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Math Shows Some Black Holes Erase Your Past and Give You Unlimited Futures (vice.com)
dmoberhaus writes: An international team of mathematicians has found that there are theoretical black holes that would allow an observer to survive passage through the event horizon. This would result in the breakdown of determinism, a fundamental feature of the universe that allows physics to have predictive power, and result in the destruction of the observer's past and present them with an infinite number of futures. The findings were detailed in a report published last week in Physical Review Letters.
Summary implies conflation of mathematical artefacts with physical reality. Real paper is probably quite dry and abstract.
Math does not apply to reality. It always only applies to an abstraction of reality and that loses accuracy, sometimes catastrophically as almost certainly happened in this case.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
I'm not in the field either, but I hope someone can explain this a little better since the actual paper is behind a paywall and the oversimplified and popularized Motherboard article doesn't make any sense.
Motherboard says that the laws of the universe, outside of black holes, are supposedly deterministic. That's news to me, I thought quantum mechanics dealt with probabilities and there was no way to predict what part a particle will take. The universe plays dice all the time, it only appears to be deterministic on a large scale when the probabilities of the individual particles average out to a largely predictable macroscopic result.
Then, what does it mean when they say your past is destroyed? Let me get this straight, you fall into one of these special black holes, you survive (which, I assume, includes your memories), yet your past is "destroyed"? I imagine they mean that the laws transfer to a different coordinate system where your past is no longer at negative time coordinates but simply nowhere at all. Which isn't really that unusual. Just use a different coordinate system (one tied to your body) and the past will be there again, still inaccessible at the usual negative coordinates (but formulas for describing your current environment will be very complicated). Pretty sure that's what they meant, right?
OK, what about the unlimited futures? Again, I though quantum mechanics already gave us those. I guess it means that the future will be a lot more undeterministic than usual?
Finally, the big discovery seems to be that you won't be destroyed by all the energy of the universe falling through the event horizon at the same time as you, thanks to the expansion of the universe. But what about spaghettification? Won't you still be killed by the enormous differential gravitation even if you survive the radiation at the horizon? How does the charge of the black hole prevent that from happening?
Thanks in advance to anyone who can clear this up a bit more.
... determinism, a fundamental feature of the universe ...
While we may wish for determinism, it has been shown long before that it does not exist.Since it was shown that we can not accurately know both the position of a particle and its speed, it has been proven that predicting the future is impossible because it is impossible to know the present, let alone calculate the future by using the present as a starting condition. So determinism is absolutely not a feature of the universe.
Nae king! Nae laird! Nae yurrupiean pressedent! We willna be fooled again!
People tend to believe that physics is applied math. It's not. The universe doesn't care about your math. General Relativity is a set of mathematical equations that were picked because they could model the observed experimental data.
The problem here isn't the mathematics or whether it applies to physics - or to reality, for that matter. The real problem is people's lack of insight - including many physicists. Take for example the idea of determinism - naively, this means that everything is pre-determined from some set of equations, which are assumed to have unique, well-defined solutions; but we already know of many cases where seemingly simple sets of equations behave chaotically. Now, I know well enough that mathematically, 'chaos' only means that a dynamic system is extremely sensitive to initial conditions, but since our understanding of quantum mechanics seems to indicate that we can't fix initial conditions of any system with arbitrary precision, there must be a limit to how deterministic any set of deterministic equations are in practise.
The point I'm making here isn't really about whether either GR or QM are 'true' or model reality correctly - we already know they don't - but the fact that we know far too little to make sweeping statements about anything as profound as determinism and causality. Apart from that, I can't see that this new calculation concerning certain types of black holes says anything of the sort; time and causality are strictly local - time experienced being the path integral of something or other in the 4-dimensional space-time manifold - and whether you travel in a closed loop or otherwise pass through events (~ 4-dim points in space-time) that you have passed before, the time you experience is still only your own, individual, highly local time, which does not necessarily have much to do with the rest of the universe.
A final point: mathematics is true - it is the only science that can claim to be absolutely tru, but the price we pay is that it is only true within its set of axioms. What this means is that as long as the axioms of any theory in the empirical sciences, match the reality we're trying to model, the conclusions of the theory MUST be correct - that is in fact the fundamental assumption behind the scientific method: it means we can falsify our assumptions by conducting experiments.
Not quite, e.g.: https://en.wikipedia.org/wiki/Superdeterminism
In quantum physics the approach of following the mathematical theory to its logical conclusion, how weird that may sound, has been quite successful. In any case such speculations make sense to test a theory and see where it leads to. Maybe it'll even lead to possible experimental tests of the theory (although I don't think humanity will have access to a black hole (specifically one that is big enough) to play around with.
The Einstein-Podolsky-Rosen-Paradoxon is a good example of following a theory (here quantum mechanics) to it's logical conclusion. Effectively the "paradoxon" exposes the nonlocality of quantum mechanics i.e. it implies "spooky actions at a distance", a picture that clashes with our classical world view. Based on this an experiment was thought up, a test of the "bell inequality". Basically any classical theory that preserves locality should always fulfil the bell inequality. OTOH quantum mechanics predicts a violation of the bell inequality in experiments specifically designed for that purpose. Such experiments then showed a violation of the inequality. This means, that a classical theory (which would include locality) can not explain those experimental results (which are predicted by quantum mechanics).
So the speculations of Einstein, Podolsky and Rosen about the strange consequences of quantum mechanic theory led to a fundamental insight about the nature of reality, namely that there are aspects of it that can not be explained by a "classical" theory that includes locality.
So if one wants to test a mathematical description of reality one has to follow the mathematics to its logical conclusions and if possible test if these apply to the real world. Even if such a test is not possible it is often helpful to see what the implications of a mathematical model are. Maybe it leads to a better understanding, uncovers contradictions or shows that a theory is incomplete, but in some cases it can also lead to a deeper understanding of reality.
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I hereby demonstrate my complete lack of understanding slashdot readers by linking to the full article on arxiv It's kind of an interesting mathematical exercise in the physics of charged black holes under various conditions but obviously does not reflect reality. For example, you would need a large positive cosmological constant, and an extreme ratio of charge to mass for this to be relevant. Further the clickbait headline implies some kind of retroactive erasure of the onserver when in reality it just means you can't reconstruct the past from future observations due to a breakdown in how the math works. This may not even be true at all because we know that general relativity does not fully describe spacetime at the extremes found at the surface horizons of black holes anyway.
> Finally, the big discovery seems to be that you won't be destroyed by all the energy of the universe
> falling through the event horizon at the same time as you, thanks to the expansion of the universe.
The catch here is that, "all the energy in the universe," may not be hitting you as you fall through the event horizon, but a lot will, more than likely enough to give you a Bad Day. You're only down from "infinity" to "the horizon observable over the black hole's future," still a pretty big number.
> But what about spaghettification?
Others have answered this, that the gravity gradients are soft enough around a big enough black hole.
There is another fun fact here... For spinning black holes, which I believe means most of them, or at least the big ones we could think of entering in the non-spaghetti state, there are actually two event horizons, and it might be possible to leave from the zone in between them. Gregory Benford, physicist and science fiction author, set several books in that region.
The living have better things to do than to continue hating the dead.