[geordief (OP)]

As I hope I have understood  Bell's theorem  has clarified the random nature of physical interactions (we do only have interactions rather than isolated events don't we?)

So if the random event is something of a ground zero in our understanding  of the physical world  what else can we say  about it aside from just accepting it and building on it?

Are we still allowed to believe that randomness  can still.be investigate to a deeper level of understanding or is this as far as things go?

[Halc]

As I hope I have understood  Bell's theorem  has clarified the random nature of physical interactions

Did it have much (anything?) to say about randomness?  It seems that quantum theory in the first place (well before Bell came along) demonstrated the fundamental probabilistic nature of empirical things.
There were two principles held shortly after the turn of the 20th century: Realism and locality. The former says that things exist (a system is in a particular state) independent of measurement. The latter says that the effect cannot be separated from its cause in a space-like manner, or that cause-effect cannot move faster than light. Bell demonstrated that (barring superdeterminism), at least one of these principles must be false.

we do only have interactions rather than isolated events don't we?

I don't know what you mean by these things. An interaction is something that happens over time between different systems. An event (as usually used in physics) is a point in spacetime, but it also might be used to describe an occurrence, such as a particle interaction, say that shown by a Feynman diagram. In that sense, an interaction is a form of event. The decay of some nucleus is an event that isn't an interaction since there is but the one system.

So if the random event is something of a ground zero in our understanding  of the physical world  what else can we say  about it aside from just accepting it and building on it?

Again, I don't understand. Our understanding of the world isn't grounded on one event, or a group of them. There's a lot more to it.

Are we still allowed to believe that randomness  can still.be investigate to a deeper level of understanding or is this as far as things go?

My apologies, but again, I don't know what's being asked. Measurements seem probabilistic by nature, but there are interpretations of QM that are not random at all, so the perceived randomness is hardly fundamental since it cannot be conclusively demonstrated.

[geordief (OP)]

As I hope I have understood  Bell's theorem  has clarified the random nature of physical interactions

Did it have much (anything?) to say about randomness?  It seems that quantum theory in the first place (well before Bell came along) demonstrated the fundamental probabilistic nature of empirical things.
There were two principles held shortly after the turn of the 20th century: Realism and locality. The former says that things exist (a system is in a particular state) independent of measurement. The latter says that the effect cannot be separated from its cause in a space-like manner, or that cause-effect cannot move faster than light. Bell demonstrated that (barring superdeterminism), at least one of these principles must be false.

we do only have interactions rather than isolated events don't we?

I don't know what you mean by these things. An interaction is something that happens over time between different systems. An event (as usually used in physics) is a point in spacetime, but it also might be used to describe an occurrence, such as a particle interaction, say that shown by a Feynman diagram. In that sense, an interaction is a form of event. The decay of some nucleus is an event that isn't an interaction since there is but the one system.

So if the random event is something of a ground zero in our understanding  of the physical world  what else can we say  about it aside from just accepting it and building on it?

Again, I don't understand. Our understanding of the world isn't grounded on one event, or a group of them. There's a lot more to it.

Are we still allowed to believe that randomness  can still.be investigate to a deeper level of understanding or is this as far as things go?

My apologies, but again, I don't know what's being asked. Measurements seem probabilistic by nature, but there are interpretations of QM that are not random at all, so the perceived randomness is hardly fundamental since it cannot be conclusively demonstrated.

Thanks for your patience.Clearly I am poorly versed in Bell's theorem and also the localism vs realism question.

Thanks for your descriptions of them

I also  assumed that randomness  was the only interpretation of QM  that  was accepted .

I suppose I may learn more from my errors than by trying to buildi on my imaginings.

I will need a little time for the lessons to sink in.

When I said that interactions were more descriptive  than events (not using  "event"  to mean a geometric  point in spacetime) I was expressing my feeling that everything has to have an environment to play out in.

So the decay of the nucleus is only of significance when it is measured (to my mind) and  this "measurement" is a synonym with "interaction"

As the saying goes ,one hand does not clap and the nucleus decays into or from something ,doesn't it?

Do you stand by your explanation that some occurrences (eg nuclear decay)  take place on their own and without a "partner" in the physical  environment (the wider system they are part of)?

More generally,perhaps are not all systems ,large or small interconnected?

[Halc]

I also  assumed that randomness  was the only interpretation of QM  that  was accepted .

There is no interpretation called 'randomness'. I think you mean the category of non-determinstic.
Of the 13 basic types of interpretations listed in wiki, 2 are agnostic, 7 non-deterministic, and 4 of them deterministic, meaning no randomness, no 'god rolling dice'. I would include relational interpretation as a 5th one there because it also has no randomness, but wiki lists it as non-deterministic.

So the decay of the nucleus is only of significance when it is measured (to my mind) and  this "measurement" is a synonym with "interaction"

Good point. For one, 'measurement' and 'interaction' are essentially the same thing in QM (with a couple exceptions). You seem to take the non-realist approach that says the decay doesn't exist until measured. I agree with that, but keep in mind that it's a choice, not something known.

Do you stand by your explanation that some occurrences (eg nuclear decay)  take place on their own and without a "partner" in the physical  environment (the wider system they are part of)?

There are valid counterfactual interpretations that say the decay happens even if not measured. Either way, the decay isn't 'caused' by anything, so whether it takes an interaction or not, it's still an uncaused and empirically random occurrence. Given the realist interpretation, it doesn't take two for the decay to occur, so no partner required. A partner is only needed for it to be measured. A tree falling in the forest makes no noise if there's nothing to measure the event. That makes no sense at the classical level since it is impossible for any part of the forest (or of Earth) to not measure the tree falling in it.

More generally,perhaps are not all systems ,large or small interconnected?

Well that's what the Schrodinger's box thought experiment illustrates. The box represents the isolation of a system from the outside, a severance of that connection. This has been demonstrated in the lab for 'large' things (something big enough to see without aid), which were isolated enough to be placed in superposition of state for a time. The procedure to isolate it would not be survived by a cat. Anyway, it constitutes a real situation where two systems were not interconnected for a time. It gets much easier with distance. A planet currently 20 BLY away is permanently not interconnected with Earth today, so there's an example of systems forever not connected, at least per a local interpretation. Given a non-local interpretation, one can influence the other faster than light. Maybe they share entangled particles or something.

[alancalverd]

So the decay of the nucleus is only of significance when it is measured (to my mind) and  this "measurement" is a synonym with "interaction"

A whiff of anthropocentrism here! The decay of a nucleus is of huge consequence to the nucleus itself, which ceases to exist or spawns daughters, even if there is no observer.
A lot of philosophical nonsense derives from the technical term "observer" that we use in science simply to denote a plane in spacetime through which information passes.

[geordief (OP)]

So the decay of the nucleus is only of significance when it is measured (to my mind) and  this "measurement" is a synonym with "interaction"

A whiff of anthropocentrism here! The decay of a nucleus is of huge consequence to the nucleus itself, which ceases to exist or spawns daughters, even if there is no observer.
A lot of philosophical nonsense derives from the technical term "observer" that we use in science simply to denote a plane in spacetime through which information passes.

I just  reread what you quoted  from me.It seems ambiguous  now.When I said  "to my mind" it was just to say "in my tentative  opinion"

Did you think I  was putting my mind  and its powers of observation  at the centre of whether  or not  the physical world exists?

I didn't intend to say that, which would of course be rubbish (but I think I have entertained the notion in the past. Is it called solipscism?

[Zer0]

*solipsism.

[geordief (OP)]

*solipsism.

I can't believe you said that ;-)

[Zer0]

*solipsism.

I can't believe you said that ;-)

I didn't.
It's all in your Mind.
You think therefore You are.
i don't, hence i'm Not!
: )

[alancalverd]

Nothing to do with anyone's mind: it's my objection to the literal overinterpretation of "observer".

Even "randomness" is a bit unscientific. Heisenberg showed that what might appear to be absolutely determined at a macroscopic level is actually microscopically indeterminate. Problem has arisen from a loose translation as "uncertainty"

Throughout the main body of his original 1927 paper, written in German, Heisenberg used the word "Ungenauigkeit" ("indeterminacy") to describe the basic theoretical principle. Only in the endnote did he switch to the word "Unsicherheit" ("uncertainty"). When the English-language version of Heisenberg's textbook, The Physical Principles of the Quantum Theory, was published in 1930, however, the translation "uncertainty" was used, and it became the more commonly used term in the English language thereafter.

....which has been embedded in many people's thoughts as a result of his original derivation of the inequality from a hypothetical measurement. Many elementary textbooks simply repeat this without considering the deeper realisation that it has nothing to do with measurement or observation but is an inherent and essential property of nature.

[geordief (OP)]

For the purposes of talking physics I take the notion of measurement to be equivalent to "interaction" and the notion of myself (or an experimenter)" observing a system to be equivalent to the "observer" physically interacting with the system.

I understand the observer (eg myself) to have a misleading  belief that they exist separate from the system they think they are observing whereas a better understanding would be that they are a physical extension of the system (and vice versa)

So I didn't feel that I had an undue(except unconscious) anthropocentric  bias  in this regard

I think I understand the difference between the inherent  uncertainty of the state of a system vs the "observer effect" (or at least enough to know that these are two distinct phenomena,)

btw I think I may recognize "Ungenauigkeit" from my stilted conversations with Austrian acquaintances  where every exchange is peppered with "genau" which seems to mean "exactly" and which we used to feign understanding  of what we were  hearing from each other.

So "Ungenauigkeit" may mean "inexactitude"?

[geordief (OP)]

*solipsism.

I can't believe you said that ;-)

I didn't.
It's all in your Mind.
You think therefore You are.
i don't, hence i'm Not!
: )

Have been playing my guitar  this evening and the thought occured to me that after a while you stop thinking about what you are playing and the instrument starts to "play itself" while you just tag along for the ride.

[alancalverd]

Have been playing my guitar  this evening and the thought occured to me that after a while you stop thinking about what you are playing and the instrument starts to "play itself" while you just tag along for the ride.

Congratulations - you have reached the Final Stage of Enlightenment - Jazzman. You become One with the Instrument and just talk to the audience through it as naturally as speaking. I think it's a fair analogy because I still struggle with classical pieces: the harmonic sequences are less obvious so it's like reading aloud a learned language instead of your native tongue.

[alancalverd]

So "Ungenauigkeit" may mean "inexactitude"?

The key distinction is between uncertainty (the image is blurred but I think there is an animal out there) and indeterminacy (it really is a woolly sheep and not just an unfocused goat).  Sicherheit is all to do with confidence, hence certainty, whilst Genauigkeit  concerns exactitude, an inherent property of the entity under discussion.

I still think you need to distinguish carefully between an "active observer", i.e. one who necessarily disturbs the system by making a measurement, and the textbook "ur-observer" (a made-up word, but you'll appreciate its very handy Germanic root), i.e  a surface in spacetime, outside of the system being observed. For instance it is quite obvious that nothing we do can affect the fusion processes that make Betelguese shine since what we observe actually happened about 700 years ago, nor for that matter can we influence the decay of a uranium nucleus a few picoseconds away from the gamma ray detector, so we are generally "ur-observers" of nuclear phenomena but "active observers" of fetal ultrasound imaging.