What Gravity Is

[Lucky]

Why is it that people think they can forego the ten years of math and science courses and just skip right to theorizing about the universe?

If you don't understand exactly what it is that is know about the behavior of the universe today, you can't make any guesses about the causes of that behavior.

This needs to be quoted again.

Yes, as an example of the type of unhelpful, contemptuous and completely inappropriate response that is unfortunately far too common here when someone expresses a view (or, in this case, makes a suggestion) that's scientifically naive (or, worse, suspected of being woo).

What's particularly silly is that it completely misses the point. No maths (and scarcely any physics) is needed to see that martu's model is a total non-starter – just a modicum of everyday observation. It fails to account for gravitational phenomena in a number of crucial and obvious ways – some of which have been pointed out.

martu, you have just considered one gravitational effect – that an object decelerates when moving away from a mass (i.e. appears to be 'attracted' to the mass). Your model is that the mass has displaced the gravitational particles, which have therefore become crowded in the vicinity of the mass (presumably this crowding thins out further away from the mass). These particles are supposed to obstruct the motion of an object moving through the crowd. There are serious problems here – in particular (as Reality Check pointed out), your model has the gravitational force depending on the object's size, not its mass. Also, you offer no explanation why the gravitational particles should 'spring back' rather than continuing to move away.

Even worse, your model fails to account for the fact that objects don't need to be moving to feel the gravitational force, and is completely wrong about the gravitational influence on an object moving towards the mass. Why doesn't it decelerate as it meets more densely crowded particles? Why does the effect of the obstructing particles work differently on objects moving towards the mass than on objects moving away from it? Your model ignores the directionality of gravity – rather a serious omission!

Other objections have been mentioned - the number and complexity of the assumptions required, and the implication of a granular, fixed space.

The lack of mathematical rigour at the concept stage isn't necessarily a problem. If it seemed at all a viable model (it isn't!) then you would need to develop a mathematical model that explains, for example, the observed distribution of gravity. Creating a descriptive model first and then developing the maths (or getting someone else to develop it) is a perfectly valid way of doing theoretical physics.

Loss Leader, you did have a point. It's mindbogglingly unlikely that a non-physicist could develop a useful descriptive model of gravity that generations of theoretical physicists have missed (and it does rather trivialise physics to suggest it). You could have said this in a friendly way (having pointed out some of the logic and physics errors - assuming you're capable of doing so).

 

[martu]

Yes, as an example of the type of unhelpful, contemptuous and completely inappropriate response that is unfortunately far too common here when someone expresses a view (or, in this case, makes a suggestion) that's scientifically naive (or, worse, suspected of being woo).

What's particularly silly is that it completely misses the point. No maths (and scarcely any physics) is needed to see that martu's model is a total non-starter – just a modicum of everyday observation. It fails to account for gravitational phenomena in a number of crucial and obvious ways – some of which have been pointed out.

Thanks

martu, you have just considered one gravitational effect – that an object decelerates when moving away from a mass (i.e. appears to be 'attracted' to the mass). Your model is that the mass has displaced the gravitational particles, which have therefore become crowded in the vicinity of the mass (presumably this crowding thins out further away from the mass). These particles are supposed to obstruct the motion of an object moving through the crowd. There are serious problems here – in particular (as Reality Check pointed out), your model has the gravitational force depending on the object's size, not its mass. Also, you offer no explanation why the gravitational particles should 'spring back' rather than continuing to move away.

I have admitted I had this round the wrong way in a post above– the particles get less dense as you get closer to a mass caused by the particles being pushed out of the way by the mass. Therefore as you get closer to a mass there are fewer particles to obstruct you hence movement is easier and the closer you get to the object the further apart the particles are making travel easier.

And it’s not just the size but also the amount of stuff – a more dense object has more atoms in it therefore less volume for the gravity particles to reside in. Therefore two objects have the same mass if they displace the same number of particles – the number of particles displaced depends on two things, the size of the object and the density of the object.

The gravity particles spring back because, when they move, they are pushed towards other gravity particles which repel them pushing them back. Think of just two particles with a spring between them – it will contract if we move one towards the other but eventually it will be pushed back by the spring. Now make this 3D….

Even worse, your model fails to account for the fact that objects don't need to be moving to feel the gravitational force, and is completely wrong about the gravitational influence on an object moving towards the mass. Why doesn't it decelerate as it meets more densely crowded particles? Why does the effect of the obstructing particles work differently on objects moving towards the mass than on objects moving away from it? Your model ignores the directionality of gravity – rather a serious omission!

As above I had it the wrong way round (I am trying to translate a picture in my head), less dense particles closer to a mass therefore easier to move towards the mass.

Other objections have been mentioned - the number and complexity of the assumptions required, and the implication of a granular, fixed space.

Can you elaborate please?

The lack of mathematical rigour at the concept stage isn't necessarily a problem. If it seemed at all a viable model (it isn't!) then you would need to develop a mathematical model that explains, for example, the observed distribution of gravity. Creating a descriptive model first and then developing the maths (or getting someone else to develop it) is a perfectly valid way of doing theoretical physics.

Loss Leader, you did have a point. It's mindbogglingly unlikely that a non-physicist could develop a useful descriptive model of gravity that generations of theoretical physicists have missed (and it does rather trivialise physics to suggest it). You could have said this in a friendly way (having pointed out some of the logic and physics errors - assuming you're capable of doing so).

Yes this is what I wanted, people who know more than me about it pointing out why it is wrong.

 

[Spud1k]

But wasn’t aether a medium for light to travel through like sound needs a medium to travel through? I am thinking the grid is things to avoid, without the grid a photon could travel no problem, in fact this is what happens when the gaps between the gravity particles gets stretched by a mass, the photon travels with less of a hindrance from the gravity particles.

I'm not really comparing your idea with the aether directly, it's just the idea of the space-time continuum being a fixed stage that everything moves within. Lorentz invariance (the phenomenon which meant that none of the aether experiments worked) dictates that any point of reference is the centre of its own stage, so to speak.

I don’t see it as gravity as being responsible per se – it’s more that the photons have to travel around the particles which is causing the photon to travel in a wave which can be explained by classical wave theory. So we have a force carrying photon avoiding the gravity particles as it travels causing an unpredictable path.

Given that the wavelength of light is variable, this can't be the case if the particles are in fixed locations.

 

[martu]

I'm not really comparing your idea with the aether directly, it's just the idea of the space-time continuum being a fixed stage that everything moves within. Lorentz invariance (the phenomenon which meant that none of the aether experiments worked) dictates that any point of reference is the centre of its own stage, so to speak.

Sorry I still don’t get it, this may well be the limit of my knowledge. Why wouldn’t any point be the centre of it’s own stage in the grid?

Given that the wavelength of light is variable, this can't be the case if the particles are in fixed locations.

It can if photons can trace different paths around the particles. Consider it in 2D, so again the graph paper idea, a photon is trying to travel along a line with a particle blocking it’s way at each line intersection. A photon with a short wavelength, indeed the shortest possible wavelength, would go over one particle then immediately under the next, over the next, under the next and so on. A longer wavelength would mean the photon goes over the first, then over the second, then under the next two, then over the next two.

 

[The Man]

I know what these are but thank you - why do you think this doesn't explain it? Or what specifically isn't explained by it?

The limitation of your assessment to a 3D spatial grid and not 4D spacetime, knowing what they are is a start but understanding and applying them is required if you truly want to consider our current understanding of gravity and wish to improve it.

 

[martu]

Redshift

Further to the post above attempting to explain different wavelengths of light - why does the wavelength of light increase as gravity gets weaker, the gravitational redshift? As gravity gets weaker the particles are getting closer together causing the photon to trace a larger wavelength between particles, put simply more particles are in it’s way.

 

[martu]

The limitation of your assessment to a 3D spatial grid and not 4D spacetime, knowing what they are is a start but understanding and applying them is required if you truly want to consider our current understanding of gravity and wish to improve it.

Again what doesn't it explain? I know it's a lot but please pick one thing you think this grid doesn't explain about spacetime?

This is all a great help, again thank you all, I have learnt a lot.

 

[The Man]

Sorry I still don’t get it, this may well be the limit of my knowledge. Why wouldn’t any point be the centre of it’s own stage in the grid?



It can if photons can trace different paths around the particles. Consider it in 2D, so again the graph paper idea, a photon is trying to travel along a line with a particle blocking it’s way at each line intersection. A photon with a short wavelength, indeed the shortest possible wavelength, would go over one particle then immediately under the next, over the next, under the next and so on. A longer wavelength would mean the photon goes over the first, then over the second, then under the next two, then over the next two.

Ah, now I think I see part of your confusion, you are thinking of waves only in terms of spatial displacement (like waves on the surface of a pound). Waves also represent varying amplitudes, which can be the spatial displacement as in waves on the surface of a pound (transverse wave), varying pressure amplitude as in sound waves (longitudinal waves). Also the varying amplitudes of electromagnetic fields as is electromagnetic radiation (photons). Additionally they can also be used to represent varying probability amplitudes as in a quantum mechanical wave function.

 

[Reality Check]

No it’s just one force, the repelling of the gravity particles. The gravity particles do not exert a force on the object they get in the way. But is that what you mean – when I say getting in the way this assumes a force that acts between them?

Thanks very good point.

I think I can answer this one believe it or not, both balls will hit the same number of particles. Though the lead ball is smaller it contains more stuff therefore more particles are being hit. So the way to think of mass is that it’s the number of particles displaced by something – though the lead ball is smaller as it’s denser more particles are displaced in a smaller volume.

What is "stuff"?

Your particles know in advance how dense the object is and collect together to produce exactly the same result as normal gravity.

In that case what is their point? You have reproduced gravity with a more complex model.

 

[The Man]

Again what doesn't it explain? I know it's a lot but please pick one thing you think this grid doesn't explain about spacetime?

This is all a great help, again thank you all, I have learnt a lot.

Time, for the third time, that is the one thing I have been talking about. Sorry, but I thought I was making that clear. Even stationary objects (those not moving in any of the three spatial dimensions or your 3D grid) are still moving in time and influenced by gravity (time dilation). This is one of the basic precepts of General Relativity that things are always moving in at least one dimension of 4D spacetime, the temporal dimension (that your 3D grid is lacking) which, due to the relativistic invariance of the speed of light, can be measured in the same units as the other three spatial dimensions or as the distance that light would travel in that time.

 

[Reality Check]

Next problem with your model:
The Earth is pushing through your particle grid and experiences a force.
The Moon is pushing through your particle grid and experiences a force.
There is no relationship between the 2 forces. There is no force between the Earth and the Moon. Therefore they cannot be orbiting each other.

 

[martu]

What is "stuff"?

Anything that takes up space. For example a photon or an atom or a gravity particle.

Your particles know in advance how dense the object is and collect together to produce exactly the same result as normal gravity.

In that case what is their point? You have reproduced gravity with a more complex model.

No it's the particles that are causing gravity*. The presence of other things that take up space, for example atoms, push the grid particles around changing the density. More atoms and the particles are more spread out.

This may be my last post until Monday, family calls, if it is thank you all again and I hope someone will be interested on Monday to carry this on.

*clarification again, this is how I picture it in my head

 

[Spud1k]

Sorry I still don’t get it, this may well be the limit of my knowledge. Why wouldn’t any point be the centre of it’s own stage in the grid?

Because you could define something's location and velocity relative to the grid. Special relativity just doesn't work like that.

It can if photons can trace different paths around the particles. Consider it in 2D, so again the graph paper idea, a photon is trying to travel along a line with a particle blocking it’s way at each line intersection. A photon with a short wavelength, indeed the shortest possible wavelength, would go over one particle then immediately under the next, over the next, under the next and so on. A longer wavelength would mean the photon goes over the first, then over the second, then under the next two, then over the next two.

That would impose a minimum wavelength at any given point in space and mean all higher wavelengths would be multiples of this. To the best of our observations, this just isn't the case. Besides, the vector of propagation for photons is in a straight line - the transverse waves exist within electromagnetic field space.

 

[Reality Check]

Anything that takes up space. For example a photon or an atom or a gravity particle.

Another problem with your model: Photons are point particles. They do not take up space and so their presence will not push the grid particles around. Your model thus predicts that gravity will have no effect on photons.
Or we can look at a photon as a wave. Then they cannot propagate through your particle grid without diffraction. This is not observed.

No it's the particles that are causing gravity*. The presence of other things that take up space, for example atoms, push the grid particles around changing the density. More atoms and the particles are more spread out.

This may be my last post until Monday, family calls, if it is thank you all again and I hope someone will be interested on Monday to carry this on.

*clarification again, this is how I picture it in my head

Two balls of iron and lead with the same number of atoms and constructed to have the same density. These will push the grid particles the same. They will have the same gravitational force applied to them according to your model. But they will have different masses and we will actually measure different forces.

The big problem with the model is that gravity is a force between two masses. This is the reason that orbits exist. The model predicts that gravity is a force that is applied to masses independently. There is no force between the masses and orbits cannot exist.

 

[davefoc]

... Also, it implies some kind of universal frame of reference, which doesn't match up with special relativity.

Does special relativity rule out a universal frame of reference? It is possible to determine one's velocity relative to the cosmic background radiation. It seems at least conceivable that an object that shows no velocity relative to the cosmic background radiation might not be moving relative to a universal frame of reference.

 

[DeiRenDopa]

.... snip ....

I think I can answer this one believe it or not, both balls will hit the same number of particles. Though the lead ball is smaller it contains more stuff therefore more particles are being hit. So the way to think of mass is that it’s the number of particles displaced by something – though the lead ball is smaller as it’s denser more particles are displaced in a smaller volume.

So, do the gravity particles also have volume?

And do gravity particles interact with (a.k.a. collide with) each other?

Finally, I may have missed it, but where did you show that your idea will produce the classical (Newtonian) formula for gravity (the one with m₁, m₂, G, and r in it)?

 

[martu]

Next problem with your model:
The Earth is pushing through your particle grid and experiences a force.
The Moon is pushing through your particle grid and experiences a force.
There is no relationship between the 2 forces. There is no force between the Earth and the Moon. Therefore they cannot be orbiting each other.

I have a quick reply to this as I saw the post just before I left for home Friday.

Consider a 2D plane, the grid is just a square if not being acted on by a mass.

Add an atom – the atom distorts the grid slightly but over a larger area the grid is still square, therefore the atom doesn’t move

Add two masses either side of the atom

The masses distort the grid – it’s no longer a square but an isosceles trapezoid, the larger mass is distorting the grid more than the smaller mass.

The atom will move towards the larger gap in the particles – towards the larger mass. The larger the gap the quicker it will move.

In 3D all you have to do is replace the square with a cube and the trapezoid becomes solid.
So the gravitational force is dependant on the two masses m1 and m2 which you can consider the lengths of the parallel sides of the trapezoid.

The force is proportional to the gaps between the particles – as we are talking about an area (between the four particles on the side of the larger mass) it is proportional to the distance between the two masses squared (in 2D it is just the distance obviously)

When the atoms vibrate they’ll tend towards the larger gaps and the larger area, this is why things move in a gravitational field.

How’s that?

 

[Reality Check]

I have a quick reply to this as I saw the post just before I left for home Friday.

Consider a 2D plane, the grid is just a square if not being acted on by a mass.

Add an atom – the atom distorts the grid slightly but over a larger area the grid is still square, therefore the atom doesn’t move

Add two masses either side of the atom

The masses distort the grid – it’s no longer a square but an isosceles trapezoid, the larger mass is distorting the grid more than the smaller mass.

The atom will move towards the larger gap in the particles – towards the larger mass. The larger the gap the quicker it will move.

In 3D all you have to do is replace the square with a cube and the trapezoid becomes solid.
So the gravitational force is dependant on the two masses m1 and m2 which you can consider the lengths of the parallel sides of the trapezoid.

The force is proportional to the gaps between the particles – as we are talking about an area (between the four particles on the side of the larger mass) it is proportional to the distance between the two masses squared (in 2D it is just the distance obviously)

When the atoms vibrate they’ll tend towards the larger gaps and the larger area, this is why things move in a gravitational field.

How’s that?

Why are there 3 objects - an atom and 2 masses?

Once again - two forces are invoved here and they are different. There is the force that the masses exert on the grid and the force that the grid particles have between each other. This is replacing one force (gravity) with 2 forces. This model is more complicated than General Relativity.

Even so if 2 masses distort the grid you need to show that the force between grid particles will produce an inverse square law acting between the masses dependant on their masses. Without that this model is just wishful thinking.

Look at an even simpler case: a 1D line of particles with spring-like forces acting between them. Add a mass at a point in the line. This moves some of the grid particles. The forces balance out - the distortion and the force between the grid particles. Thus there is no overall force. The mass at rest will stay at rest. Add another mass and that mass will also stay at rest. Therefore there is no force between the 2 masses.

This model is not a valid model of gravity in any dimension.

 

[Spud1k]

It is possible to determine one's velocity relative to the cosmic background radiation.

That's still a relative velocity - are we moving within the CMB or is the CMB moving past us?

The point is, we have no way of knowing. You can define reference frames but not one of them, even the CMB, can be defined as 'universal' in terms of any physical behaviours. This 'grid' idea would implicity falsify that.

 

[nathan]

the OP describes something that looks a lot like a viscous medium. I don't see other posts discussing that. However, contrary to the usual physics of viscous media, where smaller particles experience the viscosity more than larger particle, the OP posits a media where larger particles experience the viscosity more.

One thing that's not clear to me from the OP is the scale of disturbance in the media of a large object moving through it. In the 'iron sphere' example, does the media penetrate the iron sphere? So it is the iron atoms that cause the disturbance? If that's the case I don't see an explanation of how the disturbance can propagate beyond the atomic level.