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Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: glovesforfoxes on 03/07/2009 16:04:02

Title: Randomness and quantum mechanics
Post by: glovesforfoxes on 03/07/2009 16:04:02
Can somebody explain how the idea of randomness and quantum mechanics are often paired up? Why is it that quantum mechanics is random?
Title: Randomness and quantum mechanics
Post by: JP on 03/07/2009 17:33:36
In classical mechanics, the models you use are all based around predicting the exact state of something.  For example, you could predict exactly where a ball will go when you throw it.  The only limit to how precise your predictions are is how well you can measure things.

One of the main features of quantum mechanics is that the best your models can do is to predict the probability of finding your system in a given state.  For example, instead of predicting exactly where an electron is, you would instead predict a range of places it could be, with probabilities of finding it in each place.  This seems to be an actual property of quantum mechanical objects.  No matter how accurate your theory and measurements are, you still can do no better than give probabilities of different measurements.  I think the idea that you can't predict exact outcomes of measurements is what often gets called "randomness."
Title: Randomness and quantum mechanics
Post by: lightarrow on 03/07/2009 17:50:56
Can somebody explain how the idea of randomness and quantum mechanics are often paired up? Why is it that quantum mechanics is random?
Quantum mechanics is not random, even if this is the way some scientists thought of it. The Schrodinger equation of QM is totally deterministic: the wave equation, which describes a quantum system, evolves through that equation in a deterministic, that is totally non-random, way.

What were confused with 'random' is the fact they pretended to use classical descriptions for concepts that requires instead a totally different description.

Let's say, as a metaphor, that you want to describe the behaviour of the sea using a float which is connected to a mechanism that limits its movements because of friction. Observing the float's movements you could think that the sea's behaviour is 'random'. But you know that the sea waves, actually, are not.
Title: Randomness and quantum mechanics
Post by: glovesforfoxes on 03/07/2009 19:59:33
yeah, i was thinking about randomness in general and then thought about why quantum mechanics is considered random. my main thought is that we have just not developed the tools to predict properly what happens as such a small scale, which is confirmed by the above post. however.. hard to falsify.. still.. i can't see why everything else would be so non-random if the quantum mechanical mathematics/system/tools show it is random.

i strongly believe in Einstein's quote: "God does not play dice with the Universe" - I have seen nothing that disputes this, although of course i cannot see the entire universe.
Title: Randomness and quantum mechanics
Post by: JP on 03/07/2009 22:41:20
There's pretty good evidence that god does play dice with the universe.  In other words, there's good reason to believe that quantum mechanics isn't just a case of us not being able to see the underlying deterministic universe.
Title: Randomness and quantum mechanics
Post by: lyner on 04/07/2009 00:32:25
Surely the Heisenberg principle implies randomness - due to the uncertainty involved. I.e if the value of a body's position cannot be known exactly then is there not a randomness about that effective position?
Title: Randomness and quantum mechanics
Post by: lyner on 04/07/2009 01:33:43
I know Albert was credited with 'that quote' but, if you discount the existence of god, the statement is meaningless. It counts for nothing in any argument and need not be associated with the bits that he got right. He was human, after all.
Title: Randomness and quantum mechanics
Post by: lightarrow on 04/07/2009 08:21:35
Surely the Heisenberg principle implies randomness - due to the uncertainty involved. I.e if the value of a body's position cannot be known exactly then is there not a randomness about that effective position?
Do you want to know what Heisenberg said?

"The invisible elementary particle of modern physics does not have the property of occupying space any more than it has properties like color and solidity. Fundamentally, it is not a material structure in space and time but only a symbol that allows the laws of nature to be expressed in especially simple form."

I found this citation in this book:

"Introduction to the Quantum Theory" - David Park - Third Edition -
pag.55:

<<Much has been written on what indeterminacy means, but not many words are needed here. Most people's first reaction to it is something like: "All right, you can't measure this position or this momentum accurately but the number is there, whether you can measure it or not."

Some very distinguished older physicists thought that, but the general opinion now is that they were almost certainly wrong. Now it seems like a metaphysical assumption impossible to test by experience and useless to assume.

The general opinion is that concepts like position and momentum are formed in our minds out of daily experience with things we can see and touch and that it is a mistake to assume that particles can be discussed as if they were scaled-down versions of those things.

Consider, for example, the two-slit experiment....The size of the pattern depends on the separation between the slits. If a particle is a thing, one would like to say that it goes through one slit or the other, but if it goes through one slit, how does it know the slit separation? And if it goes through both, what is the number that tell where it is? On the whole, physics makes more sense if we do not regard photons and electrons as things.

As Heisenberg wrote (1959, p.80):
"The invisible elementary particle of modern physics does not have the property of occupying space any more than it has properties like color and solidity. Fundamentally, it is not a material structure in space and time but only a symbol that allows the laws of nature to be expressed in especially simple form."

In this view, the indeterminacy relations are a tax we pay for using classical terminology where it is not really applicable>>
Title: Randomness and quantum mechanics
Post by: lyner on 04/07/2009 13:27:55
Interesting but does it specifically rule out the random element if the outcome is measured in a conventional way? Or are you implying that what goes on at a level we don't understand and can't measure may, in fact be non-random and capable of being determined exactly?
Is it the reduction to a "simple form" that introduces the random experience?
Title: Randomness and quantum mechanics
Post by: lightarrow on 04/07/2009 16:02:07
Interesting but does it specifically rule out the random element if the outcome is measured in a conventional way?
No, certainly. I just wanted to point out something like this: what is the 'exact' position of a finite-lenght light pulse, for example? It doesn't have an exact 'beginning' or 'end' or 'centre' so our conventional ways of measuring things are not adequate any longer in these cases, isnt'it?

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Or are you implying that what goes on at a level we don't understand and can't measure may, in fact be non-random and capable of being determined exactly?
If you mean 'classical determinism' or hidden variable-like theories, no, I'm not saying that.

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Is it the reduction to a "simple form" that introduces the random experience?
Yes, it is our demand to 'measure eggs with squares', if you pass me the expression  [:)]
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 04/07/2009 17:02:44
Can somebody explain how the idea of randomness and quantum mechanics are often paired up?
When you do the twin slit experiment with a photodetector the photon arrives at a random place each time you run it; if you collect a lot of data, the shape of the probability curve of getting a hit on the photodetector if you move the photodetector around is statistically the same as the wavefunction intensity squared at the detector.
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Why is it that quantum mechanics is random?
Nobody knows.

What we do know is that when you do an experiment that displays the type of physics known as quantum mechanics, the results are somewhat different every time you perform the experiment, but the results are consistent with the passage of a quantum mechanical wavefunction.

Why the universe picks one point of the wavefunctions to decide to put an interaction, rather than another- I'm pretty sure that that is something nobody knows.

It's an assumption that this is random, but there's no way to prove it. Ockham's razor makes you pick it, because it's the simplest explanation for the results you get.
Title: Randomness and quantum mechanics
Post by: glovesforfoxes on 05/07/2009 16:02:23
ok, so let's say i believe that quantum mechanics is truly random. how is it, then, the the classical world seems so deterministic? is that just a psychological bias? also, if the quantum mechanical scale is so small, does/could it have an impact on free will?

i know these are very big questions, but they're ones that i find interesting, even if they are very hard to answer!

by the way sophiecentaur, Einstein meant God in a different way -

"I believe in Spinoza's God who reveals himself in the orderly harmony of what exists, not in a God who concerns himself with the fates and actions of human beings." in other words, Einstein believed that God & nature were exactly the same - God isn't a being, he is everything materialistic.
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 05/07/2009 16:29:22
ok, so let's say i believe that quantum mechanics is truly random. how is it, then, the the classical world seems so deterministic?
Again, nobody really knows the answer to this.

The last attempted answer I read was something along the lines that in most large scale situations all the myriad different quantum mechanical things that could happen at the microscopic level all do more or less the same thing in aggregate, so the universe diverges a lot less than you would expect, the universe you're in is sort of riding the cusp of a whole bunch of universes that are busy splitting and remerging. So quantum mechanics may be largely normative in practice.

However, some quantum events can cause large scale changes to the universe, for example Schroedingers cat, once you open the box (or don't close it) the effect of a single quantum decay can change large scale things like whether you're burying the cat or not.

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is that just a psychological bias?
Dunno. Probably not.
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also, if the quantum mechanical scale is so small, does/could it have an impact on free will?
It doesn't seem likely to me.
Title: Randomness and quantum mechanics
Post by: DoctorBeaver on 05/07/2009 23:41:32
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The last attempted answer I read was something along the lines that in most large scale situations all the myriad different quantum mechanical things that could happen at the microscopic level all do more or less the same thing in aggregate, so the universe diverges a lot less than you would expect

That's how I view it. Take the simple example of flipping a coin. We know the chance of it landing 1 way up is exactly the same as the chance of it landing the other way up; 50/50. However, if you flip the coin just 4 times, you could well end up with 4-0 or 3-1 in favour of 1 side or the other. But if you flip the coin 100 million times the divergence from 50/50 would be negligible. When you consider how many quantum events aggregate to form the material world we see around us it is not really surprising that it appears deterministic when all the "most probable" outcomes are summed.
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 06/07/2009 00:46:15
Yes, but it can't always average out, otherwise we wouldn't have quantum mechanics.

We don't really know what happens to the universes we never see; for example if you throw a bunch of photons slowly through twin slits you'll get a pattern of hits on the detector, but there was a very high chance that there could have been a different pattern. The many worlds theory says that the all the different patterns actually happen, but you're in the wrong subpart of the universe to see that. In some cases these different choices join back up again, and you can tell that happened (for example in the twin slit the photon has gone through *both* slits- it must have done so to give that interference pattern).
Title: Randomness and quantum mechanics
Post by: lyner on 06/07/2009 10:18:20
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(for example in the twin slit the photon has gone through *both* slits- it must have done so to give that interference pattern).
But, of course, it doesn't "give a pattern", does it? It is observed to arrive in just one place - it has only enough energy to interact with one atom when it arrives. You cannot assert that it has "gone through both holes"; all you can say is that the energy has probably gone through both holes because, after a lot of photons have been detected, a diffraction pattern is seen, which implies that a wave has been involved.
What 'really happened'? As you can never actually look at that level, you can only say that it behaved 'as if' blah blah.
Title: Randomness and quantum mechanics
Post by: lightarrow on 06/07/2009 11:38:05
(for example in the twin slit the photon has gone through *both* slits- it must have done so to give that interference pattern).
To be more precise: it is *the wave* that has gone through both slits, not the particle. You cannot say that the particle went through one of the slits or through both, because in this way you had enough informations to destroy the interference pattern (yes, even if you know that the particle went through *both* slits).
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 06/07/2009 11:54:07
Well, in the quantum electrodynamics formulation of QM the particle has gone every route to get from the emitter to the receiver, so, yes you can say that it has gone through both.
Title: Randomness and quantum mechanics
Post by: lyner on 06/07/2009 12:29:53
If it doesn't actually need to exist whilst the energy is on the way, I say that you needn't actually claim that it is anywhere in particular.
Which is the bigger problem to deal with - "it's in two places at once" or "it's nowhere"? It could hurt your brain to reconcile either of those with normal everyday experiences. No need to try.

wolfekeeper
Your reference to "every route" is more accurate. The two slits idea is too simple, really, because the slits need to be of finite width - hence a multitude of possible paths.
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 06/07/2009 12:45:28
If it doesn't actually need to exist whilst the energy is on the way, I say that you needn't actually claim that it is anywhere in particular.
Which is the bigger problem to deal with - "it's in two places at once" or "it's nowhere"? It could hurt your brain to reconcile either of those with normal everyday experiences. No need to try.
If QM doesn't hurt your brain, you're not doing it right!
Title: Randomness and quantum mechanics
Post by: lyner on 06/07/2009 14:51:50
I think that it will only stop stop hurting brains, when we accept and don't fight against certain ideas. We must stop triumphantly quoting 'paradoxes' and open up to the possibility that paradoxes can always be resolved by altering the way of looking at things. When we can achieve that, QM and the rest will no longer appear to resist us.
It's an Eastern mystic / Talkien thing, if you like. (You must believe I have not just gone loopy by saying that. I will not have wind chimes in my garden or rearrange the furniture in my room going "OMMM".)

Why did the particle have to go through any slits at all? Do the actors in a play 'go through' the wires when we see them on TV? Sometimes I wish!
Title: Randomness and quantum mechanics
Post by: lightarrow on 06/07/2009 23:30:43
Well, in the quantum electrodynamics formulation of QM the particle has gone every route to get from the emitter to the receiver, so, yes you can say that it has gone through both.
No, you can't. If you write the wavefunction of the particle and you impose that it goes through both slits, you'll find that it's square modulus is the probability distribution of classical particles going through the slits, that is two 'lumps' located behind the slits - no interference pattern.
What goes through both slits cannot be "the particle", unless you call "particle" the quantum system we are describing (which can act as "particle" or as "wave" according to the circumstances).
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 07/07/2009 02:03:58
Careful here, in QED the particle has a vector that rotates as the particle travels. Dyson showed that if you do that correctly then the sum of the vectors is just the wavefunction, so it's equivalent to the normal Schroedinger equation.
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 07/07/2009 02:07:46
I think that it will only stop stop hurting brains, when we accept and don't fight against certain ideas. We must stop triumphantly quoting 'paradoxes' and open up to the possibility that paradoxes can always be resolved by altering the way of looking at things. When we can achieve that, QM and the rest will no longer appear to resist us.
Well something like that. QM has lacked somebody like Einstein- even Einstein couldn't tame the QM equations like he did with the Lorentz equations. Either there's a piece missing or it's staring us in the face and nobody can put it together.
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Why did the particle have to go through any slits at all?
Because when you set up the experiment you made them?
Title: Randomness and quantum mechanics
Post by: wanhafizi on 07/07/2009 09:28:45
I don't think I can accept randomness.

Not even a single computer in this world can create a pure random number. It simply doesn't exists.

The randomness of radioactive decay can be made as an example. They say, although we know the exact rate of decay, we don't have any idea which one will decay first. For me, the notion of half life itself shows us that there are actually some system governing it. It wasn't random, it just we don't understand it yet. Otherwise, there won't be any notion of half-lives...

The facts is, we cannot measure any small stuff without 'touching' it. We used electron, photon, magnetic waves to measure by 'touching' what we are measuring. This causes the system being measured to be literally effected. Measuring the angular momentum of electron presents this problem. Yes, if the electron was spinning around, we would never know where it is at a certain time. Because, if we 'inject' an observer into the system (such as photon/light) the particle itself bounced with the electron and causes the angular momentum to change. That's why it became uncertain. Yet, some new age scientists take this notion as some esoteric findings in nature. Crazy...

To measure really small stuff in the real world is a very very tough job. Consider this, it have to be in absolute zero temperature, no light, not a single photon, not on earth because of the gravity and magnetic distortion, not to mention the absolute necessary to protect from electromagnetic waves... Just impossible...

I hope Albert Einstein is still alive today to unscrew quantum mechanic's mess...

Just a thought.
Title: Randomness and quantum mechanics
Post by: lightarrow on 07/07/2009 10:52:24
Careful here, in QED the particle has a vector that rotates as the particle travels. Dyson showed that if you do that correctly then the sum of the vectors is just the wavefunction, so it's equivalent to the normal Schroedinger equation.
Ok, but what is for you the physical meaning of the phrase "in the twin slit the photon has gone through *both* slits"? How would you prove it?
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 07/07/2009 14:09:05
You just look at the diffraction pattern, which, really, on its own, shows that it has gone through both slits, and then close either one of the slits, and the pattern goes away.

But you only ever get one click on a photodetector.

Still, photodetectors are odd beasts- they are able to multiply up a single quantum effect and make it change the macroscopic world.
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 07/07/2009 14:14:41
I don't think I can accept randomness.

Not even a single computer in this world can create a pure random number. It simply doesn't exists.
Actually there are computers that use quantum effects to generate random numbers. In fact non deterministic electronics is not at all difficult, resistors have significant random noise.
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The randomness of radioactive decay can be made as an example. They say, although we know the exact rate of decay, we don't have any idea which one will decay first. For me, the notion of half life itself shows us that there are actually some system governing it. It wasn't random, it just we don't understand it yet. Otherwise, there won't be any notion of half-lives...
Half life is a statistical property that comes about whenever there is a fixed chance of a decay in any interval. Even random processes have well defined statistical properties.

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I hope Albert Einstein is still alive today to unscrew quantum mechanic's mess...
No, he died, and he had even less luck than other physicists really with QM.
Title: Randomness and quantum mechanics
Post by: lightarrow on 07/07/2009 20:03:44
You just look at the diffraction pattern, which, really, on its own, shows that it has gone through both slits,
Yes, but *what* has gone through both slits? The particle? No, because if it was so, putting a detector behind the slits, you shoud find two simultaneous detections, which thing is impossible because it is a "single" particle, and because in this way you destroy the interference pattern.

Title: Randomness and quantum mechanics
Post by: wolfekeeper on 07/07/2009 20:16:41
You just look at the diffraction pattern, which, really, on its own, shows that it has gone through both slits,
Yes, but *what* has gone through both slits? The particle?
You don't have particles in quantum mechanics exactly. The wave/particle went through both.
Title: Randomness and quantum mechanics
Post by: wanhafizi on 08/07/2009 01:58:02
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Actually there are computers that use quantum effects to generate random numbers. In fact non deterministic electronics is not at all difficult, resistors have significant random noise.

If you read my last posting;

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To measure really small stuff in the real world is a very very tough job. Consider this, it have to be in absolute zero temperature, no light, not a single photon, not on earth because of the gravity and magnetic distortion, not to mention the absolute necessary to protect from electromagnetic waves... Just impossible...

It is literally impossible to isolate outside influence from getting into QM experiments. These influences coming from all direction and effecting our experiments in many ways, making the result unpredictable and seems to be random. For me, we cannot declare randomness exists in the QM experiments, until we get rid of all those outside influence, which is nearly impossible. Even deep in earth, neutrinos still pouring on our bedrocks.

Remember our old friend the hiss in radios? We know now it is actually came from background radiation from outer space. Most probably the same thing happened to resistors.

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I hope Albert Einstein is still alive today to unscrew quantum mechanic's mess...
No, he died, and he had even less luck than other physicists really with QM.

Exactly. Rumors has it that he died with papers on his hands trying to find his own solution for one unified theory, hoping to avoid the undeterministic nature of QM. And yes, he despised QM.
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 08/07/2009 02:23:43
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Actually there are computers that use quantum effects to generate random numbers. In fact non deterministic electronics is not at all difficult, resistors have significant random noise.

Remember our old friend the hiss in radios? We know now it is actually came from background radiation from outer space. Most probably the same thing happened to resistors.
Nope, that's not it in this case. There's something called 'shot noise' which is random noise due to the movement of individual electrons through the resistor. It's actually a measureable amount of noise, and electrons are quantum entities.
Title: Randomness and quantum mechanics
Post by: wanhafizi on 08/07/2009 02:43:26
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Actually there are computers that use quantum effects to generate random numbers. In fact non deterministic electronics is not at all difficult, resistors have significant random noise.

Remember our old friend the hiss in radios? We know now it is actually came from background radiation from outer space. Most probably the same thing happened to resistors.
Nope, that's not it in this case. There's something called 'shot noise' which is random noise due to the movement of individual electrons through the resistor. It's actually a measureable amount of noise, and electrons are quantum entities.


So... This caused by physical movement.

Not randomness, just we don't know how it was to the tiniest level. Just like water splashing at rapids. It seems random, but it's not. Just that we don't know all the factors involved
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 08/07/2009 03:54:33
No, so far as anyone knows it's random. Electrons are fundamental particles and have behaviours that are highly determined by quantum mechanics. Actually it's condensed matter physics, and condensed matter physics is just all about quantum mechanics; I studied it somewhat at degree level, it's also related to how semiconductors work.

You can certainly postulate non random underpinnings for QM, but there's absolutely no evidence for non randomness right now.
Title: Randomness and quantum mechanics
Post by: wanhafizi on 08/07/2009 05:47:02
I do think the theories of QM and its formula does serve good functions in our experiments, because the world we are living are filled with energy noises, electromagnetic waves, and countless other factors that are effecting matter at the very tiniest level.

Without those factors, QM formula will become very deterministic and highly precise. But, like I've said before, it's nearly impossible to create a 'highly-energy-clean' rooms such as being described. For starters, those rooms should be at absolute zero degree and very far away from the sun or stars.

I believe QM formula consists of probabilities defines the maximum & the minimum value in the world where QM experiments are being done with 'noises' of energy & particles flying around. It seems undeterministic because we can't possibly know the attributes of each and every single atom, photon and energy going in and out of the system while measurement was done. So, results might seems to be random within certain range, but it is only to show the existence of other factors that we didn't and couldn't possibly include in our calculations...

It means that randomness inside our data are just vectors that were not included inside our model, because we can't possibly know all of them...

Randomness doesn't exists
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 08/07/2009 11:50:27
Actually, it's the other way around, external interference acts as a measurement and destroys the interference fringes because the wavefunction loses coherence.
Title: Randomness and quantum mechanics
Post by: glovesforfoxes on 08/07/2009 14:16:16
evidence for randomness to me is like saying we have no evidence for determinism yet. that's an unscientific way of thinking about it, i guess, but i don't know.. it seems to me that in the past people have said all these things are random, but then it is shown that they are not, and i think that the same thing will happen for QM.

so, to sum up this thread: evidence for QM randomness is like evidence for god - you can believe in it, but you just don't know if it's actually true or not.

is that right?

i have another question now too. what are the things that physics in general can't accurately predict, explain or describe?
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 08/07/2009 14:30:44
so, to sum up this thread: evidence for QM randomness is like evidence for god - you can believe in it, but you just don't know if it's actually true or not.

is that right?
No. We actually have reproducible experimental evidence for quantum randomness. There is no reproducible experimental evidence for God.
Title: Randomness and quantum mechanics
Post by: glovesforfoxes on 08/07/2009 14:38:04
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No. We actually have reproducible experimental evidence for quantum randomness. There is no reproducible experimental evidence for God.

but if the experimental evidence is always altered by some extraneous variable that affects earth in the same way, then it is useless evidence, surely?
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 08/07/2009 14:48:43
There's no evidence of any extraneous variables either.

In fact, extraneous interactions are known to destroy the interference pattern; it makes it more random, not less. You only get the interference patterns when there's no perturbations.
Title: Randomness and quantum mechanics
Post by: glovesforfoxes on 08/07/2009 14:54:45
okay. so.. the view that fits best with the evidence currently is that QM is truly random. it may be shown to be deterministic one day, or it may be that it is truly random no matter how well you can measure it.

thank you all for contributing to this fascinating topic! [:)]
Title: Randomness and quantum mechanics
Post by: wanhafizi on 09/07/2009 01:40:01
Actually, it's the other way around, external interference acts as a measurement and destroys the interference fringes because the wavefunction loses coherence.

Yeah, I know. I wrote this before;
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The facts is, we cannot measure any small stuff without 'touching' it. We used electron, photon, magnetic waves to measure by 'touching' what we are measuring. This causes the system being measured to be literally effected.

Maybe not in a sentence that a scientists would like to hear, but my point was the same as yours.

The thing is, there are other factors going in and out of the system that we couldn't possibly imagine.

You see, for example, when we are doing experimentation on burning hydrogen in oxygen, we can neglect the rooms' luminosity(photon), because the reaction happened on molecular level.

But, when we are talking about QM (example Solar Cells), absolutely everything must be considered into our calculation, because what's happening is more fundamental, of which every sort of energy vectors will cause changes.

It's not that it is that important to know everything, but not knowing them makes us infer that randomness exists in QM systems.

I just don't like to hear scientists talking about philosophical stuff, like some guru from Tibet, especially when they attribute consciousness and God to randomness of QM.
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 09/07/2009 02:13:50
It actually seems to be worse than that even- there can be things going on *outside* the experiment that can randomly change the outcome of the experiment and yet when you collect all of the data together, you find it's just right to make the laws of physics work.

For example you can make an electron pair so that one is spin up, the other spin down. But you don't know which is which. But when you measure one, the other is the opposite.

Which is not surprising, except that QM theorists have managed to prove that it didn't make up its mind until you made the measurement.

And this works no matter how far apart they are, they agree with each other even if they are 10 light years apart.
Title: Randomness and quantum mechanics
Post by: wanhafizi on 09/07/2009 05:56:05
Yes, I think we all can accept QM being weird.

Once there are people calling chemists as witches, because they can't accept the weirdness. But now, we know better.

But even if something is weird, we are hoping to have some sense or absolute rules about them with solid rules and mathematical calculations.

But the concept randomness is not just weird, it also forces us to believe at the heart this orderly universe, there are chaotic world where no rules whatsoever apply. That's why they attribute pure randomness to the fabric of consciousness and God. Because randomness seems to be the only source where pure free will & pure original thoughts came from. Otherwise, you, your actions, your mind are really just a summation of of your biology, nerve fibers, electrical charges in your brain and your surroundings.
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 10/07/2009 03:42:07
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Otherwise, you, your actions, your mind are really just a summation of of your biology, nerve fibers, electrical charges in your brain and your surroundings.
Yup, welcome to the real world, forget quantum mechanics, that's how you work.
Title: Randomness and quantum mechanics
Post by: wanhafizi on 12/07/2009 20:12:38
Maybe we are, maybe everything has been put in motion since the big bang. Maybe our freewill is just an illusion to our mind. Who knows...
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 12/07/2009 21:42:03
Well, you have to look at the evidence- if you change your biology in even minor ways (drugs, strokes, surgery), it seems that you change your mind and will; so it seems to me that freewill is a product of biology (at bottom memory is a biological function).
Title: Randomness and quantum mechanics
Post by: wanhafizi on 13/07/2009 08:07:16
Well, you have to look at the evidence- if you change your biology in even minor ways (drugs, strokes, surgery), it seems that you change your mind and will; so it seems to me that freewill is a product of biology (at bottom memory is a biological function).


This could to a whole new discussion thread, even a new forum  [;)]
Title: Randomness and quantum mechanics
Post by: glovesforfoxes on 21/07/2009 17:20:32
Quote
Well, you have to look at the evidence- if you change your biology in even minor ways (drugs, strokes, surgery), it seems that you change your mind and will; so it seems to me that freewill is a product of biology (at bottom memory is a biological function).

well that's evidence certainly, but is it evidence of free will? it seems that is evidence that there is will itself, but whether that is free or not is completely different. what is exactly freedom of will? if it is the ability to make decisions to do actions that don't necessarily fit with our emotional state, then i would say we have it. but if it is the ability to make decisions without being affected by outside influences, i would say that this is wrong, and just as ridiculous as saying that we have the ability to make decisions without being affected by inside influences - both internal and external things are used to generate decisions and actions and choices, and that is all that affects them - therefore there is no "free" will, but there is will. i am a hard determinist, but less so about quantum mechanics now :)
Title: Randomness and quantum mechanics
Post by: wanhafizi on 23/07/2009 05:39:01
... i am a hard determinist ...

Same here
Title: Randomness and quantum mechanics
Post by: wolfekeeper on 23/07/2009 05:40:55
If that's still true in a few hours, you need to see a doctor about it.  [;)]
Title: Randomness and quantum mechanics
Post by: janardhan polanki on 17/10/2009 09:41:34
sir A S Eddington says  about randomness;   there is always more to the element of randomness in the universe   when the signal drops than when the lever moves ,like i say the more of the element of randomness when the seed sprouts than when the seed drops into the soil .

The Copenhagen interpretation of quantum mechanics states that the  collapse of the wave function with its infinite possibilities is againts the onely one of a born certainity of the quantum 10^-27cms during Big Bang seperating space & time from an inseperable unity , which is flux of the universal oneness of a whole.In other words it is the creative force of the quantum randomness that connects the manifest and the nonmanifest universe.
Title: Randomness and quantum mechanics
Post by: Mr. Scientist on 17/10/2009 17:03:53
Surely the Heisenberg principle implies randomness - due to the uncertainty involved. I.e if the value of a body's position cannot be known exactly then is there not a randomness about that effective position?
Yes it does, correct. The inherent uncertainty in the universe does not seem very deterministic at all.
Title: Randomness and quantum mechanics
Post by: litespeed on 02/11/2009 00:26:07
Quantum Mechanics is very successful at predicting the probablity of various events such as radioactive decay. This is very useful, of course, but entirely silent on why any given atom decided to add itself to the probablity.

I do not believe in events without cause.  Accordingly, I believe there is something behind the smoky curtain that QM has left out. IMHO the universe has very large numbers of input factors we simply do not have technology or even theory to describe. One of my favorites includes the various Plank Units.

In this world particles never move an infinite number of points to get from A to B. Instead, they simply jump from A to B. Sort of like a movie projector. I simply postulate the particles move into a timeless dimenstion as the our time laden universe moves onward, these particles simply reimerge from their timeless state and do it again and again.

I need to know more about Plank units, but the one I like best is Plank time. I have seen the big bang described Plank time unit by Plank time unit. Plank zero is null. Plank one includes the entire universe in a small area. Plank two includes inflation beyond the speed of light etc etc.

String theory gets a bit gnarly here, but I like the 9 or 11 dimensions it incorporates. Mostly I like the idea the universe has depth that might include, chuckle chuckle, human self awareness. Does each and every congnizant being create, over a lifetime, an entire universe of accumulated self experiences?  There is absolutely no physics that can explain why I seem to think I am separate from you? 

Title: Randomness and quantum mechanics
Post by: Vern on 02/11/2009 11:14:06
Quote from: litespeed
In this world particles never move an infinite number of points to get from A to B. Instead, they simply jump from A to B. Sort of like a movie projector. I simply postulate the particles move into a timeless dimenstion as the our time laden universe moves onward, these particles simply reimerge from their timeless state and do it again and again.
I have not seen creditable evidence that this is true. In certain circumstances such as tunnelling, we see the appearance of that; meaning it seems that is what happens. But in normal movement of material things I don't think there has been demonstrated any jumpy movement.

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