Is True Randomness Possible in Our Determined Universe?

[kelolasin]

Can something random occur in the sense that no factors are involved of it happening?

I would think that nothing random can occur, if a photon goes a special way, then it's determined by factors and events prior to the photon "choosing" it's way, or am I wrong? If there are any articles or papers on this topic, please share, I am very curious about this topic.

 

[abluphoton]

thats a very big question.. can there be a random thing in this universe ?? if the universe is run by a thing called a theory of everything. a simple and straight deterministic theory. but how can a deterministic theory fabricate a random phenomenon?!
but surely we can see a lot of random outcomes in nature, in experiments. that can be recreated with providing less information into the observing system. suppose, going by Heisenberg's uncertainity principle. we can create a system that can cause desired degree of randomness.
i donno, i haven found anything random in this universe other than 'life' though there are people who claim that we are destined to do whatever we do.. i don't yet have a reason to believe that, nor reject that. a deeper look into this leads to comment on god. i do not want to do it here.

 

[Lukas_23]

Heisenberg principle!

If it is a fundamental of nature, we cannot even answer the question. To see if something is random means that it contradicts the initial conditions. But we can't know the initial conditions accurately. It is the same as trying to look inside a black hole.

 

[kelolasin]

But wouldn't it be possible to theoretically figure out whether or not a random event can happen?
I would assume that it would contradict with the law of conservation, since it would have to receive the energy to do the specific event, and that energy would define what would happen to it.

 

[Lukas_23]

Reality is chaotic, which means that even if it is deterministic we will always find perfectly regular patterns as well as inexplicable random events.

Langton's ant is a deterministic iterative algorithm based on simple rules. You only move once and see what happens.



Observe what happens at :05 seconds.

I know I'm stretching the imagination here but make an analogy for the Big Bang as the first move and physical laws as the rules. Then the DNA was the the right place and time for the deterministic rules to produce a strong patter, like with the ant. In this view if we can call something a God, then it is the physical laws.

We also need a definition for random. I think that which cannot be predicted is random.

 

[gordonj005]

in short, no. the entire quantum revolution of the 1920's kind of put determinism out of a job. in the quantum world determinism is replaced by probability, as in we can't say for sure whether a particle will go one way or the other, all we can say is that there is a probability for it to go this way, or another way...etc. its a fundamental property of nature, she avoids being pinned down. so maybe we're just not looking close enough, maybe there's some even more fundamental set of laws governing these seemingly probabilistic outcome, but maybe not. so far everything points to a world of probability and not deterministic.

 

[Lukas_23]

Yes, things in general don't behave randomly but the probabilistic nature of quantum alows for random events like tunneling. As Kaku says, because of the wavy nature of everything, including a human, there is a probability you find yourself in Mars in any moment. Of course it is vanishingly small but not zero.
So who knows, maybe one of the about 100 billion people who have been alive has been to Mars afterall.

 

[jetwaterluffy]

Send one photon through a diffraction grating. Where it lands is random.

 

[tyreds_tale]

Great question with interesting responses. My understanding is that Quantum mechanics has shown that particles and photons behave in a probablistic fashion. The probability is a distribution function, but still random since the exact outcomes is not known. At least not known to us. But some think that there must be a DEEPER LOGIC that determines the position and velocity such that is appears to us as a distribution function of possibilities.

So I'd say that it appears that randomness does occur, such as when a photon travels through a diffraction grating, however we can not be certain it is absolute randonmess.

Can we ever be certain of absolute randomness? I think we can be confident but not totally certain. I don't think the scientific method sets out to make absolute claims anyway.

 

[jetwaterluffy]

Can we ever be certain of absolute randomness? I think we can be confident but not totally certain. I don't think the scientific method sets out to make absolute claims anyway.

Can we ever be certain of anything? The whole point of physics is to find out what is most likely. We don't know for sure we aren't all a computer simulation, or every physics experiment is an anomoly and some other set of rules govern the world. Maybe there is a determinism behind it all. But the most likely event, currently, is that it is random, and if not, we can't explain it, at all, so it might as well be.

Science does make absolute claims. There is an absolute speed limit (the speed of light). Some photons have absolutely zero mass. There is an absolute conservation of energy and momentum.

 

[sophiecentaur]

I have a feeling that people (even dear Albert) have always had a problem with the idea of probability governing the way things work because is just doesn't suit us. We run our lives according to rules and the more simple and straightforward those rules are, the easier it is to cope. We want our Science to be the same. We could be on to a complete loser, in this respect.
It is true to say that any continuous curve (in Euclidean Space - which is the one we 'see'), however tightly curved, will approximate to a straight line if we take a small enough portion. So this gives us confidence that the 'real world' is like it. All of our Science is reductionist and looks for straight line solutions where it can. Our Philosophy likes it that way. In many ways, the world 'looks that way', too but should we really expect it to be so? There is no reason to reject the probablistic model just because it's not convenient.

 

[MikkelM]

In a macroscopic sense, I would say that the uncertainties of quantum objects are to such a degree evened out that one could describe the universe deterministically with some defined level of accuracy.

Many people mistake randomness for unexpectedness in the colloquial understanding of these terms, although they are quite different. Unexpectedness can occur by simple lack of understanding or misidentified causal factors. Randomness would be an event occurring in the absence of causal factors, in other words fundamentally unpredictable. As far as I know, this only occurs on the quantum scale, however it is also fundamental to how the universe works. So in an absolute sense, the universe is non-deterministic.

However, as long as these non-deterministic events are similarly limited in outcome, a large enough system of non-deterministic events gives rise to statistical determinism.

The kicker for me is HOW non-deterministic events can be similarly limited in outcome, and whether this is truly non-deterministic. I.e. you can never predict the behaviour of any single electron, however all electrons are limited in the way in which they CAN behave. These limitations on the non-determinism of the universe puzzle me.

That is how I as a non-physicist understands this anyway. Please correct any misconceptions.

 

[sophiecentaur]

"These limitations on the non-determinism of the universe puzzle me."
And everybody else - if they are strictly honest. I think you just have to accept it (like all truly revolutionary ideas) - as long as the evidence is there - and treat it as a new model.
I have heard Feynman (who can do no wrong on this forum) say virtually the same thing about QM and preconceptions.
But, there again, I don't believe in any 'ultimate truth' in Science so it's just a journey from one pragmatic position to another and so on. If probability is a good explanation for what we see, then flavour of the month / decade / century / millennium is probability.

Interestingly, Chaos was almost a new flavour but it seems the Maths doesn't really support it as a way of explaining QM etc.. Is this right? I'm open to correction here.

 

[Deicider]

First let's define random.

Randomness of flipping a coin:
Once you flip the coin you can measure the spin, force, etc and determine how it will end up.
It is random to our perception but predictable with tools, and is a deterministic system.

Randomness of a quantum position:
If you try to measure it you will interfere with it and spoil its position/spin.
It is random to our perception and random with tools but STILL a deterministic system.

There is no such thing as "true randomness".
If such thing existed then physics wouldn't matter, mathematics wouldn't matter, causality wouldn't matter, logic woudn't matter etc.

Quantum states can be predicted by probabilities, just like a coin.


People constantly confuse randomness with non-determinism.
Just because something is out of our calculation, out of our reach, doesn't make it less deterministic or even random.


tl;dr the universe is deterministic if it wasn't then nothing would be possible.

 

[MikkelM]

I believe this is a common misconception. Heisenberg's uncertainty principle is not a question of the limitations of measurement or perception. It is a fundamental property of quantum particles. Even if there was a hypothetical perfect instrument that did not change the properties of what it measured, it would still not be able to determine the position or momentum of an electron, because the electron's very existence is probabilistic in nature. An example of an observable (and technologically utilized) phenomenon that relies on this is quantum tunnelling. If probability density were not a manifest property of the electron, flash drives would not work, let alone several nuclear processes that require tunnelling through a potential barrier.

 

[Deicider]

I believe this is a common misconception. Heisenberg's uncertainty principle is not a question of the limitations of measurement or perception. It is a fundamental property of quantum particles. Even if there was a hypothetical perfect instrument that did not change the properties of what it measured, it would still not be able to determine the position or momentum of an electron, because the electron's very existence is probabilistic in nature. An example of an observable (and technologically utilized) phenomenon that relies on this is quantum tunnelling. If probability density were not a manifest property of the electron, flash drives would not work, let alone several nuclear processes that require tunnelling through a potential barrier.

No, i disagree, if we had an hypothetical instrument that didn't affected the particle we could exactly know the full information of photon/electron.

 

[MikkelM]

How do you determine the position of a wave packet that does not have a discrete volume? And how is tunnelling possible if this wave packet does not have a probability density that can extend beyond a potential barrier?

 

[cbetanco]

Heisenberg principle!

If it is a fundamental of nature, we cannot even answer the question. To see if something is random means that it contradicts the initial conditions. But we can't know the initial conditions accurately. It is the same as trying to look inside a black hole.

No, this is not what Heisenberg's principal says. It says we cannot know simultaneously both the momentum and position of a particle exactly. It does NOT say that we can't know the state vector exactly, which would be enough to define an initial condition (the state vector at t=0). All Heisenberg says, when it comes down to it, is that you can't find a basis where both the momentum operator and position operator are both simultaneously diagonal. But the state vector is what it is, regardless of which basis you choose to look at it from.

 

[juanrga]

Can something random occur in the sense that no factors are involved of it happening?

I would think that nothing random can occur, if a photon goes a special way, then it's determined by factors and events prior to the photon "choosing" it's way, or am I wrong? If there are any articles or papers on this topic, please share, I am very curious about this topic.

By definition something random has no cause, otherwise it is not random.

I think that Universe is a curious mixture of random processes and causal processes.

 

[sophiecentaur]

First let's define random.

Randomness of flipping a coin:
Once you flip the coin you can measure the spin, force, etc and determine how it will end up.
It is random to our perception but predictable with tools, and is a deterministic system.

Randomness of a quantum position:
If you try to measure it you will interfere with it and spoil its position/spin.
It is random to our perception and random with tools but STILL a deterministic system.

There is no such thing as "true randomness".
If such thing existed then physics wouldn't matter, mathematics wouldn't matter, causality wouldn't matter, logic woudn't matter etc.

Quantum states can be predicted by probabilities, just like a coin.


People constantly confuse randomness with non-determinism.
Just because something is out of our calculation, out of our reach, doesn't make it less deterministic or even random.


tl;dr the universe is deterministic if it wasn't then nothing would be possible.

What sort of a definition is that supposed to be? Randomness doesn't imply 'equal likelihood' (a frequent problem that gamblers suffer from). In a deterministic system there is NO true randomness - the outcome is predictable.

That is merely a statement of opinion / faith. How could you possibly prove or disprove that? All we can say is that, on the scale we operate, many things appear to behave deterministically. otoh, as has been stated above, many things do not, once you scratch the surface.

As I wrote earlier, a nice set of rules is very attractive. It limits just how much your brain needs to work - in fact the rules were invented by human brains so it isn't surprising that they are possible to cope with.

Also, from another posts:
"if we had an hypothetical instrument that didn't affected the particle we could exactly know the full information of photon/electron."

A hypothetical instrument is purely hypothetical so any conclusion about what it would show are no more meaningful. Again, you are merely expressing 'faith'. Any measuring instrument which would do what you propose would not necessarily be part of our universe (it's not just a matter of paying enough money to develop or buy one).

Anyone who wants to restrict the way the Universe works to a 'mechanical model' cannot even explain much of what we have already experienced, let alone look any deeper.

 

[sophiecentaur]

But the state vector is what it is, regardless of which basis you choose to look at it from.

The "state vector" is a purely Mathematical way of trying to describe something. It is an abstract tail that cannot wag the dog of reality.

 

[cbetanco]

The "state vector" is a purely Mathematical way of trying to describe something. It is an abstract tail that cannot wag the dog of reality.

I was using the state vector to describe Heisenberg's principal, and how Heisenberg's principal does not say anything about randomness. I was not using it in the context of whether it actually has a physical existence (although, I actually do think it is physically relavent, but that should be saved for a different discussion).

 

[sophiecentaur]

I was using the state vector to describe Heisenberg's principal, and how Heisenberg's principal does not say anything about randomness. I was not using it in the context of whether it actually has a physical existence (although, I actually do think it is physically relavent, but that should be saved for a different discussion).

The Uncertainty Principle may not explicitly use the term "randomness" but it excludes determinism and that, surely boils down to the same thing. The UP is described and explained in terms of a thought experiment but it surely goes deeper than that. If something is unknowable, within that 'volume of uncertainty' then how can it be not random?
You said that the state vector is "what it is" and that, to me, involves an assumption about 'reality' which is not well founded - any more than the other QM concepts that are not 'really' one way or another. Your statement implies that an object is really in a certain exact state but that you just can't be sure exactly about that state because of the problem of measuring it. I say that the 'state' itself is not exact; the concept of something actually having an exact state is meaningless.
To my mind, those two views are mutually totally exclusive.

 

[cbetanco]

The Uncertainty Principle may not explicitly use the term "randomness" but it excludes determinism and that, surely boils down to the same thing. The UP is described and explained in terms of a thought experiment but it surely goes deeper than that. If something is unknowable, within that 'volume of uncertainty' then how can it be not random?
You said that the state vector is "what it is" and that, to me, involves an assumption about 'reality' which is not well founded - any more than the other QM concepts that are not 'really' one way or another. Your statement implies that an object is really in a certain exact state but that you just can't be sure exactly about that state because of the problem of measuring it. I say that the 'state' itself is not exact; the concept of something actually having an exact state is meaningless.
To my mind, those two views are mutually totally exclusive.

The state vector is infinite dimensional, which means in principal, in encompasses all the information about the (closed) system in question. Also, in principal, we can know how the state vector is projected along eigenbasis in question (like the wave function in position space), even if its got a projection along a finite, or infinite number of eigenvectors (in say, momentum or postion space). The fact that it is spread out in position or momentum space I don't think is a issue with randomness, its more an issue how the vector is pointing in Hilbert Space. The randomness of QM doesn't not come from the HP, which just says that you can't find a basis in which both X and P are diagonal. The randomness in QM comes you actually measure something, and the state vector collapses along one of the eigenvectors of the operator of the thing you wish to measure, with a probability given by the square of the projection along that eigenvector.

We CAN determine how much the state vector is pointing in a particular basis, the wave function is how much its pointing along all the eigenvectors in position space. So to me, this is not an issue of randomness, but figuring out how it points in a certain direction. I still don't that just because the wave function is spread out along position or momentum space this implies randomness, it just implies the state is in a mixture of eigenstates.

Maybe we can start a new thread if we wish to discuss this further, as I think we are slightly diverging from the OP (still about randomness, but we are more discussing HP and the reality given to the state vector). Or you can just private message me

 

[sophiecentaur]

The only 'definition' of randomness that I know is for purely random signals, for which the autocorrelation function is zero everywhere but at t = 0.
I don't know of an equivalent definition that would be suitable here, so the definition of randomness should, perhaps, be sorted out before going further. We may all have our own view of what we mean when using the word 'random'. That makes it a bit hard accept or reject what the other guy is saying.

I think that, once you say the state vector is infinite dimensional then you are, in fact, introducing the 'unknowable'. That is certainly in the general direction of 'random' (by anyone's appreciation of the term) in as far as it implies that, because an initial state is unknowable to, the following state is also unknowable.

 

[cbetanco]

I started a new thread if you wish to continue Heisenberg's principal and the definition of randomness https://www.physicsforums.com/showthread.php?t=551792