A new Stephen Hawking presentation about black holes
washingtonpost.com
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One consequence of that redefinition is that humans could theoretically survive crossing it, contrary to the firewall hypothesis (well, if they were in a sustainable capsule with a large gene pool, and the hole was rotating just right), by waiting long enough on top of it until the hole evaporates (from the capsule's point of view).
Time would indefinitely slow down for them, so they would see the rest of the universe speed up until the hole dies.
http://arxiv.org/pdf/1401.5761.pdf
I'm guessing people are taking it seriously, but as it's not a complete theory of the dynamics it's hard to say "solved" in reference to this development.
AFAIK that wasn't originally his argument, but he conceded and agreed that it was likely a better hypothesis than Hawking Radiation.
This talk seems to be a brilliant attempt at reconciling, what were previously, two competing hypothesis.
I can't even imagine how frustrating his condition must be for him though. To have full mental capabilities but have so little (and slow!!) means of communicating his ideas.
In IT we tend to train our brains to commit processes (eg ways to research information) rather than facts. But we also have the luxury of being able to be lazy (internet, functioning limbs so can write notes, etc). Heck, before IDEs and the internet I used to remember every function name and order of parameters for any particular programming languages I was proficient in. These days I just learn the function name and let the IDE remind me of the rest (sometimes I don't even learn the function name and just search for it in the package namespace).
He's not at all disabled for what he does, which is think, and he does that better than (I'm guessing here) any of us.
Also no ability to use paper and pencil, and still only a low bandwidth mechanism to store and retrieve notes to increase your effective memory.
If you, for example, start a pendulum with different initial displacements the pendulum will always end up at rest due to friction but if you could take into account the exact states of all the molecules in the air and the joint and so on you could in principle figure out in which exact positions you started the pendulum.
You could actually just very precisely measure the temperature of a pendulum in a box and infer the initial displacement from that because different initial displacements imply different initial (potential) energies and therefore different final temperatures after all the energy became thermal energy and everything in the box had time to reach the equilibrium temperature. You just couldn't figure out whether the pendulum was started to the left or to the right of the rest position with this method.
My layperson's understanding of QM always gave me the impression that it does the opposite: that it gives non-determinism a place to "hide," so-to-speak. My impression was that religious believers could use QM to argue that their unseen God, for example, does actually have a physically plausible mechanism by which he/it could intervene in the physical world. But if I'm understanding this theory correctly, unless God is a physical thing, there is no way for God or any other supernatural force to affect the physical world without itself being physical.
This theory also would seem to deny the existence of free will.
There is of course the infamous collapse of the wave function that seems to turn a quantum state into a classical state during a measurement and this with different probabilities for different outcomes. This collapse of the wave function is not unitary and there are no good reasons to assume that a measurement is in any way special and should violate the laws of quantum mechanics which have otherwise been shown to work with incredible precision.
Therefore the collapse of the wave function is probably not a thing but just an apparent artifact of our ignorance of the details of the measurement apparatus which just is a gigantic quantum mechanical systems with billions and billions of particles.
Another way to think about that are symmetries and conserved quantities. The physical laws are believed to have certain symmetries, for example time and space translation symmetry or rotation symmetry, i.e. a physical experiment should yield the exact same result no matter whether you do it here or five meters to the left, today or in three weeks, with the laser beam pointing north or east.
Space translation symmetry, for example, means that if you change all you initial say x coordinates by the same amount the calculations should nonetheless yield exactly the same result as a calculation with the unchanged coordinates besides that the final state will of course have the same offset in its x coordinates.
If you demand that your laws of physics obey such symmetries and do some math you will find that each such symmetry inevitably gives you a quantity that does not change over time, i.e. that is conserved. That is Noether's theorem and extremely general, i.e. (almost) no matter what laws you imagine, a symmetry will always give you a conserved quantity.
The conserved quantity for space translation symmetry is what we call momentum, for rotation in space it is angular momentum and for time translation it is energy. But now that we have conserved quantities it is now impossible that two states differing in any of the conserved quantities will ever evolve into the same state or have ever been in the same state because that would require the change of a conserved quantity.
So to summarize, very basic assumptions like isotropy and homogeneity of space and time inevitably lead to conserved quantities which in turn prevent certain state evolutions that would violate those conservation laws. I am not sure if those constraints force time reversibility onto you but I assume they do.
Another commenter mentioned T-symmetry, that is that the physical laws remain the same if you reverse the time axis, i.e. multiply the time coordinates by minus one flipping past and future. This is of course not the same as time translation symmetry which is about adding to the time coordinates and it is also different from the reversibility I mentioned before, i.e. the ability to retrodict past states which does not require that the evolution into the past is symmetric with the evolution into the future. T-symmetry is believed to be violated for very good reasons but that has not yet been shown experimentally although it follows from the observed CP-violation and the assumed CPT-symmetry.
And I am not a physicist, so while I believe everything I said is accurate or marked as me not being sure or not knowing it may still contain some - hopefully minor - errors.
Regarding free will -- rigorously define it for us, without evoking the supernatural, and as distinct from pure randomness and absolute determinism, and it should be easy to tell whether the law of conservation of information allows for it. Before spending too much time in e it, though, note that such a definition is widely considered impossible. IANAP
In practice, our confusion about a system does increase with time as classical systems become ever more correlated, losing distinguishability, aka decoherence.
By all means go on thinking there might be some supernatural thing called a "free will" if you want. But if it's supernatural, then the utterly natural laws of QM wouldn't have much to say about it.
Consciousness is not the same thing as agency. It is possible that we are conscious but do not actually have free will / agency.
> By all means go on thinking there might be some supernatural thing called a "free will" if you want. But if it's supernatural, then the utterly natural laws of QM wouldn't have much to say about it.
I am not sure I agree. If QM implies a strict determinism, to me that rules out free will. For free will to be plausible, there has to be a place for non-determinism to "hide." If QM can rule that out, to me that rules out free will.
at random? randomness doesn't look 'free' to me, looks.. random.
following some rules? not 'free' anymore.
This "free will" thing doesn't support well scrutiny.
(I've mentioned crows just to be able to link to https://www.youtube.com/watch?v=ZerUbHmuY04 )
I don't think this. I don't think that anything about the consciousness or agency of humans is exceptional to humans.
> The "consciousness" as a "neurological process by which the animal or the human sees it as special, the center of its attention in order to protect itself" can be seen as a product of evolution.
This is an interesting perspective that definitely made me think, but I think it ultimately begs the question. If you're talking about "seeing" or "attention," you're already speaking in concepts that presume the existence of consciousness. I'm not sure this gives us a useful framework to know when any computational process we have created does indeed have "consciousness," or where the line is between animals advanced enough to have it and animals (or even plants) that don't.
Maybe I wasn't clear enough. The world around us (and animals) is projected in our (and animal's) neurological system as some kind of the model. The question is just if the model is such that favors the representation of the uniqueness of the organism or not. I claim that there's evolutionary advantage in producing a system (hardware and software) where organism cares for itself and where the model is so formed that "me" is in the center, to the level that "me" is "conscious" in the sense, processing the stimuli as much that the dog understands that the paw is "his paw" and that it's dangerous to put the paw in the fire and up to the level of you and me considering "us" "us" and being able to talk about it. Therefore we're not so much different from the rest of the animals.
> I'm not sure this gives us a useful framework to know when any computational process we have created does indeed have "consciousness,"
I'd still like to know how you can define consciousness in a way that it doesn't sound religious. If you can't, then of course we can't progress in our discussion.
Let me give you very "primitive" and "simplified" view of the "free will" subject. I see it as a purely religious construct, based on the following history: initially, gods weren't "almighty and omnipresent." If you've read ancient Greek literature, there are such gems like "Zeus was at that moment in Egypt so he wasn't there when the soldiers he supported lost." If you've read Bible, the oldest myths (I mean, stories in the Bible) are actually based on such concept of god(s). Then the theology "theory" grew more demanding, postulating the "almighty omnipresent" but also the "loving" god. Which made the myths (stories) much absurder than they were as they were written. How can almighty loving god produce the world and then see that it's bad, so that it has to send the flood to destroy it? It's either not almighty or not loving etc. As a rescue, the priests invented the concept of "free will" as in "once god creates humans, they have their own free will (which god can't control!?) and they do what they do so then they get to deserve to suffer, go to hell and all that nice stuff." Most of the "modern" theological concepts are constructed as an attempt to make less absurd the whole "body of work." A kind of "justification by obscurity" which obviously works for believers, giving them easy covertly nonsensical sentences to answer the "hard questions" others would give them.
In reality, we just have what user jonsen formulates here as "the purpose of consciousness is to keep its organism viable. It does that by collecting an essence of past and from that predict an essence of the future."
Now you ask about the "framework to know when any computational process we have created does indeed have "consciousness."" It depends on the definition of he consciousness, but that definition can't involve gods and "nonphysical entities." As soon as that is clear we can measure the "consciousness as what we observe in a dog" or the "consciousness as what we observe in a six months kid," the "consciousness as what we observe in a twenty years old healthy human" and the "consciousness as what we observe in 80 years old human with Alzheimer's disease which progressed this much."
Note that neurologists as the part of their daily routine have to evaluate the level of consciousness in their patients. It's very instructive to read just some examples of he cases they work with.
When we're there, do you think that a human with Alzheimer's disease which progressed so much that he can't remember anybody from his life or what he did just 15 seconds ago has a "soul?" (a lot of healthy animals remember for months different things, or if you talk with the owners of pets, you'll hear that there are animals which have traumas and a lot of the psychological symptoms you'd just associate with humans). So back to the patient, do you consider him "conscious?" If not, at which point did he lost his consciousness which you equate with soul? If yes, where is he different from some good Perl script? There is no "single unique unchangeable" consciousness, there are just different levels of functioning of the model I mention at the start. Of course, when you die, the model completely stops functioning as it needs both the hardware and the software, the brain and the body as the hardware and all these nice electrical impulses and chemical reactions in the living organisms as the software. There's no such thing as the "agency of the nonphysical entity" there.
There is no other choice. By definition, random means "not following any rule or pattern".
For example, is there any physical property that is not "locked into place" by the laws we know and the observations we can make? Is there any fundamental impossibity (not practical impossibility) of snapshotting the state of the universe and using that snapshot to determine every past and future state of the universe?
There's allot of weird stuff going on on the extreme edges of theoretical physics, to the point in which also a though that some areas of theoretical physics have moved into the "Metaphysics" and Philosophy domains and are distancing them selves from certain scientific principals.
That said I like to treat black holes in the GR/SR manner they are simple massive objects not super dense hot balls of entropy, they don't have some universal cosmic powers, they are "black" simply because they red-shift all radiation to the point of invisibility, they can form, grow and break apart, and we never can see anything actually entering a black hole due to time dilation and anything that comes close to it will be red-shifted to a point in which we won't be able to see what or where it is either.
Since nothing from out POV ever enters the black hole and everything is stuck on the event horizon nothing is lost, and since black holes can evaporate (Doesn't require hawking radiation altough it's the most common explanation since Yakov Zeldovich (which Stephen hawking based his work on) and others have proposed similar mechanisms which are more compatible with physics as it is measured and perceived by hmmm reality...), no firewalls or weird mechanism are needed to protect or explain other weirdness that happens around singularities.
Singularities are well covered by GR and SR prevents naked singularities so we are good there too.
But that's just me :)
https://en.wikipedia.org/wiki/Landauer's_principle
Landauer's principle is a theoretical lower limit on the amount of energy required to perform a computation that destroys information.
No it's not. Why are so many people making things up? QM does not even define a concept of a quantity called "information".
[1] http://www.science20.com/hammock_physicist/who_todays_einste...
Something not accounted for by that illustration is age ~ proportion of realized potential. Maldacena is 47, Randall 53; no longer promising youngsters, but with decades of index-climbing potential left in them. Weinberg and Glashow are both 82, and owe the bulk of their index position to work done in the 60s and 70s. Witten is 64 and peaked in the 80s and early 90s. Polyakov is 69; for him it's 70s and 80s.
Hawking is 73. His index-driving contribution is black hole evaporation, from 1974. After that, he's mainly been a popularizer.
That's what I've got on Physics stack exchange. There's those collapsars that look exactly like black holes but are made of matter around the event horizon, infinitely falling in.
Is this right, wrong, or irrelevant?
I say who gives a shit about the point of view of the infalling object. :-)
Presumably the mathematical descriptions tell a different story because I never see it described like this.
From our point of view, not the matter's. The matter falls through just fine.
Yes it does. Quantum observations (sometimes called "collapse of the wave function") are not time symmetric. Once you've experienced one you can't derive where you were before it. Otherwise you wouldn't be using the word "probability".
This inability to recover a previous state is, by definition, the loss of information.
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There's no basis to attack Hawking or anyone else. Even the article's author should be relatively immune, because WaPo isn't in the business of writing scientific articles.
If you insist on attacking, then let's aim for the central argument. For example, a decent attack on Einstein in the 1940s would be to remark that if quantum electrodynamics agrees with experiment, then Einstein's goal -- to demonstrate that probability wasn't a fundamental component of the universe -- would be in trouble.
An excellent attack would be to cite the research, and to explain why if X is true then @physicist is wrong.
Are you sure that being mistaken is such a terrible thing? The mistakes are often more illuminating than the discoveries, as they provide a framework upon which to learn how to improve the process of discovery.
I'm extremely interested, and the question isn't meant as anything but an inquiry. Finding a gap in one's knowledge is one of the more exciting aspects of life.
Amplitudes are complex numbers, out there in the real world (as far as we understand it). This is quite different from probabilities, who are real numbers between 0 and 1 who exist only as a mental constructs. Simply put, while amplitudes share some mathematical properties with probabilities, they are not probabilities.
Now that we're done turning colloquial words into misleading jargon, we can talk about the theory itself. Namely Everett's many-worlds and decoherence.
We could play the "where's the electron" game, but I'd rather play "where's the photon" instead —it's simpler. So you throw a photon through a half-sieved mirror, to be detected by one of to judiciously placed detectors. Oh, and have one detector linked to a kitten murdering system for good measure.
If you repeat the experiment often enough, you will witness a kitten death half the time, with absolutely no way to predict the outcome in advance. The results are the same if you put the kitten in a box, and open that box after the fact. So it certainly looks like the universe is not deterministic.
The equations on the other hand are definitely deterministic. Future amplitude distributions are perfectly predicted by past amplitude distributions —which by the way you can't fully observe, but that's another issue entirely. So, if you look at the amplitude distribution, you'll see that once the photon hit the mirror, there will be a blob of amplitude for both cases: passing through and being reflected. Going further, there will be a blob of amplitude for each of the detectors being hit. Finally, there will be a blob of amplitude for the living kitten, and another one for the dead kitten. Oh, and the equations also says that the blobs quickly cease to interact —that's decoherence.
Basically, what the equations say is that the universe splits itself in two, generating one version with the dead kitten, and one version with the live kitten. The equations also say that the inhabitants of either version don't get to see the other one (they've ceased to interact).
Now the only question left is why we experimentally find ourselves to be in one version and not in another. But never forget that every time you run that Schrödinger experiment, a cat will die. If not in your universe, then the other.
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The Copenhagen interpretation, which would have the blob of amplitude corresponding to the other universe just collapse into nothingness (that is, set to zero), has no basis in the equations which by now are backed up by mountains of evidence. It is an additional hypothesis layered on top of the equations, conveniently formulated in a way that wouldn't falsify any experiment. On top of that, it violates a number of long standing principles, such as locality.
You could also call those amplitudes "probabilities", but that's just a word trick. It doesn't explain anything.
But the fact remains that blindly following the equations leads you to Many-Words. You have to modify the results to get to any sort of collapse hypotheses. Also, simply postulating that what you don't see doesn't exist doesn't help. http://lesswrong.com/lw/pb/belief_in_the_implied_invisible/
Pretend that you're talking to someone who doesn't see many-worlds as an obvious corollary of the current QM theories. What experiments do you propose to indicate the simultaneous existence of e.g. a universe in which the photon chose Slit A and another in which the photon chose Slit B?
Your appeal to BitII fails because that concerns e.g. conservation laws that are regularly observed to be true, and which therefore can be assumed true when a particular situation makes observation impossible. Many-worlds has never been shown by experiment, so it is not eligible for such treatment.
We already agree that there is no experimental difference between collapse/Copehagen interpretation, and the Many Worlds interpretation. In the name of what are you demanding experimental evidence for one interpretation, and not the other?
> Infinite uncountable infinities of universes is not parsimonious.
You need to remember that those universes are in no way postulated. They are derived —from the equations. So you can't use that impressive infinity to claim that the Many World interpretation would somehow have a higher Kolmogorov complexity than Copenhagen.
Many Worlds just takes the equations and run with them. It's Copenhagen that makes additional assumptions by manipulating the results of the equations: They're not real, or there's a collapse… Either way, that's an additional hypothesis on top of those equations (which by the way have massive amounts of experimental evidence behind them, and are accepted by everyone as the current best guess). That additional hypothesis is not very parsimonious, don't you think?
(You have to remember how Occam's razor really works. From the Wikipedia, "The principle states that among competing hypotheses that predict equally well, the one with the fewest assumptions should be selected." As a simple matter of fact, Many Worlds makes strictly fewer assumptions than Copenhagen. Parsimony is not measured by the size of the universe predicted by the theory. Parsimony is measured by the number of core assumptions. Not the same thing at all.)
To get a feel of how utterly ridiculous collapse postulates are (in 20/20 hindsight, I don't want to make fun of physicists), I must quote Eliezer Yudkowsky: http://lesswrong.com/lw/q6/collapse_postulates/
If collapse actually worked the way its adherents say it does, it would be:
1. The only non-linear evolution in all of quantum mechanics.
2. The only non-unitary evolution in all of quantum mechanics.
3. The only non-differentiable (in fact, discontinuous) phenomenon in all of quantum mechanics.
4. The only phenomenon in all of quantum mechanics that is non-local in the configuration space.
5. The only phenomenon in all of physics that violates CPT symmetry.
6. The only phenomenon in all of physics that violates Liouville's Theorem (has a many-to-one mapping from initial conditions to outcomes).
7. The only phenomenon in all of physics that is acausal / non-deterministic / inherently random.
8. The only phenomenon in all of physics that is non-local in spacetime and propagates an influence faster than light.
WHAT DOES THE GOD-DAMNED COLLAPSE POSTULATE HAVE TO DO FOR PHYSICISTS TO REJECT IT? KILL A GOD-DAMNED PUPPY?
If I were to stipulate that the Copenhagen interpretation(s) is (are) silly philosophical daydreaming, could you do the same for many-worlds?
Funny how different people perceive his writings. To me, most of what he writes feels obvious —at least in retrospect. "Obvious" doesn't feel very mystic to me. I do understand however how many people would be distrustful of his casual writing style. He tends to sound like a lowly blogger, not like a respectable academic. (Personally, I don't care for those status signals.)
> I'll read that eventually, but I won't be surprised if it turns out to be like much of the rest of LW
Hmm, if you're already familiar with this material, then don't bother just yet. Start with the first few chapters of E.T. Jayne's Probability Theory: the Logic of Science. That's more basic, less crazy sounding, and more generally applicable.
Now I don't exactly know how physicists deal with quantum mechanics. I asked one, and he didn't even bother with any interpretation, sticking with the observable consequences of the equations (a more prudent attitude than either Copenhagen or Many-World).
Something however bothers me deeply: insisting on calling amplitudes "probabilities", while they're anything but. That only makes teaching harder. Seriously, I was tempted to mass delete every occurrences of "probability" from the "Probability Amplitude" article in the Wikipedia.
> If I were to stipulate that the Copenhagen interpretation(s) is (are) silly philosophical daydreaming, could you do the same for many-worlds?
Err, it doesn't work like that. If I were to convince you, I would have learned nothing, and believe then what I believe now. I can only give you my current best guess.
Which is, many-worlds is by no means certain. At the very least we don't have a Theory of Everything, and we could miss something. Collapse postulates however are just crazy. Rejecting the existence of the amplitude you didn't observe is just as insane (no less, no more) as rejecting the existence of a photon which just passed the limits of our observable universe.
When we do find a theory of everything, I bet the equations will predict the existence of things that can't be observed —not even in theory. I just hope people won't see that as a licence to not believe in those things at all.
Other unobservable stuff may or may not be incredibly important. (Though at a first glance, QM interpretation isn't.)
My understanding of (real) probabilities is that they're really about our ignorance of a system. E.g., if I'm flipping a coin but put very little spin on it, it's easy for a human to predict what side will show. As we put more spin on it, the probability of guessing correctly goes down, but that's about perceptual and cognitive limitations.
My (layman's) understanding of quantum mechanics, though, is that there are no hidden variables. In which case, I couldn't understand why anybody would call the quantum stuff "probability". It's a relief to know that they're fundamentally different.
Most convenient reference:
> In quantum mechanics, a probability amplitude is a complex number ...
https://en.wikipedia.org/wiki/Probability_amplitude#A_basic_...
I don't understand this part: "Now the only question left is why we experimentally find ourselves to be in one version and not in another"
Surely there are different 'we' observing in both?
From the inside however, we still have the Born probabilities to contend with: apparently, our subjective probability to observe one version or another is tied to the square root of the relevant amplitudes. In the case of a half-sieved mirror, that's one chance in two. But we can easily bias this with a stronger (or weaker) mirror.
God yes. Sadly, they don't tend to help you get more funding.