What triggers radioactive nuclei decay?

[Golladzher]

I'd like to understand if a single radioactive nuclei truly decays randomly, or if any hypotheses have been posited that might lead to a theory that describes how a single nuclei decays. Though, I suspect such a theory would have sweeping consequences as it seems it would imply a purely deterministic universe.

Thanks all,

[Strange]

Completely random, as far as I know. And I think you are right, discovery of an underlying cause would be a dramatic change to quantum theory.

[tommac]

probibility

[George]

probibility

That sure seems probable. Is it likely a "disturbance in the force" (weak force) that triggers a decay?

[Ronald Brak]

What triggers nuclei decay? Some nuclei can be rearranged into more stable forms and give off energy when they do. Vaccuum fluctuations can give nuclei the push they need to rearrange. These fluctuations are random. But I know very little on this topic. Wikipedia might be able to give you the dirt on this.

[tommac]

That sure seems probable. Is it likely a "disturbance in the force" (weak force) that triggers a decay?

Can you show some proof of that? If that is the case then why would the probability be so constant?

[grant hutchison]

Can you show some proof of that? If that is the case then why would the probability be so constant?

Since George isn't on-line at present, I'll just point out that he was asking a question, not making a statement. So I doubt if "proof" will be forthcoming.

Grant Hutchison

[tommac]

Please take a look at:

http://en.wikipedia.org/wiki/Copenhagen_interpretation

[tommac]

You also may want to check out:
http://en.wikipedia.org/wiki/Many_worlds

[tommac]

Is it likely a "disturbance in the force" (weak force) that triggers a decay?

No ... or at minimum that would lead to the follow up unansweable questions of what triggers the "disturbance in the force".

[George]

Since George isn't on-line at present, I'll just point out that he was asking a question, not making a statement. So I doubt if "proof" will be forthcoming.

Yes. "Poof" maybe. I am fairly sure that the weak force is responsible for decay, not that I understand it. I also vaguely recall trinitree convincing me (w/ at least one paper) that neutrinos are not responsible for triggering decay.

[tommac]

Yes. "Poof" maybe. I am fairly sure that the weak force is responsible for decay, not that I understand it. I also vaguely recall trinitree convincing me (w/ at least one paper) that neutrinos are not responsible for triggering decay.

Nope. Maybe the quantum jitters.

[George]

Nope.

? Nope to the weak force responsible for decay?

Maybe the quantum jitters.

I like that one. Perhaps when a given number of jitters pile on one another probalistically, then a decay takes place.

[Strange]

Perhaps when a given number of jitters pile on one another probalistically, then a decay takes place.

Maybe you have found a way to combine chaos theory with quantum theory!

[George]

Maybe you have found a way to combine chaos theory with quantum theory!

Don't forget String "theory"! I've always liked "Good Vibrations". It must have been the surfing.

[Strange]

Turns out there is a field called quantum chaos but rather than trying to apply chaos theory to explain quantum mechanics, it looks at how classical chaos could emerge from quantum effects.

[antoniseb]

Sorry for all the glib answers. The answer is not entirely trivial, but you can think of the nuclei as being complex systems with the many forces binding and repulsing the component parts. There are, at times, external contributions to the decay process, such as neutrino capture, or some other kind of particle capture for certain types of decay. For spontaneous fission, or alpha emission, it may be as simple as there just being an unlikely but possible set of motions (speaking in a Newtonian way about a quantum phenomenon) that result in the breaking apart of a borderline stable nucleus (like U235 for example). The chance of having this set of motions at any given time is like once in 13.2 billion years for Thorium, and quite a bit shorter to Beryllium-8

[George]

Sorry for all the glib answers. The answer is not entirely trivial, but you can think of the nuclei as being complex systems with the many forces binding and repulsing the component parts. There are, at times, external contributions to the decay process, such as neutrino capture, or some other kind of particle capture for certain types of decay. For spontaneous fission, or alpha emission, it may be as simple as there just being an unlikely but possible set of motions (speaking in a Newtonian way about a quantum phenomenon) that result in the breaking apart of a borderline stable nucleus (like U235 for example). The chance of having this set of motions at any given time is like once in 13.2 billion years for Thorium, and quite a bit shorter to Beryllium-8

Is it that the "motions" are known and the probability of decay comes from calculations of these motions, or is it that the decay rate is known so the motion conditions are assumed from this?

[Jeff Root]

Is it that the "motions" are known and the probability of decay comes
from calculations of these motions, or is it that the decay rate is known
so the motion conditions are assumed from this?

I don't know the answer, but I will bet you any amount of ice cream
that it is neither. I know that the motions aren't known (depending
somewhat on just what you mean by "motions" and by "known").
The decay rates are known, but I'm betting the ice cream that
knowing the the decay rate doesn't tell us anything about the
motions of the particles. It just tells us the probability of the
required conditions occurring.

I think the "conditions" simply amount to the particles being in
the same place at the same time-- in other words, colliding, The
particles are in random motion, so there is nothing to measure
that could serve as an indicator of when they will collide. Thus
the time is completely unpredictable.

-- Jeff, in Minneapolis

[antoniseb]

Is it that the "motions" are known and the probability of decay comes from calculations of these motions, or is it that the decay rate is known so the motion conditions are assumed from this?

Don't try to get too precise with this hand-waving non-quantum explanation. There is evidence that heavy nuclei behave as though they have a shell model describing the placement of the nucleons in the nucleus (based on the spin of Pions that escape when the nucleus is struck with 142MeV gammas) so we have some crude view into the physical structure of the motions in the nucleus, but realistically, each proton and neutron are a triad of quarks held together by strong force all interacting in very complex ways. You can't write a Hamiltonian to describe it. All you can do is look at the fission or alpha decay rate and say, that must be it. As it happens, IIRC, that rate can depend on the ionization state of the nucleus to a small degree, so surrounding fields have a small impact. I expect that in a magnetar's surface field, the decay rates would change quite a bit, since the magnetic field would exceed cause the nuclei to be less spherical, and therefor more subject to having local charge exceed the weak force.

[George]

I don't know the answer, but I will bet you any amount of ice cream
that it is neither. I know that the motions aren't known (depending
somewhat on just what you mean by "motions" and by "known").
The decay rates are known, but I'm betting the ice cream that
knowing the the decay rate doesn't tell us anything about the
motions of the particles. It just tells us the probability of the
required conditions occurring.

I won't hold my breath for someone to take that bet.

I think the "conditions" simply amount to the particles being in
the same place at the same time-- in other words, colliding, The
particles are in random motion, so there is nothing to measure
that could serve as an indicator of when they will collide. Thus
the time is completely unpredictable.

Is collision between other atoms or nuclei what you suspect triggers decay? That would be testable by comparing rates with particles in a vacuum.

As it happens, IIRC, that rate can depend on the ionization state of the nucleus to a small degree, so surrounding fields have a small impact.

That's interesting. Anything in georgeeze when it involves quantum anything is appreciated.

I expect that in a magnetar's surface field, the decay rates would change quite a bit, since the magnetic field would exceed cause the nuclei to be less spherical, and therefor more subject to having local charge exceed the weak force.

Perhaps other factors would also contribute to the rate given such extreme conditions, though we don't have normal radioactive material to work with.

[Jeff Root]

I won't hold my breath for someone to take that bet.

Will you hold your spoon?

Is collision between other atoms or nuclei what you suspect triggers
decay? That would be testable by comparing rates with particles in
a vacuum.

No, collisions between quarks in a single nucleon, I think. It has been
years since I read about this. I have only the vaguest memory of it.
I know that individual quarks cannot be extracted from a nucleon.
As I'm sure you also know, any attempt to knock a quark out of a
nucleon adds so much energy to the assemblage of quarks that a new
mate for the freed quark is created from that energy, so that we end
up with a meson instead of a free quark... That fact may be relevant
somehow, but I'm not quite sure how...

-- Jeff, in Minneapolis

[Grey]

As a side note, it's not just radioactive decay. Quantum mechanics always gives a probabilistic prediction for the behavior of any system, whether it's a radioactive isotope emitting an alpha particle, the decay of a single muon, a randomly polarized photon passing through a polarized filter, where an electron lands in a diffraction experiment, or anything else. We have no idea whether those processes are fundamentally random, or if there are underlying mechanisms that produce the apparently random behavior we see. It's entirely possible that we may not ever be able to know the answer to that.

[tommac]

With respect ...
I dont know much about the quantum ( and would be argued by people on this board ... any ) physics but the one thing I know is you must be very careful making any Newtonian references or analogies when dealing with quantum physics. I believe Bohr often took exception to similar such wording. From what i understand the world of quantum physics lives in a world where possibilities are the reality rather than a manipulation about reality. Trying to make Newtonian references to such things can trivialize this major philosophical point.

Sorry for all the glib answers. The answer is not entirely trivial, but you can think of the nuclei as being complex systems with the many forces binding and repulsing the component parts. There are, at times, external contributions to the decay process, such as neutrino capture, or some other kind of particle capture for certain types of decay. For spontaneous fission, or alpha emission, it may be as simple as there just being an unlikely but possible set of motions (speaking in a Newtonian way about a quantum phenomenon) that result in the breaking apart of a borderline stable nucleus (like U235 for example). The chance of having this set of motions at any given time is like once in 13.2 billion years for Thorium, and quite a bit shorter to Beryllium-8

[tommac]

In quantum physics probabilities are REAL ... the cat is both dead and alive. It is a totally different paradigm that is not compatible with newtonian physics.

I don't know the answer, but I will bet you any amount of ice cream
that it is neither. I know that the motions aren't known (depending
somewhat on just what you mean by "motions" and by "known").
The decay rates are known, but I'm betting the ice cream that
knowing the the decay rate doesn't tell us anything about the
motions of the particles. It just tells us the probability of the
required conditions occurring.

I think the "conditions" simply amount to the particles being in
the same place at the same time-- in other words, colliding, The
particles are in random motion, so there is nothing to measure
that could serve as an indicator of when they will collide. Thus
the time is completely unpredictable.

-- Jeff, in Minneapolis

[tommac]

Whatever it is I would be willing to bet that it wouldnt make sense to anything we can observe.
One thing like Bells theorem about quantum entanglement ( instantaneous communication between quantum particles ) proves that no localized theory could be used to explain it.

As a side note, it's not just radioactive decay. Quantum mechanics always gives a probabilistic prediction for the behavior of any system, whether it's a radioactive isotope emitting an alpha particle, the decay of a single muon, a randomly polarized photon passing through a polarized filter, where an electron lands in a diffraction experiment, or anything else. We have no idea whether those processes are fundamentally random, or if there are underlying mechanisms that produce the apparently random behavior we see. It's entirely possible that we may not ever be able to know the answer to that.

[tommac]

One source ...
http://bigthink.com/ideas/20525
There are many other similar linsk

my bolds ...

This theory offers a very different way to view the world they we live in—one where the simple laws of conventional physics simply don’t apply at all. Quantum theory is so eccentric and peculiar that even Einstein himself couldn’t wrap his head around it. The great physicist, Richard Feynman once stated that “It is impossible, absolutely impossible to explain it in any classical way”.

Some of what quantum theory predicts and states is almost like something out of science fiction. Matter can essentially be in an infinite number of places at any given time; it is possible that there are many worlds or a multiverse; things disappear and reappear somewhere else; you cannot simultaneously know the exact position and momentum of an object; and even quantum entanglement (Einstein referred to it as spooky action at a distance) where it’s possible for two quantum particles to link together effectively making them part of the same entity or entangled. Even if these particles are separated, a change in one is ultimately and instantly reflected in it’s counterpart. At the end of the day, the world of entanglement caused physicists like Einstein to both dislike the predictions and feel nothing more as if their were serious errors in the calculations. As Einstein once wrote: "I find the idea quite intolerable that an electron exposed to radiation should choose of its own free will, not only its moment to jump off, but also its direction. In that case, I would rather be a cobbler, or even an employee in a gaming house, than a physicist".

[antoniseb]

With respect ... you must be very careful making any Newtonian references or analogies when dealing with quantum physics. ...

Are you saying I was not careful, or that you believe what I said (in its entirety) to be in error or not a useful way to think about it?

[caveman1917]

Tommac i think you are focusing on that aspect in Antoniseb's explanation which is not the main gist of the answer. As far as i understand, what happens (recall the other thread on entropy) is that you get a possible set of states and a probability distribution over that set. Some of these states will give decay. What happens then just boils down to in essence taking a random walk over that set of states & probability distribution, and whenever you land upon a 'decay state' you get a decay.

But wether you want to think about those states themselves in classical terms or quantum terms is not all that pertinent to the underlying behaviour concerning decay. It will only start to matter when you're actually trying to calculate the states and which ones are 'decay states'.

[tommac]

While I partially agree ... why is there the need for the classic terms. It is only against using the classic terms that is my protest. The probability itself does a better job in explaining what is "really" going on.

Tommac i think you are focusing on that aspect in Antoniseb's explanation which is not the main gist of the answer. As far as i understand, what happens (recall the other thread on entropy) is that you get a possible set of states and a probability distribution over that set. Some of these states will give decay. What happens then just boils down to in essence taking a random walk over that set of states & probability distribution, and whenever you land upon a 'decay state' you get a decay.

But wether you want to think about those states themselves in classical terms or quantum terms is not all that pertinent to the underlying behaviour concerning decay. It will only start to matter when you're actually trying to calculate the states and which ones are 'decay states'.