Muhammad Owais Isaac Posted February 26 Posted February 26 gravity by muhammad owais pdf_2602242145004.pdf
KJW Posted February 26 Posted February 26 I am not going to download your file, and I doubt anyone else will. Please provide something that at least initially does not require us to download your file.
Muhammad Owais Isaac Posted February 26 Author Posted February 26 21 minutes ago, KJW said: I am not going to download your file, and I doubt anyone else will. Please provide something that at least initially does not require us to download your file. 👍
Moontanman Posted February 26 Posted February 26 Isn't it the current consensus that the flow of time and mass causes gravity?
swansont Posted February 26 Posted February 26 ! Moderator Note Rules require that material for discussion must be posted. Files are for supporting information 54 minutes ago, Moontanman said: Isn't it the current consensus that the flow of time and mass causes gravity? Time causes gravity? No, that not the current consensus
Moontanman Posted February 26 Posted February 26 (edited) 25 minutes ago, swansont said: ! Moderator Note Rules require that material for discussion must be posted. Files are for supporting information Time causes gravity? No, that not the current consensus I tried to find a source that didn't include a video but this is the best I could do on short notice. I'll try to find more suitable sources but the OP has not explained his own idea yet so I'll wait and see, it's possible this is his idea. https://www.technology.org/2021/02/28/does-time-cause-gravity/ https://mediaplayer.whro.org/program/pbs-space-time/e/does-time-cause-gravity-5hns3m Edited February 26 by Moontanman
MigL Posted February 26 Posted February 26 Gravity is what makes things weigh We anxiously await the OP to clarify what he wants to know about gravity. ( without the hand gesture emoji )
swansont Posted February 26 Posted February 26 3 hours ago, Moontanman said: I tried to find a source that didn't include a video but this is the best I could do on short notice. I'll try to find more suitable sources but the OP has not explained his own idea yet so I'll wait and see, it's possible this is his idea. https://www.technology.org/2021/02/28/does-time-cause-gravity/ https://mediaplayer.whro.org/program/pbs-space-time/e/does-time-cause-gravity-5hns3m First video is all you need. Merely by asking the question you can infer that this isn’t the consensus, and it confirms that mass warping spacetime is the basic idea of general relativity, which, of course, is the consensus. Time dilation is a consequence of the postulates of relativity. But you can look at the equations and decide what causes what is different. If y= mx, does x cause y or does y cause x? It depends on the framework you use. If you don’t have some mechanism in place you can go either way. So sure, you can interpret things to say time dilation causes gravity. Is it the consensus? No, it’s not. ‘ IMO it’s a game. In SR time dilation is a consequence of motion, but does anyone insist that time dilation causes things to move? No. We still have Newtonian physics as a basis (even though the math is an approximation, valid at low speeds) where something starts moving only if there’s a force on it. Time isn’t a force. In GR things get muddled because gravity isn’t a force..But kinematic time dilation doesn’t cause gravity. The kinematic term is the wrong sign. Satellites at a radial distance of ~9600 km (~3200 km in altitude) have the kinematic and gravitational time dilation cancel. Is there no gravity at that altitude? 1
Moontanman Posted February 27 Posted February 27 1 hour ago, swansont said: First video is all you need. Merely by asking the question you can infer that this isn’t the consensus, and it confirms that mass warping spacetime is the basic idea of general relativity, which, of course, is the consensus. Time dilation is a consequence of the postulates of relativity. But you can look at the equations and decide what causes what is different. If y= mx, does x cause y or does y cause x? It depends on the framework you use. If you don’t have some mechanism in place you can go either way. So sure, you can interpret things to say time dilation causes gravity. Is it the consensus? No, it’s not. ‘ IMO it’s a game. In SR time dilation is a consequence of motion, but does anyone insist that time dilation causes things to move? No. We still have Newtonian physics as a basis (even though the math is an approximation, valid at low speeds) where something starts moving only if there’s a force on it. Time isn’t a force. In GR things get muddled because gravity isn’t a force..But kinematic time dilation doesn’t cause gravity. The kinematic term is the wrong sign. Satellites at a radial distance of ~9600 km (~3200 km in altitude) have the kinematic and gravitational time dilation cancel. Is there no gravity at that altitude? Thankyou, I had first learned of this "interpretation" several months ago and the way it was worded and my own ignorance of the subject made it sound interesting. I had assumed it to be mainstream science, I wish such information was graded a bit when it is consumed by interested laymen like me.
Muhammad Owais Isaac Posted February 27 Author Posted February 27 16 hours ago, Muhammad Owais Isaac said: gravity by muhammad owais pdf_2602242145004.pdf 599.3 kB · 2 downloads "It's better to imagine the universe in a different way than lying down like a dead " In this topic we not only going to discuss gravitational binding that holds the things remotely in space - time continuum but we will also try to comprehend the nature and source of this binding . Is this binding , a force or something else ? Reader should note that this imaginative stuff need not be a true delineation but a possible explanation . It must be noted that big bang is not centre of the universe but it marked the emergence and merging of the time dimension with point where density of energy was infinite or maximum possible. The universe is expanding and I assume that space time fabric density is decreasing in all the regions equally except the regions occupied by matter . There is no preferred centre of the universe but it has got point where expansion of the universe does not cause decrease in density of the space time fabric but it increases unlike in the regions away from this point where fabric density decreases with expansion and it is probably because of the supper massive black hole or any other giant celestial stuff in the pseudo centre of the universe . Now let us try to unfold why matter appears to be attracting each other , let us call this attraction by the well known term gravitation . This gravitation in my view is a tendency of matter to occupy the space - time fabric of higher density in its vicinity and this density is always higher in the regions occupied by the massive material bodies as compared to lighter bodies . It means that density of space time fabric in any region occupied by matter is directly proportional to its mass . Hence we conclude that lighter objects spiral towards the heavier objects in space time fabric or towards the region of higher density space time fabric ( planets do not spiral into the star because star itself spiral towards the region of the higher density space - time fabric and so on . In addition to this tendency , matter has another tendency to spiral towards the pseudo centre of the universe or the region of most dense space - time fabric formed by the supper massive black hole or X body . The density of space - time fabric at this point of the universe increases with time . Magnitude of sum of the increase in density of the spacetime fabric by all matter is more than the increasing density of the space - time at the pseudo centre of the universe but it does not mean influence of density of the space time fabric at the pseudo centre is negligible ; it plays a vital role in holding the celestial clusters in the universe . Matter is uniformly and randomly distributed in space which means that mass of bodies do not make them region specific or confined to particular region but distributed randomly . All the heavy bodies are not near the pseudo centre but away from it also hence smaller celestial bodies or their clusters move away from this pseudo centre and some towards it and the net movement is not zero but it goes unnoticed on cosmic scale . The tendency of matter to spiral towards the centre of the universe and towards the region of higher density produced by the giant matter have no doubt different intensities because of the different densities of space time fabric at these two regions . The distance is also a factor that determines where the material bodies move , hence the smaller bodies spiral towards the regions of higher density created by the giant bodies and we shall also note that those giant bodies are continuously in attempt to spiral towards the higher density region in their vicinity which maintains the constant distance between the celestial bodies or systems . There are some regions in the universe where space time fabric is altered by the giant matter to such an extent that other neighbouring clusters tend to merge with them or to occupy their high density space fabric and this merging further increases space time fabric density of that region. We should also keep in mind that these events of space-time fabric density changes are so balanced such that the net change goes unnoticed but these changes are accumulating and once they reaches the critical value when density of the space-time fabric at pseudo centre will be greater than individual sum of the change in density of space-time fabric due to matter At that point all the matter will begin to condense at this point of highest space- time fabric density and there will be a stage when no further changes will occur at this stage time dimension will cease to exist. Hence though the change goes unnoticed at but gradually magnitude of this change will be enough that the magnitude of density of the spacetime fabric at pseudo centre will be highest which will cause all matter to condense in a single point. There will be no more matter outside this point and space time fabric is only meaningful if two bodies are existing at two different locations separated by the space-time fabric since whole space time fabric will be concentrated in a point, this event will cause the cessation of the time dimension since there will be no more changes occurring, no expansion etc. Hence universe would need a new beginning and how will it begin depends on the laws or information states that guides the infant universe to develop. "Imagination is the first step to discover things "
dimreepr Posted February 27 Posted February 27 4 hours ago, Muhammad Owais Isaac said: The universe is expanding and I assume that space time fabric density is decreasing in all the regions equally except the regions occupied by matter . What makes you think space-time has a density? Fabric is a poor word to choose, it only explains things on one level, thereafter it's a hindrance to understanding; imagination only work's to expand our understanding, when diving from the right platform...
MigL Posted March 3 Posted March 3 pointless arguing with religion, Dim. "So let it be written; So let it be done."
KJW Posted March 3 Posted March 3 (edited) On 2/27/2024 at 8:46 AM, swansont said: So sure, you can interpret things to say time dilation causes gravity. Is it the consensus? No, it’s not. The familiar gravity that we all experience on earth is caused by gravitational time dilation. I have devised "the slinky analogy" to provide some insight: Note that as the slinky is bent, the side away from the direction of bending is longer than the side towards the direction of bending. Furthermore, the sharper the bending, the greater the relative difference in the length of the two sides. There is a geometric relationship between the relative change in the length of an arc with respect to the radial distance and the curvature of the arc. Gravitational time dilation is the change in the length in spacetime of a timelike worldline with respect to height and is geometrically related to the curvature of the worldline, which corresponds to the acceleration we experience standing on the ground on earth. [math]a^\mu = -c^2 g^{\mu\nu} \dfrac{1}{T} \dfrac{\partial T}{\partial x^\nu}[/math] where: [math]a^\mu[/math] is the upwardly directed acceleration of an observer at rest on the ground. [math]T[/math] is the relative spacetime length of a timelike Killing vector at a given location in three-dimensional space. [math]\dfrac{1}{T} \dfrac{\partial T}{\partial x^\nu}[/math] is the gravitational time dilation. [math]g^{\mu\nu}[/math] has signature [math](1, -1, -1, -1, -1)[/math] [math]c[/math] is the speed of light in a vacuum (used to relate the curvature of a worldline to its acceleration) The rubber sheet analogy that is frequently used to explain gravity is incorrect even as an analogy. Of the various problems it has, the one that is relevant to this post is that the familiar gravity that we all experience is not caused by the curvature of three-dimensional space, as suggested by the rubber sheet analogy. It is specifically time dilation that gives rise to such gravity. Edited March 3 by KJW
swansont Posted March 3 Posted March 3 8 minutes ago, KJW said: The familiar gravity that we all experience on earth is caused by gravitational time dilation. I have devised "the slinky analogy" to provide some insight: Note that as the slinky is bent, the side away from the direction of bending is longer than the side towards the direction of bending. Furthermore, the sharper the bending, the greater the relative difference in the length of the two sides. There is a geometric relationship between the relative change in the length of an arc with respect to the radial distance and the curvature of the arc. Gravitational time dilation is the change in the length in spacetime of a timelike worldline with respect to height and is geometrically related to the curvature of the worldline, which corresponds to the acceleration we experience standing on the ground on earth. aμ=−c2gμν1T∂T∂xν where: aμ is the upwardly directed acceleration of an observer at rest on the ground. T is the relative spacetime length of a Killing vector at a given location in three-dimensional space. 1T∂T∂xν is the gravitational time dilation. gμν has signature (1, -1, -1, -1, -1) c is the speed of light in a vacuum (used to relate the curvature of a worldline to its acceleration) The rubber sheet analogy that is frequently used to explain gravity is incorrect even as an analogy. Of the various problems it has, the one that is relevant to this post is that the familiar gravity that we all experience is not caused by the curvature of three-dimensional space, as suggested by the rubber sheet analogy. It is specifically time dilation that gives rise to such gravity. All you’ve shown is an equality. That’s not causality. Are there any other equations for gravitational acceleration in GR? Also, please address my comments about kinematic dilation, which you’ve ignored.
Genady Posted March 3 Posted March 3 1 hour ago, KJW said: The familiar gravity that we all experience on earth is caused by gravitational time dilation. Yes, it is, in this sense: "This is extremely general. In any kind of gravitational field, as long as it is more or less constant with time, and not doing anything too radically relativistic, the coefficient in front of \(dt^2\) in the metric is always one plus twice the gravitational potential." Susskind, Cabannes. General Relativity: The Theoretical Minimum (p. 155).
KJW Posted March 4 Posted March 4 4 minutes ago, swansont said: All you’ve shown is an equality. That’s not causality. The gravitation time dilation and the curvature field of a Killing vector field of an arbitrary stationary spacetime are concomitant. But gravitational time dilation is a property of the spacetime geometry whereas gravity is a phenomenon that we observe. It is thus natural to say that gravitation time dilation causes gravity. We might say that gravity causes gravitational redshift, but this doesn't really explain gravity. The crucial point is that anywhere there is time dilation in a stationary spacetime, a stationary observer will accelerate as if in a gravitational field. This is a fact that everyone who proposes a cause of gravity must take into account. That is, we have an explanation of gravity, a second explanation is not only unnecessary, but is too many. It also provides some detail to the understanding of gravity that "spacetime curvature" may not provide. It should be noted that gravitational time dilation does not distinguish between true gravity and artificial gravity produced by an accelerated frame of reference in the absence of true gravity (so gravitational time dilation is accelerational time dilation). Thus, I am not addressing a cause of gravity in terms of an energy-momentum source. One thing I should mention is that gravitational redshift is directly proportional to the frequency of the redshifted radiation. Therefore, any amplitude modulation of the radiation is also redshifted by the same relative amount. This means that any mechanical clock will be observed to tick slower. Thus, gravitational redshift is a gravitational time dilation. 4 minutes ago, swansont said: Are there any other equations for gravitational acceleration in GR? One can always obtain the acceleration of an arbitrary worldline in an arbitrary spacetime using the absolute derivative of [math]\dfrac{dx^\mu}{d\tau}[/math] with respect to proper time [math]\tau[/math]. But I specifically considered the familiar gravity that we all experience on earth to provide an understanding of the phenomenon that we all experience without the complication of trying to understand the complexities that GR has to offer. 4 minutes ago, swansont said: Also, please address my comments about kinematic dilation, which you’ve ignored. I ignored it because it wasn't relevant to what I was discussing. Time dilation in general is about comparing proper times of different spacetime trajectories. It's also about how to relate the endpoints of the different spacetime trajectories so that any comparison is meaningful. In the case of a stationary spacetime, the time translational symmetry along a Killing vector field provides a natural way to define time dilation. There is no suggestion that just any time dilation will cause gravity. My derivation was specific to stationary spacetimes, which is approximately true for earth (spinning rigid objects are stationary, btw).
swansont Posted March 4 Posted March 4 2 minutes ago, KJW said: The gravitation time dilation and the curvature field of a Killing vector field of an arbitrary stationary spacetime are concomitant. But gravitational time dilation is a property of the spacetime geometry whereas gravity is a phenomenon that we observe. It is thus natural to say that gravitation time dilation causes gravity. Natural? That’s rather subjective. 2 minutes ago, KJW said: We might say that gravity causes gravitational redshift, but this doesn't really explain gravity. Why does it have to? In the first case you’re explaining what causes the redshift. Nothing else. 2 minutes ago, KJW said: It should be noted that gravitational time dilation does not distinguish between true gravity and artificial gravity produced by an accelerated frame of reference in the absence of true gravity (so gravitational time dilation is accelerational time dilation). True gravity? The equivalence principle says you can’t distinguish it from other acceleration. 2 minutes ago, KJW said: Thus, I am not addressing a cause of gravity in terms of an energy-momentum source. But one can make that association. And that’s also an equality one can write down. 2 minutes ago, KJW said: One can always obtain the acceleration of an arbitrary worldline in an arbitrary spacetime using the absolute derivative of dxμdτ with respect to proper time τ . But I specifically considered the familiar gravity that we all experience on earth to provide an understanding of the phenomenon that we all experience without the complication of trying to understand the complexities that GR has to offer. I hardly think time dilation can be considered a phenomenon we all experience, considering the sophistication of the equipment necessary to detect it. 2 minutes ago, KJW said: I ignored it because it wasn't relevant to what I was discussing. Well, that’s rather convenient. 2 minutes ago, KJW said: Time dilation in general is about comparing proper times of different spacetime trajectories. It's also about how to relate the endpoints of the different spacetime trajectories so that any comparison is meaningful. In the case of a stationary spacetime, the time translational symmetry along a Killing vector field provides a natural way to define time dilation. There is no suggestion that just any time dilation will cause gravity. The original suggestion was that time causes gravity, and that this was a consensus. What textbooks teach this, as apposed to energy-momentum and curvature? What’s the breakdown in the literature? Not liking an explanation is not really a consideration. And how does a clock “know” that its time dilation is gravitational?
KJW Posted March 4 Posted March 4 (edited) 3 hours ago, Genady said: Quote The familiar gravity that we all experience on earth is caused by gravitational time dilation. Yes, it is, in this sense: "This is extremely general. In any kind of gravitational field, as long as it is more or less constant with time, and not doing anything too radically relativistic, the coefficient in front of dt2 in the metric is always one plus twice the gravitational potential." Susskind, Cabannes. General Relativity: The Theoretical Minimum (p. 155). The other aspect of what I wrote is the analogy that enables someone to appreciate the esoteric nature of gravity in terms of the geometry of something as familiar as a slinky or a disc. In fact, for a disc, one has: [math]b_r = -\dfrac{1}{C} \dfrac{dC}{dr} = -\dfrac{1}{2 \pi r} \dfrac{d(2 \pi r)}{dr} = -\dfrac{1}{r}[/math] where: [math]b_r[/math] is the radially directed curvature of the circumference of a disc at radius [math]r[/math] [math]C[/math] is the circumference of the disc at radius [math]r[/math] [math]r[/math] is the radius [math]C[/math] increases with [math]r[/math] [math]\Rightarrow[/math] [math]b_r[/math] is directed inward towards the centre. Edited March 4 by KJW
KJW Posted March 4 Posted March 4 (edited) 4 hours ago, swansont said: Quote The gravitation time dilation and the curvature field of a Killing vector field of an arbitrary stationary spacetime are concomitant. But gravitational time dilation is a property of the spacetime geometry whereas gravity is a phenomenon that we observe. It is thus natural to say that gravitation time dilation causes gravity. Natural? That’s rather subjective. Not really. Suppose you have a hole in the bottom of a bucket of water. Water is leaking out of the bottom of the bucket. Surely it is natural to say that the hole is causing the bucket to leak rather than the leak is causing the hole in the bucket. 4 hours ago, swansont said: Quote We might say that gravity causes gravitational redshift, but this doesn't really explain gravity. Why does it have to? In the first case you’re explaining what causes the redshift. Nothing else. Gravitational redshift and gravity are concomitant. The question is what is causing what? Is there a principle to decide this? 4 hours ago, swansont said: Quote It should be noted that gravitational time dilation does not distinguish between true gravity and artificial gravity produced by an accelerated frame of reference in the absence of true gravity (so gravitational time dilation is accelerational time dilation). True gravity? The equivalence principle says you can’t distinguish it from other acceleration. The equivalence principle only applies locally. The tidal effect distinguishes true gravity from an artificial gravity. However, given that we are discussing the familiar gravity that we all experience on earth, which is true gravity, I felt it was necessary to point out that it isn't only true gravity that is caused by time dilation. In fact, the formula I gave expresses acceleration (not gravity) in terms of time dilation. 4 hours ago, swansont said: Quote Thus, I am not addressing a cause of gravity in terms of an energy-momentum source. But one can make that association. And that’s also an equality one can write down. That's a different question. If one wants to know why there is time dilation surrounding a massive object such as the earth, then one probably needs to understand the Einstein equation. But if given that there is time dilation surrounding a massive object such as the earth, then the above explains why that time dilation produces gravity. 4 hours ago, swansont said: Quote One can always obtain the acceleration of an arbitrary worldline in an arbitrary spacetime using the absolute derivative of dxμ/dτ with respect to proper time τ . But I specifically considered the familiar gravity that we all experience on earth to provide an understanding of the phenomenon that we all experience without the complication of trying to understand the complexities that GR has to offer. I hardly think time dilation can be considered a phenomenon we all experience, considering the sophistication of the equipment necessary to detect it. Gravity is the phenomenon we all experience, time dilation is the property of the surrounding spacetime that causes us to experience gravity, and the slinky analogy is the geometric principle that allows ordinary folk to understand it. 4 hours ago, swansont said: Quote Time dilation in general is about comparing proper times of different spacetime trajectories. It's also about how to relate the endpoints of the different spacetime trajectories so that any comparison is meaningful. In the case of a stationary spacetime, the time translational symmetry along a Killing vector field provides a natural way to define time dilation. There is no suggestion that just any time dilation will cause gravity. The original suggestion was that time causes gravity, and that this was a consensus. What textbooks teach this, as apposed to energy-momentum and curvature? What’s the breakdown in the literature? Not liking an explanation is not really a consideration. There are different aspects to the question of what causes gravity. I chose to explain why time dilation causes objects to fall to the ground. After all, why should an object be attracted to a location with slower time (or repelled from a location with faster time)? Apart from what I said above, does this seem natural? 4 hours ago, swansont said: And how does a clock “know” that its time dilation is gravitational? Clocks don't "know" about time dilation. They only measure time at the same intrinsic rate regardless of their location or motion. What determines that a time dilation is gravitational (or accelerational) is that it depends on position. By contrast, the time dilation usually considered in SR depends on speed. Edited March 4 by KJW
Markus Hanke Posted March 4 Posted March 4 4 hours ago, swansont said: The original suggestion was that time causes gravity In fairness, I think this misrepresents what KJW is trying to say. How does a freely-falling test particle under the influence of gravity move? It follows a geodesic in spacetime, which is a particular solution to the geodesic equation. This equation is itself a particular form of the principle of extremal ageing, ie the tendency will be for the test particle to move such that a comoving clock will record an extremum of proper time between any given pair of events along the trajectory. When you actually perform this variational problem, of course all components of the metric are technically involved. However, when you are dealing with situations that are in some sense close to being Newtonian / not too relativistic, such as Earth for example, the tt-component of the metric will be much larger than the rest of the metric, by a factor of ~c^2. It will dominate the calculation - meaning time dilation plays a much larger role than tidal effects. In that sense, it is indeed almost exclusively time dilation that gives rise to our daily experience of “downward gravity” here on Earth. Of course, this would not be true in other situations, like near the EH of a solar mass BH, where tidal gravity plays a major role. This doesn’t mean that the source of gravity isn’t energy-momentum and curvature, it just means that under certain circumstances the tidal components don’t play a major role, leaving mostly just time dilation as the dominating effect.
Genady Posted March 4 Posted March 4 12 hours ago, KJW said: Gravitational time dilation is the change in the length in spacetime of a timelike worldline with respect to height and is geometrically related to the curvature of the worldline, which corresponds to the acceleration we experience standing on the ground on earth. This ^^^^, I understand. 8 hours ago, KJW said: the analogy that enables someone to appreciate the esoteric nature of gravity in terms of the geometry of something as familiar as a slinky or a disc. This ^^^^, is only a distraction to me. (But generally, more often than not, I dislike analogies. Perhaps something individual.)
swansont Posted March 4 Posted March 4 10 hours ago, Markus Hanke said: In fairness, I think this misrepresents what KJW is trying to say. KJW responded to/quoted me, not the other way around, so if they were not engaging in the context of what I was talking about it’s on them, not me. To add to that, I had already written about some of the points raised. These were ignored.
swansont Posted March 4 Posted March 4 13 hours ago, Markus Hanke said: the tt-component of the metric will be much larger than the rest of the metric, by a factor of ~c^2. It will dominate the calculation - meaning time dilation plays a much larger role than tidal effects. What is the algebraic form of that component?
DanMP Posted March 5 Posted March 5 On 3/4/2024 at 8:03 AM, Markus Hanke said: This doesn’t mean that the source of gravity isn’t energy-momentum and curvature, it just means that under certain circumstances the tidal components don’t play a major role, leaving mostly just time dilation as the dominating effect. Time dilation is the "dominating effect" or the dominating [apparent] cause? I wrote apparent because, in my opinion, the actual cause of gravity is the one that creates "the curvature" ...
Genady Posted March 5 Posted March 5 6 minutes ago, DanMP said: Time dilation is the "dominating effect" or the dominating [apparent] cause? I wrote apparent because, in my opinion, the actual cause of gravity is the one that creates "the curvature" ... Since energy-momentum and curvature are not timelike separated, there is no meaningful causal relation between them.
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