swansont Posted March 3, 2016 Posted March 3, 2016 No, space-time is not energy. However, it is possible to interpret some part of the curvature of space time (aka gravity) as having energy. And that, in part, accounts for the non-linear nature of gravity in GR (because the energy of the gravitational field also contributes to space-time curvature). Which sounds related to saying that there is energy contained in the Newtonian gravitational field, similar to there being energy in an electric field. 1
Mike Smith Cosmos Posted March 3, 2016 Author Posted March 3, 2016 (edited) Which sounds related to saying that there is energy contained in the Newtonian gravitational field, similar to there being energy in an electric field.?Well I can vouch for the electro magnetic field ( being an active Radio Transmitting Amateur ( HAM Radio G4HMA ) I am licences to pump 150 watts into the ( great beyond ) , have and do . Interesting , you are saying then :- " that there is conventional 'Energy ' in the conventional Gravitational Field . Like ( Newton meters ) . " which sort of 'stands to reason ' because we can turn water behind a Dam into Electricity ? By the Megawatt Mike Did I? ). This is one comment about stiffness , I think you made another , perhaps in another thread about gravity , when you spoke about ' tension or twist ' I think , I will look . Here is this one , to one of ajb's posts Quote Strange, on 02 Mar 2016 - 2:13 PM, said: The "medium" is space and time itself. I do wonder (and I really don't know) if some parameter(s) in the Einstein Field Equations can be interpreted as something analogous to "stiffness" or "density", or something else that would define the speed at which waves travel. Similar to how the vacuum permittivity and permeability define the speed of light. Mike Edited March 3, 2016 by Mike Smith Cosmos
swansont Posted March 3, 2016 Posted March 3, 2016 ? Well I can vouch for the electro magnetic field ( being an active Radio Transmitting Amateur ( HAM Radio G4HMA ) I am licences to pump 150 watts into the ( great beyond ) , have and do . Interesting , you are saying then :- " that there is conventional 'Energy ' in the conventional Gravitational Field . Like ( Newton meters ) . " which sort of 'stands to reason ' because we can turn water behind a Dam into Electricity ? By the Megawatt I'm talking about a static field. The energy stored in an electric field is proportional to E2, integrated over all space.
Mike Smith Cosmos Posted March 3, 2016 Author Posted March 3, 2016 (edited) I'm talking about a static field. The energy stored in an electric field is proportional to E2, integrated over all space..I am not sure about quantities. But there has been a lot of talk about huge quantities of energy , beyond the amount represented by ordinary matter in the universe. It has got to be somewhere , all this extra energy , so surely it must be in Space time somewhere , there is no where else for it to be . So what better place for it to be, than bound up , in the fabric of Gravity and Space Time ? Mike Ps . Of course the maths of all this Energy/ Gravity may well be formalised by all these Richie Tensors , Edited March 3, 2016 by Mike Smith Cosmos
Strange Posted March 4, 2016 Posted March 4, 2016 Here is a description, with moving pictures, that might help you see what happens: http://www.universetoday.com/127255/gravitational-waves-101/
Mike Smith Cosmos Posted March 8, 2016 Author Posted March 8, 2016 I'm talking about a static field. The energy stored in an electric field is proportional to E2, integrated over all space. Could I ask you ,possibly to be more specific, as to what you say is integrated across all space? Are you saying an electric field is integrated across all space ? Or are you saying Energy is integrated across all space ? Here is a description, with moving pictures, that might help you see what happens: http://www.universetoday.com/127255/gravitational-waves-101/ Makes some interesting viewing the different images of Space , and Waves in space. My first reaction was that the images of something ,looking like a digestive tract , did not have the same esoteric feeling as a purple starburst. However one comes from maths no doubt , the other from wishful thinking . Mike
swansont Posted March 8, 2016 Posted March 8, 2016 Could I ask you ,possibly to be more specific, as to what you say is integrated across all space? Are you saying an electric field is integrated across all space ? Or are you saying Energy is integrated across all space ? [math]\smallint E^2[/math] The value of the integral, with the limits over all space. All variables from zero to their maximum value
Mike Smith Cosmos Posted March 8, 2016 Author Posted March 8, 2016 (edited) Yes , but it took someone with imagination to think , maybe Einstein " , well now "said Einstein ," there are electro magnetic waves , because they were predicted by others including maxwell. And we now use them in Radio Communication. So just maybe , gravity has waves in this ' general theory of relativity , that I have just produced . Now I need to see if I can predict ( Gravity Waves ) to go with this Theory " . Einstein must have said . And now nearly a 100 years later there is something to measure . And LIGO has measured something ? Mike [math]\smallint E^2[/math] The value of the integral, with the limits over all space. All variables from zero to their maximum value Yes but , surely you are talking about a humungous value . But what is this you are saying ? An electric field all over space And/ or an Energy field all over space ? Or are you referring to all matter that exists , across all of space time? Mike Edited March 8, 2016 by Mike Smith Cosmos
swansont Posted March 8, 2016 Posted March 8, 2016 Yes but , surely you are talking about a humungous value . But what is this you are saying ? An electric field all over space And/ or an Energy field all over space ? Or are you referring to all matter that exists , across all of space time? Mike The integral drops off as 1/r^2. It will have a finite value proportional to 1/r, where r is the radius of your charge distribution. There are problems with point charges, since this is a classical calculation and you need to do some fun/weird things in QED to get around this. It's often discussed in terms of the energy density, so you have a finite volume.
Mike Smith Cosmos Posted March 8, 2016 Author Posted March 8, 2016 (edited) The integral drops off as 1/r^2. It will have a finite value proportional to 1/r, where r is the radius of your charge distribution. There are problems with point charges, since this is a classical calculation and you need to do some fun/weird things in QED to get around this. It's often discussed in terms of the energy density, so you have a finite volume. Why are we talking about electric charge , when the issue at steak is Gravity , Gravity waves , and Energy . Or are you saying there is some , connection of electric charge with the force of Gravity ? I'm talking about a static field. The energy stored in an electric field is proportional to E2, integrated over all space.Is this what you are talking about ? Do they somehow overlap, if they do ? If so where and how ? Or are you saying , that they occupy the same space ( eg space time ) You must be suggesting .. :.. :- The sum total of all ' particle charge,' across all space and time . or That the Big Bang caused an astronomical single charge at the beginning and it has been spreading out with the expansion to make " electric field is proportional to E2, integrated over all space. " ? Mike Edited March 8, 2016 by Mike Smith Cosmos
swansont Posted March 8, 2016 Posted March 8, 2016 Why are we talking about electric charge , when the issue at steak is Gravity , Gravity waves , and Energy . Or are you saying there is some , connection of electric charge with the force of Gravity ? NO, absolutely NOT. There is no connection. But you keep insisting that gravity can't behave in certain ways, and yet E&M does. So your objections don't have much merit.
Mike Smith Cosmos Posted March 8, 2016 Author Posted March 8, 2016 (edited) NO, absolutely NOT. There is no connection. But you keep insisting that gravity can't behave in certain ways, and yet E&M does. So your objections don't have much merit.o.k. That's a shame , I thought you were suggesting something pretty spectacular ! Well , I struggle enough with Electro Magnetic waves not having a medium , with the disproval by the Michelson Morley optical reasoning and experiment . But I just about , get my mind , to imagine this pair of oscillating , in and out of electrical field to magnetic field , and back again . Moving to gravity ? Where is the restorative force ? Rubber sheet is o.k as an illustration, but what is the rubber sheet representing . Unless these tubes illustrated are so contorted , gravity turns so upside down it pulls back on itself? Mike Edited March 8, 2016 by Mike Smith Cosmos
swansont Posted March 8, 2016 Posted March 8, 2016 Moving to gravity ? Where is the restorative force ? Why is one needed? What is the restorative force in an EM wave?
Mike Smith Cosmos Posted March 8, 2016 Author Posted March 8, 2016 Why is one needed? What is the restorative force in an EM wave?Well in an electrical wave , when the wave falls to zero from peak it induces a magnetic field to peak coming up from zero . Similarly as a magnetic field falls from its peak to zero , it creates an electrical wave to come up from zero to peak . So the restorative force is the opposite . ( magnetic to electrical and electrical to magnetic ) . I presumed that's why the wave could propagate in empty space. . I would sooner believe the two forces work within a medium . ( but it seems it's not to be. ) So with gravity , I would sooner it worked in some form of medium . ( but if it's not to be) . I still ask what restorative force can cause the gravity to bounce or restore ? Mike
swansont Posted March 8, 2016 Posted March 8, 2016 Well in an electrical wave , when the wave falls to zero from peak it induces a magnetic field to peak coming up from zero . Similarly as a magnetic field falls from its peak to zero , it creates an electrical wave to come up from zero to peak . So the restorative force is the opposite . ( magnetic to electrical and electrical to magnetic ) . I presumed that's why the wave could propagate in empty space. But that's not a restorative force.
Strange Posted March 8, 2016 Posted March 8, 2016 I would sooner believe the two forces work within a medium . ( but it seems it's not to be. ) So with gravity , I would sooner it worked in some form of medium . ( but if it's not to be) . I still ask what restorative force can cause the gravity to bounce or restore ? If you look at the diagrams of how gravitational waves distort space, you will see that they cause space to stretch in one direction(x) and shrink in the other (y), then shrink in x and stretch in y. And so on. Maybe that helps you make sense of needing two components.
swansont Posted March 8, 2016 Posted March 8, 2016 If you look at the diagrams of how gravitational waves distort space, you will see that they cause space to stretch in one direction(x) and shrink in the other (y), then shrink in x and stretch in y. And so on. Maybe that helps you make sense of needing two components. This is way outside of my expertise, but that may be the two polarization components, which are not linear polarizations and are tied in with this being a rank-2 tensor (and I think that's tied with why gravitons would be spin 2). There's an analogous term to E&M's Poynting vector, being the Heaviside vector, and the term that would be in place of the B field is the gravity torsion field. So this is a lot more complex than, say, a wave on a rope. It's even more complex than EM waves.
Mike Smith Cosmos Posted March 8, 2016 Author Posted March 8, 2016 (edited) This is way outside of my expertise, but that may be the two polarization components, which are not linear polarizations and are tied in with this being a rank-2 tensor (and I think that's tied with why gravitons would be spin 2). There's an analogous term to E&M's Poynting vector, being the Heaviside vector, and the term that would be in place of the B field is the gravity torsion field. So this is a lot more complex than, say, a wave on a rope. It's even more complex than EM waves. The small amount I have attempted to read deep explanations of these subjects , very specialised definitions of mathematical functions , seem to appear out of nowhere. Many seem to describe these matters , in a way which uses expressions not common in ordinary scientific arenas. This makes life very difficult to anyone other than the specialist. What is needed is an interpreted presentation .in everyday terms. Unfortunately string theory has gone off on a whirlwind of mathematical investigation into areas and dimensions that loose the listener at an early turn. Perhaps it will be beneficial to bring gravity in from a Top- Down direction. Rather than trying to understand things from the very smallest , direction. Mike Edited March 8, 2016 by Mike Smith Cosmos
StringJunky Posted March 8, 2016 Posted March 8, 2016 The small amount I have attempted to read deep explanations of these subjects , very specialised definitions of mathematical functions , seem to appear out of nowhere. Many seem to describe these matters , in a way which uses expressions not common in ordinary scientific arenas. This makes life very difficult to anyone other than the specialist. What is needed is an interpreted presentation . Mike I don't think it can be done. Unfortunately, it appears the price of true enlightenment is to slog through the maths. As Einstein explained once, you can only make certain things so simple.
Mike Smith Cosmos Posted March 8, 2016 Author Posted March 8, 2016 I don't think it can be done. Unfortunately, it appears the price of true enlightenment is to slog through the maths. As Einstein explained once, you can only make certain things so simple. Yes but what if the answer IS NOT in the MATHS . What if Gravity emanates from the very Large , rather than from the very small. After all it is concerned with the structure of the very large ( like the whole universe) and it permeates the whole universe , and would seem to have effects across the whole universe . So maybe it is best understood by looking from the Outside looking in , rather than from the Micro,microscopically small looking up! Mike
StringJunky Posted March 8, 2016 Posted March 8, 2016 (edited) Yes but what if the answer IS NOT in the MATHS . What if Gravity emanates from the very Large , rather than from the very small. After all it is concerned with the structure of the very large ( like the whole universe) and it permeates the whole universe , and would seem to have effects across the whole universe . So maybe it is best understood by looking from the Outside looking in , rather than from the Micro,microscopically small looking up! Mike Whether it is very large or very small, I don't it is the scale that's the problem explaining, it is the fundamental nature of these things.There's nothing in our sensory world that we can correlate with them accurately, just resorting to analogies, which can only ever be coarse approximations. Edited March 8, 2016 by StringJunky
Mike Smith Cosmos Posted March 8, 2016 Author Posted March 8, 2016 Whether it is very large or very small, I don't it is the scale that's the problem explaining, it is the fundamental nature of these things.There's nothing in our sensory world that we can correlate with them accurately, just resorting to analogies, which can only ever be coarse approximations. O.k. But I still think that is a good place to start , even if the analogies are ' coarse approximations ' Mike O.k. But I still think that is a good place to start , even if the analogies are ' coarse approximations ' Mike The SEA is a good analogy . It is vast . It weighs a good deal, it goes nearly everywhere . It is self levelling .... Mike
swansont Posted March 9, 2016 Posted March 9, 2016 Yes but what if the answer IS NOT in the MATHS . What if Gravity emanates from the very Large , rather than from the very small. After all it is concerned with the structure of the very large ( like the whole universe) and it permeates the whole universe , and would seem to have effects across the whole universe . So maybe it is best understood by looking from the Outside looking in , rather than from the Micro,microscopically small looking up! Then you'd need evidence for that, and you'd need a model to make predictions. You can't avoid the maths. But we've had this discussion before, and it's off-topic here.
Mike Smith Cosmos Posted March 9, 2016 Author Posted March 9, 2016 (edited) The integral drops off as 1/r^2. It will have a finite value proportional to 1/r, where r is the radius of your charge distribution. There are problems with point charges, since this is a classical calculation and you need to do some fun/weird things in QED to get around this. It's often discussed in terms of the energy density, so you have a finite volume. Back tracking a bit ! There is something , surely , we can pull out of the similarity yet difference between ' electrical charge ' and ' Gravity ' Static Field lines emanate out from a point source in a similar manner , if my memory serves me right . Gravity field lines look very similar to electrostatic field lines , if I am correct ? Yet the difference is in the 'spin' ? Am I correct? Which is the characteristic that makes it either a Boson or a Fermion . Is that correct ? Which makes it have mass or not ? Am I correct ? Or have I got in a muddle again? . Mike Edited March 9, 2016 by Mike Smith Cosmos
swansont Posted March 9, 2016 Posted March 9, 2016 Mike, you've already been told that Fermion vs Boson has nothing to do with this, and that spin is not an issue. Bringing these questions up again isn't going to change the answer.
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