question4477

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

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Space time is something that was created by einstein because it is vague. Its much easier to imagine time contracting (time isnt a thing its an idea) than it is a physical object (speaking to the michaelson-morley experiements obviously). As to your question it is neither, it is simply a fudge factor.

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That would depend on your model, wouldn't it?

It seems so fundamental to me.. How would a choice of model change things? Any observation has to involve a signal from the area investigated and that signal can surely only emanate from an area that contains energy. It is possible to extrapolate from a collection of results that a particular local area is seemingly or probably devoid of "returns" and so ,in this case an area of darkness.

 

But this "darkness finding" cannot be found directly -only by inference.

 

Are there any models that allow one to detect darkness directly?

Edited by geordief

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But this "darkness finding" cannot be found directly -only by inference.

A light-meter in spot mode? It will measure shades of darkness or luminance; depends which way you want look at the readings.

Edited by StringJunky

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A light-meter in spot mode? It will measure shades of darkness or luminance; depends which way you want look at the readings.

I was thinking in terms of absolute darkness or presence of light.

 

Did I lose the plot?

 

Look at Swansont's post#66 that I answered.(and#63)

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It seems so fundamental to me.. How would a choice of model change things? Any observation has to involve a signal from the area investigated and that signal can surely only emanate from an area that contains energy. It is possible to extrapolate from a collection of results that a particular local area is seemingly or probably devoid of "returns" and so ,in this case an area of darkness.

 

But this "darkness finding" cannot be found directly -only by inference.

 

Are there any models that allow one to detect darkness directly?

 

Energy? What's that, absent a model to explain it?

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Energy? What's that, absent a model to explain it?

Are you getting round to saying that there are no areas without energy as I may have implied-and so no areas which can actually be described as dark?

 

And so absolute darkness doesn't exist ,just gradations?

 

Is that quantum theory?

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I am not sure that using instruments is any different than using our senses. They are just instruments for observing the world.

Referring to this ^ and the OP:

Gravitational waves...do they not substantiate the existence of space-time?

Also what about this: NASA Announces Results of Epic Space-Time Experiment?

 

PS. Sorry, I just noticed that Gravity Probe B was already covered in the first few posts of this thread.

Edited by Memammal

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Referring to this ^ and the OP:

Gravitational waves...do they not substantiate the existence of space-time?

Also what about this: NASA Announces Results of Epic Space-Time Experiment?

 

PS. Sorry, I just noticed that Gravity Probe B was already covered in the first few posts of this thread.

he results support the model of spacetime but it doesn't mean spacetime exists as a phenomenon, as described in GR. It is known that GR is incomplete and a more complete model using quantum mechanics may arise and what is called 'spacetime' in GR now may be called something else in a quantum model later, with modified or different formulas, probably,. and a different explanation behind the results. The only thing that won't change is the data.

Edited by StringJunky

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Think of an OS map as an analogy. Although the elevation contours on a map look instinctively like hills to us, they are really abstractions of the real thing.
Are those lines real? They are not a direct impression of hills, like in a photograph, are they; it require some extra mental gymnastics and interpretation.
Truth be told, we are heading down a rabbit-hole...fast. :)

 

i have lost episodes, sorry for that.

 

In your example, the coast line is just another of these lines, the first one. If the level of waters increase, the new coast will follow one of these lines.

And the coast is real.

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In your example, the coast line is just another of these lines, the first one. If the level of waters increase, the new coast will follow one of these lines.

And the coast is real.

 

 

Is it?

https://en.wikipedia.org/wiki/Coastline_paradox

 

In other words, the coast is model-dependent.

Edited by Strange
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Is it?

https://en.wikipedia.org/wiki/Coastline_paradox

 

In other words, the coast is model-dependent.

You are tragic.

----------------

The level of accuracy does not erase the coast line.

 

And yes the whole map is model dependent. In all cases topographical maps are based on a projection system. National as far as I know.

But I don't think this comment or yours add anything to the discussion. Except maybe that the model is just an approximation of reality. Even if you increase the accuracy to a hilarious level you will miss the reality.

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i have lost episodes, sorry for that.

 

In your example, the coast line is just another of these lines, the first one. If the level of waters increase, the new coast will follow one of these lines.

And the coast is real.

The point of my example, as I already said, was about the contour lines representing altitutude./height is an abstraction.

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The point of my example, as I already said, was about the contour lines representing altitutude./height is an abstraction.

Yes and I said that if the water level increase it stops to be an abstraction and becomes reality.

You can sometimes see it in real life with the vegetation suddenly changing with altitude.

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Are you getting round to saying that there are no areas without energy as I may have implied-and so no areas which can actually be described as dark?

 

And so absolute darkness doesn't exist ,just gradations?

 

Is that quantum theory?

 

 

Quantum theory is another model. You keep reconfirming that everything we deduce from observation is model dependent.

 

And yes the whole map is model dependent. In all cases topographical maps are based on a projection system. National as far as I know.

But I don't think this comment or yours add anything to the discussion. Except maybe that the model is just an approximation of reality. Even if you increase the accuracy to a hilarious level you will miss the reality.

 

Whether the model is the reality is what the discussion seems to be about, so I fail to see how this does not add to the discussion.

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Quantum theory is another model. You keep reconfirming that everything we deduce from observation is model dependent.

 

 

I didn't realize that I was arguing against that (I could easily have implied it without realizing it)

 

Can you point out where I was doing or did that ? (or maybe I was off topic?)

 

I hope that my lack of proper understanding of the subject is a given (if that has any bearing).

Edited by geordief

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I didn't realize that I was arguing against that (I could easily have implied it without realizing it)

 

Can you point out where I was doing or did that ? (or maybe I was off topic?)

 

I hope that my lack of proper understanding of the subject is a given (if that has any bearing).

 

 

I said whether you are detecting light or dark depends on your model and you seemed to disagree with that.

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I said whether you are detecting light or dark depends on your model and you seemed to disagree with that.

Was I not claiming that we cannot detect dark and so (according to that hypothesis ) any model would be equivalent in that regard.?

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Was I not claiming that we cannot detect dark and so (according to that hypothesis ) any model would be equivalent in that regard.?

 

 

But what if my model is that there is a quantity of dark, and what we consider to be light/bright is just the absence of dark? We have light meters. They would just have the scales backwards on them for dark.

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But what if my model is that there is a quantity of dark, and what we consider to be light/bright is just the absence of dark? We have light meters. They would just have the scales backwards on them for dark.

At the time I entered the discussion I thought it was reasonable to talk of absolute darkness (perhaps as an example of any gap).

 

Yes of course if you have a model that works in terms of gradations of light then total darkness is a limit of the lack of light reading.

 

But even in this model does not the light reading have a different quality to the dark reading?

 

It surely makes no sense to talk of light as an absence (inverse?) of darkness,does it whereas it may do the other way round .

 

Why is that?

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"Dark" is absence of light. Isn't "dark" just a concept which is not dependent on models? How does that correlate with spacetime being or not being real/a model ?

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At the time I entered the discussion I thought it was reasonable to talk of absolute darkness (perhaps as an example of any gap).

 

Yes of course if you have a model that works in terms of gradations of light then total darkness is a limit of the lack of light reading.

 

But even in this model does not the light reading have a different quality to the dark reading?

 

It surely makes no sense to talk of light as an absence (inverse?) of darkness,does it whereas it may do the other way round .

 

Why is that?

 

"Dark" is absence of light. Isn't "dark" just a concept which is not dependent on models? How does that correlate with spacetime being or not being real/a model ?

 

It only makes sense because of the models we have in place. If we had different models, our interpretation of what we observed would be different.

 

We used to think the sun went around the earth, and interpreted our observations accordingly. This is a problem of growing up and being immersed in models we have embraced because they work well.There was a time when that wasn't the accepted model, and the worldview was different as a result. We could very well develop a model where dark was the phenomenon, and light was the absence of dark.

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In science, nothing is written in stone. On the scale of centuries, science is always in flux.

Edited by StringJunky

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In science, nothing is written in stone. On the scale of centuries, science is always in flux.

 

 

And we always interpret science in terms of the best model of the day. But there's always a model.

 

Getting back to the OP, if spacetime is a real physical entity and it comes from GR, what of the fact that we know that GR fails at the quantum level? Can any classical model be considered to be describing real, physical things, given that the model fails at some scale?

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And we always interpret science in terms of the best model of the day. But there's always a model.

Yes, that's what I understand, so far.

 

 

Getting back to the OP, if spacetime is a real physical entity and it comes from GR, what of the fact that we know that GR fails at the quantum level? Can any classical model be considered to be describing real, physical things, given that the model fails at some scale?

Yes, that's what I understand and was getting at earlier in post 83:

 

 

he results support the model of spacetime but it doesn't mean spacetime exists as a phenomenon, as described in GR. It is known that GR is incomplete and a more complete model using quantum mechanics may arise and what is called 'spacetime' in GR now may be called something else in a quantum model later, with modified or different formulas, probably,. and a different explanation behind the results. The only thing that won't change is the data.

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It only makes sense because of the models we have in place. If we had different models, our interpretation of what we observed would be different.

 

We used to think the sun went around the earth, and interpreted our observations accordingly. This is a problem of growing up and being immersed in models we have embraced because they work well.There was a time when that wasn't the accepted model, and the worldview was different as a result. We could very well develop a model where dark was the phenomenon, and light was the absence of dark.

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?

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