Double slit experiment at event horizon of a BH

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Discussion Overview

The discussion revolves around a hypothetical double slit experiment conducted at the event horizon of a black hole, examining the implications for observers inside and outside the horizon. It explores concepts of interference, communication, and the nature of black holes from both theoretical and conceptual perspectives.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant suggests that an observer inside the black hole should see interference due to the equivalence principle, while an outside observer would not, leading to a potential paradox if they later compare observations.
  • Another participant expresses skepticism about the feasibility of the scenario, questioning the existence of black holes and the utility of the thought experiment.
  • Some participants argue that communication between observers inside and outside the black hole is impossible due to the nature of the event horizon, which prevents any signals from escaping.
  • Others contend that the paradox arises from conflicting predictions about the state of the detector, emphasizing the lack of a unified theory explaining black holes.
  • A participant proposes that if a paradox is identified, it indicates either a flaw in current theories or a misunderstanding of the event horizon's properties.
  • There is a discussion about the implications of interference patterns and the conditions under which they might be observed, with some asserting that no pattern would be visible to an outside observer.
  • Concerns are raised about the physical realities of approaching a black hole and the impossibility of communication once past the event horizon.

Areas of Agreement / Disagreement

Participants express a range of views, with no consensus reached on the feasibility of the thought experiment or the implications of the event horizon. Disagreement exists regarding the nature of communication between observers and the existence of paradoxes related to black holes.

Contextual Notes

Limitations include the speculative nature of the thought experiment, the unresolved status of theories regarding black holes, and the dependence on definitions of the event horizon. The discussion highlights the complexities and uncertainties surrounding the intersection of general relativity and quantum mechanics.

upurg
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Consider a double slit experiment at the event horizon of a black hole, with 1 slit on each side of the horizon, one observer inside and 1 outside, inside observer should observe interference by equivalence principle, whereas outside one should not, since the photons can't enter the second slit and exit the BH. But if the slit records interference or not, ie it draws a bunch of points on the screen where photons hit, then if afterwards both observers enter the BH and look at the screen, then there will be a paradox if they disagree? How is it resolved?

See also http://physics.stackexchange.com/q/2750/394
 
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Reads very much as an exercise in futility. You describe using a poorly understood phenomenon to do a (mental exercise?) in an environment that has not been proven to actually exist.

Interesting. Have you worked on the math any?

DC
 
No I have not, my hope is that some smart brains has already studied this in the literature
 
I'm sorry, but there is no way that the two observers could communicate. There is no resolution, but I'm not sure there's an issue to begin with.
 
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Afterwards the outside observer goes inside and they have a nice little chat, they use rockets to counter gravity ofcourse.
 
upurg said:
Afterwards the outside observer goes inside and they have a nice little chat, they use rockets to counter gravity ofcourse.

They can't chat... in fact, they can't even see each other. They can exchange no signals, even if the other follows unless they use means that exceed light. The event horizon is not PHYSICAL: it represents the point at which all future communication beyond the horizon is lost. There's no reason to assume that you can "catch up" inside the horizon.


Now, putting all of this aside... why does any of this matter? What is it that you expect to demonstrate here?
 
Communication is not lost between two persons inside the black hole. Why it matters? Because its physics and there is an apparent paradox that needs to be resolved ?
 
upurg said:
Communication is not lost between two persons inside the black hole. Why it matters? Because its physics and there is an apparent paradox that needs to be resolved ?

What paradox? As far as we know, black holes are the very engine that breaks causality (unlikely). This is the problem with Black Holes: they exist on paper, but what they ARE is a debate with no certain answer for the foreseeable future.

You're talking about taking a Bell-State Measurement at the event horizon, then going past it to have a chat?

It's an EVENT HORIZON... IF you can catch your friend... which given you'd both be accelerating towards the singularity, with him in the lead... you still get no talky. Then, to top it off, that information may be lost entirely (HR), and CERTAINLY lost to humanity.
 
If you don't know what a black hole is, i suggest you stop posting in this thread, the proposition that they can't talk doesn't resolve the fact that there are two contradicting predictions for the state of the detector.
 
  • #10
upurg said:
If you don't know what a black hole is, i suggest you stop posting in this thread, the proposition that they can't talk doesn't resolve the fact that there are two contradicting predictions for the state of the detector.

I think you misunderstand... there isn't a single theory to explain black holes. Usually they're useful as a place where, at the singularity, GR ceases to be useful. QM can't help, so we're left with an apparent conflict between two (so far) perfectly predictive theories. There are people on this site, although I'm not one of them, who don't even believe event horizons form around all black holes, or at all.

I'll ask again... what do you expect to learn about wave-particle duality, or the Bell ansatz at a gravitational event horizon?
 
  • #11
Ok, let us use the definition of an event horizon simply as a boundary where matter and information can go only one way. If we then get a paradox, we know either our theories are wrong, or that the horizon does not work like that, that i how physics is done
 
  • #12
upurg said:
Ok, let us use the definition of an event horizon simply as a boundary where matter and information can go only one way. If we then get a paradox, we know either our theories are wrong, or that the horizon does not work like that, that i how physics is done

OK, we agree so far. The EH is a non-physical boundary that represents a one-way ticket for Information. The other issue is... there is no paradox. Unless you're in a very COLD universe and the black hole is emitting Hawking Radiation, you won't have an interference pattern on the portion outside of the EH.

You can't get both parties together, because there's no means by which they can communicate while all signals are (presumably) headings towards a singularity. This is the problem I see with this experiment: no paradox to begin with, and no way to resolve it if you had one.

I'd add, there ARE real paradoxical issues around GR and QM at the limits of black holes... your example isn't one that I'm aware of, nor does it appear to exist.
 
  • #13
Why would you think you can't get both parties together, you just need large enough rockets and a brain. Which paradoxes are you talking about?
 
  • #14
upurg said:
Why would you think you can't get both parties together, you just need large enough rockets and a brain. Which paradoxes are you talking about?

The closer you get to a black hole, the faster you have to go to escape, until the event horizon when all paths lead into the singularity. At that point, what signal do you use to communicate with Bob who went into the hole first? I mean, for a thought experiment we can ignore things like them being dead, but you can't ignore the facts that touch on your experiment.

Interference patterns require... INTERFERENCE! No signal can exit the event horizon, so what pattern are you going to see? NONE! Bob might (who the hell really knows), but you won't because information can't escape to form the interference pattern.

EVEN if you include exotic interpretations of QM, the event horizon might as well be the end of the universe for an external observer: no retrocausality here.

edit: I forgot... why can't you get them together: All paths beyond the event horizon lead to the singularity, and you're accelerating to that point. Alice (outside at first) can't use a rocket to catch Bob: he'll be accelerating to near (at?!) lightspeed, and how do you overtake that? Beyond that, any question of what it's "like" beyond the event horizon of a black hole has to be, by the very definition, unknown.
 

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