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Dale
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IMO, Mach's principle is way too sloppy to be of any actual use in physics, and discussions of it tend to degenerate into rather distasteful discussions of other fantasy universes.
yuiop said:Are you sure about that? If you are free falling in a gravitational field, and there is another observer falling with you but below you, then they will be moving away from you. In order to stay at a constant distance from you the other observer would have to accelerate constantly towards you. Even when they maintain constant distance from you there clock will be ticking at a different rate to yours. In a true inertial reference frame in flat space, observers at rest in the reference frame are stationary with respect to each other, all experience zero proper acceleration and all their clocks are running at the same rate. Clearly there is no arrangement of the vertically separated fallers in the gravitational field that can duplicate being in a true inertial reference frame in flat space. The falling observers only approximate an inertial reference frame, if they are very close together, so that the errors are small. All these difference come about as a result of tidal effects and that is what distinguishes a real gravitational field from the pseudo-gravitational field that results of artificial acceleration in gravitationally flat space.
yuiop said:I gave you some facts. Here...
.. and here ...
.. but you have chosen to ignore them and have not responded to these counter arguments.
I mention what people understand by Mach's principle, but since he did not clearly define it and since you seem to be championing the principle, then the only way to proceed with a sensible discussion would be for you to define what you think Mach's principle is or whatever principle it is that you are championing that you think demonstrates that the predictions of General Relativity are wrong.
Your claims about accelerometers are in direct opposition to the predictions of general relativity.Mueiz said:I did not claim at all my opinion (which is that all frames in zero-gravity region are inertial )
imply that the predictions of general relativity are wrong
DaleSpam said:Mueiz, please respond to the points raised in post #66. You misunderstand what an accelerometer measures in GR and you are coming to incorrect conclusions based on that error.
Also, this statement is false:Your claims about accelerometers are in direct opposition to the predictions of general relativity.
Whether or not you are going to do a calculation is not relevant, nor is the choice of reference frame, nor presence or absence of gravity. (1) An accelerometer measures proper acceleration by definition and (2) in GR the proper acceleration is the frame invariant magnitude of the covariant derivative. If you cannot accept those two statements then there is no reason for further discussion.Mueiz said:No my understanding of accelerometrs is similar to yours i just use a quality terms(deviation from inertial frames ) because i am not going to do calculation I want the accelorometr just to tell me whither there is acceleration or not ,so need not quantity terms of your (magnitude of the covarian derivative) is it not true that an accelerated observer is that who is not inertial
the point of disagreement is the work of the accelerometer in zero-gravity
Which post? I don't think there is much point to further discussion while you don't understand how an accelerometer works in GR.Mueiz said:I want you to disscus the paradox i gave in aprevious input
But it is important to show whither Rotating Disc Experiment correct or incorrect because it is used in two of the most important books in physics (The meaning of Relativity and The Evolution of Physics both by Einstein ) and many beginners and advanced student of physicsDaleSpam said:IMO, Mach's principle is way too sloppy to be of any actual use in physics, and discussions of it tend to degenerate into rather distasteful discussions of other fantasy universes.
I accept those two statement in a gravitational fieldDaleSpam said:Whether or not you are going to do a calculation is not relevant, nor is the choice of reference frame, nor presence or absence of gravity. (1) An accelerometer measures proper acceleration by definition and (2) in GR the proper acceleration is the frame invariant magnitude of the covariant derivative. If you cannot accept those two statements then there is no reason for further discussion.
post #47... I think the Paradox could be an easy way to show me and other users of this forumDaleSpam said:Which post? I don't think there is much point to further discussion while you don't understand how an accelerometer works in GR.
But Einstein use this approximation in his calculation (without even improving it by supposing that the disc is very large)yuiop said:You conclude that the observer on the edge of a very large disc is inertial because locally they appear to traveling in approximately a straight line, but that is not the definition of inertial motion. Inertial motion is motion with zero proper acceleration and the observer on the edge of the large disc would be experiencing very large proper acceleration at high velocities and is therefore not inertial by definition.
not only is there no inertia in the absence of gravity there is nothing..zero-gravity is out of the range of applicability of such conceptsMentz114 said:State your belief that there is no interia in the absence of gravity.
here to attain this predicts you use Mach Principle with other Assumptions regarding zero gravity region such as that object can be accelerated in the absence of gravity which can not be proved by GR which based on Equivalence Principle related to gravitational field and cannot also be prove experimentally till now(to the best of my knowledge none did any experiment in zero-gravity region) . in fact the properties of zero gravity can be predicted using pure intellectual principles such as Postulates of Symmetry and Simplicity.yuiop said:I will give you a simple though experiment for discussion purposes. Imagine we have a very large gravitational body that is rotating at 1 rpm...
In summary the Machian interpretation predicts:
1) Objects really can orbit at velocities much greater than the speed of light.
2) Gravity does not act on objects at a certain critical distance and stationary objects can hover.
3) Gravity attracts or repels depending on distance.
4) The force of gravity depends on the orbital direction and not just on orbital velocity.
5) The speed of light is not locally isotropic in all directions to an inertial observer.
Is that how you see things?
This has got to be one of the most absurd positions that I have ever seen anyone take. So, a rocket in deep space suddenly turns on its engines. The fuel burns and according to you what happens? Do the exhaust gasses just build up because they cannot accelerate away, or do they accelerate away but the rocket's accelerometer reads 0 despite the thrust force generated by the rocket engine?Mueiz said:I also accept them in zero gravitation field if i agree that there could be acceleration there
Mueiz said:not only is there no inertia in the absence of gravity there is nothing..zero-gravity is out of the range of applicability of such concepts
DaleSpam said:This has got to be one of the most absurd positions that I have ever seen anyone take. So, a rocket in deep space suddenly turns on its engines. The fuel burns and according to you what happens? Do the exhaust gasses just build up because they cannot accelerate away, or do they accelerate away but the rocket's accelerometer reads 0 despite the thrust force generated by the rocket engine?
Mueiz said:It does not contradict GR because GR is based on Equivalence Principle which is related to gravity
we can use the phrases gravity .. gravitational field and so on, only to mean non-zero curvature and i think that is not a problemAltabeh said:Not gravity but "curvature"! We no longer have gravity in GR!
this is a quite different situationAltabeh said:I think the only problem you have here is that you've completely misunderstood one big idea! If gravitational constant G was zero, then the universal effect of gravitational fields would disappear and you were surely right!
This is somewhat new attitude toward the question... i will try to discuss you if you give your reasons and arguments or deny those of mine mentioned in different stages of this discussion for other people may complain if i repeat them hereAltabeh said:There is nothing like a pure flat spacetime in any region in reality and due to this fact the always use "asymptotically" flat when the theory is trying to get special relativistic! You cannot think of zero-gravity at all!AB
Mueiz said:we can use the phrases gravity .. gravitational field and so on, only to mean non-zero curvature and i think that is not a problem
This is somewhat new attitude toward the question... i will try to discuss you if you give your reasons and arguments or deny those of mine mentioned in different stages of this discussion for other people may complain if i repeated them here
It is absurd because it is directly contradicted by decades of experience burning rocket fuel in zero gravity. "Symmetry and simplicity" as you put it are irrelevant in the face of contradictory experimental evidence.Mueiz said:The fuel will not burns for burning is microscopically a type of motion
Can you tell me why did you describe this position as absurd
DaleSpam said:It is absurd because it is directly contradicted by decades of experience burning rocket fuel in zero gravity. "Symmetry and simplicity" as you put it are irrelevant in the face of contradictory experimental evidence.
So how far out do you believe we have to go until suddenly all of the laws of chemistry, quantum mechanics, electromagnetism, etc. fail?Mueiz said:can you tell me please one experiment
nobody could claim this . all the outer-space regions attained by people and their instruments are not of zero-gravitational field even if you were out of our solar system you are in gravitational field
Altabeh said:Please don't play with words. Gravity ...
I've not read any of your ideas yet, but you can list them in a post briefly so I can decide whether they deserve to be given a shot or not by me!
AB
DaleSpam said:I would like to remind you that this forum is not the place for speculation about personal theories. Please click on the Rules link at the top of the screen and review what you agreed to when you signed up.
DaleSpam said:No, there are mainstream theories and there are personal theories. Yours here is personal, not mainstream, and is in direct opposition to GR.
So how far out do you believe we have to go until suddenly all of the laws of chemistry, quantum mechanics, electromagnetism, etc. fail?
You are more optimistic than I am.Altabeh said:We can discuss these and convince the guy of his misunderstandings on the issue of gravity or whatever the problem is!
DaleSpam said:So how far out do you believe we have to go until suddenly all of the laws of chemistry, quantum mechanics, electromagnetism, etc. fail?
atyy said:Within GR, all matter fields (defined as fields with localizable stress-momentum-energy) require the metric for their definition.
In that sense, it is true that there is nothing without gravity.
Mueiz said:Second observer in the edge of the disc ...then he is in uniform motion relative to the first observer(because the disc can be made large enough) so his frame is also inertial and he sees geometry as Euclidean
Altabeh said:I try to proceed step by step to clear up any misunderstanding you have here and until the first problem is not solved, I won't keep going!
I think you could be smarter than Paul Ehrenfest but never can be as pedantic as John Stachel is! Even if the disc is very large, the rim is still a part of the disc which means that we are out of the zone! The special relativity holds only for inertial Lorentzian systems which always deal with the objects in the state of non-constrained motions! In contrary, constrained motions never allow you to have a pure inertia in the sense that,
1) Supposing there is no strong gravity to hold your shoes on disc, at each point along the circumference you may have a different angular velocity as recorded by the observer at rest and thus you gain a non-zero centrifugal acceleration! This is because your shoes have to be glued to the disc to remain on the disc so you're a part of the solid disc! This fallacy was made in the Ehrenfest's thought experiment which later was noticed by Stachel!
2) In case there is gravity and you're standing on the disc by gravitational force, you're no longer attached to disc and its enternal tensions won't affect your position (it seems like at quantum mechanical scales, the position of particles of disc are changing under your shoes). But in this case Lorentz contraction happens and the inert observer understands that the body of observer on disc shrinks so that using a simple calculation the result obtained by Einstein appears to be true, again!
Up to this point I can say that your thought experiment is fallacious! Do you have anything to say, now?
AB
Then your objection in post 50 doesn't make any sense:Mueiz said:Nowhere ... in fact.. even if we go to a place where there is no gravitation then our own masses will case gravitation to exist then affect the particles used for the study
this show the impossibility to study zero gravitational field experimentally
Mueiz said:In your experiment you suppose that one observer can have zero acceleration and another one have non-zero acceleration in the absence of gravitational field
DaleSpam said:Then your objection in post 50 doesn't make any sense:
According to you even the miniscule mass of the accelerometers would create a gravitational field sufficient to result in exactly the behavior I suggested.
So why did you object to my post 49? What I described is perfectly correct even according to you.Mueiz said:So the accelerometers is not able to study zero-gravitational field and this confirm what i and my friend atty said previously ; nothing exist in zero-gravitational field
if you use accelerometers or even thermometer you will be in gravitational field this fact with other facts made me say previously that the properties of zero-gravitational field is only attainable by pure intellectual principles
DaleSpam said:So why did you object to my post 49? What I described is perfectly correct even according to you.