"Event separation " of objects

[geordief]

As a measure of a distance between objects does the term ,"event separation " mean exactly  the same  thing  as  "the spacetime interval"? (as the terms are commonly used)

 

Do physical objects only exist in the framework  of the events that went into making them up and changing them?

 

 

[swansont]

1 hour ago, geordief said:

As a measure of a distance between objects does the term ,"event separation " mean exactly  the same  thing  as  "the spacetime interval"? (as the terms are commonly used)

It might. It depends on the context of how the phrase is used.

[geordief]

16 minutes ago, swansont said:

It might. It depends on the context of how the phrase is used.

Well ,apart from the terms used  can we say that it is meaningless to talk about the separation  or distance between physical objects except  in a context of a physical connection between them?** 

 

Can we even say that ,if no interaction occurs then there is no connection at all btw the objects?

 

**(btw can we say -or define it so - that all physical objects are composed of "events"-perhaps not "events" as commonly used  to mean coordinate points on a 4d spacetime diagram but as actual physical interactions)

[studiot]

2 hours ago, geordief said:

Do physical objects only exist in the framework  of the events that went into making them up and changing them?

 

No

But they may look different to an observer in a different frame.

[geordief]

34 minutes ago, studiot said:

No

But they may look different to an observer in a different frame.

Are not all objects created one event at a time?

 

And the spacetime  interval (as I have learned) is independent of frame of reference. -not strictly  relevant  ,but might it show that the objects are composed of "events" ,the connections between    which all frames can agree on?

[swansont]

1 hour ago, geordief said:

Well ,apart from the terms used  can we say that it is meaningless to talk about the separation  or distance between physical objects except  in a context of a physical connection between them?** 

Again, there must a be a context to this - it might be meaningless under certain circumstances but not in general.

 

1 hour ago, geordief said:

Can we even say that ,if no interaction occurs then there is no connection at all btw the objects?

No. 

1 hour ago, geordief said:

**(btw can we say -or define it so - that all physical objects are composed of "events"-perhaps not "events" as commonly used  to mean coordinate points on a 4d spacetime diagram but as actual physical interactions)

No.

[geordief]

7 minutes ago, swansont said:

No (in response to  myquote"Can we even say that ,if no interaction occurs then there is no connection at all btw the objects")

What about 2  events ,one of which is outside the light cone of the other.

Eg I cannot today have any causal effect on the life SwansontT's  activities yesterday.

Can I not say that there is no connection between an event in my today and your yesterday? 

But I can't extrapolate  that to SwansontT yesterday  having no connection to my today even if no interaction occurs?(is it enough that the probability of an interaction is not zero?)

 

 

[swansont]

3 hours ago, geordief said:

What about 2  events ,one of which is outside the light cone of the other.

Eg I cannot today have any causal effect on the life SwansontT's  activities yesterday.

Can I not say that there is no connection between an event in my today and your yesterday? 

But I can't extrapolate  that to SwansontT yesterday  having no connection to my today even if no interaction occurs?(is it enough that the probability of an interaction is not zero?)

If the two events are outside of the other's light cone, then you can say that they have no interaction, when considering that event. 

[geordief]

47 minutes ago, swansont said:

If the two events are outside of the other's light cone, then you can say that they have no interaction, when considering that event. 

Including any quantum effects?

 

(Not that I can think of any)

Edited August 30, 2022 by geordief

[Markus Hanke]

13 hours ago, geordief said:

Including any quantum effects?

The relativistic formulation of quantum mechanics respects all the usual laws of SR, so there can be no physical interaction (as in: exchange of information) if the events are not within or on each other’s light cones. There can, however, be a correlation between measurements that are space-like separated, as is the case with quantum entanglement.

18 hours ago, geordief said:

Can I not say that there is no connection between an event in my today and your yesterday? 

What swansont did yesterday can very well affect your state of affairs today - but not vice versa. So this isn’t a mutual “interaction” as such, but rather a one-way causal influence.

Just be careful with the term “event” - in relativity, this term has a very specific meaning, being a point in space at a single instant in time. It doesn’t mean an occurrence with temporal extension, such as a car accident.

[studiot]

4 hours ago, Markus Hanke said:

Just be careful with the term “event” - in relativity, this term has a very specific meaning, being a point in space at a single instant in time. It doesn’t mean an occurrence with temporal extension, such as a car accident.

 

+1

And a single point in space, ie a single point in spacetime.

So it is not just not a car crash it is also not a car.

Edited August 31, 2022 by studiot

[geordief]

1 hour ago, studiot said:

 

+1

And a single point in space, ie a single point in spacetime.

So it is not just not a car crash it is also not a car.

 

On 8/30/2022 at 11:53 AM, geordief said:

(btw can we say -or define it so - that all physical objects are composed of "events"-perhaps not "events" as commonly used  to mean coordinate points on a 4d spacetime diagram but as actual physical interactions)

Well ,I thought I had been  observing (trying to ,anyway) the  distinction insofar as my level of education allows

I am very interested in "events"as physical interactions and I do not understand why it should not be possible to  view physical objects as being "composed" of them.(I realize I will be as wrong as I normally am but am I any way close to how the models are to be interpreted?)

 

Of course a physical object is composed of smaller objects  but as we get to the fine (fundamental?) detail  is it not possible  that we are  just "looking" at  interactions?

I have heard it said "everything is fields" 

Are physical objects the result of those fields (self?) interactions  and  do those interactions "make up" what we observe as physical  objects on the macro and micro level?

[studiot]

On 8/30/2022 at 10:16 AM, geordief said:

As a measure of a distance between objects does the term ,"event separation " mean exactly  the same  thing  as  "the spacetime interval"? (as the terms are commonly used)

 

Do physical objects only exist in the framework  of the events that went into making them up and changing them?

Your original question implied to me at any rate larger objects than 'point object', which can be truly modelled by single events.

When you consider objects made up of some/many event points you can run into simultaneity issues. I think this is what Markus was referring to, but I should wait for his and swansont's comments as well.

[geordief]

1 hour ago, studiot said:

Your original question implied to me at any rate larger objects than 'point object', which can be truly modelled by single events.

 

Is a point object the  excitation of its relevant field?

And does excitation equate to "interaction " ?Do those concepts   just overlap -are they distinct?

 

(Apologies  if I am shifting goalposts but they do say that the definition  of madness is to keep repeating  the same mistake over and over  and not making different mistakes one after the other  )😉

 

Edit:I had all kinds of physical  objects in mind  and assume that there must be a connection  between macro and micro objects.

Edited August 31, 2022 by geordief