Is this a new paradox of energy?

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Offline Geezer

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Is this a new paradox of energy?
« Reply #50 on: 01/03/2011 21:34:02 »
I think you missed my last post.

It depends on the perspective of the observer. Just because the observer cannot detect the presence of gravity, that does not mean it does not exist.

As an alternative, in my suggested experiment, you could also try chanting, "I cannot detect you gravity, therefore you do not exist."
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline Geezer

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« Reply #51 on: 01/03/2011 22:18:40 »

And any uniform motion, including the one seen as a gravitational acceleration when standing on Earth is defined by no 'gravity' perceptible inside a 'black box'.


That's my whole point. If the system boundaries are confined within the black box, the Earth, and the rest of the Universe do not exist! (It's impossible to prove they do.)

If you are going to involve the Earth, the "black box" better include the Earth too, otherwise you are simply moving the goal posts around.
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline yor_on

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« Reply #52 on: 01/03/2011 22:20:17 »
Did you read the pdf?

Try it.
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Offline Geezer

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« Reply #53 on: 01/03/2011 22:38:29 »
Did you read the pdf?


No. If you try to blow me off with PDFs, I'll have to assume you don't understand your model well enough to explain it in your own words.

How about you try to explain my objection to your black box argument instead? It's not a very complicated argument, is it?


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Offline yor_on

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« Reply #54 on: 01/03/2011 22:50:45 »
I just meant that it is a very nice explanation of those 'straight lines'. It also gives an excellent example of how A. an apple thrown up, falling down is described, as well as B. the difference in Newtons theory compared to Einsteins holding a apple over the ground. It's the best one I've seen actually. But you don't need to read it if you don't want too.

As for you arguing that in a black box nothing can be 'real'?
Take it up with Einstein :)
==

And Newton too btw:)

Both used them, in Einsteins world the assumption is that all laws of physics existing, also will exist in a 'black box scenario/laboratory'. And if they are equivalent, as in a constant uniform acceleration, with for example 'gravity'. Then it is 'gravity'. And if you can't differ your speed from the inside, uniformly moving, then all uniform motion is the same, however you then want to define that, as being at rest or not. But that's where the idea of inertial frames come from as I understands it. That you can't differ a uniform motion from being at rest. There are a lot of other assumptions you can draw from those concepts too, But you have to accept them first. And doing so will clash with the world of Newton, although both are very good at describing the world we live in.
« Last Edit: 01/03/2011 23:15:03 by yor_on »
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« Reply #55 on: 01/03/2011 23:08:08 »
Everything is real in a black box. That is the only possible reality within its confines. However, you cannot simply superimpose that reality on to a different black box, because that black box has a different reality.

I am confident that Einstein would agree that if we want to talk in terms of black boxes we have to define their boundaries carefully. I suspect he would take a very dim view if we continually moved the boundaries around.
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Offline yor_on

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« Reply #56 on: 01/03/2011 23:15:30 »
Geezer.

I'll let it rest now.
==

One thing though "However, you cannot simply superimpose that reality on to a different black box, because that black box has a different reality." In a way it's the opposite actually. If you can create a 'black box scenario' in where you find an exact equivalence to what you observe otherwise then the chances are pretty good that they are the same. That's why all black boxes uniformly moving are seen as the same, no matter their speed relative each other. and that's why a constant acceleration at one G is equivalent to Earths gravity (or any gravitational field of one G). It's a minimalistic approach to 'reality' you might say.

But if you meant "superimpose that (uniformly moving) reality on to a different (accelerating) black box, because that black box has a different reality." then I agree, and that's also what black boxes test, if they are the same or not (the physical laws).
« Last Edit: 01/03/2011 23:29:59 by yor_on »
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« Reply #57 on: 01/03/2011 23:18:37 »
Too late! I was just about to post this.

The flaw in the argument about the "black box" elevator is that it is decribed as an elevator. From the perspective of the occupants, if it really is a "black box" they cannot "know" it is an elevator. All they know is that it's a black box.

Other observers might know it is an elevator, but only because they have a different frame of reference, so they define the system differently.
« Last Edit: 01/03/2011 23:21:03 by Geezer »
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Offline yor_on

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« Reply #58 on: 01/03/2011 23:26:33 »
Hmm, read my post before, and you'll see how I see it :)
Seems we wrote 'past each other' there.

But try the pdf. It's really good.
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Offline JP

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« Reply #59 on: 01/03/2011 23:28:34 »
[???]

Sorry to butt in, but I'm trying to figure out where this gravity discussion ties in to the original question.  Is it that general relativity says one thing about energy being put into a system that's raised under gravity, while Newtonian gravity says another?

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« Reply #60 on: 01/03/2011 23:31:05 »
Ahh, yes, I'm sort of confused too. But hey, no news there :)
And the discussion is lively.. :)
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Offline Geezer

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« Reply #61 on: 01/03/2011 23:32:41 »
No - (at least I don't think so.)

It's simply that Yoron refuses to bow to my obviously superior intellect.
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Offline yor_on

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« Reply #62 on: 01/03/2011 23:39:03 »
We have saying in Sweden, loosely interpreted it states that 'opinions reminds of an a*s, there will aways be found a split somewhere." ah, that was very loosely interpreted.

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Can't seem to stop this. Maybe we should put a X-rating on this topic?
« Last Edit: 01/03/2011 23:42:34 by yor_on »
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« Reply #63 on: 01/03/2011 23:44:51 »
Aw come on!

Have you never heard of proof by loud assertion???

......

It's interesting to note that JP has relocated to Switzerland.
« Last Edit: 01/03/2011 23:50:17 by Geezer »
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« Reply #64 on: 01/03/2011 23:49:33 »
Yeah, well.. Ahh, yes. :)

...

Tricky tricky ::))
« Last Edit: 01/03/2011 23:57:48 by yor_on »
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« Reply #65 on: 02/03/2011 00:21:04 »

I'm trying to figure out where this gravity discussion ties in to the original question.


Seems fairly clear to me JP. Which part of

"On lifting a system from the floor to a height..."

did you not understand?
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« Reply #66 on: 02/03/2011 00:30:47 »
"Is it that general relativity says one thing about energy being put into a system that's raised under gravity, while Newtonian gravity says another."

I think that is perfectly clear too?

What JP meant was that when we lift a system on the floor the gravity naturally need to be adjusted to whom it is. And as it states, it's either Newton nor Einstein?

But he seems to forget to adjust for the apple?
==

Maybe you didn't read the pdf JP?
There you can find everything about it.

It's important in all systems under, as well as over, gravity.
Ultimately it's EMR that needs to be considered of course.

Apples or no apples.


« Last Edit: 02/03/2011 00:42:45 by yor_on »
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« Reply #67 on: 02/03/2011 01:09:30 »
Maybe you didn't read the pdf JP?
There you can find everything about it.

It's 94 pages!  [:o]

I'm curious, but (no offense) I don't think I'll find the time to read all that!

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« Reply #68 on: 02/03/2011 01:36:20 »
I know I'm going to get PBLA'ed for this, but aren't you just arguing over which of two models is right, even though they happen to agree?  Newtonian gravity deals with forces and potentials, while general relativity deals with topology and geodesics.  They both agree very well for something being lifted off the earth, though, since gravity is relatively weak and slowly varying.  In that case, it's a bit silly to use general relativity, since the equations are a nightmare to solve.

Thermodynamics generally relies on energy and work, so I'm pretty sure you couldn't easily use general relativity to describe what happens to a thermodynamic system as you lift it.  I guess you could work out the coordinate transformations and particle geodesics needed for that case in general relativity and apply those to the equations of thermodynamics, but... isn't that a bit overkill?  Plus, it should still agree with the Newtonian result here on earth.

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Offline Geezer

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« Reply #69 on: 02/03/2011 02:46:08 »
I know I'm going to get PBLA'ed for this, but aren't ....

Actually, I'm not using a Newtonian model  [;D]

Geodesics are all about the interaction between space-time and matter. But whatever model we choose to use, the laws of thermodynamics (until they are repealed) will still govern the energy transactions.
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« Reply #70 on: 02/03/2011 06:56:06 »
"However, you cannot simply superimpose that reality on to a different black box, because that black box has a different reality." In a way it's the opposite actually. If you can create a 'black box scenario' in where you find an exact equivalence to what you observe otherwise then the chances are pretty good that they are the same. That's why all black boxes uniformly moving are seen as the same, no matter their speed relative each other. and that's why a constant acceleration at one G is equivalent to Earths gravity (or any gravitational field of one G). It's a minimalistic approach to 'reality' you might say.

But if you meant "superimpose that (uniformly moving) reality on to a different (accelerating) black box, because that black box has a different reality." then I agree, and that's also what black boxes test, if they are the same or not (the physical laws).

Let's try a practical experiment.

You are in a black box. Within the black box, you are completely weightless. Because you are in a black box, you cannot have any knowledge of your position relative to anyting else (otherwise, it would not be a black box).

I am in a different black box. My black box happens to include your black box, as well as the Earth. I can see that your black box is accelerating towards the Earth at 9,81 m/s/s.

You cannot know that your black box is accelerating towards the Earth at 9,81 m/s/s. Does that mean it will not collide with the Earth?

Seems like a fairly straightforward question to me. I hope it does not require a 92 page answer.
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Offline yor_on

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« Reply #71 on: 02/03/2011 09:54:23 »
:)

Of course I will collide with Earth, if you say so :)
How can I avoid it?

But the proper way as they say on the British telly is to use 'black boxes'  to test how physics work, or not work. To do that you make some assumptions, one is that any law in physics will, if found being the exact same in your 'black box' as well as outside it, have an connection. For example the idea of gravity being equivalent to a constant acceleration. If that would have been wrong then the equivalence would not be there. It's not Russian boxes in boxes in .. It's just a minimalistic way to test the laws of physics.
==

Geezer, if we had a real acceleration, energy expended, so to speak I think you might be right in the energy changing in the books 'SpaceTime distortion'. It's just that we don't have a acceleration in this case. You might argue that any motion increase the energy in the geometric properties of space-time but to me it's a question about what is measurable. What you can measure is the distortion, but if that is 'energy'? Maybe, but if so it's not anything 'tapped' by the object moving uniformly. In a acceleration there will be a difference though.

'Energy' is a very slippery subject that we seem to use to connect 'events' with each other. I prefer to look at it as something causing something to 'jiggle', adding to a mass, and if it does not do so then it's not what I call 'energy'. That 'SpaceTime' distorts both in a uniform motion and a acceleration seems to me to be a proof for it not being any 'energy' at all, in fact. There is nothing measurable 'jiggling' anywhere there. The distortion is something connected to SpaceTime itself, brought about by motion. But if we like to use 'energy', and also believe in the conservation of 'energy', and think that a Lorentz contraction is real, then we 'concentrate' the universes 'energy' locally by any 'motion', uniform or not as the universe contracts locally. And if you like turn the complementary 'slowing/time dilation' into a proof for SpaceTime needing to 'concentrate' its 'energy' relative the moving frame.

But I don't like it. All motion, except uniform motion, expend some 'energy', and that fuel transforming into energy gets used up too, some of it as 'radiation', which in its turn gets used up in other interactions, leaving? 'Used Energy?' or 'work done' if you like. :) that nobody ever have touched or seen, more than as a mental crutch, a concept. At the same time as all 'uniform motions', no matter what 'speeds' you assign to them, are the same in that none of them is distinguishable from each other, inside that black box, and also in that none of them expend any 'energy', ever.

I'm not happy over that use of 'energy'. But yeah, if I stop looking at 'energy' as something measurable as 'jiggling'? Maybe you can define it your way. But the book will still not have any more 'energy' :) But to me such a definition of energy seem to set a uniform motion equivalent to a acceleration? And that one clash with my ideas rather strongly. Then 'energy' seems to become a description of geometries, not anything specifically connected to the difference between 'work' and 'work done'.
« Last Edit: 02/03/2011 14:56:40 by yor_on »
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« Reply #72 on: 02/03/2011 15:35:34 »
I know I'm going to get PBLA'ed for this, but aren't ....

Actually, I'm not using a Newtonian model  [;D]

Geodesics are all about the interaction between space-time and matter. But whatever model we choose to use, the laws of thermodynamics (until they are repealed) will still govern the energy transactions.

I know we've been through this in another thread in great detail, but gravitational energy in general relativity doesn't always satisfy energy conservation.  You can't always define a general work-energy theorem.  There are special cases where you can, such as over tiny patches of space-time, where things are close to flat, or when you move far away from gravitating objects where things are also flat.

The actual problem, as I remember, is that conservation of gravitational energy gives you an equation that needs only hold for one observer.  Another observer might look in and see it violated.  This would be a problem for thermodynamics, since some observers would see the second law broken if you chose to write it in terms of energy.

The thing is that if you go back to derive the laws of thermodynamics, they start off as much simpler equations involving the motions of various particles.  Energy arrives because energy can describe the motions of particles and from that you can build the second law of thermodynamics in terms of energy.  In general relativity, the motions of the particles are described by geometry, and so you'd arrive at a second law of thermodynamics governed by geometry if you worked it up from first principles.  It should then hold for all observer in GR, and in the Newtonian limit, it should agree with the energy formulation.

Of course, my disclaimer here is that I'm not a GR expert, so I don't really know how badly conservation of energy breaks down in GR and in what cases it does so, but I'm pretty sure that when it does, you can't formulate the second law in terms of energy transactions and expect it to be general-relativistically sound.

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Offline yor_on

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« Reply #73 on: 02/03/2011 16:20:28 »
Thanks for that one JP.

Nice to see that I don't have to start thinking of 'energies' from a solely geometric perspective. Not that I would. It would make all understanding I have of that concept wrong, and if it is something I cherish it has to be my presumptions :) So easy to get, almost impossible to lose ::))

Whatever I mean by that?
==

I will need to think about it of course. Still, 'energy' as a concept is alway connected to interactions, either happening or at least having the 'potential of them happening'. So in that motto you can use it for describing the effects of relativistic motion too. Myself I prefer to use it in it's measurable form (interactions), as it simplifies a lot that otherwise would get me confused.

And if you look at radiation interacting with your eye then that 'energy' surely 'transform', but its final stage can't be 'energy'. The only definition I have for that is 'work done' which I see as a thermodynamic concept. And as such actually better than the idea of 'energy' that I find so hard to define.

In thermodynamics doing work is often seen as heat, like a gas driving a piston in your cars engine. There it is the heat that does work on your engine, not the 'energy'.


"The First Law of Thermodynamics is the law of Conservation of Energy. It states that energy cannot be created or destroyed. Instead it is converted from one form to another, such as from mechanical work to heat, from heat to light, from chemical to heat or such."

Now, this is all good and fine, but what happened with that photon hitting your eye? Isn't heat, all said and done, just something 'jiggling'? I think it is, and it has three ways to make stuff do so. Convection (warmer areas of a liquid or gas rises to cooler areas mixing in the process), Conduction (two object at different temperatures in contact with each other equalizing their temperature) and Radiation (a method of heat transfer that does not rely upon any contact between the heat source and the heated object.)

But when the 'jiggling' stops then? Well, that's what I call 'work done', and where that 'stuff' went that made it 'jiggle'? Dissipating into the universe if we want the conservation laws to hold, but as what? Not 'heat' as that makes stuff 'jiggle'? Not 'energy' as that also causes a 'jiggling'? And this 'jiggling' had stopped.

But, it's definitely 'work done' in its most simple meaning.
« Last Edit: 02/03/2011 18:03:19 by yor_on »
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« Reply #74 on: 02/03/2011 19:19:54 »

but what happened with that photon hitting your eye? Isn't heat, all said


Wouldn't some of the energy also be converted int chemical energy? Ultimately, I would think all the energy in the photon will be conserved, even if it only goes to increase the entropy in the Universe.
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« Reply #75 on: 02/03/2011 20:13:49 »
But, it's definitely 'work done' in its most simple meaning.

Except that in general relativity, two observers don't necessarily agree on gravitational work and gravitational energy conservation, so there is no general work-energy theorem.  Energy conservation doesn't necessarily hold in general relativity if you try to account for gravitational energy.  That's why it's so confusing to try to get the GR picture to agree with conservation of gravitational energy--it doesn't in all cases. 

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« Reply #76 on: 02/03/2011 20:24:31 »
I got my answer and everything else is crap actually what happens is that a systems internal energy is defined from a frame of reference in which the center of mass is at rest and hence adding potential energy to the system does not add to its internal energy. A steady state is established in terms of internal energy for these works performed.

Doesn't it depend on the material? Our bodies produce heat, as form of energy, if the materail has the ability to store that heat then surely there would be an energy increase and so a weight change in the material while that heat was present. As a simple point.
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Offline Geezer

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« Reply #77 on: 02/03/2011 21:23:36 »
But, it's definitely 'work done' in its most simple meaning.

Except that in general relativity, two observers don't necessarily agree on gravitational work and gravitational energy conservation, so there is no general work-energy theorem.  Energy conservation doesn't necessarily hold in general relativity if you try to account for gravitational energy.  That's why it's so confusing to try to get the GR picture to agree with conservation of gravitational energy--it doesn't in all cases. 

JP - Is that because the observers will disagree about distance, force, distance and force, or something else?
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« Reply #78 on: 02/03/2011 21:45:18 »
"Ultimately, I would think all the energy in the photon will be conserved, even if it only goes to increase the entropy in the Universe."

One of the truly strange things that Geezer :) I don't know, but I sure would like too. And yeah, a body produces heat, and heat is a form of 'energy' that should be expressed as mass, but here we were talking about if a book would gain energy by getting moved in a gravity well. I think we was at some point at least? :)  

And yes, I agree on that JP. There is very little resembling 'energy' in gravity although there will be more or less 'energy' freed in a interaction depending on the books position in the gravity well.

So, if the energy released can't be situated in the book and neither, as I see it, in the uniform motion as that 'gravitational acceleration' becomes to me, where do I find the reason for it? In the relation between its original position relative its interaction?

But I can't speak of any 'work' being done by gravity, and there is no measurable 'energy build up' introduced by that uniform motion either, even though it do accelerates relative the Earth. In fact, all real acceleration presumes a energy loss, doesn't it? One way or another someone has to expend energy to get a object accelerating.

What is 'speed', and what is 'energy'?
It would be easy if we could ignore the Lorentz contraction, then we could say that there is a 'objective' way to define the relation, but with the contraction nothing becomes clear as we now have two points of view, and both valid, the far observer being 'still', and the gnomes in the book. And in a uniform motion there is no 'energy', and in a acceleration you expend energy to accelerate.

I'm sure we will solve this :)
==

As soon as I write Lorentz contraction it is as well to assume that I include the time dilation, because i do. I do do :) It's just that I find the Lorentz contraction the one most weird, for the moment :)

==

Could I assume a slower 'energy burn' with a time dilation? Assume that normal earth time/speed is one meter per second. If I now go ten meters in five seconds, being the moving twin, could the earthly observer equate that 'time dilation' he find me to have done later (coming back), with a slower 'metabolism/ energy consumption?' How would that fit with him having watched me move in his telescope the whole time? There he saw me move ten meters in ten seconds, did he not? From the moving twins position it becomes simpler in that the distance actually have 'halved' so that he find himself moving at normal 'speed' but only needing to do half the distance from what he expected from the starmaps on Earth. He would agree to needing 'half the energy' I think, but our earth friend with the telescope I doubt to agree, even though finding his twin being 'time dilated' at his return.
« Last Edit: 02/03/2011 22:24:38 by yor_on »
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« Reply #79 on: 02/03/2011 22:24:08 »
But, it's definitely 'work done' in its most simple meaning.

Except that in general relativity, two observers don't necessarily agree on gravitational work and gravitational energy conservation, so there is no general work-energy theorem.  Energy conservation doesn't necessarily hold in general relativity if you try to account for gravitational energy.  That's why it's so confusing to try to get the GR picture to agree with conservation of gravitational energy--it doesn't in all cases. 

JP - Is that because the observers will disagree about distance, force, distance and force, or something else?

It's something about gravitational energy itself.  If you add up all other forms of energy, they satisfy a conservation law in any reference frame in GR.  If you try to do the same for gravitational energy, it doesn't.  I understand the math pretty well, so I'm confident in this.  What I don't have is a physical intuition for it. 

Certainly other forms of energy are distributions living over a region of curved space-time.  The laws of GR are set up so that equations relying on these functions remain the same as you change reference frames within that geometry.  The difference is that gravitational energy somehow "is" the geometry, rather than being a distribution on top of it.  That makes it special, and makes formulating conservation of energy over regions of curved space-time difficult. 

By the way, I believe the problem only occurs when you want to look at regions of space-time living within a larger, curved region.  If you look at the entire system of gravitating objects all within a volume such that the "curviness" is minimal by the edges of the volume, then you can define an energy of the entire box.  But when you peek in and ask about the energy of a tiny piece of space-time within that box, you run into trouble. 

Edit: here's a link on the subject (not quite 90 pages).  It explains it in words, but I still think it's lacking physical intuition. 
http://www.phys.ncku.edu.tw/mirrors/physicsfaq/Relativity/GR/energy_gr.html
« Last Edit: 02/03/2011 22:28:43 by JP »

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« Reply #80 on: 02/03/2011 22:34:53 »
Gravitational energy is weird. It's the stress-energy tensor and what more JP?
The way Space shapes to motion?

That's included in a way in the tensor, isn't it? Its when you put a whole SpaceTime together it becomes more than weird. Because treating each description/frame by it self you have a skewed SpaceTime although possible to connect to your own frame by untwisting it, but when all descriptions come together SpaceTime becomes a contradiction in terms. There is no simple way to describe the 'wholeness' of it that we see looking out. As long as you assume it to be geometric twistings you can calm yourself, but then you also will need to assume that a time dilation and Lorentz contraction is a illusion. As I understands it?

But I still think I find GR treatment of 'energy' making more sense than the idea of an unmeasurable 'energy' hiding in the book, created in its motion relative that gravity well. And if it now isn't definable other than as a expression of its curvature, then that still gives a consequent measurement. I like that. Because then we do change the 'energy' by moving that book relative the gravity well. But we don't change any objects 'energy' per se, we change the relation they have in SpaceTimes 'stress-energy tensor 'field'/potential gravity' instead. And by doing so they get a new 'energy definition' which in fact will reflect relative all other objects you compare their 'potential energy' too.

It's like the universe/space was a dynamically changing tension, and when you move matter inside in it, that tension will adapt to your motion, giving each object moved a new definition, what we call energy. But the energy, even though unique to what we moved don't rest inside the object but as a property of that position relative the object, if that now makes sense :)
==

If I look at 'energy' that way it becomes easy to see why a uniform motion, although not expending any energy by itself, still will have an added 'energy' relative its position in this tension. And looking at it that way transforms space from being a nothing to a something even classically. Space is a 'tension' but not as something resisting. What we see as its 'tension' is to space being at 'rest' creating no resistance relative anything we can measure. And its 'energy' is a intrinsic property relative the dynamics influencing that specific position we look at. Then comes the question if we can say that the 'tension' will be the same for two different observers? And there I don't think so, because that tension is very much a relation to who observes, but if the observers can agree on a time and position translating each other frames they should find it to be the same, I think ::))

Maybe?

Da*n, this one was tricky, but very nice..
« Last Edit: 02/03/2011 23:47:26 by yor_on »
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« Reply #81 on: 03/03/2011 01:09:17 »

But I can't speak of any 'work' being done by gravity,
 

Yoron, I don't think you could be saying that gravity "cannot do work" are you? There are lots of examples of work being done that seem to depend on gravity. Hydroelectric generation might be a reasonable example. [:D]
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« Reply #82 on: 03/03/2011 01:12:40 »
Thanks JP. Looks fairly couterintuitive as you say, but then, so does most of GR!
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« Reply #83 on: 03/03/2011 12:24:46 »
Nooo :)

It does no work.. I'm sure about that. To me it's like Earth, you can as easily say that the hill are doing work upon your body as you climb it. And in a way it does, it's like all definitions we use. They become ambiguous and that's why you see mathematician's barricaded behind equations, ready to defend them down to their smallest dissolution. Don't you ever tease a physicist or mathematician Geezer, fearsome in deed, defenders of truth.  Ahh, might have gone a little overboard here? Maybe??
==

But the idea of 'energy' is a weird one, just like transformations. It suits me admirably to find 'energy' removed from 'reality' into the fabric of SpaceTime. That's where I think it belong, it's such a weird concept. But if you let it be a property instead of a 'substance' then it's acceptable as description between 'work' and 'work done'. And as always it's nothing 'set', just a description of something constantly changing, depending on relations. We live in a relational universe, from how we define a speed to energy. What I've been wondering about is why matter exist? It has to be a function of 'time' and ?

But definitely what we call time. That's so simple to see if we are correct in our ideas of virtual particles able to become real. That has to be a function of time. But then again, if 'time' is part of the fabric it seems very difficult to lift time out from it, they all fuse into one SpaceTime, don't they? But we can lift out is its arrow, and that one we seem to be able to influence by gravitation and 'speed'. The funny thing about that 'arrow' that it seems to belong only to you, and you, and you. It's easy to see why we 'invented' thermodynamics as those concepts never looks away from the processes taking place locally, as I understands it? It's a way of defining the 'arrow' as decay.
« Last Edit: 03/03/2011 12:39:01 by yor_on »
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« Reply #84 on: 03/03/2011 18:33:37 »
Nooo :)

It does no work.. I'm sure about that.


So, if no work is done, how do you explain what's producing the electricity? Or is the electric power generated completely imaginary? Or, is it instance of perpetual motion?

Give me something to work with here.
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« Reply #85 on: 03/03/2011 20:41:25 »
It's ambiguous I agree. If you look at it as something wanting to go in one direction then all matter, and light, will do so relative gravity. And it produces a lot of things, like electricity, as it do so. But gravity is no 'force' acting on those. Gravity is more of a 'topology' that 'stuff' follows. What it really is, and why it can do those things I don't know.

Imagine a universe without matter in where you assume that gravity still 'exist'. Myself I think of it as a 'plane' then, and that this plane should be smooth, having no granularity to it. Like a invisible sphere maybe made of those planes but still without any differentiating signs in any direction. It's not 'energy' but if you introduce stuff like matter and light I expect us to get energy from the interactions created. You could also consider such a universe as a 'point' only, getting 'stretched' into 'dimensions' as we introduce matter and light. This is my way of looking at it only, and I think I'm free to do so as long as we can't say what gravity is.

If gravity is like that then it is at rest, not a force. And what introduce the topology is the rest of what makes our universe. That this also deform gravity into a topology is no problem to me, as you could imagine that 'pure gravity' as a singularity, which then makes all motion into something searching to be at rest relative what gravitational potential they meet. And the unlimited possibly 'original' type of gravity should then be the singularities we think us have, Black Holes. That also transform everything we call 'speed' into something just searching a equilibrium, unless we accelerate it, expending 'energy'.

How's that?
==

If you look at gravity this way it should exist at a QM level too as that is quanta, not smooth, and if you ask yourself how virtual particles can become real for us then the logical conclusion seems to be that they already was 'real', although not accessible for us, and that as a function of SpaceTime, expressed through 'times arrow'. That we can't define limits to virtual particles is no stranger than imagining a 'limitless' gravity. If I take one single particle and place it in my 'original gravity sphere' I expect gravity to equal out, no tidal forces introduced, and to the particle become as 'not existing'. Gravity seems coupled to light and mass, and to the 'energy' we define from their interactions.
« Last Edit: 03/03/2011 21:06:52 by yor_on »
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« Reply #86 on: 03/03/2011 21:19:21 »
Yes, but how can a generator produce electricty without work being done on it? Something has to be doing the work.
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« Reply #87 on: 03/03/2011 22:06:07 »
Maybe this could be cleared up if you defined work?  I think I see at least part of the confusion, which is that work classically is defined as force applied over distance.  Due to the way that forces are related to energy, this is equivalent to energy transferred into a system. 

In general relativity, you give up the concept of a gravitational force, but you can still transfer gravitational energy into a system.  Since you literally cannot define force times distance within the theory, does this mean that gravitational work doesn't exist in the model?  I don't know, but certainly Geezer's example does show that there must be some quantity that accounts for energy transfer into a system due to gravity.

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« Reply #88 on: 03/03/2011 22:35:51 »
You can take the term "work" out of it if you like. It's just a form of energy, and that energy has to be coming from somewhere, although it might be very difficult to exclude the term "work" entirely, because even if gravity is not doing work on the turbine, the turbine has to be doing work on the generator, and, at that point, it clearly is a torque (force) times distance.

So, I'll still be able to prove that gravity did work, or at least produced equivalent work.
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« Reply #89 on: 03/03/2011 22:45:19 »
So, I'll still be able to prove that gravity did work, or at least produced equivalent work.

I definitely agree with the second part!

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« Reply #90 on: 03/03/2011 23:05:29 »
Depends on what I should define 'energy' as doesn't it? If I do it by saying what it's not? Then 'energy' isn't 'measurable' in itself. There is no such thing as 'pure energy'. Either you define it as something that you know 'exist' in a future interaction as well as existing in any interaction you observe, or as I like to do, as only existing as a concept. We have a lot of concepts that we can't measure, thoughts being a perfect example. We can observe the brains electrochemical activities but you can't weight a thought, you don't even know how it comes to be or how it 'look'. Still, nobody here is going to argue that thoughts doesn't exist I presume :) And so I have to assume that 'energy' exist too.

The difference between work and 'work done' is 'energy expended' as i see it. If I thought of the universe as one kg of 'ka' this 'ka' transforms constantly, and what it ultimately expend is 'work done'. Energy should belong to 'work' in all transformations, but what 'work done' is I don't know? You might want to call it 'energy expended' instead? But as we expect the conservation laws to be valid, that too should stay inside our universe, in some form.

Space is empty classically, that's what planets and suns move through, meeting no 'resistance' from space itself, if they did the universe should be constantly retarding. I don't need to define what 'work' is really, we all agree on it being transformations, don't we?

The really weird thing is that we have a universe in where it exist, and also that we can't see where 'work done' goes. It would be simpler to assume that you can't have it. That all universes only consist of one substance that just 'is'. If it was heat our universe might be assumed to heat up, but heat is also radiation. I've never seen any proofs for the universe getting warmer, or producing more radiation?

What we are trying to do is to find some few components that will build us a universe working as ours, but if the Big Bang is correct it's rather weird to assume that it spewed out ah, let's say 44 elements :) seems more probable that it just was one, why not SpaceTime itself? And so I'm perfectly comfortable with thinking of 'energy' as something expressed as/in SpaceTimes curvature, as that 'curvature' is 'everywhere'.
« Last Edit: 03/03/2011 23:12:43 by yor_on »
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« Reply #91 on: 03/03/2011 23:11:54 »
Yes, but where does the generator get its energy from?
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« Reply #92 on: 03/03/2011 23:30:15 »
Geezer, that question is impossible to answer. Do you believe in the conservation laws? That nothing ever is 'lost'? Can you tell me where that energy goes then? Can you measure 'work done'. What you measure is differences giving that difference a name and counting on it. How many 'Giga tons' 'work done' has the universe produced until now for example? It should, if you believe in that all transformations come to a state from where only 'work done' is possible. Or else you know a substance unknown to me that represent just that?

Where does anything get 'energy' from Geezer? Perhaps you can tell me where I can measure pure energy? How about the 'energy' thought to exist in SpaceTime?
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« Reply #93 on: 03/03/2011 23:48:27 »
It has to do with 'time' I think? As all transformations macroscopically uses our arrow to express itself. If I was to assume that a Feynman diagram actually described a reality in where 'times arrow' could go two ways simultaneously then QM:s arrow becomes very weird. If so it doesn't just go forward or backward but actually has the ability to do both, simultaneously. So the way we have a arrow is a must for the causality chains we see.
==

And if you to that add Feynman's idea of 'many paths' with probability deciding which path that will be chosen you will find all paths taken from a QM perspective, the arrow being no hindrance to choosing which one that should 'exist' for us. In fact you might imagine all paths being taken for real, then unraveling themselves, leaving only one existing, creating a 'clock tick' in our macroscopic 'reality'.
« Last Edit: 03/03/2011 23:58:25 by yor_on »
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« Reply #94 on: 04/03/2011 00:16:28 »
"Geezer, that question is impossible to answer."

Ah! So it's the trolls at work again  [;D]

"Do you believe in the conservation laws? That nothing ever is 'lost'?"

Yes.

"Can you tell me where that energy goes then?"

It all ends up as heat in the Universe.

"Can you measure 'work done'."

Yes. It's just a form of energy.

"What you measure is differences giving that difference a name and counting on it. How many 'Giga tons' 'work done' has the universe produced until now for example?"

I don't know, but I'm only interested in the generator at the moment.

"It should, if you believe in that all transformations come to a state from where only 'work done' is possible. Or else you know a substance unknown to me that represent just that?"

It's just a way of expressing energy.

"Where does anything get 'energy' from Geezer?"

Lot's of places. It can get it from position, change of position, chemical reaction, etc.

"Perhaps you can tell me where I can measure pure energy?"

The energy stored in a rotating flywheel would be a pretty good example. A photon with a particular wavelength might be another.

"How about the 'energy' thought to exist in SpaceTime?"

Well, we could measure it by elevating a certain mass, then see how much work it could do, which would be equivalent to the energy it had gained by a change in position.
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« Reply #95 on: 04/03/2011 00:50:30 »
Okay, you say it ends up as heat. If so you won't be able to prove it other than as interactions with invariant mass, as space don't 'interact' with radiation, it's a interesting thought. And 'work done' is also 'energy'? 

Okay.

And no, I withhold that there is no extra energy in that book :)
As for how a water driven turbine gets its electricity :)

You don't measure the 'energy' itself but the strength of the photons interaction. 'energy' transform and ultimately disappear in interactions, just as that 'photon' you measured did. And that's what I'm trying to point out too. And your flywheel may have a certain momentum/energy but you cant lift that energy out from the interaction to measure by itself, as I know?

Depending on how you look at it you can say that 'energy' exist as a property of SpaceTime, but that doesn't say that it is gravity. All energy 'measured', as you look at it, will need to interact to be measured. Not measuring a interaction but just counting on the possibility becomes 'potential energy'. If you measured that book it will have the same invariant mass no matter where you put it.
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« Reply #96 on: 04/03/2011 01:20:17 »
OK - try this experiment.

We make a small model of the water reservoir and turbine which we test. Not surprisingly, it produces electrical energy which we can use to produce, for example, photons.

We transport this model far into outer space and park it there. Not surprisingly, it produces no electrical energy at all.

The only thing that changed was the model's proximity to other massive objects. It seems reasonable to conclude that the energy produced is something to do with proximity to mass.

BTW, I didn't mention "work", "force", or even "gravity".
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« Reply #97 on: 04/03/2011 01:44:13 »
Maybe we are talking past each other?
Here are some of my definitions.

'Energy' is a description of a relation relative a interaction.

'Potential energy' is a description of what a 'potential/possible interaction' might bring.

'Relative mass' and its 'energy' is a description of invariant mass relative motion, that is motion as defined relative a 'inertial frame' as our Earth. I guess you could define it relative other objects too, like accelerating frames, but then it would lose all meaning.

Invariant mass is a definition of a invariant quality belonging to matter, invariant in all frames, and motions.

When something moves faster we find that its inertia grows, that is, it gets more 'unwilling' to budge from its direction of motion. We also find it to have more 'energy' when interacting, as colliding. You may want to look at that as an effect of the object only but, as I see it, it is a combined effect of the objects invariant mass and relative motion in space and time (and inertia is one of the things that, to me, seem to point to that SpaceTime have its own way of defining 'absolute' motion?). When Einstein referred to mass I understand that as 'invariant mass'

"Energy may be stored in systems without being present as matter, or as kinetic or electromagnetic energy. Stored energy is created whenever a particle has been moved through a field it interacts with (requiring a force to do so), but the energy to accomplish this is stored as a new position of the particles in the field-- a configuration that must be "held" or fixed by a different type of force (otherwise, the new configuration would resolve itself by the field pushing or pulling the particle back toward its previous position).

This type of energy "stored" by force-fields and particles that have been forced into a new physical configuration in the field by doing work on them by another system, is referred to as potential energy.

A simple example of potential energy is the work needed to lift an object in a gravity field, up to a support. Each of the basic forces of nature is associated with a different type of potential energy, and all types of potential energy (like all other types of energy) appears as system mass, whenever present. For example, a compressed spring will be slightly more massive than before it was compressed. Likewise, whenever energy is transferred between systems by any mechanism, an associated mass is transferred with it."

So yes, a compressed spring has more measurable energy, the book on the other hand won't. As I see it :)
==

Actually the wiki is wrong there as I see it. The compressed spring will have a greater 'invariant mass' and so 'energy' in its rest frame, as well as all other frames, whilst the other examples discuss 'relative mass/momentum and 'potential energy' (invariant mass+motion).
==

Saying that gravity 'does work' on Earth but not in Space is true but, as I see it again, that is a relative effect of matters equilibrium, where it can be 'at rest', as I call it, relative that gravitational potential. If you could 'hang' that model above a black hole in space I would expect the water to start running :) as it then would find a gravitational potential giving it a direction. I'm not saying that I know what 'gravity' is, neither do I know what 'energy' is. I'm more or less using what I think me know it not to be to define it I'm afraid. Your definitions makes sense too Geezer, it's just that looking at it my way won't really destroy any of your calculations, but helps me see what Einstein thought.
==

If you were the only thing existing in a universe, and you affected a course change/acceleration, would inertia exist? If it does it's definitely a support for my weird idea of gravity, as any reaction to a course change/acceleration should be the result of a 'interaction' with something, or a relation if you like.

I mean, why would there be a 'inertial reaction' otherwise?
Against what, SpaceTime itself? Then inertia and gravity should be two different things, right?
« Last Edit: 04/03/2011 02:44:42 by yor_on »
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« Reply #98 on: 05/03/2011 23:40:03 »
That's all very well Yoron, but how do you explain what is doing the work on the generator?

The input to the generator is driven by the water turbine. We know work is being done on the generator, otherwise it would not produce useful electricity, so we are forced to conclude that the work is coming from the water turbine.

Now, from the little I know about water turbines, the reason they function is because of the kinetic energy of the water impinging on their blades. So, if gravity was not responsible for creating that kinetic energy and therefore doing the work, what was?   
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« Reply #99 on: 06/03/2011 04:19:36 »
"how do you explain what is doing the work on the generator"

The water :)

It has to do with matter (water) free falling in a geodesic, following the gravitational potential. And as it get obstructed by the impellers, interacting with them, delivering the 'kinetic energy'. Gravity is no force in itself, but matters interactions under its influence is.

Or you go for Newtons concept.
Your choice, I'll stay with my geodesics.
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