question4477

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

Recommended Posts

Model of the sun orbiting the earth was a bad model which did not reflect reality - Can we agree on that? What you wrote about building a model where dark is a phenomenon and light is the absence of dark implies that nothing can be established and used as refference

.

Hypotheticaly...if string theory or some other new theory manages to put QM, GR and gravity gracefuly together proving on its way that spacetime is part of something far greater and far more complex than what we know now, would this mean that spacetime would become "unreal" or "real" all of the sudden? Would mass suddenly stop having an impact on spacetime if that new fantastical theory of everything would become available?

If a quantum explanation comes to fruition then gravity will be mediated by graviton virtual particles and spacetime curvature, as a way of describing gravity, will fade away, I think. I reckon there'll still be some sort of geometry to hang things on though and perhaps describe the paths of the gravitons.

Edited by StringJunky

Share this post


Link to post
Share on other sites

The question at hand is seriously flawed in my opinion:

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

Einstein's equations which deal with spacetime are a MODEL of spacetime. Spacetime is not a model unless Einstein's equations are a model of a model? As far as I know, these equations have been experimentally confirmed numerous times - time dillation, gps time compensation in sattelites, etc. If we agree that Einstein's model is accurate in describing spacetime this should mean that its an accurate model. I realise that its not accurate in describing the quantum world and many other fenomena but that doesnt mean that spacetime is a model nor that spacetime is or is not an entity does it- for the same reason that you do not use scissors to hammer in a nail.

Share this post


Link to post
Share on other sites

Model of the sun orbiting the earth was a bad model which did not reflect reality - Can we agree on that? What you wrote about building a model where dark is a phenomenon and light is the absence of dark implies that nothing can be established and used as refference

I agree totally. But at the time, it was considered a good model. We can build a model of dark should we choose to. It won't be a very good one, but it will be a model nonetheless.

 

But the point is that models that fail can't represent reality. All models fail at some point.

 

Hypotheticaly...if string theory or some other new theory manages to put QM, GR and gravity gracefuly together proving on its way that spacetime is part of something far greater and far more complex than what we know now, would this mean that spacetime would become "unreal" or "real" all of the sudden?

That's the issue I have been trying to illuminate. But it's only a problem if you think the model depicts reality. Since I am not, I don't see why I would need to defend this shortcoming.

 

Would mass suddenly stop having an impact on spacetime if that new fantastical theory of everything would become available?

As I said before, the effects are real, even if the model itself is not. Again, this is only an issue for someone advancing the notion that models are depicting reality.

The question at hand is seriously flawed in my opinion:

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

Einstein's equations which deal with spacetime are a MODEL of spacetime. Spacetime is not a model unless Einstein's equations are a model of a model? As far as I know, these equations have been experimentally confirmed numerous times - time dillation, gps time compensation in sattelites, etc. If we agree that Einstein's model is accurate in describing spacetime this should mean that its an accurate model. I realise that its not accurate in describing the quantum world and many other fenomena but that doesnt mean that spacetime is a model nor that spacetime is or is not an entity does it- for the same reason that you do not use scissors to hammer in a nail.

 

 

Spacetime is part of the model. Is there some way to confirm its existence independent of the model?

  • Upvote 1

Share this post


Link to post
Share on other sites

The question at hand is seriously flawed in my opinion:

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

Einstein's equations which deal with spacetime are a MODEL of spacetime. Spacetime is not a model unless Einstein's equations are a model of a model? As far as I know, these equations have been experimentally confirmed numerous times - time dillation, gps time compensation in sattelites, etc. If we agree that Einstein's model is accurate in describing spacetime this should mean that its an accurate model. I realise that its not accurate in describing the quantum world and many other fenomena but that doesnt mean that spacetime is a model nor that spacetime is or is not an entity does it- for the same reason that you do not use scissors to hammer in a nail.

Forget about the ontology because science doesn't deal with it; it only deals with models. Ontology is a philososophical subject.

Share this post


Link to post
Share on other sites

I agree totally. But at the time, it was considered a good model. We can build a model of dark should we choose to. It won't be a very good one, but it will be a model nonetheless.

 

But the point is that models that fail can't represent reality. All models fail at some point.

 

You agree that a model of the sun orbiting the earth was flawed. We have a new model now which states that the earth is orbiting the sun. You state that all models fail at some point. I'm sory but Im having difficulties agreeing with that logic.

Share this post


Link to post
Share on other sites

You agree that a model of the sun orbiting the earth was flawed. We have a new model now which states that the earth is orbiting the sun. You state that all models fail at some point. I'm sory but Im having difficulties agreeing with that logic.

 

 

For example, a better model is that the Sun and the Earth both orbit a common point, the barycentre.

 

And then ... we might consider that they both orbit the centre of the galaxy. But then we have to start thinking about dark matter, otherwise the model is not accurate.

 

But then we have to ask what dark matter is ...

  • Upvote 1

Share this post


Link to post
Share on other sites

 

 

For example, a better model is that the Sun and the Earth both orbit a common point, the barycentre.

 

And then ... we might consider that they both orbit the centre of the galaxy. But then we have to start thinking about dark matter, otherwise the model is not accurate.

 

But then we have to ask what dark matter is ...

When you are at the stage of asking what dark matter is (or any previous stage for that matter) does it mean that the earth orbiting the sun model has failed? Or even remotely has it become inaccurate? Edited by koti

Share this post


Link to post
Share on other sites

You agree that a model of the sun orbiting the earth was flawed. We have a new model now which states that the earth is orbiting the sun. You state that all models fail at some point. I'm sory but Im having difficulties agreeing with that logic.

Our model of the earth going around the sun was part of Newtionian physics, which was replaced by GR, which is incompatible with QM.

 

Do you have a model without known flaws that has supplanted GR?

Share this post


Link to post
Share on other sites

 

 

 

 

Do you have a model without known flaws that has supplanted GR?

 

This question is unfair and is an invitation into a quarrel.

 

 

 

how does this support koti's position? (which seems to be "we can't tell, so let's call it real")

 

This false statement of yours about my position is also unfair and is alao an attempt to get into a quarrel.

 

Would you consider changing your rhetoric with me? :)

Share this post


Link to post
Share on other sites

 

This question is unfair and is an invitation into a quarrel.

 

 

 

This false statement of yours about my position is also unfair and is alao an attempt to get into a quarrel.

 

Would you consider changing your rhetoric with me? :)

You are over reacting IMHO. Nobody is driving you into a quarrel.

However, thank you because I learned the word "quarrel" in English.

Share this post


Link to post
Share on other sites

Forget about the ontology because science doesn't deal with it; it only deals with models. Ontology is a philososophical subject.

...is good advice but a bit impractical . Scientists (or people interested in science ) will never drop that subject and the best that can be done is to compartmentalize the question.

 

My personal workaround is to refer to the model and the "modeled",.(evading the elephant in the room perhaps)

 

As to actual nature of "reality" I wonder if it is infinitely multi -faceted or unitary ( but that is way off topic and completely speculative).

 

A final point, much is made of different posters' "word salad" and it is plain to see at times but I do think clarity of language ,insofar as it is actually achievable is an important tool in the locker in these difficult subjects.

 

pps: Is the "ontological" question actually an aide to scientific understanding like the pea under the princess' bed or or distraction from the task in hand?

Edited by geordief

Share this post


Link to post
Share on other sites

This question is unfair and is an invitation into a quarrel.

 

 

Why is it unfair?

Share this post


Link to post
Share on other sites

As to actual nature of "reality" I wonder if it is infinitely multi -faceted or unitary ( but that is way off topic and completely speculative).

Perhaps as in processed (by the brain) reality vs unprocessed reality..?

Share this post


Link to post
Share on other sites

 

 

Why is it unfair?

"Do you have a model without known flaws that has supplanted GR?"

Obviously you do not believe that I can answer this question positively. If you know the answer to your question which is "no" then what is it exactly that you are trying to achieve by asking it? Thank you for fixing my post properly btw.

Edited by koti

Share this post


Link to post
Share on other sites

"Do you have a model without known flaws that has supplanted GR?"

Obviously you do not believe that I can answer this question positively. If you know the answer to your question which is "no" then what is it exactly that you are trying to achieve by asking it? Thank you for fixing my post properly btw.

 

 

To support my position. I thought that would be obvious.

Share this post


Link to post
Share on other sites

 

 

To support my position. I thought that would be obvious.

 

Noted.

Share this post


Link to post
Share on other sites

Perhaps as in processed (by the brain) reality vs unprocessed reality..?

Not what I had in mind. I wondered if even the unprocessed reality might be as likely to be multi-faceted as unitarian .

 

I don't see any consequences that could be attached to it. except as a further invitation to treat the "reality" subject as just mind games(no harm in that of course) .

Share this post


Link to post
Share on other sites

Koti: Veni, Vidi, quod imitentur. - I came, I saw. I modelled it. That's all a scientist does. Ultimately, that's all anyone can do.

Edited by StringJunky

Share this post


Link to post
Share on other sites

Going back to the original question - "Is Space Time a Physical Entity or a Mathematical Model"

It would be nice to establish and agree on some reference points which we can use to cope with finding a potential answer to this twisted question:

 

Reference points:

 

Einstein's General Relativity provides a model of space-time. That model has been confirmed experimentally. That model does not reflect a complete picture of our reality. That model fails at explaining how small scale reality works which QM deals with. GR and QM are not compatible with each other. That incompatibility does not mean that Einstein's model is flawed, it means that it is not complete.

Can we all agree on the above or am I mistaken somewhere?

 

Edit:

Example:

 

A sail boat equipped with a motor has more functionality than a sailboat without a motor installed. This does not mean that a sailboat without a motor is faulty or flawed.

Edited by koti

Share this post


Link to post
Share on other sites

Going back to the original question - "Is Space Time a Physical Entity or a Mathematical Model"

It would be nice to establish and agree on some reference points which we can use to cope with finding a potential answer to this twisted question:

 

Reference points:

 

Einstein's General Relativity provides a model of space-time. That model has been confirmed experimentally. That model does not reflect a complete picture of our reality. That model fails at explaining how small scale reality works which QM deals with. GR and QM are not compatible with each other. That incompatibility does not mean that Einstein's model is flawed, it means that it is not complete.

Can we all agree on the above or am I mistaken somewhere?

In the context of this discussion, I think most scientists would say GR is incomplete but correct within it's domain of application, up to the point where it fails. Ultimately, this happens to all models. What you've said is right so what's the problem?

Edited by StringJunky

Share this post


Link to post
Share on other sites

Going back to the original question - "Is Space Time a Physical Entity or a Mathematical Model"

It would be nice to establish and agree on some reference points which we can use to cope with finding a potential answer to this twisted question:

 

Reference points:

 

Einstein's General Relativity provides a model of space-time. That model has been confirmed experimentally. That model does not reflect a complete picture of our reality. That model fails at explaining how small scale reality works which QM deals with. GR and QM are not compatible with each other. That incompatibility does not mean that Einstein's model is flawed, it means that it is not complete.

Can we all agree on the above or am I mistaken somewhere?

 

Edit:

Example:

 

A sail boat equipped with a motor has more functionality than a sailboat without a motor installed. This does not mean that a sailboat without a motor is faulty or flawed.

 

Your example of what you mean is fine, as is your reasoning about models in general.

 

However your reasoning starts from the premise that spacetime and relativity (general or special) are synonymous.

 

They are not.

 

Relativity provides a (mathematical) model of something (our universe) that would still be there if the model were at some time shown to be incorrect or inadequate.

 

It is a matter of semantics whether we call that something 'the universe', 'spacetime' or my 'backyard'.

 

Edit : added comment.

 

I take the question to mean,

 

Is there a separate fabric (like the grid on my avatar) that everything (matter etc) exists in that we can call spacetime?

Edited by studiot
  • Upvote 1

Share this post


Link to post
Share on other sites

 

Your example of what you mean is fine, as is your reasoning about models in general.

Good to hear.

 

However your reasoning starts from the premise that spacetime and relativity (general or special) are synonymous.

No it does not. Spacetime as I see it is an entity in which relativity effects are having their show and that entity plays an active role in the play. These relativity effects are explained by Einstein's equations. These equations are a model.

 

They are not.

I agree.

 

Relativity provides a (mathematical) model of something (our universe) that would still be there if the model were at some time shown to be incorrect or inadequate.

I agree.

 

It is a matter of semantics whether we call that something 'the universe', 'spacetime' or my 'backyard'.

I agree as well. For that reason I'm close to the conclusion that trying to answer this twisted question is beyond me.

I don't think I can come up with a better answer to this (flawed) question than what I wrote above:

 

"Spacetime as I see it is an entity in which relativity effects are having their show and that entity plays an active role in the play. These relativity effects are explained by Einstein's equations. These equations are a model"

Share this post


Link to post
Share on other sites

 

Relativity provides a (mathematical) model of something (our universe) that would still be there if the model were at some time shown to be incorrect or inadequate.

 

 

But the question is about spacetime specifically, and that's part of relativity. Is there anything in the theory that says that spacetime is a real, physical thing? Prior to that, we considered space and time separately. Were both of those already considered to be actual, physical things?

Share this post


Link to post
Share on other sites

 

 

But the question is about spacetime specifically, and that's part of relativity. Is there anything in the theory that says that spacetime is a real, physical thing? Prior to that, we considered space and time separately. Were both of those already considered to be actual, physical things?

 

I was called away whilst adding to post 121 so Koti didn't see my last comment.

 

I don't know if you did either, but it addressed your question.

 

Put another way I am suggesting that the question (as I understand it) asks if there is a 'container' , separable from the contents, which would still be there if our current version of the equations of relativity were changed again?

 

Don't forget that

 

1) There is more than one solution to the equations of relativity, we try to pick the most appropriate.

 

2) The equations themselves have chaged several times over the last century.

The equations of relativity have changed m

Share this post


Link to post
Share on other sites

 

I was called away whilst adding to post 121 so Koti didn't see my last comment.

Noted.

 

I don't know if you did either, but it addressed your question.

 

Put another way I am suggesting that the question (as I understand it) asks if there is a 'container' , separable from the contents, which would still be there if our current version of the equations of relativity were changed again?

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

 

Don't forget that

 

1) There is more than one solution to the equations of relativity, we try to pick the most appropriate.

 

2) The equations themselves have chaged several times over the last century.

The equations of relativity have changed m

Someone got called out again while typing? :)

 

As for the question you stated:

"Is there a separate fabric (like the grid on my avatar) that everything (matter etc) exists in that we can call spacetime?"

I am a physics hobbyist and I'm sure I lack many crucial tools (especially math) to understand this stuff properly therefore my comments I'm sure might be crude to you.

Having that out of the way, the answer I got is pretty straight forward - No.

First of all, spacetime as I understand it, is not separate from anything. Matter, mass and gravity are inevitably and firmly connected and related to spacetime - opposite of separate to me.

Matter doesn't exist within spacetime, it co-exist with it - it cannot exist without it. If I understand correctly, spacetime in large scales always reacts in repeatable ways with mass and velocity (I'm not sure if I'm correct here, are there any repeatable, experimental findings confirming that?)

My crude explanation of relativity above, leads me to assume that spacetime is an entity.

 

Edited by koti

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now