- #1
Aidyan
- 180
- 13
I know that has been discussed elsewhere but never could find for a satisfying answer, so I try this here again.
Let us not take into account that an observer (an astronaut or a clock or just let us take both: an astronaut with a clock) falling into a black hole (BH) will be killed and torn apart by tidal forces. Just imagine what an observer falling towards the BH and an external observer will report.
If someone falls into a black hole (BH), then, as I understand it, due to gravitational time dilation the external observer should see the infalling clock ticking slower and slower until it almost stops ticking when nearing the event horizon (EH). But, as I understand it, this implies that also the speed with which I see the astronaut/clock nearing the EH should slow down after a certain point and then remain 'frozen' in time forever almost at the Schwarzschild radius. Some object that due to gravitational redshift the external observer would see nothing because light signals are becoming weaker and redshifted and nothing can be said. I don't find that a good objection that means much. Because in principle on can follow at it in the infrared and radio wave until to a certain point. One can follow the descend into a BH until a certain point 'asymptotically' so to speak, in principle until the EH.
On the other side, so goes the theory, the infalling observer with the clock (proper time) would notice nothing by crossing the EH and could not observe anything of the external universe and would see how he/she would fall towards the singularity very quickly. My understanding however is that the infalling observer, as long he/she will be able to still receive light form the external universe, will see it evolve faster and faster until it nears to the EH where (if equipped to observe the extreme blueshifted light with the same reasoning above there is in principle no limitation until the EH) and would see the entire history of the universe to play out in almost an instant.
I saw several explaining away the discrepancy by saying that nothing can be said because, for the infalling observer the external universe is outside the light cone and, since there is no meaning of a present moment in this context, these speculations are therefore meaningless. The two points of view are said to be compatible despite its intrinsic logical contradiction. This however, sounds incorrect to me as well. We can in principle avoid any consideration about proper or coordinate time and consider Hawking radiation. After an extreme long but still not infinite time, the BH will evaporate completely and the infalling observer who still did not cross the EH will indeed be able to observe again the universe trillions and trillions of years later (depending from the mass of the BH).
The bottom line is that nothing can really cross an EH. Not only, an EH can not form in the first place because the formation of a BH is an asymptotic process in time which however never will be completed.
Please tell me why this is wrong?
Let us not take into account that an observer (an astronaut or a clock or just let us take both: an astronaut with a clock) falling into a black hole (BH) will be killed and torn apart by tidal forces. Just imagine what an observer falling towards the BH and an external observer will report.
If someone falls into a black hole (BH), then, as I understand it, due to gravitational time dilation the external observer should see the infalling clock ticking slower and slower until it almost stops ticking when nearing the event horizon (EH). But, as I understand it, this implies that also the speed with which I see the astronaut/clock nearing the EH should slow down after a certain point and then remain 'frozen' in time forever almost at the Schwarzschild radius. Some object that due to gravitational redshift the external observer would see nothing because light signals are becoming weaker and redshifted and nothing can be said. I don't find that a good objection that means much. Because in principle on can follow at it in the infrared and radio wave until to a certain point. One can follow the descend into a BH until a certain point 'asymptotically' so to speak, in principle until the EH.
On the other side, so goes the theory, the infalling observer with the clock (proper time) would notice nothing by crossing the EH and could not observe anything of the external universe and would see how he/she would fall towards the singularity very quickly. My understanding however is that the infalling observer, as long he/she will be able to still receive light form the external universe, will see it evolve faster and faster until it nears to the EH where (if equipped to observe the extreme blueshifted light with the same reasoning above there is in principle no limitation until the EH) and would see the entire history of the universe to play out in almost an instant.
I saw several explaining away the discrepancy by saying that nothing can be said because, for the infalling observer the external universe is outside the light cone and, since there is no meaning of a present moment in this context, these speculations are therefore meaningless. The two points of view are said to be compatible despite its intrinsic logical contradiction. This however, sounds incorrect to me as well. We can in principle avoid any consideration about proper or coordinate time and consider Hawking radiation. After an extreme long but still not infinite time, the BH will evaporate completely and the infalling observer who still did not cross the EH will indeed be able to observe again the universe trillions and trillions of years later (depending from the mass of the BH).
The bottom line is that nothing can really cross an EH. Not only, an EH can not form in the first place because the formation of a BH is an asymptotic process in time which however never will be completed.
Please tell me why this is wrong?