Quantum uncertainty

[geordief]

Would I be right to understand that this is a description of the impossibility of knowing the simultaneous  position and  momentum of a particle?

If it is not an example of the "how not why" question could I ask why (or how) this  is the case?

Is this an observer related phenomenon or is it the case that the particle itself cannot actually be in a particular place with a particular momentum? (as applied to a particular frame of reference if that does not  in itself imply an observer)

 

I wanted to post in this thread

https://www.scienceforums.net/topic/125204-life-was-inevitable/?do=findComment&comment=1178225

but thought it was better to start a new thread......

Edited June 6, 2021 by geordief

[swansont]

 

Quote

Would I be right to understand that this is a description of the impossibility of knowing the simultaneous  position and  momentum of a particle?

It applies to any pair of conjugate variables, so in QM it includes energy & time, and angular momentum & angular position as well. These variables don’t commute, so the order you do the operation matters.

 

Quote

If it is not an example of the "how not why" question could I ask why (or how) this  is the case?

Is this an observer related phenomenon or is it the case that the particle itself cannot actually be in a particular place with a particular momentum? (as applied to a particular frame of reference if that does not  in itself imply an observer)

It’s inherent in QM i.e. it’s in the math. These variables are fourier transforms of each other.

The observer effect is a distinct phenomenon 

 

edit: more detail here -  https://www.forbes.com/sites/startswithabang/2017/08/12/ask-ethan-where-does-quantum-uncertainty-come-from/?sh=60c0a134794e

[exchemist]

6 hours ago, geordief said:

Would I be right to understand that this is a description of the impossibility of knowing the simultaneous  position and  momentum of a particle?

If it is not an example of the "how not why" question could I ask why (or how) this  is the case?

Is this an observer related phenomenon or is it the case that the particle itself cannot actually be in a particular place with a particular momentum? (as applied to a particular frame of reference if that does not  in itself imply an observer)

 

I wanted to post in this thread

https://www.scienceforums.net/topic/125204-life-was-inevitable/?do=findComment&comment=1178225

but thought it was better to start a new thread......

To give a less mathematical response, it is the latter. For a QM entity to be in an exact place with an exact momentum is just not something that is even defined, in QM. The uncertainty is intrinsic to nature.

From reading Carlo Rovelli's "Helgoland", it seems the "relational interpretation" of QM in effect denies that a QM entity even has any properties on a continuous basis.

According to this view, all properties become manifest only in the course of interactions involving the QM system in question. In between interactions, it is not necessary to assume that it has any properties at all. The wave function (when the QM operator for a property is applied to it) tells you what range of values of the property the system may manifest when it interacts.  

Tying properties to interactions gets rid of the tiresome issue of "the observer", which has led all sorts of people astray over the years, even sometimes to the extent of  speculating that QM gives a special place to conscious observers. This last is something that has spawned an entire industry of quantum woo (Deepak Chopra et.al.).  But, on the contrary, any "observation" necessarily requires an interaction. It is the interaction that counts, not an act of observation. 

The further implication of this is that what we call "reality" is made up of the interactions going on all the time between QM entities. Which is not as crazy as it sounds. After all, something only provides evidence that it exists when it interacts with something else.

Classically, we interpolate  between interactions by assuming that objects possess properties with defined values all the time, in a continuous manner. But in QM it seems the only thing that unambiguously persists is the wave function, which represents the potential properties exhibited when an interaction "collapses" it.   

This, at least is my understanding. I find it elegant, as it seems to resolve a number of the paradoxes that QM throws up.

Edited June 6, 2021 by exchemist

[geordief]

15 hours ago, exchemist said:

To give a less mathematical response, it is the latter. For a QM entity to be in an exact place with an exact momentum is just not something that is even defined, in QM. The uncertainty is intrinsic to nature.

From reading Carlo Rovelli's "Helgoland", it seems the "relational interpretation" of QM in effect denies that a QM entity even has any properties on a continuous basis.

According to this view, all properties become manifest only in the course of interactions involving the QM system in question. In between interactions, it is not necessary to assume that it has any properties at all. The wave function (when the QM operator for a property is applied to it) tells you what range of values of the property the system may manifest when it interacts.  

Tying properties to interactions gets rid of the tiresome issue of "the observer", which has led all sorts of people astray over the years, even sometimes to the extent of  speculating that QM gives a special place to conscious observers. This last is something that has spawned an entire industry of quantum woo (Deepak Chopra et.al.).  But, on the contrary, any "observation" necessarily requires an interaction. It is the interaction that counts, not an act of observation. 

The further implication of this is that what we call "reality" is made up of the interactions going on all the time between QM entities. Which is not as crazy as it sounds. After all, something only provides evidence that it exists when it interacts with something else.

Classically, we interpolate  between interactions by assuming that objects possess properties with defined values all the time, in a continuous manner. But in QM it seems the only thing that unambiguously persists is the wave function, which represents the potential properties exhibited when an interaction "collapses" it.   

This, at least is my understanding. I find it elegant, as it seems to resolve a number of the paradoxes that QM throws up.

Perhaps you still remember Harold14370 from the .com  site?(Dirty Harry😀 )

Some years ago I fell into the trap of  asking about "events" in a GR context and was curtly dismissed by him **because I did not know what an "event" was  (it is just a point on the spacetime  graph,I think)

Seems like those "events" I was clumsily introducing then may be the kind of thing you are talking about ; another way of describing a fundamental interaction.

 

A kind  of a phenomenological "atom" (in the historical sense where it was applied to a supposed irreducible  building block of nature)?

**well he was one of the leading experts on GR there  then ,as well as being the Admin.

Edited June 7, 2021 by geordief

[iNow]

40 minutes ago, geordief said:

Perhaps you still remember Harold14370 from the .com  site?

I remember him from even before that on yet another site called Hypography.  

[exchemist]

8 hours ago, geordief said:

Perhaps you still remember Harold14370 from the .com  site?(Dirty Harry😀 )

Some years ago I fell into the trap of  asking about "events" in a GR context and was curtly dismissed by him **because I did not know what an "event" was  (it is just a point on the spacetime  graph,I think)

Seems like those "events" I was clumsily introducing then may be the kind of thing you are talking about ; another way of describing a fundamental interaction.

 

A kind  of a phenomenological "atom" (in the historical sense where it was applied to a supposed irreducible  building block of nature)?

**well he was one of the leading experts on GR there  then ,as well as being the Admin.

Yeah I remember him. Stroppy git, he was.😁

I rather think the relativity issue you refer to would be to do with the physicists' dismissal of the notion of time "passing", as in relativity it is just a coordinate axis and therefore doesn't have a "direction". Anyway I don't think it's related to this QM issue of interactions being what make reality tangible.