativistic velocities as you free fall toward the singularity and the external universe appears redshifted as photons struggle to catch up with you. For further discussion see: http://casa.colorado.edu/~ajsh/singularity.html.
 
Chronos said:
No, it doesn't work that way. The only way to view the distant future of the universe is to remain stationary near the EH, which is impossible. You must choose your coordinate system carefully to understand what a free falling observer sees during his brief journey into the spaghetti factory. Keep in mind you achieve relativistic velocities as you free fall toward the singularity and the external universe appears redshifted as photons struggle to catch up with you. For further discussion see: http://casa.colorado.edu/~ajsh/singularity.html.
Ok, thanks :P
 

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