What triggers radioactive nuclei decay?

[tommac]

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?

the latter. Specifically this part:

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).

EDIT: however as usual I could be totally wrong ... but if I am I would like to ask what you base this statement on.

[antoniseb]

... however as usual I could be totally wrong ... but if I am I would like to ask what you base this statement on.

I make this statement actually knowing quite a bit about the inner workings of the nucleus, but preferring in this forum to use terminology that helps the layman better visualize what's happening than if I laid out the quantum chromodynamic details.

[tommac]

I make this statement actually knowing quite a bit about the inner workings of the nucleus, but preferring in this forum to use terminology that helps the layman better visualize what's happening than if I laid out the quantum chromodynamic details.

I wanted to make sure that I used the words respectfully in my protest. But I am not sure that trying to make the newtonian analogy helps or hurts the situation. It seems to me to cause more harm to a layman ( SUch as myself ) to have such an analogy presented in the name of simplification than the benefit that the analogy provides.

I in no way meant the protest to question your understanding on the matter.

[Jeff Root]

Tom,

Exactly what analogy are you referring to? I don't consider what
antoniseb said about motions (of quarks I presume) to be an analogy.

-- Jeff, in Minneapolis

[caveman1917]

I had understood the analogy as somewhat like thinking of the nucleus as the solar system with the planets being alpha particles which are normally bound together. But you can have a set of possible motions which will give for example Neptune such velocity that it exceeds solar escape velocity and is thus ejected from the system, which would by the analogy correspond to alpha decay.

[antoniseb]

I had understood the analogy as somewhat like thinking of the nucleus as the solar system with the planets being alpha particles which are normally bound together. But you can have a set of possible motions which will give for example Neptune such velocity that it exceeds solar escape velocity and is thus ejected from the system, which would by the analogy correspond to alpha decay.

Maybe more like a small globular cluster... except that in the nucleus includes significant repulsive forces, AND the attractive forces don't follow the inverse square law AND includes some doubt as to the actual position of any particle inside it, AND that sometimes the motions and quantum shell-filling result in a football shaped nucleus suddenly becoming a little more dumbbell shaped, resulting in fission.

[tommac]

Can you please define motion? Or clarify the definition of motion that is being used?

Tom,

Exactly what analogy are you referring to? I don't consider what
antoniseb said about motions (of quarks I presume) to be an analogy.

-- Jeff, in Minneapolis

[tommac]

I had understood the analogy as somewhat like thinking of the nucleus as the solar system with the planets being alpha particles which are normally bound together. But you can have a set of possible motions which will give for example Neptune such velocity that it exceeds solar escape velocity and is thus ejected from the system, which would by the analogy correspond to alpha decay.

Yes ... and this at least from me is what my protest is about. While it may paint a nice picture it really has little to do with what is happening. What is happening has much less to do with Newtonian motion than it does with probabilities being real ( and possibly fully descriptive) .

[tommac]

Maybe more like a small globular cluster... except that in the nucleus includes significant repulsive forces, AND the attractive forces don't follow the inverse square law AND includes some doubt as to the actual position of any particle inside it, AND that sometimes the motions and quantum shell-filling result in a football shaped nucleus suddenly becoming a little more dumbbell shaped, resulting in fission.

And time and space probably doesnt exist as we know it ... and relativity probably doesnt exist and particles can be in multiple places at the same time and ....

[caveman1917]

Maybe more like a small globular cluster... except that in the nucleus includes significant repulsive forces, AND the attractive forces don't follow the inverse square law AND includes some doubt as to the actual position of any particle inside it, AND that sometimes the motions and quantum shell-filling result in a football shaped nucleus suddenly becoming a little more dumbbell shaped, resulting in fission.

All very true. While the various forces can be easily considered in a newtonian way, i don't know how you would incorporate something as inherently quantum as the uncertainty principle in a newtonian model.

[grant hutchison]

And time and space probably doesnt exist as we know it ... and relativity probably doesnt exist and particles can be in multiple places at the same time and ....

And so no explanation is possible? But then you disappear in nihilistic solipsism, and you can't do any science.
When we do science, we tell coherent stories that describe the maths of our theories, and those stories turn out to be like the story antoniseb gave you. We need to bear in mind their limitations, for sure, but the limitations don't render the stories invalid.

Grant Hutchison

[caveman1917]

and relativity probably doesnt exist

Doesn't QCD fully incorporate SR? At least QED does, so i wouldn't expect chromodynamics to be different in this aspect, but i may be wrong of course.

[tommac]

Doesn't QCD fully incorporate SR? At least QED does, so i wouldn't expect chromodynamics to be different in this aspect, but i may be wrong of course.

How is quantum entanglement explained using SR?

[korjik]

How is quantum entanglement explained using SR?

It isnt. It is explained using Quantum Mechanics. Quantum Mechanics is fully compatable with Special Relativity. That is what Caveman was talking about.

[korjik]

And time and space probably doesnt exist as we know it ... and relativity probably doesnt exist and particles can be in multiple places at the same time and ....

Special relativity works fine with Quantum Mechanics. General Relativity dosent.

And particles dont exist at multiple places at the same time.
And space and time can be defined perfectly fine.

You really ought to learn the physics before you try to apply it.

[antoniseb]

Doesn't QCD fully incorporate SR? At least QED does, so i wouldn't expect chromodynamics to be different in this aspect, but i may be wrong of course.

Relativistic QCD includes SR, but inside the nucleus, the nucleons and pions (and within these the quarks and gluons) are not working at energies where SR really changes the solutions. RQCD is important when analyzing LHC results.

[tommac]

And particles dont exist at multiple places at the same time.

I guess it depends on how you define a particle. But look at hte double slit experiment. Also unless you observe a particle it exists in all states.

[Hornblower]

I have no quarrel with antoniseb's use of a Newtonian analogy such as a globular cluster. It provides novices with a more visualizable mental picture in which random fluctuations occasionally result in the ejection of a component of what would be a metastable system in the absence of those fluctuations.

[Jeff Root]

Tom,

Exactly what analogy are you referring to? I don't consider what
antoniseb said about motions (of quarks I presume) to be an analogy.

Can you please define motion? Or clarify the definition of motion that is being used?

That's a good question, especially considering I said to George,
"depending somewhat on just what you mean by "motions" and
by "known". But in that case George is the one who used the term,
and in this case antoniseb is the one who used it, so they should
be the people to define what they mean.

It might possibly help if you can explain what difficulty you have
conceptualizing motion of quarks, or what you hope a definition
might accomplish. I, myself, intuitively understand motion of
quarks as like any other motion, and don't worry about it at all.
A thing is one place, then it is another place, and the thing's
motion is that change of location.

I do not consider motion of quarks to be an analogy, because I do
not make an analogy between quarks and anything else. I do not
consider their motion to be analogous to the motions of planets
in a solar system or stars in a globular cluster. Quarks have their
own properties that are different from the properties of planets
and stars. They follow their own rules.

I would say that if it were possible to know the positions and
velocities of the quarks in a nucleon at a given instant, then one
might be able to say something about what the nucleon would be
doing in the next instant. But it is never possible to know the
positions and velocities of the quarks in a nucleon. So their
behavior can only be predicted statistically. But that doesn't
mean the quarks aren't really buzzing around inside the nucleon.
We can't see them, and will never be able to see them, we can't
say anything at all about where they are or what direction they
are moving at a given instant, and never will, but quarks have
properties that are particle-like, so they can be described as
particles, and that is how I conceptualize them.

I don't accept the notion that a particle can be in different places
simultaneously. That is a reality of the statistics, not of the
particle. You can't know where the particle is until it is detected,
and statistically, until it is detected, it is everywhere. But that
is just statistics. The same statistics could be applied to people.
You don't know where a person is until he is detected, so until
he is detected, he could statistically be everywhere at once.
The only difference is that with people, you could watch them
constantly, while fundamental particles cannot be watched.
Just don't watch the people, pretend that you can't watch them,
and you can have a Copenhagen interpretation of people being
everywhere at once.

-- Jeff, in Minneapolis

[tommac]

It might possibly help if you can explain what difficulty you have
conceptualizing motion of quarks, or what you hope a definition
might accomplish. I, myself, intuitively understand motion of
quarks as like any other motion, and don't worry about it at all.
A thing is one place, then it is another place, and the thing's
motion is that change of location.

Well it is just one of the issues I have .... but when you say it is in one place then it is in another place .... which places are you referring to?
I would think that some quantum physicists might argue that the quark occupies all of the places where it could possibly be simultaneously.

Also as the quark is also a wave then I just dont get how any useful newtonian analogy could be used describing them or their "Motion".

Say we had a pattern of polka dots on a computer screen. After a few minutes the same dots appearsed in another different pattern. COuld we say that was motion?

Here is an article written about hte "Motion" of quarks:
http://www.sciencedaily.com/releases...0927105029.htm

Over several years it became increasingly clear that the way in which the left-handed and right-handed quarks come together can be described using a massive quantities of random numbers.

This doesnt sound in the least Newtonian or even as movement.

They use the words swing and dance .... which I hope werent meant to be taken literally but to which I hsort of have the same objection to.

[tommac]

I don't accept the notion that a particle can be in different places
simultaneously.

Do you accept the notion that entangled particles can have non-local instantaneous communication?

That is a reality of the statistics, not of the
particle.

That is the point .... the statistics are the particle. The statistics are real. The same way the dog is both alive and dead.


From: http://www.sciencenews.org/view/feat...Quantum_Titans

At the heart of these disputes is the very nature of reality itself, and whether quantum physics is the last word on how to describe it. Zeilinger, of the University of Vienna, advocates the standard quantum view of reality’s fuzziness. “It turns out that the notion of a reality ‘out there’ existing prior to our observation … is not correct in all situations,” he points out.

Yet some physicists cling to the prejudice that cause-and-effect determinism will someday be returned to its privileged status, and physics will restore objectivity to reality.

“I basically understand why people have this position,” Zeilinger responds. “But the evidence is overwhelming that this approach would not succeed.”

[tommac]

I have no quarrel with antoniseb's use of a Newtonian analogy such as a globular cluster. It provides novices with a more visualizable mental picture in which random fluctuations occasionally result in the ejection of a component of what would be a metastable system in the absence of those fluctuations.

But is there any cause and effect? Or is it just that a random percentage of the time a state happens where a photon is emmited. From what I have read there is no cause and effect relationship. So why try to explain something, that is fairly simple in terms of probabiliies, in newtonian terms so as to simplify it for the layman like myself? Why not just leave it as saying if it is probable then it just is.

[tommac]

I have no quarrel with antoniseb's use of a Newtonian analogy such as a globular cluster. It provides novices with a more visualizable mental picture in which random fluctuations occasionally result in the ejection of a component of what would be a metastable system in the absence of those fluctuations.

To go back to the OQ :

What triggers radioactive nuclei decay?

Wouldnt it just be easiest to say that the radioactive nuclei decay is non-deterministic? and that the reason it happens is because there is a probability of it happening.

Could anything more be proven?

[macaw]

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,

The process is random. The nuclei of radioactive materials exhibit an unstable equilibrium between the repulsive electrostatic force (which decays with 1/r^2) and the stronger, attractive nuclear force (which decays much faster than 1/r^2 but dominates the electrostatic force for small distances). The nuclei of radioactive materials cram together a very large number of protons and this increases their size, thus increasing the probability for the electrostatic force to overcome the nuclear force. If such a nucleus is "tapped" lightly by the arrival of a slow neutron (that acts as a catalyst), the nucleus breaks down freeing a large amount of energy in the process. The arrival of "catalysts" is random, thus the whole process is random.

One might want to ask two corollary questions:

1. What keeps the atoms together? Why don't the electrons "fall" into the nucleus ?
Answer : Heisenberg uncertainty principle says that if the electrons were confined in an ever smaller space their momenta would be ever increasing, balancing the attempt to "collapse" them into the nucleus.

2. Why don't the electrons or the protons "fly apart" under the influence of their own charge? Is there a sort of "nuclear force" that balances the electrostatic force as in the case of atoms above?
Answer: no one knows. This is an open question.

[Jeff Root]

Well it is just one of the issues I have .... but when you say it is in one
place then it is in another place .... which places are you referring to?
I would think that some quantum physicists might argue that the quark
occupies all of the places where it could possibly be simultaneously.

Also as the quark is also a wave then I just dont get how any useful
newtonian analogy could be used describing them or their "Motion".

A quark or other fundamental particle is not a wave. It is described
by a wave function, and behaves according to the mathematics
which describes particular types of waves.

Say we had a pattern of polka dots on a computer screen. After a
few minutes the same dots appearsed in another different pattern.
Could we say that was motion?

Excellent confounding example. I can only assert that individual
particles are distinct entities, and maintain a continuous existence
and separate identity from other particles, even if the particles
are completely identical to each other in every way. If you had
a dozen bearing balls that were completely indistinguishable, I
think you would not say that they were exchanging identities with
one another. Each bearing ball would be in a different location at
any given time. The difference between bearing balls and quarks
is that you could keep track of the individual bearing balls if you
wanted to, but you couldn't keep track of the quarks. The fact
that you can't keep track of something, even in principle, doesn't
mean that the thing isn't in any particular place. You just have no
way of knowing what that place is.

-- Jeff, in Minneapolis

[Jeff Root]

Do you accept the notion that entangled particles can have non-local
instantaneous communication?

No.

I accept that they are entangled, though.

.... the statistics are the particle. The statistics are real. The same
way the dog is both alive and dead.

The statistics are not the particle. The statistics describe the particle.
The statistics accurately describe the dog as both alive and dead, but
the dog is not both alive and dead. The dog is either alive or dead,
but you don't know which. Statistically it is both. A dog is a dog, not
a statistic.

The statistics are real, and they do a great job of describing the
behavior of various things. But the statistics are not the things
whose behavior they describe.

-- Jeff, in Minneapolis

[tommac]

You just have no
way of knowing what that place is.

How are you defining place? Centainly nothing like a newtonian place!
I am by no way any expert but it would see m that space and time as we know it breaks down at the quantum level
If space and time are not newtonian ... then any newtonian analogies would be like explaining what the inside of a black hole looks like.

[Jeff Root]

I'm not defining "place" because the concept doesn't seem to
me to require definition. I can understand that it would seem
to others to require definition. To me, it is such a basic concept
that it isn't possible for me to define it.

If I say that we have no way of knowing what place a thing is in,
perhaps you will want to simply interpret that as meaning that
I *am* using a newtonian definition of place. Although I can't
imagine any definition that *would* allow us to know the place.

I have no reason to think that space and time "break down"
at small scales. I have plenty of reason to think that there are
limits to how small any space or time measurement can be,
but that does not imply that space and time somehow stop
being space and time.

I do not consider application of the ideas "space" and "time" to
very small scales to be analogies.

-- Jeff, in Minneapolis

[tommac]

Although I can't
imagine any definition that *would* allow us to know the place.

This is the point. It is not the technology that is not yet up to par but that it just cant be done. We will never know the place.

Why are you so against space and time breaking down on very small scales?
Can you explain the double slit experiment using anything in the macro world?
Can you explain quantum entanglement using anything in the macro world?

Also even if it didnt break down ... does it really matter if we could never measure anything? Is there a difference between a true break down or a break down in the sense that we cant prove otherwise?

Is there a difference between a world in which probability is the reality vs a world where nothing can be observed other than probabilities no matter what you do.

[Hornblower]

I continue to concur with antoniseb. Of course we cannot use a Newtonian analysis to study the actions in an atomic nucleus, but the same sort of entry level novice's mental picture makes sense to me. In a globular cluster we have chaotic gravitational interactions that once in a while gang up on a star and eject it from the cluster, while causing other stars to settle into lower energy states in the center. I am imagining the possibility that random quantum mechanical interactions in a nucleus are occasionally ganging up on an alpha particle and ejecting it. In each case the impetus was redistribution of energy that was inherent in each system. Very different mathematical details, but otherwise a good analogy as I see it.