mistermack

I don't think anyone is disputing that if this process was happening, there would have to be acceleration. If you think it's not relative to the inverse square of the radius, the best refutation would be a mathematical calculation. I'm not going to do it, but if you are mathematically adept, then that's the best way to approach it. As I said, I may be able to persuade a friendly mathematician to dash it off. But it's pointless me giving my opinion without it, because I'm just guessing. Edit : Just to add a link to the full text of the river model study that I linked the summary of earlier : https://archive.org/stream/arxiv-gr-qc0411060/gr-qc0411060_djvu.txt

I don't think anyone is disputing that if this process was happening, there would have to be acceleration. If you think it's not relative to the inverse square of the radius, the best refutation would be a mathematical calculation. I'm not going to do it, but if you are mathematically adept, then that's the best way to approach it. As I said, I may be able to persuade a friendly mathematician to dash it off. But it's pointless me giving my opinion without it, because I'm just guessing.

Well, acceleration IS change in velocity. So your statement actually reads that acceleration IS proportional to the inverse square. I would think it would be an easy calculation for a habitual mathematician to do, so I'll see if I can persuade one to do it for me.

I don't see how you arrived at that conclusion. I would say that it's related to the difference in volume of the sphere, divided by the difference in the radius, which means it's proportional to the inverse square.

I have to issue a health warning here, and that is that anything that I write is just a reflection of my own level of education in physics, and therefore should not be taken as gospel, or theory, or anything other than my own understanding of the subject, with all it's flaws. So if I answer your points, you need to bear in mind that I'm just giving you an opinion, it's what I think I know. And it may well be wrong. What causes the objects to accelerate? The point is that once you are off the cliff, you are not accelerating relative to the space that you inhabit. You are just floating free in that space. It's the space itself that is accelerating, relative to the Earth, for the reasons I gave earlier. There would have to be a transfer of energy, from potential energy of the initial state, to kinetic energy because of the relative motion of the two bodies. I'm not confident I could go into fine detail on that. I'm afraid I don't really understand the rest of the question.

There wouldn't be any observable difference to objects falling normally under gravity. That's the point really. All observed phenomena would be the same. It's just a different cause, or a different way of looking at the cause. I'm still looking for a reason why it couldn't be valid. I'm sure it's out there. In your example, the object dropped from higher would be accelerated from it's initial position, so it would arrive moving at speed v relative to the cliff edge object. At that point, they would both be accelerating at 9.81 mps², but the first would fall past the second, and leave it behind, as at that point, it has velocity v, whereas the second has velocity 0. (relative to the cliff) This is exactly the same as you would expect under Newtonian Physics. The idea of space flowing into a massive body has been worked on, and published, having passed peer review by the American Journal of Physics. ( thanks Strange for the link) http://aapt.scitation.org/doi/10.1119/1.2830526 It was applied only to black holes, but I can't see any reason why it can't be applied to less massive bodies like the Earth or Sun. If space can flow towards a source of gravity, it will have no way of "knowing" what is causing the gravity. If space can disappear into black holes continuously for billions of years, then it doesn't seem impossible that it could do the same into the Earth on a smaller scale. The concept seems to offer a simpler view of gravitational time dilation. Instead of two types of time dilation, there is just one, motion through space. And it seems to offer an explanation why the effects of gravity, and acceleration, appear identical and interchangeable. Maybe it's because they ARE the same thing. Having said that, I'm still looking for ways to prove that it's not valid. That's still the object of the exercise.

Thanks for all of the comments. I've learned more than I expected from this thread, and as far as I'm concerned, the answer is no. You may be able to slow time with a tuning fork, but only by an incredibly small fraction, that would never be measurable.

If you picture a funnel, which you keep filled with water, the water at the wide end moves down slowly, but much faster at the narrow end. If you picture a sphere as lots of funnels, bound together, then you have a picture of what I proposed might be happening.

Yes, if you read back through, I'm proposing that space is not only flowing inwards, but also accelerating all of the way, relative to the massive body that is causing the effect. (Earth, in our case) So if you step off a cliff, then you free fall at 9.81 mps², because the space you occupy is doing exactly that. If you don't step off the cliff, then you are being accelerated at 9.81 mps² upwards, relative to the space that you occupy, and the force for that to happen is supplied by the Earth that you are standing on. The speed of the flow past you would have no effect at all, that you could feel. But it would explain why your clock runs slower than a clock in remote space.

Thanks Strange. I'm completely numb from the first link, but the second about the space waterfall into black holes is nice to see. It's not dissimilar to what I was picturing happening at a black hole so according to that writer, the maths match the hypothetical picture, in that case. If a black hole CAN cause space to flow towards it, then I don't see why any source of gravity isn't doing the same thing, obviously at a lesser scale. After all, black hole gravity is no different to any other gravity, outside of the event horizon.

I don't understand where you get the idea of drag from. There is no drag in empty space, no matter what your velocity. I'm not proposing that there is some sort of substantial medium, any different to the space time that is currently accepted. If a solid body can continue in motion relative to space, without drag, then why should there be drag if space were to move relative to the body? It's the same situation.

I suppose a fairly obvious way to prove this wrong, would be to set up a time dilation experiment, on the surface of the Earth, with one clock moving down, and the other moving upwards. Maybe that's already been done?

I don't really see that there has to be contradiction, between this picture and the picture that general relativity paints. If you say that space time curves, are you not saying that the shape of space is changing with time? So the idea of space in motion is inherent in GR. The stronger the gravitational field, the more curvature of space time. The more curvature of space time, the more space is in motion.

I wouldn't picture it like that. I don't see the need for a source or anti-gravity. If you have two pipes draining water in an ocean, a certain distance apart, then there is no need for a source of water. The surrounding water of the ocean moves to occupy the space vacated by the water you are draining away.

Not contents, or you would see solid objects shrinking. The force of gravity is very weak, compared to the other forces, at particle level. I would expect the effect to be identical to gravity as we know it, so I don't see why there should be any drag effect, other than what we observe of gravity. I don't think the inflow velocity has anything to do with acceleration. If the space at the surface of the Earth was accelerating downwards at 9.81 m/s2, then if you are standing stationary on the surface, you will be accelerating in an upward direction relative to the space that you occupy, (not relative to the Earth), and this would require a force, which is provided by the solid surface that you stand on.

I think it's easier to picture in two dimensions first. I was picturing something like a pipe near the surface of a very shallow pond, down which water escapes. The water near the pipe will move faster towards the pipe, than water further away. The flow gets faster and faster as you get near the pipe, because all of the flow is concentrated. If you imagine a sunken circular concentric string around the pipe, the flow down into the pipe has to be passing across that string. A bigger circle has a bigger circumference, and so the flow speed across it will be less. So it's directly related to the circumference of a concentric circle at any given radius. If you then picture the same thing in 3D, then it's related to the surface of a concentric sphere, in the same way.

Thanks, I take your point. It's just terminology, easily remedied. I wasn't trying to be precise with the word, but just to convey the idea. You would need to know the precise mechanism, to be able to accurately describe it anyway. But does a magnet pull on iron, or is it pushed?

No apology needed, all comments are warmly welcomed. I did mean that. It appears that time is relative in a similar way to space, in that a clock is only faster or slower, relative to another clock, just as you can only detect movement, relative to another body. So I was really assuming that the deeper in the gravity well you are, the slower your clock is running, RELATIVE to a clock that is somewhere out in deep space, unaffected by the gravity well. Which corresponds to a clock at the very top of the gravity well.

I should have included the pretty obvious point, that this scenario would predict the existence of black holes, if they hadn't already been predicted and detected. The more massive a body, the greater would the final velocity of space being pulled into it, and there would surely be an instance where a body was big enough to cause a final velocity approaching the speed of light. A photon emitted at that stage would still travel at c, but wouldn't make any headway away from the massive body, so no light could escape. In bodies more massive still, there would be a point in the gravitational well, at which c was reached, and that would be the event horizon, below which no light could escape the massive body.

I enjoy building up speculative ideas and knocking them down again. I find that I often do learn a bit in the process. I wrote this about six months ago, as an attempt to make a mental picture of how gravity could work. Then I found a flaw that killed it, so I left it at that. Now, I read it again, and can't remember what knocked it on the head, for me. I think it was something to do with gravitational time dilation, but can't remember what. And it turns out I had the wrong idea about that anyway. So please feel free to pull it apart, I'm not begging or pushing it as anything other than a thought experiment, that you might enjoy taking apart, as I like to do. So this is it, copied and pasted from six months ago: --------------------------------------------------------------------------------------------------- What would happen if every particle of matter in the Universe is actually constantly sucking in and absorbing space from around it? On objects that have a huge mass, like a planet, there would be a great inward flow of space, because there are so many particles concentrated in one place. Here on the surface of the Earth, we would be living in a high-speed flow of space, as it was sucked past us into the Earth. How could you tell that this was happening? If you move at a constant speed through space, there is no indication or sensation of speed. You can’t tell if you are moving, or staying still. So, if space was whizzing past us at high speed down into the Earth, we wouldn’t feel anything. However, one thing about moving fast relative to space, is that time slows. The faster you move, the slower your clock will run. The effect is called time dilation. So if space is being sucked into the Earth, whizzing past us on the surface at high speed, a clock that is positioned here on the surface of the Earth should have space whizzing past faster, and so run slower than one that is out in the depths of space, well away from the Earth. Does this actually happen? Yes, it does. It’s called gravitational time dilation under General Relativity. It happens close to any substantial massive object. It’s been accurately measured many times over, so it’s not a controversial idea, it’s a known fact. The only difference in GR is that it’s attributed to gravity, rather than relative motion through space. But time dilation has the same effect, whether it’s gravitational, or through motion. It should be possible, if we know the gravitational time-dilation figure for the surface of the Earth, compared to remote space, to work out the speed that space would need to be passing us by, to cause the same time-dilation. So if this is actually happening, it should be an easy calculation to give a figure for the speed at which space is being sucked past us on the surface of the Earth. But, what if here on the surface of the Earth, space is not just being sucked into the planet at a constant speed, but at the surface, the space is actually accelerating at a rate of 9.81 metres per sec² ? So, without the support of the Earth beneath you, you too would fall downwards with an acceleration of 9.81 mps². This is exactly what does happen, and we experience it as gravity. You would expect this to be the case, if space from a practically infinite volume was being sucked into a smaller and smaller volume. Like water approaching a sink hole. It has to speed up as it gets concentrated into a smaller and smaller volume. In other words, what we think of as gravity on Earth, could actually be space that is accelerating downwards. The pull of gravity on Earth, and an acceleration in space of 9.81 mps² are indistinguishable. They feel exactly the same. It’s called artificial gravity. And it also works the other way. In planes that are used to train astronauts, they produce artificial gravity pointing away from the Earth of 9.81 mps², and for a short while, the trainees are weightless and floating. The gravity due to the Earth, and the opposite artificial gravity due to the plane’s acceleration, are an exact match and cancel each other out. So gravity and acceleration feel exactly the same. Maybe, it’s because they ARE the same. If this sucking in of space were actually happening, then two massive objects freely floating in space would accelerate towards each other because they are both trying to pull in the same bit of space. Also, any light that was passing close by a very massive object, like a super-massive black hole, would be deflected, as the space that it was passing through would be in accelerating motion, towards the black hole. So you would be able to see multiple images of objects that were directly behind the black hole. This happens too and is known as gravitational lensing. The obvious question that arises, is what happens to the space that is being sucked into matter? If the Earth has been sucking in space for 4 billion years, where has it gone? I don’t have an answer for that, except to point out that according to big bang theory, all of the universe was once smaller than a pin head, and space is basically nothing, so there is nothing that appears obviously impossible about the concept from that angle. One interesting consequence of this notion, is that if it’s right, then space can and must ‘pull’ on its neighbouring space. If the Earth is sucking in space in its immediate vicinity, then that would be resulting in the adjoining space moving to replace it, and the space adjoining that space moving to replace that, and so on. As the process radiates outwards from the Earth, it’s happening over a bigger and bigger area, as the process radiates outwards, like an inflating bubble. So, the strength of the effect in any one place diminishes in line with the growing surface area of a sphere, in relation to its distance from the centre. Space will be moving slower and slower, the further you get from the Earth. This is why the space would be accelerating as it moves in, and the rate of acceleration rises, as you get nearer to the Earth. Also, any sudden change in the position of large amounts of mass will result in a ripple in the normally constant and even pulling of space on its neighbouring space. This ripple should travel at the speed of light, in line with other massless disturbances in space. This would be an equivalent of gravitational waves, which were predicted by Einstein, and are just recently being confirmed. I thought of a problem with this idea, but I can’t remember it at the moment. But it did knock it on the head, as far as I was concerned. I’ll try to recall what it was. Should have written it down. I think it’s to do with gravitational time dilation. ------------------------------------------------------------------------------------------------------------------------------------------------ That's what I wrote back then. Janus just put me right about time dilation in a gravitational well, and at first sight, it doesn't conflict with this scenario, as the deeper you are in the gravitational well, the faster space will be passing you by, and hence, the slower your clock. I wish I could remember what I saw originally wrong with this, but it's gone from my head. I should have written it down. Another lesson learned. Anyway, I hope you can have a bit of fun with this.

Thanks Janus. I have got my head around some of that, thanks to the mental picture you provided. So the deeper in the gravity well you are, the slower your clock is running, even if there is no increase in the actual pull of gravity. That's counter-intuitive at first thought, but I think I get it now. So the event horizon of a black hole is as much to do with position, as the force at that point. It's the point from where the frequency of a photon would drop to zero, before it could escape. A combination of field strength and position in the field. ??

That does strike me as pretty amazing. What physical difference can there be, between the two clocks?

I thought that it was related to the strength of the gravitational field at the point in question, and that that was directly related to the g force at that point, which is directly comparable to the g force of an accelerating body.

So are you saying that the acceleration doesn't come into the equation? I thought that in General Relativity, time dilation occurs in a gravitational field, and acceleration is not distinguishable from gravity.

Just an odd thought that occurred to me seconds ago. Time slows, for objects under acceleration. The tip of a tuning fork is constantly accelerating one way, then the other. The g forces must be very high. Could you set up an experiment to slow the ageing of a radioactive isotope right down, by putting it on the tip of a similar spring, and maintaining it's vibration?