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Author Topic: An essay in futility, too long to read :)  (Read 279405 times)

Offline yor_on

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Re: An essay in futility, too long to read :)
« Reply #1350 on: 29/07/2013 15:47:15 »
And another thing, the equivalence principle, if I get this right, is one defining the equivalence between a uniformly, constantly accelerating rocket and a homogeneous gravitational field, as we can assume a perfect sphere of matter, non spinning. But to me it also follows from defining a ' commonly shared 'global SpaceTime' '. Assuming locality to define it instead, I don't think I need to define it this way. Because then I eliminate, at least ignore, observer dependencies. Although they are necessary from a global perspective, it locally becomes a definition where "what you see is what you get". And that is consistent with the way we define a experiment, always locally accomplished, not globally.

We infer from the assumption of a commonly same universe, that if I locally find a experiment to give me one result, and you doing a equivalent experiment find it to give you the same, then we must have such a common universe. As I think it shows you a logic instead.
 

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Re: An essay in futility, too long to read :)
« Reply #1351 on: 29/07/2013 15:55:36 »
Locally defined any absence of gravity and tidal forces should be a place without gravity.
 

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Re: An essay in futility, too long to read :)
« Reply #1352 on: 29/07/2013 15:57:54 »
Also, if matter is what defines gravity, and gravity is what defines a vacuum?
 

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Re: An essay in futility, too long to read :)
« Reply #1353 on: 29/07/2013 16:01:18 »
and then we have accelerations? How about different uniform motions, would they give a different relative mass? assume you could accelerate a spaceship to 99,99 % of lights speed in a vacuum. Then you stop accelerating, would you now expect the relative mass to be gone? And, would you then define that uniform motion to be equivalent to all other uniform motions?
 

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Re: An essay in futility, too long to read :)
« Reply #1354 on: 29/07/2013 16:15:48 »
The point there is that locally, you inside a room in that ship, measuring the output of a lightbulb, shouldn't notice any difference. Globally it becomes something else though.
 

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Re: An essay in futility, too long to read :)
« Reply #1355 on: 29/07/2013 16:52:25 »
So why can't a ship become a black hole at some relativistic speed? That one goes back to 'frames of reference', if you can't find a frame of reference from where that black hole isn't a black hole, then it has to be a black hole. If you can find a frame of reference in where you can be 'at rest' with what another frame would observe as a black hole, observing it differently, then it isn't a black hole. In the cause of the relativistically speeding rocket you just need another rocket, them being at rest with each other, to find that it still is a ship, but trading this for a real black hole no such 'rest frame' should exist as I get it.

You can also consider the definition of lights speed in a vacuum for this. There is no frame of reference possible for fermions in where you can be 'at rest' with light. What a photon sees looking at another photon, 'co-moving' with it, is a question without a answer as I get it.

It also goes back to our definitions of what a 'proper mass' is. "The invariant mass, rest mass, intrinsic mass, proper mass, or (in the case of bound systems or objects observed in their center of momentum frame) simply mass, is a characteristic of the total energy and momentum of an object or a system of objects that is the same in all frames of reference related by Lorentz transformations. If a center of momentum frame exists for the system, then the invariant mass of a system is simply the total energy divided by the speed of light squared. In other reference frames, the energy of the system increases, but system momentum is subtracted from this, so that the invariant mass remains unchanged."

And then we have relativistic mass, defined by "The Einstein field equations (EFE) or Einstein's equations are a set of 10 equations in Albert Einstein's general theory of relativity which describe the fundamental interaction of gravitation as a result of spacetime being curved by matter and energy. First published by Einstein in 1915 as a tensor equation, the EFE equate local spacetime curvature (expressed by the Einstein tensor) with the local energy and momentum within that spacetime (expressed by the stress–energy tensor).

Similar to the way that electromagnetic fields are determined using charges and currents via Maxwell's equations, the EFE are used to determine the spacetime geometry resulting from the presence of mass-energy and linear momentum, that is, they determine the metric tensor of spacetime for a given arrangement of stress–energy in the spacetime. The relationship between the metric tensor and the Einstein tensor allows the EFE to be written as a set of non-linear partial differential equations when used in this way. The solutions of the EFE are the components of the metric tensor. The inertial trajectories of particles and radiation (geodesics) in the resulting geometry are then calculated using the geodesic equation.

As well as obeying local energy-momentum conservation, the EFE reduce to Newton's law of gravitation where the gravitational field is weak and velocities are much less than the speed of light.

Exact solutions for the EFE can only be found under simplifying assumptions such as symmetry. Special classes of exact solutions are most often studied as they model many gravitational phenomena, such as rotating black holes and the expanding universe. Further simplification is achieved in approximating the actual spacetime as flat spacetime with a small deviation, leading to the linearised EFE. These equations are used to study phenomena such as gravitational waves."

and

"The nonlinearity of the EFE makes finding exact solutions difficult. One way of solving the field equations is to make an approximation, namely, that far from the source(s) of gravitating matter, the gravitational field is very weak and the spacetime approximates that of Minkowski space. The metric is then written as the sum of the Minkowski metric and a term representing the deviation of the true metric from the Minkowski metric, with terms that are quadratic in or higher powers of the deviation being ignored. This linearisation procedure can be used to investigate the phenomena of gravitational radiation."

The last idea seems as a analogue to magnifying and shrinking, doesn't it? What was it Einstein thought of magnifying a patch of vacuum? That it would become a 'flat SpaceTime', containing no 'gravity'? Here we have a reasoning suggesting that if you just get far enough from, a neutron star for example, its gravity become negligible, and so you can find a solution.

I don't know. I think gravity is what defines a space myself, but I also think it's observer dependent. If we then include us all, we all should have a unique definition of the gravity, relative ourselves (frame of reference). Makes it real hard to find what joins those differing representations to me. We are here together, on that here can be no doubt, and we can define being 'at rest', at least from a macroscopic point of view.
« Last Edit: 29/07/2013 22:05:37 by yor_on »
 

Offline yor_on

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Re: An essay in futility, too long to read :)
« Reply #1356 on: 29/07/2013 17:04:44 »
Being at rest becomes another mystery to me, when trying to define microscopically. All mass acts on all mass, a particle of restmass (proper mass) should then have a gravitational influence on the vacuum surrounding it. If it has it also should have a time dilation as well as its symmetry, the so called Lorentz contraction. Can you imagine this? The particles making up your body interacting through time dilations and Lorentz contractions? In what way are they 'at rest' with each other? It's more like a equilibrium isn't it, than being 'at rest'? Or maybe one can exchange that for being at rest?

Macroscopically we can ignore microscopic influences though, using the same reasoning as above, them being too small to be noticeable from our macroscopic reality. So, why can't we do something equivalent with gravity, magnifying a space, finding gravity to disappear? Pauli thought it possible if I remember right, but I don't think Einstein agreed on that.
 

Offline yor_on

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Re: An essay in futility, too long to read :)
« Reply #1357 on: 29/07/2013 17:34:28 »
What about gravity as a 'field' then? Disconnect it from mass, existing as a (vacuum?) property possibly, interacting with mass (and 'energy)? That seems to have been Einsteins thoughts about it? If we assume that he didn't seem to enjoy the notion of shrinking a 'space', so disappearing 'gravity'.
 

Offline yor_on

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Re: An essay in futility, too long to read :)
« Reply #1358 on: 29/07/2013 17:35:40 »
That idea seem rather close to the one using Higgs bosons, doesn't it?
 

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Re: An essay in futility, too long to read :)
« Reply #1359 on: 29/07/2013 17:37:26 »
What would proper mass be from such a notion?
 

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Re: An essay in futility, too long to read :)
« Reply #1360 on: 29/07/2013 17:40:12 »
But I don't see how it solves observer dependencies.
 

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Re: An essay in futility, too long to read :)
« Reply #1361 on: 29/07/2013 17:42:46 »
Translating it between frames, doesn't state that you've solved it. It's like the question why 'c' exist. It's what relativity finds its ground in as I think, but it's not solved. Not if you want this minimalistic description of something being 'invariant', representing some ideal universe without observer dependencies. Don't mix those two.
 

Offline yor_on

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Re: An essay in futility, too long to read :)
« Reply #1362 on: 29/07/2013 18:14:30 »
Of course, being foolhardy and brave, we then can define 'gravity' as a 'observer dependent' 'field' :) Or, as a 'observer independent' 'field', if you like, assuming one then able to prove in what way it is observer independent. Although, if it is observer independent, what would a time dilation be, and a Lorentz contraction?
 

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Re: An essay in futility, too long to read :)
« Reply #1363 on: 29/07/2013 21:22:03 »
You know, the more I read about how Einstein thought about gravity, the less I know :) It's very different. Hopefully I will be able to assimilate some of it. A important point with it is that it is assumed to be covariant though, able to translate between metrics, coordinate systems, and masses, presenting you with different inertial frames depending on what coordinate system and metric you use. The best approximation I get to, at the moment, is that he thought of it as 'fields', observer dependent fields when defining it locally, although also as one 'field' defining a SpaceTime. I will blame this on me not looking at gravity before, accepting the equivalence principle as a expression of gravity, although in a restricted fashion, as you need to get away from frame dragging/ tidal forces (as Earth spinning). Using that description one might consider the equivalence principle as some sort of extension to Special relativity, as SR ignore 'gravity', although that would be wrong. The equivalence principle do describe General relativity, and gravity.

We define SpaceTime from the 'inside', and looking at it we find light to bend. It should be possible to turn that around, assuming that what we see 'bending' indeed could be considered a straight line, remaking everything we observe into something different topologically, sort of mind-bending that one though :) If gravity is a acceleration, then Earth accelerates us at one constant uniform gravity. But Einstein clearly differed between a earthly gravity, relative the gravity you find in a uniformly accelerating frame.

It's strange, because I find it so hard to imagine this 'unified field' acting. I can see how it comes from observer dependencies, as ones local position in time and space, also depending on accelerations (as spin), and mass. But using the equivalence principle strictly I'm starting to suspect it may be wrong assuming all accelerated motions able to be expressed as gravity, although it should be so in my mind? Maybe it will become clearer rereading it, maybe not :)

There is one other thing, to me contradicting the idea of not all accelerating motions being a equivalence to gravity. Einstein found a equivalence between inertia and gravity. If I assume all accelerating systems to find a inertia, then they also should have a equivalence to gravity. Just goes to show that I really need to reread this :)

As an example, assume you're living on a neutron star, you measure a distance to some 'patch of space', hey, it's just an idea, not a thesis. You have a observer outside the neutrons stars gravitational field, at rest with it. Will you both agree on a same distance? If there is one 'global field', why won't your coordinate systems fit? Translating it doesn't state that your measurement is wrong, and his right or vice versa. Both should be right, but, if I assume one 'field' then this reasoning becomes inconsistent to me?

Anyway, here's one description of what differs, or joins, a coordinate system, and a metric.
Coordinate Systems and Metrics
« Last Edit: 29/07/2013 22:01:20 by yor_on »
 

Offline yor_on

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Re: An essay in futility, too long to read :)
« Reply #1364 on: 29/07/2013 22:19:03 »
And one more thing, if now gravity is what defines a space, isn't this close to an aether? One could think of it as a aether distorting a space, interacting with densities, as matter/mass, 'energy', accelerations, and uniform motion (if defining it through Lorentz contractions and time dilations). But you would then also need to define this aether as dynamically changing with motion etc, as well as being observer defined from local definitions. It would be a really weird aether, wouldn't it? the original idea was that a aether would give us a fixed point from where we could decide 'absolute motion' etc, but that wouldn't be this one.
 

Offline yor_on

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Re: An essay in futility, too long to read :)
« Reply #1365 on: 31/07/2013 20:44:45 »
I argue for that a arrow points one way, not two, calling time reversal a 'logic', not a proof of time being able to reverse.

Quantum Moxie have thought some about that subject. He also makes a point of " the “law” of physics that has to be maintained under the transformation is the Minkowski metric. This means that time and space must have opposite signs in the signature! Thus, time and space cannot be perfectly interchangeable. If they were, they would have the same sign in the metric and this gedankenexperiment shows the importance of maintaining the metric signature. Anyone who says time and space are the same must explain the origin of the metric signature. I have yet to hear anyone provide a good rationale for this that is not ad hoc." Which, to me then, relates to any and all discussions of how 'space and time change signs' inside a event horizon. It doesn't make sense to me, assuming a world in where you at some point would be able to change your overall temporal direction, while still finding the cup to break locally as it normally would do.

There is one possibility, maybe? If we assume everything to reverse, not only that arrow, then your cup may break as 'normally', while still enabling you to define the arrow as going 'backwards'. Maybe it's possible to think of it as something flowing,  creating whirlpools, as a river? Whirlpools in it can change 'direction', although everything inside a flow behaving normally (locally measured)? In fact, that should be the only version of a arrow 'going backwards' that makes sense to me, and it would then also again open for what is more 'real'. The global 'commonly same' universe we think us see, or the 'local version'. From a philosophical view, defining it locally, then a arrow won't reverse, ever. It points one way, giving you a same life span no matter what you define it to have done relative a universe, no different from the way you find a clock observed close to a event horizon to 'freeze'. The arrow is a local phenomena to me.

Time symmetry and the laws of physics
Closed timelike curve.
 

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Re: An essay in futility, too long to read :)
« Reply #1366 on: 31/07/2013 22:08:49 »
Nah, I can't make it make any sense, although it is alluring to imagine a universe steered by 'something', behind the measurable processes we find. Assuming a arrow is equivalent to 'c' (always locally measured), which I do. How would I reverse 'c'? I can't locally, and neither can I do so 'globally'? So how?
 

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Re: An essay in futility, too long to read :)
« Reply #1367 on: 31/07/2013 22:17:36 »
I think of it this way. I can split 'c' to Planck scale. After that it stops making sense to me. What is under Planck scale is not what we observe assuming the arrow to stop making sense there. Assuming a time reversal connected to 'c' should then mean that instead of not making sense as a arrow, we then should find it reverse, passing Planck scale? With Planck scale then being some sort of 'limit' for a arrow, where it doesn't 'run' any more. Well, it's symmetric I guess :) Good for an SF.
 

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Re: An essay in futility, too long to read :)
« Reply #1368 on: 31/07/2013 22:23:48 »
Even so I expect to be correct macroscopically. The arrow won't turn for you, ever. Although we might be able to find 'immaterial precedents' for lack of a better name, for processes, that behave outside of a arrow, maybe :)
=

But if I really assume it to 'reverse', then you must find a way to show both a effect, and its cause(s), reversed?
Wouldn't that be a interesting universe :)

Even entanglements won't make that proposition, they are, well, 'instantaneous', aren't they? But you don't see any of those 'pairs' giving us a outcome before the measurement. Even if you find them to adapt to your manipulations, 'knowing' them instantaneously, they do it in 'real time', similar to the way we can imagine a clock to 'stop' at a eventhorizon.

A real proof must be giving me a effect, to then after its outcome let me observe the causes of it. And what would that say about energy conservation? Maybe it is allowable though? Depends on how you think of it, as a linear cause and effect, or as some equilibrium that has to be preserved, possibly?
« Last Edit: 31/07/2013 22:39:38 by yor_on »
 

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Re: An essay in futility, too long to read :)
« Reply #1369 on: 28/08/2013 15:59:53 »
A weird musing this will be :)

Think of a inflation, define it as any point chosen in it must find a equal, evenly and equivalently distributed, new space, constantly coming into existence, around it. Could I from such a reasoning assume that I would be able to define a 'original center'? Now assume that all points are able to present us with this, new as old. Frozen at some moment in time, will those 'new points' of space also see the same behavior? Finding themselves surrounded by a constantly inflating space, evenly and equivalently distributed for all?

Seems like a one way proposal to me that one? In the direction of our arrow, but not able to retract to any origin, even if we could 'compress' that inflation? So what about a time reversal then? I'm so totally unsure on what a distance mean (as well as of what a motion really is:) Relativistically it stops making sense as a objective reality, Quantum mechanically it to me seems to do the same, although we find a different reasoning as to why. It's just here, at our current 'regime', non relativistically, macroscopically, and at rest, those two makes sense as some commonly agreeable 'objective truth'.

But you need something to go out from.
=

The point here is that although you at any moment in time can define a center, it will (should?) be a time dependent center, as with new space and time there will be displacements of what you defined as a point. You can consider it as although restmass binds restmass, it does not tell you where it 'exists' as all vacuum then must inflate, inside as well as outside this restmass.
« Last Edit: 28/08/2013 16:41:38 by yor_on »
 

Offline yor_on

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Re: An essay in futility, too long to read :)
« Reply #1370 on: 28/08/2013 16:03:03 »
Assuming such a scenario a time reversal shouldn't solve it either. If you think it would, how?
 

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Re: An essay in futility, too long to read :)
« Reply #1371 on: 28/08/2013 16:11:57 »
And what does such a reasoning make matter, aka rest mass? Assume a inflationary existence in where the only thing defining a distance is matter. That is what we use, we can't use two ideal (non materialistic) points in a vacuum, without first having a reference to something measurably there, becoming anchors for our ideal measurements. Theoretically we can do all sorts of things but even there I think it would be hard to take a ideal inflationary vacuum, possibly boundless, or as a matter of fact, surely boundless, as what sets a boundary to a vacuum practically is matter. Anyway, from inside such a 'place', define two points to measure a distance in between?
 

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Re: An essay in futility, too long to read :)
« Reply #1372 on: 30/08/2013 18:23:57 »
The real question there, if you now missed it :)
Is 'reality' time-reversible?

And what exactly would you base such a assumption on?
Memory? Histories?

So, you know how to 'back track' a inflation then?
 

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Re: An essay in futility, too long to read :)
« Reply #1373 on: 30/08/2013 18:34:51 »
The point I'm making is that a time reversibility presumes a 'box'. We need predestination actually to make it work:)
Because it presumes that what happens will be reversible, and that demands a box of sorts, limiting it.

Are you that sure that you can be played backwards?
 

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Re: An essay in futility, too long to read :)
« Reply #1374 on: 30/08/2013 18:41:04 »
You could see it as a open horizon, before a outcome. As soon as that outcome is existing though, you must have your 'box, defining a time reversibility. Don't think that way myself :)
 

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Re: An essay in futility, too long to read :)
« Reply #1374 on: 30/08/2013 18:41:04 »

 

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