Gravity. Please knock this down

[mistermack]

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.

[J.C.MacSwell]

2 hours ago, mistermack said:

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.

You are using gravity as an explanation of how it works.But what, in the model, causes both objects to accelerate at 9.81 m/s²? How is the acceleration imparted? They both need 9.81 m/s² but totally different flows to impart it...unless...what? Other than hand wave "works like gravity". (if it's nothing imparted but just "space removal" why more and faster for one object than the other? One would require more of a reduction of space in the same time frame)

With your model (steady flow) space is inflowing and accelerating toward the centre. But unless it is expanding as well the acceleration will not follow an inverse square law (the velocity would). Where does the extra space come from to allow it?

Edited October 16, 2017 by J.C.MacSwell

[mistermack]

3 hours ago, J.C.MacSwell said:

You are using gravity as an explanation of how it works.But what, in the model, causes both objects to accelerate at 9.81 m/s²? How is the acceleration imparted? They both need 9.81 m/s² but totally different flows to impart it...unless...what? Other than hand wave "works like gravity". (if it's nothing imparted but just "space removal" why more and faster for one object than the other? One would require more of a reduction of space in the same time frame)

With your model (steady flow) space is inflowing and accelerating toward the centre. But unless it is expanding as well the acceleration will not follow an inverse square law (the velocity would). Where does the extra space come from to allow it?

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.

[J.C.MacSwell]

3 hours ago, mistermack said:

I'm afraid I don't really understand the rest of the question.

In a simple, steady state flow model in 3 dimensions, at a given distance from the centre the flow should be accelerating at 1/2 of what it is at half the distance (inverse relationship...goes up by twice as it moves to half the distance)

With gravity the acceleration is 1/4 that of half the distance. (inverse squared relationship...goes up by 4X as it moves to half the distance).

So for the acceleration to more than double you need more space accelerating than you have a supply of...

 

 

[mistermack]

4 hours ago, J.C.MacSwell said:

In a simple, steady state flow model in 3 dimensions, at a given distance from the centre the flow should be accelerating at 1/2 of what it is at half the distance (inverse relationship...goes up by twice as it moves to half the distance)

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.

 

 

 

[J.C.MacSwell]

10 hours ago, mistermack said:

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 think it's the velocity that changes proportionally to the inverse square of the radius.

[mistermack]

1 hour ago, J.C.MacSwell said:

I think it's the velocity that changes proportionally to the inverse square of the radius.

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. 

 

[J.C.MacSwell]

Just now, mistermack said:

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. 

 

Acceleration is change in velocity with respect to time, not distance.

[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.

[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   

[Mordred]

The River model at one time was one of the more popular models towards understanding GR. It was one of the earliest studies, that I personally took when I was first starting to learn GR.

 Nothing wrong with using this platform, to start wading into the depths of GR.

[mistermack]

15 hours ago, Mordred said:

The River model at one time was one of the more popular models towards understanding GR. It was one of the earliest studies, that I personally took when I was first starting to learn GR.

 Nothing wrong with using this platform, to start wading into the depths of GR.

Yes, it seems to be all over the web at various locations, so it seems to still have some popularity.

It's occurred to me that the hypothetical velocity for the flow of space at the Earth's surface would be equal to Earth's escape velocity of about 11.186 km/s, so you could use the the resulting time dilation that that would cause, and compare it to the figure for gravitational time dilation at the surface, to see if they were the same. If they were significantly different, I think that would be a problem for the notion.

Not being very mathematical though, I would struggle with that.

[mistermack]

To put it into perspective, if space WAS accelerating towards the Earth at the same rate that gravity causes things to drop, then the speed that it's passing us by, on the surface, has to equal the escape velocity of the Earth, as it's the same thing in reverse.

That means that we would be in a flow of space of about 11.186 km/s going vertically down.
That compares to about 0.5 km/s rotation at the equator, and about 30 km/s around the Sun.
Then the Sun goes round the Milky Way at 220 km/s .

The nearest thing in the Universe to a special, or universal reference frame, is the cosmic microwave background, which permeates the entire Universe, and they recently got a fix on that.
We are moving at 390 km/s relative to that.

Also, the galaxies in our neighborhood are also moving at a speed of nearly 1,000 kilometers per second towards something called the Great Attractor which is an area of space with a lot of gravity.

So the 11.186 km/s figure for this idea is pretty small in comparison to what we know is happening to us on a grand scale.

[mistermack]

Just found a pdf full version of the river model study with the illustrations, it can be viewed and downloaded here : 

https://ia801009.us.archive.org/6/items/arxiv-gr-qc0411060/gr-qc0411060.pdf   

 

[mistermack]

I've thought of one difference this process would produce, compared to general relativity.
Unfortunately, it would probably be impossible to measure.
If this were actually happening, then the time dilation at the centre of the Earth would be LESS than at the surface, because there would be no flow of space due to gravity at that point. 
Using GR, the dilation would be greater as you descend because you are going deeper in the gravitational well. Although it would be complicated, as the pull would reduce, as the amount of matter above you increases. But clocks would still run slower at the centre. With this process, they would run faster than at the surface.

When I was first chewing over this idea, it was the similarity between acceleration and gravity that was nagging at me.
Why would they be so similar? When you open the throttle of a powerful bike, you immediately feel a new "gravity" pulling your body backwards. Yet there is one big problem staring at you, if you try to picture the two phenomena being the same. And that is the speed of light.

I have a force of about 80kg pushing at my feet 24/7. I'm obviously not going anywhere, so how can this be due to acceleration? Ok, so introduce the idea of space accelerating past me into the Earth. Now I could be accelerating, relative to space. BUT, if I keep accelerating at 9.81 m/s², I worked it out that I would hit the speed of light in less than a year. (353 days and 20 hrs to nearest hour, if you're interested.) 
So in less than a year, I would have broken the speed of light, relative to the space passing me by.

So how can you constantly accelerate, and yet not go any faster? And that's what's answered by the funneling of space into a smaller and smaller sphere. There HAS to be a constant acceleration, at any point in the gravitational well, as it decreases in volume.
 

[mistermack]

Using online calculators, I’ve compared the time dilation at the Earth’s surface due to gravity with that due to the notional time dilation due to a speed relative to space of 11.186 km/sec. If  they had been radically different, I think it would have positively refuted the idea.

They come to 1.0000000006600 and 1.0000000006961 respectively. Given that the 11.186 km/sec figure for the Earth’s escape velocity is obviously not accurate to a large number of decimal places, it looks like gravitational time dilation is coming out the same as what the velocity-caused dilation would be.

I can’t give my workings because I used an online calculator and figures that NASA give. But here are the links, if anyone wants to do their own check :    http://keisan.casio.com/exec/system/1224059993     and   http://www.relativitycalculator.com/pdfs/NASA_Time_Dilation_Earth.pdf  

Is it too much of a coincidence, that the known time dilation at the Earth’s surface is coming out the same as what would be caused by the velocity of space flowing by us, if this proposal was correct?   

[J.C.MacSwell]

So near Earth surface, distance 1r from Earth centre, your model has:  inflow of space at 11.18 km/s and acceleration of that inflow at 9.81m/s²

What does it have at 2r?

[mistermack]

I'm not a mathematician, as I've said several times. I've shown how I arrived at what I've posted, hopefully  without any ambiguity, so that people can challenge what I've said. 

I'm surprised that this idea wasn't ripped to shreds in the first hour, that's what I was expecting to happen. It's more than a week now. I'm not sure that my original reason for discarding it (whatever it was) was valid, but there must be plenty wrong with it, or it would have been proposed before.

[mistermack]

I find the picture of a cliff edge one of the best for visualising gravity, as you often take it for granted, when just standing or sitting on level ground. A cliff edge sort of forces you to be aware that gravity is with you 24/7 and the only thing stopping you falling very quickly is the force exerted by the Earth beneath your feet.

My understanding of  general relativity is that if you step off the cliff, you then follow the path of a non-accelerating inertial frame, through curved space time. And of course we know that that path takes yoou straight down, accelerating at 9.81 m/s² relative to the cliff. If you stretch out your hand and touch the cliff, it will be immediately obvious that ONE of you is accelerating. If it’s not you, then it has to be the cliff.

Which sounds very weird, but actually, the cliff is the one that is experiencing a force from below, whereas you are not experiencing any force, according to GR.

But how could a cliff in the UK be accelerating upwards, and a cliff in New Zealand be also accelerating, at the same rate, but in the opposite direction? It would seem impossible, without the Earth being rapidly stretched out of shape. But in this proposed scenario, it does seem actually possible.

[mistermack]

To be fair to this thread, it's been here for two weeks, asking to be refuted, but nobody's refuted it. 

So I think it should go back to physics, if it's not refutable. 

[Strange]

On 21/10/2017 at 6:42 PM, mistermack said:

Is it too much of a coincidence, that the known time dilation at the Earth’s surface is coming out the same as what would be caused by the velocity of space flowing by us, if this proposal was correct?

I think they should be the same (and I assume one could show this from the equation for gravitational time dilation). I haven't tried it but I think if you apply the Lorentz transform to the equation for escape velocity (which is the same as the speed when falling from infinity, which is your 11.186km/s) then you should end up with the equation for gravitational time dilation. Because equivalence.

36 minutes ago, mistermack said:

So I think it should go back to physics, if it's not refutable.

There is a big difference between not being refuted on an Internet forum and being mainstream science!

9 minutes ago, Strange said:

I haven't tried it but I think if you apply the Lorentz transform to the equation for escape velocity (which is the same as the speed when falling from infinity, which is your 11.186km/s) then you should end up with the equation for gravitational time dilation.

Turns out to be pretty straightforward:

Escape velocity: [latex]v_e = \sqrt{\frac{2GM}{r}}[/latex]

Lorentz transform: [latex]\frac{1}{ \sqrt{1 - \frac{v^2}{c^2}}}[/latex]

Substitute for v: [latex]\frac{1}{ \sqrt{1 - \frac{\sqrt{\frac{2GM}{r}}^2}{c^2}}}[/latex]

Simplify: [latex]\frac{1}{ \sqrt{1 - \frac{2GM}{rc^2}}}[/latex]

Which is the equation for gravitational time dilation.

Edited October 28, 2017 by Strange

[J.C.MacSwell]

On 10/16/2017 at 5:01 PM, J.C.MacSwell said:

In a simple, steady state flow model in 3 dimensions, at a given distance from the centre the flow should be accelerating at 1/2 of what it is at half the distance (inverse relationship...goes up by twice as it moves to half the distance)

With gravity the acceleration is 1/4 that of half the distance. (inverse squared relationship...goes up by 4X as it moves to half the distance).

So for the acceleration to more than double you need more space accelerating than you have a supply of...

 

 

(At some point I have to get better at showing the math on the computer)

2 hours ago, mistermack said:

To be fair to this thread, it's been here for two weeks, asking to be refuted, but nobody's refuted it. 

So I think it should go back to physics, if it's not refutable. 

In physics you will come up against that, and the fact that you are suggesting a mechanistic model without defining the mechanism (how the moving space interacts with the matter, in particular comparisons at varying velocities in the same position) 

Accelerations aside, compare the velocity of the inflow at 2r (1/4 of that at 1r based on continuity) to the escape velocity at 2r (1/square root 2 of that at 1r). Or is that too difficult?

 

 

[mistermack]

1 hour ago, J.C.MacSwell said:

compare the velocity of the inflow at 2r (1/4 of that at 1r based on continuity) to the escape velocity at 2r (1/square root 2 of that at 1r). Or is that too difficult?

Too difficult. (for me).

This is as far as I got :

Modelling the situation as an intake, submerged in a sea, I wanted to work out the acceleration of any particle of the fluid, in relation to it's distance r in metres from the intake.

Fixed flow rate down the pipe f = Volume V cu metres/T seconds f = V/T
Take two concentric spheres at radius r, inner(ri) and outer (ro). Outer sphere has area Ao, inner has area Ai. 

Flow speed at outer = f/Ao Flow at inner = f/Ai     So increase in velocity is f/Ai - f/Ao.   = f(Ao-Ai)/AiAo

The area of the spheres is proportional to the radius squared. ie 4πro² and 4πri².
So the increase in velocity is f(4πro²-4πri²)/(4πri²)(4πro²) = f(4πro²-4πri²)/16π²ri²ro²

So the increase in velocity divided by the time T is f(4πro²-4πri²)/16π²ri²ro²T metres per sec per second.

Which gives the acceleration for an elapsed period of T seconds. (In the unlikely event that something isn't
wrong with the calculation.)

How you get from that to acceleration at any individual point, as T tends to zero, requires calculus I believe, and that's a
complete void in my memory. I did actually use maths at university, so I did once know some of it, fifty years ago,
although there's no sign of it now.

 

 

4 hours ago, Strange said:

There is a big difference between not being refuted on an Internet forum and being mainstream science!

True.  But this was suggested as an alternative way of looking at mainstream science, not a replacement for it. If there was a contradiction to GR inherent in it, I would think that that would refute it. There are lots of things suggested in the physics forum that are not mainstream science, but equally don't contradict it.

The River Model seems to fall into that category too. It's been published, been used, doesn't contradict established science, but you wouldn't call it mainstream. (or maybe you would?)

On the time dilation calculation, thanks for that. I suspected that that was the case, but couldn't prove it, as my maths has been going stale for fifty years now. 

But doesn't it seem too much of a coincidence, that gravitational time dilation, and the hypothetical time dilation that would be caused by space falling into the large body as postulated, are identical?

Is it more likely that there are two unconnected types of time dilation, which just happen to produce the identical quantity?
Or that there is just one type of time dilation, due to motion through space? Both apparently match the facts, but wouldn't Occam's Razor favour the simpler of the two?

[mistermack]

I have to say I'm quite disappointed that nobody on this site has torn into the basic premise of this thread and refuted it. 

I'm still trying to refute it myself, and would have welcomed some input.

The thoughts that I've had about it recently are based around the fundamental question, of 'can space move?', as I postulated. It's certainly modelled as moving, in the published river model, so I have my doubts if there is a simple refutation available to the concept of a flow of space. Otherwise, the physics world would have refuted the river model. As I understand it, a flow of space in that model is a valid interpretation for curved space time.

The basic idea, that small amounts of space are constantly being "gobbled up" by massive matter and energy might seem to be counter intuitive at first sight. But the more I've read, the less constant and unchanging space becomes.

You have the idea of inflation, which is fundamental to the big bang model. Space is definitely changing at an incredible rate on a gigantic scale. Then you have the idea of the metric expansion of space, which is supposed to be happening constantly, everywhere, all around us.

If space can expand everywhere, 24/7 spontaneously without any known cause, then surely it can be absorbed, or shrink, or be annihilated on a small scale in the vicinity of massive particles? It doesn't seem to be a ludicrous possibility, bearing in mind the energies involved at that tiny scale.

And if it can, and did, then the process that I postulated in the OP pretty well follows on as an inevitable result, and explains the action of gravity.

[Strange]

10 minutes ago, mistermack said:

I have to say I'm quite disappointed that nobody on this site has torn into the basic premise of this thread and refuted it. 

I think the Gullstrand–Painlevé coordinates show that it is a valid concept, at least in the case of a Schwarzschild solution (a spherically symmetrical, non-spinning object). Whether it can be applied more generally, I don't know.

...

Apparently, it can: https://arxiv.org/abs/0905.3244