curved spacetime = ether exist ?

[Kedas]

If we assume that gravity curves spacetime doesn't that mean that we accept there is an ether otherwise there is nothing to curve.

[swansont]

The ether as described as the preferred reference frame doesn't exist, as demonstrated by the existence of stellar aberration and the Michelson-Morley experiment (i.e. we are neither moving nor at rest with respect to it). Space does appear to have have properties, however, but calling those properties the either instead of the previously-used definition confuses the issue if you don't define the term. Call it something else, like the fnarb.

 

Regardless, I think the answer is no. Curved space is a mathematical construct/description. The vacuum has a permeability and permittivity. Does Euclidian/flat space mean the fnarb exists? Or doesn't exist?

[Kedas]

Is it then not more 'correct' to talk about 'curved objects' in a gravity field.

 

 

The vacuum has a permeability and permittivity

I don't see this as a property of space but the property of a field when it isn't changed with matter.

[swansont]

Is it then not more 'correct' to talk about 'curved objects' in a gravity field.

 

I'm not sure I know what you mean by a curved object

 

I don't see this as a property of space but the property of a field when it isn't changed with matter.

 

What field would that be?

[Kedas]

I'm not sure I know what you mean by a curved object

Well if space isn't curved then the same effect can be reached if you curve the object in it instead of the space.

an object is somethng so it can be curved.

What field would that be?

electric and magnetic field

[swansont]

Well if space isn't curved then the same effect can be reached if you curve the object in it instead of the space.

an object is somethng so it can be curved.

 

electric and magnetic field

 

No, I don't think "curving the object" gives you the same effect.

 

The permeability and permittivity are independent of an electric or magnetic field.

[guardian]

Actually, to be more correct, we assume that energy (predominantly locked as mass) curves spacetime OR gravity is the curvature of spacetime. Gravity is not the cause of spacetime curvature it is the resulting effect of it.

 

Nevertheless, aether is a misleading term for space(-time) as Swansont has mentioned for the reasons given however I would beg to differ in that it is merely a mathematical construct (MC). If we do that, IMO, everything becomes just a mathematical construct. We know spacetime curvature exists (it has been observed many a time) just like for example the velocity of a particle exists. If we call spacetime curvature a MC then so is velocity.

 

In my opinion, the way we have modelled space is an approximation to reality and as a result the way we use spacetime becomes a mathematical construct but in reality nothing is a mathematical construct because all that we observe 'exists' - even space.

 

Does Euclidian/flat space mean the fnarb exists? Or doesn't exist?

...I'd say that all it means is that there are many ways to interpret fnarb but regardless, we are modelling something - that something does exist. How approximate to reality that is depends on how well the model describes everything that we can & will observe. Now, we know that neither relativity or QM or any other theory out there describes everything that we observe completely. Holes are abound. More precisely, to describe what we observe we often result to using different models of space. Euclidian space, Minkowski space, etc. and now some exotic forms of space in the various forms of string theory - they're still trying to model something that is real.

[swansont]

Yes, we are modeling something. What I want to know is why it's assumed that flat spacetime is the default, hence the question - does flat spacetime imply the existence or nonexistence of the fnarb?

 

If we grew up in a more pronounced curvature, we might think of flat spacetime as being the strange concept, instead of the other way around. Similar to someone investigating physics in a rapidly rotating system - would they come up with Newton's first law? Travelling in a straight line would not seem to be the normal state of things. Which is similar to curved spacetime - the system is an accelerating frame of reference.

[ydoaPs]

Similar to someone investigating physics in a rapidly rotating system - would they come up with Newton's first law? Travelling in a straight line would not seem to be the normal state of things. Which is similar to curved spacetime - the system is an accelerating frame of reference.

they may well come up with it. we did it being in a location where gravity is apparent.

[swansont]

they may well come up with it. we did it being in a location where gravity is apparent.

 

 

I said more pronounced than our current gravity/curvature. i.e. g cannot reasonably be approximated as a constant

[guardian]

Exactly Swansont. The more I follow Einstein's logic, the more I see that it has been left unfinished. To me (at least), it seems that curvature is the norm and flat space is the anomaly. Afterall, we'd be hard pushed to find flat spacetime within our solar system. Flat spacetime would result from the superposition of equally opposite curvatures of spacetime eg. half-way between 2 planets of equal mass and in that space you would not fall (or feel the effects of gravity from either planet) to either planet - this too would be very difficult to detect as the mid-point would have to be precise.

 

The assumption that spacetime is flat by default IS the fundamental flaw. It is a consensus, AFAIK, that spacetime emerged with the Big Bang and it is only logical that it was not flat as it emerged because of the high energies (& densities) in the primordial universe - so why is it assumed that it was flat. As far as I can gather if energy is the cause of spacetime curvature (and IMO the source of spacetime) there never was any flat space - just superpositions that momentarily resulted in flat space here and there. That's why I say that Einstein's work is unfinished - he also worked on the assumption that spacetime is flat by default.

 

The correction of this fundamental flaw will undoubtedly, IMO, lead to new spacetime model(s)/geometric model(s) and eventually new physics. It is strange though, there seems to be a universal 'evolution' & shift among 'thinkers' (I don't want to isolate great findings - new thoughts only to physicists - it's a collective effort) to questioning the fundamental components of the universe - energy + spacetime. We pretty much have a good grasp of the former, but flaws about the latter stop us from unifying all that we know.

[Kedas]

The permeability and permittivity are independent of an electric or magnetic field.

I know permeability and permittivity don't change based on field strength etc. but they do change based on the material the field is in.

 

Let me give you an simple example about what I mean:

If you throw a ball in empty space it will have certain behavior properties. Now when you do the same in air it will be different.

Instead of saying these are properties of air I say it are the properties of the ball when it's influented by the air.

(the ball is the field)

 

Why the little 'twist', because then you don't give 'nothing alias empty space' a property, because then you say a field property when it's not influented.

[swansont]

Exactly Swansont. The more I follow Einstein's logic' date=' the more I see that it has been left unfinished. To me (at least), it seems that curvature is the norm and flat space is the anomaly. Afterall, we'd be hard pushed to find flat spacetime within our solar system. Flat spacetime would result from the superposition of equally opposite curvatures of spacetime eg. half-way between 2 planets of equal mass and in that space you would not fall (or feel the effects of gravity from either planet) to either planet - this too would be very difficult to detect as the mid-point would have to be precise.

[/quote']

 

Perhaps I'm not making my point very well - given what you said you shouldn't be agreeing with me. The problem is that there are large regions where spacetime is approximately flat. Just like local terrain may seem flat, even though the earth is a sphere. Relativistic effects are foreign to us because normal experiences are way on the other end of the scale - speeds much smaller than c, and only gradual curvature - so the world seems linear to us. Put another way, the linear approximation works well, and that becomes our common point of reference. So when the approximation breaks down, and the nonlinear reality surfaces, we think it odd (until we get used to the idea, though some choose to deny the existence of the nonlinear effects. But I digress...)

 

So we think that space is flat and Galilean transforms are right because they are approximately so in everyday experiences. I doesn't seem unusual to think that space has no properties, and only the new idea of curvature promted the question of the OP. What I'm saying is what if the nonlinearities were more pronounced - we might then think that flatness was the special case.

 

Imagine you are on a rotating disk, sealed away from everything - no external references to give you an indication that you are rotating. You throw a ball, and it curves noticably - if you want it to reach some specific target, you have to throw it in another direction. That's what's "normal" to you. I think under those circumstances, you wouldn't come up with the concept of "no force = straight line motion" Cartesian coordinates wouldn't be useful - you'd probably come up with a curved coordinate system to explain motion in the most straightforward way. And that's what GR basically is - a curved coordinate system that takes the place of what we used to think was a force.

[guardian]

I do get what you are saying Swansont. I'm agreeing with your questioning of the assumption of default flat space Perhaps I've clouded my response with a view from another angle. I think I was just trying to elaborate and question further this assumption (of default flat space). What makes you think I should be disagreeing? I am not disagreeing with relativity - I just believe there should have been a 3rd installment to it ie. SRT, GRT, URT - unfortunatelly Einstein stopped short (I think he ran out of gedankens ) My gedankens have picked up where he left off.

 

And I also agree totally with your last post.

[swansont]

Maybe I just misunderstood what you had said. (I have a cold and my thoughts are a little cloudy) I thought you were stating a different position while saying, "I agree." No problem.