Timeline for Can matter really fall through an event horizon?
Current License: CC BY-SA 4.0
11 events
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| Apr 12, 2021 at 7:22 | history | edited | John Rennie | CC BY-SA 4.0 |
Tweak
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| Oct 30, 2013 at 16:47 | comment | added | Terry Bollinger | I just looked at your new version of the question. Wow, 1642 views already -- that some quick attention! Thanks for the tip, and I'm heading over there now... :) | |
| Oct 29, 2013 at 18:22 | comment | added | John Rennie | @TerryBollinger: courtesy of Michael Brown I have an answer for you. The freely falling observer does not see the end of the universe. See physics.stackexchange.com/questions/82678/… for the details. | |
| Oct 23, 2013 at 3:12 | comment | added | Terry Bollinger | But "what you see" is what I'm asking! I'm very fine with the field of view narrowing, but the question is what is seen inside that narrowing stream. So, same question, this time phrased to accommodate your point about view narrowing: If the falling view of the distant clock narrows to a point, what is the very last time stamp from the distant clock that the falling clock sees in that point of light? For the falling clock, I don't easily see how this is anything but an experimentally answerable question. If it is not, then what specifically makes it unmeasurable? | |
| Oct 13, 2013 at 10:01 | comment | added | John Rennie | Just to clarify the above, I'm talking about the view looking outwards. The view looking inwards is just, well, black! :-) | |
| Oct 13, 2013 at 9:22 | comment | added | John Rennie | Sadly, you do not see the end of the universe :-) | |
| Oct 13, 2013 at 9:22 | comment | added | John Rennie | When you ask "what does it see" I assume you mean what would a camera carried by the infalling observer record. If so, there have been various calculations of this over the years, though surprisingly Googling hasn't found anything. If you can find a copy of William Kaufmann's book The Cosmic Frontiers of General Relativity this describes the results (but not the details) of the calculation. In my edition it starts on page 122. As you approach the event horizon your field of view narrows to a point. This is because you are now moving at the speed of light. | |
| Oct 13, 2013 at 0:48 | comment | added | Terry Bollinger | Ben Crowell, thanks for both comments. John Rennie, your reiteration of the standard explanation is appreciated, but try this: since the "freely falling observer" clock undergoes real time dilation where the ratio of its seconds to those of most clocks in the embedding universe becomes infinite, what is the exact objective meaning of "freely falling"? That is, if the falling clock sees a span equal to the entire history of the outside universe going by before it hits the EH, is it really "freely falling" at $v=c$, or does it require actual infinite external time to fall in? What does it see? | |
| Sep 30, 2013 at 15:19 | comment | added | user4552 | [...] unique. A distant observer who collects data from the region near the horizon is making indirect inferences about what he believes to be happening there. He can choose to apply various corrections for effects such as time dilation, or not to apply them. He can choose one notion of simultaneity or another. He can infer that matter has "really" "already" fallen in, or not. | |
| Sep 30, 2013 at 15:15 | comment | added | user4552 | There's nothing I can object to here as a matter of technical fact, but I disagree with your interpretation. We can construct coordinate systems like Kruskal-Szekeres coordinates that are continuous and well behaved across the event horizon, but these coordinate systems do not correspond to measurements real observers would make. I think the key here is your word "correspond." You seem to have in mind a certain notion of correspondence that you feel is natural. I don't agree that this particular notion of correspondence (which you have only defined implicitly) is natural or [...] | |
| Sep 30, 2013 at 10:58 | history | answered | John Rennie | CC BY-SA 3.0 |