question4477

Is Space-Time a Physical Entity or a Mathematical Model?

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koti

 

I understand the question differently - more literally. I much more prefer to try to answer the question as you see it though.

 

But I am addressing the original question, though I would agree that it was not well phrased since the word 'physical' is arguably redundant.

 

 

Oxford English Dictionary

 

Entity

 

Existence of a thing as opposed to its qualities or relations.

 

This is exactly what I am saying.

 

You need to separate the thing (spacetime) from its properties (qualities or relations) to decide if it is an entity.

 

If this cannot be done then spacetime is not an entity.

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You need to separate the thing (spacetime) from its properties (qualities or relations) to decide if it is an entity.

 

That is extremely questionable.

 

Something that could exist without any attributes?

 

As easy to require that something must have attributes to be considered as an entity in the first place.

 

I know there may be a dictionary definition of "entity" that may specify an attributeless quality but I would not be inclined to go along with that.

 

Rather no entities than such an appalling vista ;)

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Don't you get the feeling we're going in cicrcles trying to answer "this" "question"

We can't even formulate the question properly.

I think I already answered best I can but I answered a question which I formulated myself it seems.

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Here's an issue that came to mind. Anything that is an actual, physical thing must either have mass or be massless. There's no third option. If spacetime has mass, you will quickly run into issues with relativity. If it's massless, it must move at c, which again makes you run into problems.

 

So which is it, and how do you reconcile that property with relativity?

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That is extremely questionable.

 

Something that could exist without any attributes?

 

As easy to require that something must have attributes to be considered as an entity in the first place.

 

I know there may be a dictionary definition of "entity" that may specify an attributeless quality but I would not be inclined to go along with that.

 

Rather no entities than such an appalling vista ;)

Spacetime is an abstraction comprised of some measurable properties. An association has been made between those properties and called 'spacetime'. That association can change or be added to if someone comes up with a more complete idea.

Edited by StringJunky

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Don't you get the feeling we're going in cicrcles trying to answer "this" "question"

 

Guilty , your honour.

Here's an issue that came to mind. Anything that is an actual, physical thing must either have mass or be massless. There's no third option. If spacetime has mass, you will quickly run into issues with relativity. If it's massless, it must move at c, which again makes you run into problems.

 

So which is it, and how do you reconcile that property with relativity?

Are you not hoist on your own petard ? You have insisted that it all depends on the model you go by and are now bringing us back to relativity as if it has the top seat at the table.

 

Relativity may be useless when applied to this kind of a reality /entity question (which may not be a proper question in the first place)

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That is extremely questionable.

 

Something that could exist without any attributes?

 

As easy to require that something must have attributes to be considered as an entity in the first place.

 

I know there may be a dictionary definition of "entity" that may specify an attributeless quality but I would not be inclined to go along with that.

 

Rather no entities than such an appalling vista ;)

 

 

Forgive me for using a standard English word in a standard manner.

 

Let us consider the implications of this.

 

Is a human an entity?

 

If we agree to say yes then

 

Cut off a hand.

 

Is the hapless human still an entity?

 

Yes again I think.

 

Now say I (a human entity) am angry.

 

Anger Is a property, not an entity.

 

I can transfer it to you by shouting names at you so you become angry.

 

I may even become no longer angry as a result.

 

Am I no longer an entity?

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Forgive me for using a standard English word in a standard manner.

 

Let us consider the implications of this.

 

Is a human an entity?

 

If we agree to say yes then

 

 

Do we agree that? It seems far from obvious to me.

Edited by geordief

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Do we agree that? It seems far from obvious to me.

I await your substantiation for this.

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I await your substantiation for this.

 

You mean I have to agree or not (that a human is an entity) ? Then ,I probably disagree on the basis it is not proven (to repeat what I already implied)

 

Or do you want me to disprove what I simply think is unlikely or unprovable?

Edited by geordief

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Here's an issue that came to mind. Anything that is an actual, physical thing must either have mass or be massless. There's no third option. If spacetime has mass, you will quickly run into issues with relativity. If it's massless, it must move at c, which again makes you run into problems.

 

So which is it, and how do you reconcile that property with relativity?

If spacetime is moving at c what would be the problem?

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Are you not hoist on your own petard ? You have insisted that it all depends on the model you go by and are now bringing us back to relativity as if it has the top seat at the table.

 

Relativity may be useless when applied to this kind of a reality /entity question (which may not be a proper question in the first place)

 

Bring me a better model, then. We'll discuss it in terms of that (but then, that would be an admission that GR is wrong and how can it represent reality?)

If spacetime is moving at c what would be the problem?

 

How do you move with respect to spacetime at any other speed? How can you be at rest in a coordinate system, if it's moving at c?

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Bring me a better model, then. We'll discuss it in terms of that (but then, that would be an admission that GR is wrong and how can it represent reality?)

 

 

I will (but you may have to wait a while :mellow: ) If GR is right then it seems it is possible for models to only apply under certain conditions. Is that a problem?

 

If there is no model that applies in all circumstances we can imagine , is that a problem or is a patchwork quilt of models a reasonable method of analysing the physical processes we observe?

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I will (but you may have to wait a while :mellow: ) If GR is right then it seems it is possible for models to only apply under certain conditions. Is that a problem?

 

If there is no model that applies in all circumstances we can imagine , is that a problem or is a patchwork quilt of models a reasonable method of analysing the physical processes we observe?

If GR is right then other models that work will look just like it.

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If GR is right then other models that work will look just like it.

Why? GR doesn't look like Newtonian physics,does it ? Wasn't Newtonian physics as right then as GR Is right now?

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If GR is right then other models that work will look just like it.

Could you elaborate on this statement?

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Why? GR doesn't look like Newtonian physics,does it ? Wasn't Newtonian physics as right then as GR Is right now?

GR embodies Newtonian gravity where the latter is correct. Quantum gravity theory will embody GR where it is correct.

Could you elaborate on this statement?

Where GR is correct, other models will have to agree with it in those same areas and not give different predictions because, otherwise, they will be wrong.
Edited by StringJunky

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So new models fit over old models like Russian dolls.

 

What about my question though as to a patchwork quilt arrangement of models...Is that ruled out ? Do we have to have one model that rules them all or is an ad hoc arrangement feasible ?

 

Is "adhocery" a sure signal that something is wrong or could the universe be built so that multiple models do apply and there really is no one"overarching" model ? (and never will be)

 

 

Also ,is it possible that we are restricted in our understanding of the universe because we are a part of it and can never look at it from the outside.?

 

Is there some kind of principle involved with that ?

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Also ,is it possible that we are restricted in our understanding of the universe because we are a part of it and can never look at it from the outside.?

 

Is there some kind of principle involved with that ?

Yes, I think the principle is called "going in circles on an internet forum"

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Yes, I think the principle is called "going in circles on an internet forum"

You are having a laugh or you think I am wasting my time and learning nothing?

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You are having a laugh or you think I am wasting my time and learning nothing?

No, he's having problems getting his head around the way science works, just like you are; it's not easy.

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You are having a laugh or you think I am wasting my time and learning nothing?

I'm having a laugh. I don't think you are wasrimg your time nor do I think you are not learning. Just a joke, thats all.

No, he's having problems getting his head around the way science works, just like you are; it's not easy.

I dont know about geordief but you are partially right about me. Maybe not that Im having problems with how science works because the scientific method is pretty straight forward but Im having difficulties in applying it due to the lack od knowlesge and tools (especially math)

However, we are discussing a philosophical issue here which in many ways is beyond the scope of science.

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Why? GR doesn't look like Newtonian physics,does it ? Wasn't Newtonian physics as right then as GR Is right now?

 

 

Well, Newtonian gravity was suspect when it couldn't account for the precession of Mercury. That was part of the motivation behind GR.

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I'm having a laugh. I don't think you are wasrimg your time nor do I think you are not learning. Just a joke, thats all.

 

I dont know about geordief but you are partially right about me. Maybe not that Im having problems with how science works because the scientific method is pretty straight forward but Im having difficulties in applying it due to the lack od knowlesge and tools (especially math)

However, we are discussing a philosophical issue here which in many ways is beyond the scope of science.

But it's about a purely scientific concept, isn't it? It can't be beyond the scope of science because Einstein's mentor, Minkowski, conceived it. Einstein curved it in GR as a way of describing gravity. Spacetime is a model.

Edited by StringJunky

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