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So does anyone know a random phenomena?

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So does anyone know a random phenomena?

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What do you mean by “truly random”?

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I mean that if we had all of the data we could have on the phenomena, then even theortically it will still be random.What do you mean by “truly random”?

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That is circular.I mean that if we had all of the data we could have on the phenomena, then even theortically it will still be random.

And presumably “all of the data” would include quantum data, so the “not related to quantum physics” restriction in the OP becomes problematic.

The topic of randomness is difficult to pin down.

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Radiodecay? Or is that quantum because it's in Schrödinger's box

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Lord Jestocost

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A truly random phenomena means that an event occuring in space and time can

So does anyone know a random phenomena?

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Nugatory

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If the dynamics of a system are accurately and completely described by a deterministic theory, then its phenomena will not be "truly random" as you mean that (unexpectedly slippery) term; only if the theory is complete (as far as we know) and non-deterministic can we get what you're looking for. At the moment quantum mechanics is the only candidate theory, so all examples of "true" randomness we can come up with will be quantum mechanical in origin.I mean that if we had all of the data we could have on the phenomena, then even theoretically it will still be random.

But be aware that I am counting on that parenthesized note about slipperiness to do a lot of work hiding sloppy thinking. One of the more important caveats is that the apparent determinism of classical mechanics emerges (analogous to how the ideal gas law emerges from the statistical behavior of large numbers of atoms) from the collective behavior of enormous numbers of particles each governed by non-deterministic quantum mechanics. Thus, your quest for "true randomness" comes down to considering:

A completely random theory (using your definition) might, given some initial conditions, assign a probability of ##1-10^{-500}## to outcome A and a probability of ##10^{-500}## to outcome B. The outcomes predicted by this theory are indistinguishable in every way from the outcomes predicted by a non-deterministic theory in which for those initial conditions the probability of outcome A is one and outcome B zero; and that in turn is indistiguishable from a deterministic theory that predicts outcome A.

Thus it is not clear that the distinction between "true" randomness and the randomness that comes from incomplete information is meaningful.

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sophiecentaur

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Filip Larsen

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To me it sounds like the OP is not likely to let such "deterministic unpredictability" imply "true randomness" because unpredictability through chaos in a physical system in a sense is rooted at quantum randomness with deterministic chaos "just amplifying" this quantum randomness to macroscopic scale, but I thought I would mention it anyway.

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But the most omniscient opponent is a red herring. What is important are our actual opponents. A box with identical balls with numbers on them that get mixed extensively produces truly random phenomena, at least if we can ensure that our opponents have not manipulated things to their advantage. And the overall procedure must be such that also all other possibilities for manipulation (or cheating more generally) have been prevented. The successes of secret services in past wars indicate that this is extremely difficult to achieve.

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No, it is only random in the practical game-playing situation you describe. In physics theory it would just be a classical set of movements and would not be random.A box with identical balls with numbers on them that get mixed extensively produces truly random phenomena

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sophiecentaur

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Baluncore

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To quote an answer from a more knowledgeable person than myself on the topic, given to me from a question I posed as, "Can you generate a random number from a machine?"

Not sure that's all relevant, or that I can support the assertion, but that is the mostly complete answer. He seemed to be aware of something similar vis a vis white noise generators for randomness.This is in fact one of the tri[c]kiest jobs to do in computing.

An actual random number has some qualities that are impossible to emulate nowadays, and this numbers are needed in fields like cryptograpy.

In the analogic world, the ramdom signals generators where always based on quantum phenomena, like the tuneling of a diode for white noise generation.Even today the hardware random number generators are based on that phenomena.

Roger Penrose did a fantastic job stressing the limitations of the computational systems, a[nd] wrote a book about that "The Emperor new mind", among other issues.

...

I want to also reiterate that I believe radioactive decay is considered stochastic (random?) at the individual atomic level. From the wikipedia on radioactive decay, we can see there are some applied methods that work from the premise that radioactive decay is random:

from: https://en.wikipedia.org/wiki/Radioactive_decayOn the premise that radioactive decay is truly random (rather than merely chaotic), it has been used inhardware random-number generators. Because the process is not thought to vary significantly in mechanism over time, it is also a valuable tool in estimating the absolute ages of certain materials. Forgeologicalmaterials, theradioisotopesand some of their decay products become trapped when a rock solidifies, and can then later be used (subject to many well-known qualifications) to estimate the date of the solidification. These include checking the results of several simultaneous processes and their products against each other, within the same sample. In a similar fashion, and also subject to qualification, the rate of formation ofcarbon-14in various eras, the date of formation of organic matter within a certain period related tothe isotope's half-life may be estimated, because the carbon-14 becomes trapped when the organic matter grows and incorporates the new carbon-14 from the air. Thereafter, the amount of carbon-14 in organic matter decreases according to decay processes that may also be independently cross-checked by other means (such as checking the carbon-14 in individual tree rings, for example).

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Filip Larsen

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I guess no one would argue that such a bit stream in principle can have unpredictable bits in the sense that there would be no way for anyone, based on measurements of the state of the initial system, to produce a predicted stream that would stay correlated with the actual stream over time.

But I also guess that Johnson noise is a very clear example of "directly amplified" thermodynamic noise, i.e. quantum noise. I think it is an interesting question if it is possible to make an unpredictable system where the source of uncertainty is not quantum noise, not directly at least. Since classical deterministic theory makes everything predictable with perfect knowledge, its seem to follow rather directly that unpredictability of the dynamics of a closed system has to be introduced either as a lack of perfect knowledge (i.e. non-perfect measurements of the initial state), a lack of full dynamic determinism (i.e. part of the dynamic is a "truly" stochastic processes), or by the system not being fully closed after all (i.e. some external disturbances sneaking in).

By the way, when the last condition is relaxed (non-closed systems) you can also get phenomenons like undecidability in an otherwise fully deterministic (computational) system, but while undecidability do seem to lead to (a certain kind of) unpredictability it does so in a different way than a "true random" process would.

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That assumes that in some sense classical physics provides an accurate description of the physical system.No, it is only random in the practical game-playing situation you describe. In physics theory it would just be a classical set of movements and would not be random.

That classical physics is not random does not imply that the system itself is not random.

For example, you may assume that infinitely precise positions and momenta are known for all objects in the system. That assumption may be true of the physical model, but is not necessarily true of the physical system.

I might argue that even theoretically the initial conditions cannot be indefinitely precisely known. And, therefore, the question of whether the system is random is not decided by the model that classical physics provides.

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sophiecentaur

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I don't think that gets you anywhere, in fact. Two deterministic processes can't generate randomness - although there may be practical reasons for using your system in some situations.

But we're just chasing our tails. If we are not allowed to use QM to introduce randomness then we are stuck with deterministic situations. But this is essentially an Engineering problem and, for Engineers, near enough is good enough. (And that doesn't imply sloppiness in any way.) Autocorrelation is the ultimate test for randomness and the sharper the spike, the better the randomness. Signal to noise ratio raises its head here.

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I have no argument at all w/ what you are saying. My point was that in the kind of game of chance he's talking about, it was random in the sense that colloquial English defines random (e.g. "drawing a card at random" kind of thing). None of the players would have any possible way to determine the outcome in advance.That assumes that in some sense classical physics provides an accurate description of the physical system.

That classical physics is not random does not imply that the system itself is not random.

For example, you may assume that infinitely precise positions and momenta are known for all objects in the system. That assumption may be true of the physical model, but is not necessarily true of the physical system.

I might argue that even theoretically the initial conditions cannot be indefinitely precisely known. And, therefore, the question of whether the system is random is not decided by the model that classical physics provides.

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sophiecentaur

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I don't think any of us can.I tried to think of a truly random phenomena thatis not related to quantum physics, and i can't.

In the context of classical physics it does. Classical Physics is not adequate to describe even the simplest phenomena to a 'satisfactory' level, once we scratch the surface so the answer to the OP is that we basically agree with him but that many classical based 'machines' have enough significant QM effects to treat them as behaving randomly.That classical physics is not random does not imply that the system itself is not random.

The only truth about non random / random distinction is that a mathematical based attempt at a RN generator will have to be a Pseudo Random Number Generator.

Remember ERNIE? In those days (especially) they needed a non-digital source of randomness because computers were far too limited to have even a reasonably good PRNG. I wonder if a PRNS from Deep Blue would be 'distinguishable' from ERNIE's output.

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I have been thinking about this response and have decided that is a good one. If you think about it in phase space, an event that cannot be undone would be a place where the phase space lines converge such that two different initial states lead to a single final state. I think that a good definition of “truly random” would be the reverse of that. So one phase space line would diverge such that one initial state leads to two final states.A truly random phenomena means that an event occuring in space and time canin principlenot be undone.

Then, Liouville’s theorem proves that classical physics forbids “truly random” systems.

Note: I am not aware if there is already literature on this topic

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Crumpling a sheet of paper. It is HUGELY complicated/impossible to mathematically model.

So does anyone know a random phenomena?

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Filip Larsen

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Branches in state space sounds similar to symmetry breaking, and that at least has some literature. As I understand it symmetry breaking in an otherwise symmetric system is only considered to be a result of quantum effects (spontaneous or dynamical symmetry breaking) or, for in case of purely classical system, due to the system not being precisely symmetric after all.Note: I am not aware if there is already literature on this topic

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As I see it, the difference between random events and non-random events is

But information is

Let's choose a different form of symmetry breaking: the needle test. Imagine a horizontal rigid surface in a vacuum in neutral gravitational and electromagnetic fields. You have a device that tosses the needle so that at least sometimes that needle lands balanced on its tip. The game is to bet on which way it eventually will topple. Laplace does not forbid such a possibility, and offers no prediction.

The needle and surface offer no information to the universe about how that symmetry will break. To the extent that information on any bias

If you happen not to like the needle, try the ball test: start with a rigid surface and vacuum as already described. Take a vertical, symmetrical stack of rigid, notionally perfect spheres of excellent coefficient of restitution, and drop them. As long as there is no information on any asymmetrical bias (not just your ignorance, and ignoring any quantum asymmetry, those balls, in obedience to F=ma, will bounce vertically for a long time till they stop and remain balanced. Right?

Wrong.

For that to happen there would have to be

It follows that,

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Is information finite classically?

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A "typical" real number contains an infinite amount of information. There was a thread a couple of years ago about whether physics could be done using only the computable numbers. In any case, using a real continuum for position of a particle, say, creates a conundrum.Is information finite classically?

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