5 ms·

Some black holes erase your past (2018)

48 points by gone35 5y ago

WhiteWolf21 5y ago
I found this may be true but still not convincing enough, but at least there are some evidences in the research to take further investigation.
rmbyrro 5y ago
> "If a physicist knows how the universe starts out, she can calculate its future for all time and all space." This seemingly innocent statement could render a prolific discussion. Branching so many ways... Which one would you like to pick? Loss of simultaneity, from relativity theory [1] Consistent histories and probabilistic future prediction by quantum mechanics [2] Free will -- upfront this can sub-branch into biology, psychology, philosophy, artificial intelligence... [3] [4] [5] "The Best Way To Predict The Future Is To Create It", so if we can create stuff, then it's possible to (at least partially) predict the future? [6] Futurism or Future Studies [7] [1] https://www.bbc.com/reel/video/p04s223f/physics-suggests-that-the-future-has-already-happened https://www.bbc.com/reel/video/p04s223f/physics-suggests-tha... [2] https://quantum.phys.cmu.edu/CHS/histories.html https://quantum.phys.cmu.edu/CHS/histories.html [3] https://www.frontiersin.org/articles/10.3389/fpsyg.2013.00131/full https://www.frontiersin.org/articles/10.3389/fpsyg.2013.0013... [4] https://www.wired.com/story/algorithmic-prophecies-undermine-free-will/ https://www.wired.com/story/algorithmic-prophecies-undermine... [5] https://projects.iq.harvard.edu/predictionx/week-3-free-will-determinism-and-predictability https://projects.iq.harvard.edu/predictionx/week-3-free-will... [6] https://quoteinvestigator.com/2012/09/27/invent-the-future/ https://quoteinvestigator.com/2012/09/27/invent-the-future/ [7] https://en.wikipedia.org/wiki/Futures_studies https://en.wikipedia.org/wiki/Futures_studies
- ccvannorman 5y ago
  Exactly this! First, if all the initial conditions of the Universe at the highest granularity possible were known (10^1000? likely higher), then to calculate the current state of the Universe (10^17 seconds) at every step along the way, once per Planck time (10^44 per second), ... a calculation on the order of 10^1000^10^17^44 states (did I get that right?) No computer which exists IN our universe could hope to tackle such a calculation ABOUT said universe, in any reasonable amount of time. (Of course you could cheat like game developers do, but that's another conversation.) Second, if a conscious entity is able to calculate and predict step N+1, they can choose to alter that step. This kind of article and comment is fun to think about -- does it even make sense to ask the question in the first place?
  - rmbyrro 5y ago
    Interesting angle. One question arises for me: if no computer IN the universe can calculate this, how are these rules being applied? I mean, something must be enforcing, there's no "magic" voodoo in the Universe, that's for sure. So how can these rules keep being enforced, so that the outcomes follow the "predicted" path, if the universe can't possibly be able to "calculate" everything?
radu_floricica 5y ago
It's the first time I've been excited to learn about black holes since... 20 years ago, probably.
thelittleone 5y ago
Ok no scientific basis for this at all but I often wonder if some future inventions are so potent that their "gravity" for lack of a better word, manifests itself into being.
dataflow 5y ago
> In the real world, your past uniquely determines your future. If a physicist knows how the universe starts out, she can calculate its future for all time and all space. [Layman here] Is this ignoring quantum mechanics? Or is the claim that you can reconstruct the original wavefunction a collapse? I thought randomness was pretty intrinsic to quantum mechanics.
- totetsu 5y ago
  Is this refering to simulations to recreate The Large Scale Structure, by specifying initial conditions?
- bjornsing 5y ago
  I have a master in physics, but I share your surprise over this paragraph in the OP. I’m a bit unsure though how widely and quickly the probability mass dissipates over possible future states. E.g. the existence of quantum computers implies that at least in some physical systems the probability mass stays concentrated on a few possible future states. I wouldn’t expect that to hold for the universe as a whole though.
- deleted 5y ago
  [deleted]
- byteware 5y ago
  I thought it is mostly accepted (citation needed) that apparent wave function collapse is due to the coupling of the microsystem to the measurement apparatus, together they continue to evolve deterministically
  - codethief 5y ago
    Yes, in my experience (master's in physics) this is a widely held belief among physicists studying foundational issues[0]. In some sense it's the Many Worlds interpretation of QM but all inside one single world. [0] I specifically remember some podcast by Sean Carroll where he expressed this exact same view.
- tempodox 5y ago
Archelaos 5y ago
> In the real world, your past uniquely determines your future. If a physicist knows how the universe starts out, she can calculate its future for all time and all space. No (or only in very special configurations). See for example the n-body problem.[1] [1] https://en.wikipedia.org/wiki/N-body_problem https://en.wikipedia.org/wiki/N-body_problem
- 7373737373 5y ago
  Individual particle decay is also truly random/unpredictable
  - infiniteL0Op 5y ago
- ben_w 5y ago
  The reason we can’t predict the outcome of an N-body problem is that arbitrarily small mistakes radically change the result, the maths itself is fine. Quantum mechanics, as several other commenters have observed, is where to look for the fundamental unpredictability. I wonder how long it takes for the quantum uncertainty of a planet to become macroscopic due to the chaotic behaviour in N-body problems…
- progval 5y ago
  > In the physical literature about the n-body problem (n ≥ 3), sometimes reference is made to the impossibility of solving the n-body problem (via employing the above approach).[citation needed] However, care must be taken when discussing the 'impossibility' of a solution, as this refers only to the method of first integrals
algon33 5y ago
https://physics.stackexchange.com/questions/403574/what-situations-in-classical-physics-are-non-deterministic https://physics.stackexchange.com/questions/403574/what-situ... Non deterministic dynamics occurs in Newtonian physics as well. These things are worrying philosophically, but we can take some comfort in that the initial conditions for which these occur are "measure zero" i.e. if you were defining a probability measure over initial conditions, then the non-deterministic initial conditions would have measure zero. It doesn't sound like we have that option here though. But in my view, this result is good news. We knew GR was unphysical anyhow. Now we've increased our understanding of how unphysical it is, potentially ruling out more replacement theories.
- codethief 5y ago
  > We knew GR was unphysical anyhow. We did? That is news to me. Would you mind elaborating?
  - algon33 5y ago
    My statement was too strong. By "knew" I meant that it was pretty likely that strong cosmic censorship wouldn't work out [1]. In addition, I think QFT and GR are both probably broken in some way given that they're incompatible and that no one has coerced one of the theories into working with the other. That feels like evidence that the problem is not as simple as just rejecting QM or GR to me. But again, calling that "knowing GR is unphysical" was too strong a statement. [1]https://en.wikipedia.org/wiki/Cosmic_censorship_hypothesis https://en.wikipedia.org/wiki/Cosmic_censorship_hypothesis
dtgriscom 5y ago
> "No physicist is going to travel into a black hole and measure it." Cowards...
largbae 5y ago
So let me get this straight... you enter the event horizon of a black hole, from which nothing can escape. This "frees" you from your deterministic past so that you have infinite possible futures... but since you're in a black hole these infinite futures all probably occur in the ultrahot ultrasqueezy confines of a black hole.
- hammock 5y ago
  It's a Faustian bargain (selling your soul to gain the universe and eternal damnation) in scientific terms.
dav_Oz 5y ago
This article unfortunately imho does a poor job in putting the mathematical modeling and Hintz' effort into greater focus and context. Possibly to make it more exciting for the casual science interested reader. "Some carefully constructed mathematical objects (similar to observed black holes) erase your past (makes it possible to cross the Cauchy horizon)" in GR would be more precise. Here [0] is a good article about the kind of mathematical manipulation involved (not directly related). This [1] quora answer goes right to the obvious issues. [0]https://www.quantamagazine.org/to-test-einsteins-equations-poke-a-black-hole-20180308/ https://www.quantamagazine.org/to-test-einsteins-equations-p... [1]https://www.quora.com/Is-the-violation-of-strong-cosmic-censorship-derived-by-Peter-Hintz-relevant-to-the-interiors-of-astrophysically-realistic-black-holes/answer/Alessandro-Takeshi https://www.quora.com/Is-the-violation-of-strong-cosmic-cens...
denton-scratch 5y ago
> In effect, all the energy the black hole sees over the lifetime of the universe hits the Cauchy horizon at the same time, blasting into oblivion any observer who gets that far. I don't understand that. It sounds as if the reason all the stuff reaches the horizon "at the same time" is because time slows to a stop at the horizon. But doesn't that also apply to the "observer who gets that far"? How can the observer overtake all the other stuff? Maybe I should stay clear of articles dealing with GR; I'm clearly not clever enough to understand them.

48 points by gone35 5y ago

I found this may be true but still not convincing enough, but at least there are some evidences in the research to take further investigation.

rmbyrro 5y ago

> "If a physicist knows how the universe starts out, she can calculate its future for all time and all space." This seemingly innocent statement could render a prolific discussion. Branching so many ways... Which one would you like to pick? Loss of simultaneity, from relativity theory [1] Consistent histories and probabilistic future prediction by quantum mechanics [2] Free will -- upfront this can sub-branch into biology, psychology, philosophy, artificial intelligence... [3] [4] [5] "The Best Way To Predict The Future Is To Create It", so if we can create stuff, then it's possible to (at least partially) predict the future? [6] Futurism or Future Studies [7] [1] https://www.bbc.com/reel/video/p04s223f/physics-suggests-that-the-future-has-already-happened https://www.bbc.com/reel/video/p04s223f/physics-suggests-tha... [2] https://quantum.phys.cmu.edu/CHS/histories.html https://quantum.phys.cmu.edu/CHS/histories.html [3] https://www.frontiersin.org/articles/10.3389/fpsyg.2013.00131/full https://www.frontiersin.org/articles/10.3389/fpsyg.2013.0013... [4] https://www.wired.com/story/algorithmic-prophecies-undermine-free-will/ https://www.wired.com/story/algorithmic-prophecies-undermine... [5] https://projects.iq.harvard.edu/predictionx/week-3-free-will-determinism-and-predictability https://projects.iq.harvard.edu/predictionx/week-3-free-will... [6] https://quoteinvestigator.com/2012/09/27/invent-the-future/ https://quoteinvestigator.com/2012/09/27/invent-the-future/ [7] https://en.wikipedia.org/wiki/Futures_studies https://en.wikipedia.org/wiki/Futures_studies

ccvannorman 5y ago
Exactly this! First, if all the initial conditions of the Universe at the highest granularity possible were known (10^1000? likely higher), then to calculate the current state of the Universe (10^17 seconds) at every step along the way, once per Planck time (10^44 per second), ... a calculation on the order of 10^1000^10^17^44 states (did I get that right?) No computer which exists IN our universe could hope to tackle such a calculation ABOUT said universe, in any reasonable amount of time. (Of course you could cheat like game developers do, but that's another conversation.) Second, if a conscious entity is able to calculate and predict step N+1, they can choose to alter that step. This kind of article and comment is fun to think about -- does it even make sense to ask the question in the first place?
- rmbyrro 5y ago
  Interesting angle. One question arises for me: if no computer IN the universe can calculate this, how are these rules being applied? I mean, something must be enforcing, there's no "magic" voodoo in the Universe, that's for sure. So how can these rules keep being enforced, so that the outcomes follow the "predicted" path, if the universe can't possibly be able to "calculate" everything?

radu_floricica 5y ago

It's the first time I've been excited to learn about black holes since... 20 years ago, probably.

thelittleone 5y ago

Ok no scientific basis for this at all but I often wonder if some future inventions are so potent that their "gravity" for lack of a better word, manifests itself into being.

dataflow 5y ago

> In the real world, your past uniquely determines your future. If a physicist knows how the universe starts out, she can calculate its future for all time and all space. [Layman here] Is this ignoring quantum mechanics? Or is the claim that you can reconstruct the original wavefunction a collapse? I thought randomness was pretty intrinsic to quantum mechanics.

totetsu 5y ago
Is this refering to simulations to recreate The Large Scale Structure, by specifying initial conditions?
bjornsing 5y ago
I have a master in physics, but I share your surprise over this paragraph in the OP. I’m a bit unsure though how widely and quickly the probability mass dissipates over possible future states. E.g. the existence of quantum computers implies that at least in some physical systems the probability mass stays concentrated on a few possible future states. I wouldn’t expect that to hold for the universe as a whole though.
deleted 5y ago
[deleted]
byteware 5y ago
I thought it is mostly accepted (citation needed) that apparent wave function collapse is due to the coupling of the microsystem to the measurement apparatus, together they continue to evolve deterministically
- codethief 5y ago
  Yes, in my experience (master's in physics) this is a widely held belief among physicists studying foundational issues[0]. In some sense it's the Many Worlds interpretation of QM but all inside one single world. [0] I specifically remember some podcast by Sean Carroll where he expressed this exact same view.
tempodox 5y ago

Archelaos 5y ago

> In the real world, your past uniquely determines your future. If a physicist knows how the universe starts out, she can calculate its future for all time and all space. No (or only in very special configurations). See for example the n-body problem.[1] [1] https://en.wikipedia.org/wiki/N-body_problem https://en.wikipedia.org/wiki/N-body_problem

7373737373 5y ago
Individual particle decay is also truly random/unpredictable
- infiniteL0Op 5y ago
ben_w 5y ago
The reason we can’t predict the outcome of an N-body problem is that arbitrarily small mistakes radically change the result, the maths itself is fine. Quantum mechanics, as several other commenters have observed, is where to look for the fundamental unpredictability. I wonder how long it takes for the quantum uncertainty of a planet to become macroscopic due to the chaotic behaviour in N-body problems…
progval 5y ago
> In the physical literature about the n-body problem (n ≥ 3), sometimes reference is made to the impossibility of solving the n-body problem (via employing the above approach).[citation needed] However, care must be taken when discussing the 'impossibility' of a solution, as this refers only to the method of first integrals

algon33 5y ago

https://physics.stackexchange.com/questions/403574/what-situations-in-classical-physics-are-non-deterministic https://physics.stackexchange.com/questions/403574/what-situ... Non deterministic dynamics occurs in Newtonian physics as well. These things are worrying philosophically, but we can take some comfort in that the initial conditions for which these occur are "measure zero" i.e. if you were defining a probability measure over initial conditions, then the non-deterministic initial conditions would have measure zero. It doesn't sound like we have that option here though. But in my view, this result is good news. We knew GR was unphysical anyhow. Now we've increased our understanding of how unphysical it is, potentially ruling out more replacement theories.

codethief 5y ago
> We knew GR was unphysical anyhow. We did? That is news to me. Would you mind elaborating?
- algon33 5y ago
  My statement was too strong. By "knew" I meant that it was pretty likely that strong cosmic censorship wouldn't work out [1]. In addition, I think QFT and GR are both probably broken in some way given that they're incompatible and that no one has coerced one of the theories into working with the other. That feels like evidence that the problem is not as simple as just rejecting QM or GR to me. But again, calling that "knowing GR is unphysical" was too strong a statement. [1]https://en.wikipedia.org/wiki/Cosmic_censorship_hypothesis https://en.wikipedia.org/wiki/Cosmic_censorship_hypothesis

dtgriscom 5y ago

> "No physicist is going to travel into a black hole and measure it." Cowards...

largbae 5y ago

So let me get this straight... you enter the event horizon of a black hole, from which nothing can escape. This "frees" you from your deterministic past so that you have infinite possible futures... but since you're in a black hole these infinite futures all probably occur in the ultrahot ultrasqueezy confines of a black hole.

hammock 5y ago
It's a Faustian bargain (selling your soul to gain the universe and eternal damnation) in scientific terms.

dav_Oz 5y ago

This article unfortunately imho does a poor job in putting the mathematical modeling and Hintz' effort into greater focus and context. Possibly to make it more exciting for the casual science interested reader. "Some carefully constructed mathematical objects (similar to observed black holes) erase your past (makes it possible to cross the Cauchy horizon)" in GR would be more precise. Here [0] is a good article about the kind of mathematical manipulation involved (not directly related). This [1] quora answer goes right to the obvious issues. [0]https://www.quantamagazine.org/to-test-einsteins-equations-poke-a-black-hole-20180308/ https://www.quantamagazine.org/to-test-einsteins-equations-p... [1]https://www.quora.com/Is-the-violation-of-strong-cosmic-censorship-derived-by-Peter-Hintz-relevant-to-the-interiors-of-astrophysically-realistic-black-holes/answer/Alessandro-Takeshi https://www.quora.com/Is-the-violation-of-strong-cosmic-cens...

denton-scratch 5y ago

> In effect, all the energy the black hole sees over the lifetime of the universe hits the Cauchy horizon at the same time, blasting into oblivion any observer who gets that far. I don't understand that. It sounds as if the reason all the stuff reaches the horizon "at the same time" is because time slows to a stop at the horizon. But doesn't that also apply to the "observer who gets that far"? How can the observer overtake all the other stuff? Maybe I should stay clear of articles dealing with GR; I'm clearly not clever enough to understand them.