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Korrente
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I have an interference-proof box with a perfect vacuum. In that box is an atom. Is it possible to know when it will decay? I'm guessing no, Heisenberg Principle and etc, so how about if I knew everything there is to know about this atom, could I then accurately predict when it will decay? How would I do this (with the information I have)? Wikipedia uses the term 'spontaneous' more than I am comfortable with, and I'm not sure if it means totally random or just unpredictable because to predict it would involve changing it.

One more question, though I understand the principles here much less: When a particle is superimposed (that is, it may exhibit any possible state for a given situation), can the state it chooses be random? I would think that although it could exist in any one (or all) of a possibly infinite set of states, it doesn't because the vast majority (all but one?) would be negated by outside influences and causation. Am I correct?

My main concern here is whether or not Random exists. I don't believe it does because of causation and I think that if you knew all available information about a particle or a system, you could accurately predict its outcome in every situation. I could be wrong though.

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### Re: Radioactive Decay

Sorry, but you are wrong. With radioactive decay, the prediction of decay through half-life only works when you have a large number of nuclei. When you get down to a single nucleus it just isn't possible to predict that precisely. Think about it as being like rolling 2d6: If you roll them lots and lots of times, you know that the mean result will be 7, but that doesn't mean you can predict the next roll.
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Tass
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### Re: Radioactive Decay

Korrente wrote:I have an interference-proof box with a perfect vacuum. In that box is an atom. Is it possible to know when it will decay? I'm guessing no, Heisenberg Principle and etc, so how about if I knew everything there is to know about this atom, could I then accurately predict when it will decay? How would I do this (with the information I have)? Wikipedia uses the term 'spontaneous' more than I am comfortable with, and I'm not sure if it means totally random or just unpredictable because to predict it would involve changing it.

One more question, though I understand the principles here much less: When a particle is superimposed (that is, it may exhibit any possible state for a given situation), can the state it chooses be random? I would think that although it could exist in any one (or all) of a possibly infinite set of states, it doesn't because the vast majority (all but one?) would be negated by outside influences and causation. Am I correct?

My main concern here is whether or not Random exists. I don't believe it does because of causation and I think that if you knew all available information about a particle or a system, you could accurately predict its outcome in every situation. I could be wrong though.

Edit: Sorry for the tl:dr, but now I think i managed to answer your question.

Well, quantum mechanics is pretty well proven true. Whether or no "Random" exists depends on how you interpret it.

The inside of the box (the atom) will have a wave function that behaves completely deterministic. As time goes by the wave function will gradually change from high amplitude at "undecayed atom" to a high amplitude at "decayed atom plus one high energy photon". So the atom will be in a superposition. If you put another atom in the box which can interact with the first atom in such a way that it changes from state A to state B if and only if the first atom is decayed, and you can bring this interaction about at a time you choose; then when you let them interact the second atom will also go into a superposition between A and B with the same relative amplitudes. Furthermore they are both entangled, so if you in some way got the second atom out of your perfect coherence box and measured it to be in state B, then you would know that the first atom was decayed, but before you measured it would still be in superposition.

How is this possible? Suppose you were the second atom in the box (a big and complicated one). If state B happened to be "dead" you would now be Scrödingers cat. So you interact with the atom (measure it) but do not find a superposition. Instead your wave function becomes entangled with the atoms so you are in a superposition between you in state A (seeing an undecayed atom), and you in state B (seeing a decayed atom) both of you would say "the wavefunction has collapsed, now the atom is no longer in a superposition", but to the outside world you are simply part of the superposition - until they open the box. When I open the box you look at me and say either "the atom has decayed" or "the atom has not decayed", the wavefunction of both you and the atom has collapsed- chosen just one of the possible options. Or am I merely also part of it now?

This is the difference between the two big interpretations in quantum mechanics: In the many-world interpretation wave functions evolve completely deterministically in accordance with the Scrödinger equation, unfortunately this means that it tends to split of into an infinity of different parts which are exceedingly unlikely to affect each other except on the atomic level. The thing is that the bigger a superposition gets the more it tends to grow, and unless you catch all parts of it you can't make the parts interfere correctly. Currently people working on quantum computers are struggling to just to keep the superposition of a handful of atoms under control, so a box perfectly maintaining a human superposition is pretty unlikely. A superposition that size will grow at the speed of light, and the other you will therefore never affect you.

In the Copenhagen interpretation you cut away all parts of the wave function that is unlikely to affect you anymore, saying "they don't exist, the wave function has collapsed", but this also means that you get the completely Random choice between the parts and the rather arbitrary choice of when to say that a wave function collapses.

So there is basically two choices: Either you believe in an infinity of other worlds which you can't observe, or you believe in true randomness deciding which one gets to be real. My signature will tell you what I think describes reality, others will speak warmer for the Copenhagen interpretation (despite not being from Copenhagen), and possibly also a third or fourth choice.

Plasma Man wrote:Sorry, but you are wrong. With radioactive decay, the prediction of decay through half-life only works when you have a large number of nuclei. When you get down to a single nucleus it just isn't possible to predict that precisely. Think about it as being like rolling 2d6: If you roll them lots and lots of times, you know that the mean result will be 7, but that doesn't mean you can predict the next roll.

That is only because of quantum mechanics and incomplete information. In a newtonian universe with complete information and unlimited computing power you could predict the die. He asks how it can be that it is not so in quantum mechanics. (Come to think of it maybe I should have written more about Bells inequality and Aspects experiments and less about interpretations.)

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### Re: Radioactive Decay

Plasma Man wrote:With radioactive decay, the prediction of decay through half-life only works when you have a large number of nuclei. When you get down to a single nucleus it just isn't possible to predict that precisely.

The half-life still gives you a probability distribution of when it will decay, in that there is a 50% chance it will decay within one half-life, 75% within two, 87.5% within three, and so on.
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Korrente
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### Re: Radioactive Decay

Thanks for that, Tass. I'm actually trying to make an argument for philosophical determinism by saying that if basic particles don't behave randomly, neither can people. However, I'm not really sure what to say now .These 18th century philosophers should have thought a little more about quantum physics before they started arguing.

PM 2Ring
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### Re: Radioactive Decay

You may find this relevant:

Wikipeda wrote:Free will theorem

The free will theorem of John H. Conway and Simon B. Kochen states that, if we have a certain amount of "free will", then, subject to certain assumptions, so must some elementary particles. Conway and Kochen's paper was published in Foundations of Physics in 2006.

Fume Troll
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### Re: Radioactive Decay

Has it been proven that nuclear decay is random? Could it be chaotic, be perturbed by mechanisms we are not yet aware of?

Among the conclusions of this paper is the line, "Insofar as emissions and decay events are appropriately interrelated, the evidence is inconsistent with the thesis of decay independence"

This paper has a round-up of more current research: This paper presents an overview of recent research dealing with the question of whether nuclear decay rates (or half-lives) are time-independent constants of nature, as opposed to being parameters which can be altered by an external perturbation.

Tass
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### Re: Radioactive Decay

Fume Troll wrote:Has it been proven that nuclear decay is random? Could it be chaotic, be perturbed by mechanisms we are not yet aware of?

You mean like there is some chaotic but deterministic timing mechanism inside the atom which decides when it decays? That smells like a local hidden variable theory. Einstein tried hard to construct a local hidden variable theory, this would basically mean that an atom in a superposition has already decided all measurements outcomes beforehand, but we just have no way to know before we actually measure one thing or the other. However Bell's inequality shows that quantum mechanics would predict results not possible with local hidden variables., and experiments like Aspects rule in favor of quantum mechanics.

Korrente wrote:Thanks for that, Tass. I'm actually trying to make an argument for philosophical determinism by saying that if basic particles don't behave randomly, neither can people.

That statement is of course correct. It is just that the premise might be wrong.

Korrente wrote:However, I'm not really sure what to say now .These 18th century philosophers should have thought a little more about quantum physics before they started arguing.

Yeah, they should have listened to the 20th century physicists.
Last edited by Tass on Thu Apr 08, 2010 7:35 am UTC, edited 1 time in total.

PM 2Ring
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### Re: Radioactive Decay

Tass wrote:
Fume Troll wrote:Has it been proven that nuclear decay is random? Could it be chaotic, be perturbed by mechanisms we are not yet aware of?

You mean like there is some chaotic but deterministic timing mechanism inside the atom which decides when it decays? That smells like a local hidden variable theory.

How about something chaotic outside the atom, like ambient neutrino flux? I've always assume that these neutrinos have such a low probability of interacting with anything that they can be discounted as causing spontaneous decay, but I guess it'd be nice to see some calculations that support this hypothesis.

Fume Troll
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### Re: Radioactive Decay

That's more the sort of thing I had in mind. Or if a virtual particle of some sort is required to kick the nucleus over the hump towards decay, then perhaps the appearance of those is chaotic rather than random? Bohmian mechanics and, as far as I can tell, Pilot wave theories in general doesn't seem to hold much water with modern physicists, but I still have a nagging feeling that "random" might just mean "not yet understood", and there are still proponents of the theory.

Korrente
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### Re: Radioactive Decay

Fume Troll wrote:...I still have a nagging feeling that "random" might just mean "not yet understood"...

Agreed. And asserted, as far as my paper is concerned .

BlackSails
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### Re: Radioactive Decay

Korrente wrote:
Fume Troll wrote:...I still have a nagging feeling that "random" might just mean "not yet understood"...

Agreed. And asserted, as far as my paper is concerned .

Bell's theorem, the TCP theorem and the Kochen-specker theorem, as well as several no-go theorems without names beg to differ.

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### Re: Radioactive Decay

I don't think they say that the decay of a nucleus couldn't be influenced by an outside stimulus, do they?

Tass
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### Re: Radioactive Decay

No, but it wouldn't change quantum mechanics in its core.

Obviously a large neutrino flux could facilitate a beta decay by allowing the atom to absorb a neutrino rather than emit an anti neutrino, but the events would be distinguishable. Actually that is one of the things that happens in neutrino detectors.

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### Re: Radioactive Decay

PM 2Ring wrote:How about something chaotic outside the atom, like ambient neutrino flux? I've always assume that these neutrinos have such a low probability of interacting with anything that they can be discounted as causing spontaneous decay, but I guess it'd be nice to see some calculations that support this hypothesis.

But then you're talking about a nuclear reaction induced by particles from outside, which is a different thing to a radioactive decay. Radioactive decay happens to an unstable nucleus spontaneously, without any outside influence at all.
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Seraph
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### Re: Radioactive Decay

Minerva wrote:Radioactive decay happens to an unstable nucleus spontaneously, without any outside influence at all.

This isn't always true. Decay by electron capture can be weakly affected by outside factors like pressure or the chemical makeup of the environment the atom is in.

BlackSails
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### Re: Radioactive Decay

And constant irradiation by high frequency photons suppress decay via the quantum zeno effect.

Antimony-120
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### Re: Radioactive Decay

Minerva wrote:
PM 2Ring wrote:How about something chaotic outside the atom, like ambient neutrino flux? I've always assume that these neutrinos have such a low probability of interacting with anything that they can be discounted as causing spontaneous decay, but I guess it'd be nice to see some calculations that support this hypothesis.

But then you're talking about a nuclear reaction induced by particles from outside, which is a different thing to a radioactive decay. Radioactive decay happens to an unstable nucleus spontaneously, without any outside influence at all.

Basically quantum mechanics says "it's random". It doesn't say anything about not being able to load the dice. You can view it as a waveform that is changing from "completely undecayed" to "completely decayed" over some interval. The exact amplitude of the two parts of the function (decayed versus undecayed) will change along the inverse exponential, such that at one half-life they are of equal amplitude, at two half-lives the decayed waveform is 3 times the amplitude of the undecayed waveform (3/4 = 3*1/4) and so on and so forth.

However there is no particular problem in this theoretical framework with the idea of affecting the RATE at which the waveform changes. So yes, conditions can affect the half-life, in theory as much as you want (short of making it 0 or infinite), but that doesn't change that for any length of time you still have a probablility of measuring a decay. You're just mucking with that probability.

A similar example would be the time it takes for an excited electron to decay into it's ground state. You can affect this by changing the thermodynamic equilibrium of the surrounding space. A very hot space is likely to keep the electron in a higher state for extended periods of time. Somewhat different in that in this case a higher equilibrium will tend to bump the electron into an even HIGHER state, but that's the same process (reverse decay operates along the same theoretical smooth waveform change framework).
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PM 2Ring
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### Re: Radioactive Decay

Thanks, Antimony-120.

Tass wrote:No, but it wouldn't change quantum mechanics in its core.

Obviously a large neutrino flux could facilitate a beta decay by allowing the atom to absorb a neutrino rather than emit an anti neutrino, but the events would be distinguishable. Actually that is one of the things that happens in neutrino detectors.

I was being a bit sloppy & using the term "neutrino" to cover both neutrinos & antineutrinos. But consider: antineutrinos may induce spontaneous emission, just like what happens in a laser, where a photon of the right energy can cause an excited atom to emit an identical photon.

But I will repeat that the neutrino effective cross section is so tiny that I don't expect that ambient (anti)neutrinos have a significant effect on half-lives, just that they may have some effect. My inspiration for this is Brownian motion, where particles much larger than atoms are jiggled around by atomic-scale motions.

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### Re: Radioactive Decay

Seraph wrote:
Minerva wrote:Radioactive decay happens to an unstable nucleus spontaneously, without any outside influence at all.

This isn't always true. Decay by electron capture can be weakly affected by outside factors like pressure or the chemical makeup of the environment the atom is in.

Ah, yes. I remember when this was published a few years ago, creationists jumped on this as the damning evidence that radiometric dating isn't accurate and god is real.

Basically... only for electron capture, under extreme conditions of pressure, you can get a small perturbation in the decay rate.
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### Re: Radioactive Decay

Interesting stuff. Having an effect on the rate is of course very different to triggering the events. What I am still not clear on is, given that the standard model isn't complete, why do we conclude that the decay is random, rather than wondering if it is a pseudorandom process, triggered by something we are not detecting?

According to what I've read about quantum electro dynamics, "spontaneous emission in free space depends upon vacuum fluctuations to get started." So is it these fluctuations which are random? And if so, how do we know?

andyisagod
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### Re: Radioactive Decay

Fume Troll wrote:Interesting stuff. Having an effect on the rate is of course very different to triggering the events. What I am still not clear on is, given that the standard model isn't complete, why do we conclude that the decay is random, rather than wondering if it is a pseudorandom process, triggered by something we are not detecting?

According to what I've read about quantum electro dynamics, "spontaneous emission in free space depends upon vacuum fluctuations to get started." So is it these fluctuations which are random? And if so, how do we know?

Even if you invent a particle that causes radio active decay by interacting with the nucleus you have two problems.

Firstly even without considering this external particle the nucleus is capable of decaying by itself. You would have to somehow rewrite quantum mechanics so that this is no longer possible. This is difficult since there's currently no evidence for such a particle and quantum mechanics works very well by itself.

Secondly if we ignore the first problem and instead imagine a new particle and attempt to describe the process as best we can using quantum mechanics then you are still left with a random process in the interaction between the new particle and the nucleus.

I'm not entirely sure but I would think that there would be definite restrictions or possibly even the ability to rule out such a particle by considering the difference kinematics and spins (I think the new particle might have to be a scalar if its allowed at all) between a 1 -> 3 or 2 -> 4 (or 3? is the new particle scattered elastically?) process.

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### Re: Radioactive Decay

Interesting: http://www.physorg.com/news202456660.html
A team of scientists from Purdue and Stanford universities has found that the decay of radioactive isotopes fluctuates in synch with the rotation of the sun's core.
The fluctuations appear to be very small but could lead to predictive tools for solar flares and may have an impact on medical radiation treatments.
This adds to evidence of swings in decay rates in response to solar activity and the distance between the Earth and the sun that Purdue researchers Ephraim Fischbach, a professor of physics, and Jere Jenkins, a nuclear engineer, have been gathering for the last four years. The Purdue team previously reported observing a drop in the rate of decay that began a day and half before and peaked during the December 2006 solar flare and an annual fluctuation that appeared to be based on the Earth's orbit of, and changing distance from, the sun, Jenkins said.
"If the relationship between solar activity and decay rates proves to be true, it could lead to a method of predicting solar flares, which could help prevent damage to satellites and electric grids, as well as save the lives of astronauts in space," Jenkins said. "Finding that the decay rates fluctuate in a pattern that matches known and theoretical solar frequencies is compelling evidence for a solar influence on decay rates."

Edited to add: Being discussed here: viewtopic.php?f=9&t=63837

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### Re: Radioactive Decay

Korrente wrote:My main concern here is whether or not Random exists. I don't believe it does because of causation and I think that if you knew all available information about a particle or a system, you could accurately predict its outcome in every situation. I could be wrong though.

Hi guys,

the Nukleus seems inhomogeneous. The inhomogeneousities appears as protons and neutrons. The constellation in the nucleus may change over time. Some of the constellations May cause instabilities and decay.

What do You think?

This is easy to understand because of we live in the World of particles.

P.P.S.:
Everything is a particle.

Last edited by Ray Steel on Mon Mar 19, 2018 12:06 am UTC, edited 1 time in total.
P.S.:
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gmalivuk
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### Re: Radioactive Decay

Please don't post three times in a row. You can edit your most recent post to add more if you want to.

P.S. Everything is also a wave.
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Ray Steel
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### Re: Radioactive Decay

gmalivuk wrote:You can edit your most recent post to add more if you want to.

Never ever

gmalivuk wrote:P.S. Everything is also a wave.

Every particle has a Set of properties.
Waves are a property of more than one particle.

P.S.:
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### Re: Radioactive Decay

Right. So things aren't really particles or waves, they're fields. Much better.
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### Re: Radioactive Decay

Ray Steel wrote:
gmalivuk wrote:You can edit your most recent post to add more if you want to.

Never ever

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