Handy andy Posted May 28, 2017 Posted May 28, 2017 For clarification using the Gullstrand-Painlevé coordinates. Which can be interpreted as space flowing towards a mass. https://en.wikipedia.org/wiki/Gullstrand–Painlevé_coordinates Is Gravitational attraction simply the contraction of space around a mass? Could this also be worded as gravity is caused by the absorption of space by mass? Whilst Gravitational repulsion is the expansion of space between masses or galaxies? Worse still, Could space be regarded as being made up of gravitons, or little strings?
swansont Posted May 28, 2017 Posted May 28, 2017 For clarification using the Gullstrand-Painlevé coordinates. Which can be interpreted as space flowing towards a mass. https://en.wikipedia.org/wiki/Gullstrand–Painlevé_coordinates Still don't see anything about space flowing toward a mass in that link (you've claimed this before) . How do you justify saying that's an interpretation of the coordinates?
Handy andy Posted May 28, 2017 Author Posted May 28, 2017 Still don't see anything about space flowing toward a mass in that link (you've claimed this before) . How do you justify saying that's an interpretation of the coordinates? The link was posted by strange, this one includes kerr, and is more specific regarding the flow of space https://arxiv.org/pdf/0805.0206.pdf
swansont Posted May 28, 2017 Posted May 28, 2017 The link was posted by strange, this one includes kerr, and is more specific regarding the flow of space https://arxiv.org/pdf/0805.0206.pdf Where does it say space is flowing toward a mass? It says "the acceleration of free-falling objects is generally not in the direction of this flow " So if a free-falling object is accelerating toward a mass, it means the flow is not. And AFAICT this says nothing about purported expansion, contraction or absorption (!) of space
Mordred Posted May 28, 2017 Posted May 28, 2017 If you ignore the poor descriptives in the article and look strictly at the math. The geometry of the global metric is static. What is flowing is the assigned inertial frames. ie assign for every value of velocity a Euclidean (Minkowskii) 3d inertial frame. The volume of space itself isn't flowing what is flowing is the field values. The math clarifies that.
Roger Dynamic Motion Posted May 28, 2017 Posted May 28, 2017 Where does it say space is flowing toward a mass? It says "the acceleration of free-falling objects is generally not in the direction of this flow " So if a free-falling object is accelerating toward a mass, it means the flow is not. And AFAICT this says nothing about purported expansion, contraction or absorption (!) of space How ? can a body be accelerated , without force fallowing. << explaine please ../
Mordred Posted May 28, 2017 Posted May 28, 2017 (edited) If you ignore the poor descriptives in the article and look strictly at the math. The geometry of the global metric is static. What is flowing is the assigned inertial frames. ie assign for every value of velocity a Euclidean (Minkowskii) 3d inertial frame. The volume of space itself isn't flowing what is flowing is the field values. Specifically the values that make up a Rheimannian 3 manifold. A manifold is often referred to as a space. However each manifold is its own space regardless if they overlap other metric spaces over an identical volume. The above is described as embedded spaces and is fundamentally a differential geometry technique. How ? can a body be accelerated , without force fallowing. << explaine please ../ The particle is following a geodesic ( curved spacetime path) Here http://curious.astro.cornell.edu/physics/140-physics/the-theory-of-relativity/general-relativity/1059-if-gravity-isn-t-a-force-how-does-it-accelerate-objects-advanced A couple of key notes mass doesn't matter in freefall. There is no force in freefall and a geodesic plots freefall motion. The article covers these notes in greater detail without getting too technical. Edited May 28, 2017 by Mordred
studiot Posted May 28, 2017 Posted May 28, 2017 A manifold is often referred to as a space. Yes, unfortunately. A space has more structure than a manifold as it not only includes the stage or region where the activity takes place but also the sets of quantities involved ie the actors and the relationships between them ie the text of the play. A manifold is little more than the stage.
Roger Dynamic Motion Posted May 28, 2017 Posted May 28, 2017 If you ignore the poor descriptives in the article and look strictly at the math. The geometry of the global metric is static. What is flowing is the assigned inertial frames. ie assign for every value of velocity a Euclidean (Minkowskii) 3d inertial frame. The volume of space itself isn't flowing what is flowing is the field values. Specifically the values that make up a Rheimannian 3 manifold. A manifold is often referred to as a space. However each manifold is its own space regardless if they overlap other metric spaces over an identical volume. The above is described as embedded spaces and is fundamentally a differential geometry technique. The particle is following a geodesic ( curved spacetime path) Here http://curious.astro.cornell.edu/physics/140-physics/the-theory-of-relativity/general-relativity/1059-if-gravity-isn-t-a-force-how-does-it-accelerate-objects-advanced A couple of key notes mass doesn't matter in freefall. There is no force in freefall and a geodesic plots freefall motion. The article covers these notes in greater detail without getting too technical. There is no force in freefall ? How do you explain the beginning of the acceleration from the start .
Mordred Posted May 28, 2017 Posted May 28, 2017 (edited) The very definition of freefall means no force acting upon it. It is a mathematical treatment. The detail to recognize is that under GR the geodesics (path of freefall motion) removes the need of a force which is problematic anyways under Newton gravity as the mass term factors out. ie different objects of different mass will fall at the same rate. So how does one apply f=ma in this scenario when the mass term makes no difference.? This is what GR recognizes. Instead we map the freefall paths according to the path of least action which forms the basis behind the geodesic equations. The path of least resistance correlates the particles kinetic energy to the potential energy due to gravity in this particular case. http://www.feynmanlectures.caltech.edu/II_19.html Yes, unfortunately. A space has more structure than a manifold as it not only includes the stage or region where the activity takes place but also the sets of quantities involved ie the actors and the relationships between them ie the text of the play. A manifold is little more than the stage. Agreed fairly apt descriptive. One of the greatest confusions is heuristic explanations. Particularly with embedded geometries. What is an embedded geometry. Well lets give a simple example. Lets say we have a global spacetime geometry in 4D. ( where every coordinate is a freefall vector). Then we want to describe a lightbeam under this but under greater detail. We don't need all 4 dimensions to describe the wavelength of the lightbeam. (we only require 2 dimensions to describe the amplitude changes.) So we can embed this 2d (Hilbert space) to each coordinate of our 4d space. The same trick happens in strictly GR. The Rheimannian 3 space describes a specific set of symmetry relations that can be found at various locations under our 4D spacetime metric. This is a handy technique especially when you start involving a particular type of vector called "complex vectors" Edited May 28, 2017 by Mordred
studiot Posted May 28, 2017 Posted May 28, 2017 (edited) How ? can a body be accelerated , without force fallowing. << explaine please ../ Rogers you might like to consider the following situation:- A container (on Earth and subject to gravity) is partly filled with liquid and moving in a straight line. It is subject to a constant acceleration. Can you describe and explain the forces acting and the shape of the surface of the liquid? Edited May 28, 2017 by studiot
Mordred Posted May 28, 2017 Posted May 28, 2017 (edited) Rogers you might like to consider the following situation:- A container (on Earth and subject to gravity) is partly filled with liquid and moving in a straight line. It is subject to a constant acceleration. Can you describe and explain the forces acting and the shape of the surface of the liquid? Nice example, two major lessons of GR can be taught from this. Three including how embedded geometries work. Edited May 28, 2017 by Mordred
Roger Dynamic Motion Posted May 28, 2017 Posted May 28, 2017 (edited) Rogers you might like to consider the following situation:- A container (on Earth and subject to gravity) is partly filled with liquid and moving in a straight line. It is subject to a constant acceleration. Can you describe and explain the forces acting and the shape of the surface of the liquid? Well !~ The surface of the water will rise to the opposite side of the acceleration of the bocket at a maximum of 45 dégrée at the first acceleration of 32 ft second <<I think ? And I explain << If the bocket is 6 inches square and contain 2 inches thick of water , and _ the surface of the water is being push down at 32 f second by the Gf.~ and the inertia of the water is being push back from the linear acceleration at 32 f s for the first second _therfore the water will rise of two inches to 4 inches at the opposit side of the acceleration and loose two inches and become 4 inches at the base from the right side of the bocket if the acceleration is to the right ; witch will balance the two forces ~ vertical and horizontal. so the C2 will be 5.66 inches . Edited May 28, 2017 by Roger Dynamic Motion
swansont Posted May 28, 2017 Posted May 28, 2017 How ? can a body be accelerated , without force fallowing. << explaine please ../ I don't understand your question. Did I mention a force?
Roger Dynamic Motion Posted May 28, 2017 Posted May 28, 2017 I don't understand your question. Did I mention a force? Your quote _ Where does it say space is flowing toward a mass? It says "the acceleration of free-falling objects is generally not in the direction of this flow "So if a free-falling object is accelerating toward a mass, it means the flow is not.
swansont Posted May 28, 2017 Posted May 28, 2017 Your quote _ Where does it say space is flowing toward a mass? It says "the acceleration of free-falling objects is generally [/size]not [/size]in the direction of this flow "[/size]So if a free-falling object is accelerating toward a mass, it means the flow is not. Indeed it does.
Roger Dynamic Motion Posted May 28, 2017 Posted May 28, 2017 (edited) Indeed it does. Stil, the body needs to be accelerated at some time if _ it is moving trought space with the ''Cone'' ...in other words <<When is the begining of Motion.? Edited May 28, 2017 by Roger Dynamic Motion
swansont Posted May 28, 2017 Posted May 28, 2017 Stil, the body needs to be accelerated at some time if _ it is moving trought space with the ''Cone'' ...in other words <<When is the begining of Motion.? Seems like a more general question; these coordinates describe a rotating system.
Roger Dynamic Motion Posted May 28, 2017 Posted May 28, 2017 Seems like a more general question; these coordinates describe a rotating system. I would thing !~that today the origine of Motion has been understood. If one claims, that somthing is in motion or moving in space ; I want to know the vectors responsible .
swansont Posted May 28, 2017 Posted May 28, 2017 I would thing !~that today the origine of Motion has been understood. If one claims, that somthing is in motion or moving in space ; I want to know the vectors responsible . Then start a thread to discuss it, instead of hijacking another discussion.
Handy andy Posted May 29, 2017 Author Posted May 29, 2017 If you ignore the poor descriptives in the article and look strictly at the math. The geometry of the global metric is static. What is flowing is the assigned inertial frames. ie assign for every value of velocity a Euclidean (Minkowskii) 3d inertial frame. The volume of space itself isn't flowing what is flowing is the field values. Specifically the values that make up a Rheimannian 3 manifold. A manifold is often referred to as a space. However each manifold is its own space regardless if they overlap other metric spaces over an identical volume. The above is described as embedded spaces and is fundamentally a differential geometry technique. The particle is following a geodesic ( curved spacetime path) Here http://curious.astro.cornell.edu/physics/140-physics/the-theory-of-relativity/general-relativity/1059-if-gravity-isn-t-a-force-how-does-it-accelerate-objects-advanced A couple of key notes mass doesn't matter in freefall. There is no force in freefall and a geodesic plots freefall motion. The article covers these notes in greater detail without getting too technical. When I looked at Minkowski coordinates in Euclidean dimensions I wondered if I should take up religion for a simpler life . But then breathed a sigh of relief when I realized Minkowski coordinates are just a mathematical construct. Also the link you posted above is an excellent description and negates the need for me to take up religion When I read the link I initially posted by strange, I assumed it was a strange referring to the gradients, indicating a flow of space. I followed up and found various references to Kerr https://arxiv.org/pdf/0805.0206.pdf whereby the flow of space is repeatedly mentioned. I understand the thing with gravity it is gradients in gravitational potential that causes things to move and develop mass. The mechanism by which gravity is transmitted is not a mathematical equation, albeit describable by various equations. Gravity is one of the four forces in the standard model promoted by CERN https://home.cern/about/physics/standard-model this includes the graviton. The concept of the graviton being a force transmitter seems to have been dropped by some but is still promoted by CERN and is mentioned in string theory as a means of transmitting gravity. Using the concept of the graviton, do gravitons not move or flow? Can all of space not be assumed to be full of gravitons, which appear in an expanding space, and disappear in a contracting space, inside particles with inertia? Can particles be viewed as vortices sucking gravitons or space into them. Space dragging on a larger scale around planets. Are gravitons still assumed to exist by a majority of scientists or are they now another idea kicked quietly into the bin.
Mordred Posted May 29, 2017 Posted May 29, 2017 (edited) Assuming a graviton exists and there is still the possibility (nor is it wrong to feel it may exist). It would be a spin 2 boson. In effect would mediate the gravitational force in the particle to particle interactions in the same manner as other bosons. Beyond that I can only conjecture as the spin is about the only property the majority of the papers I've read on predicting its properties agree on. edit must also be massless, due to the gravity interactions being at c. A means of getting all the gory mathematical details is to look at the quantum geometrodynamics field of study. It is a branch of QFT that deals specifically with the gravity. It also tries to incorperate the graviton with spacetime curvature. Edited May 29, 2017 by Mordred
swansont Posted May 29, 2017 Posted May 29, 2017 I understand the thing with gravity it is gradients in gravitational potential that causes things to move and develop mass. Gravity does not give things mass.
Handy andy Posted May 29, 2017 Author Posted May 29, 2017 (edited) Gravity does not give things mass. Yes, good point. Has anyone ever tried re writing general relativity in terms of accelerated inertias. As I understand it, a complete mathematical understanding of gravity still eludes theoretical physicists and peasants alike. @ All Speculation: Does the cause of gravity have to be a boson or a fermion? The reason I ask this, is it possible it is neither, ie has no spin, but only flows along gradients. Further Speculation: Particles when destroyed become waves in space, (fermions become bosons) Photons can become part of a particle. Waves are fluctuations in space and are a part of space. What would happen to a gamma ray with 511eV of energy in a black hole, would it become an electron or positron? Could it be that bosons and fermions are made of space, and space is the fundamental building block of everything, that transmits all forces that everything is made from. Edited May 29, 2017 by Handy andy
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