Model Gravity as a Repelling Force?

[goforbass]

I was playing with the thought experiment of modeling gravity as a repulsive force instead of an attractive force. That is, we perceive gravity as the attraction two bodies of mass exert on each other. Can you accurately model the same end result using no (gravitational) force exerted between bodies of mass and instead use only a repulsive force between a body of mass and another unknown substance.

For example, assume there is a field (it helps to imagine this in 2 dimensions at first) of some substance which has the property of repelling objects of mass and repelling itself. The field is evenly distributed. Assume it extends indefinitely.

Now drop a body of mass in the field. The substance will be forced away from the body, but the body's repulsive force acting on individual particles of the substance will weaken with distance from it. This results in a least dense region of the substance immediately surrounding the body, and increasing density as you move away from it. This trend of increasing density continues throughout the entire field. As far away as you like to test, you will still see denser regions one step further away from the body. Also note that no matter where in the field the body may be moved, it will feel an equal force from the sum of the individual particles throughout the entire field.

Next, drop a second body of mass in the field some distance away from the first. The field feels repulsion from the body and is dispersed in a fashion similar to the first with one difference. The combined forces from the two bodies create regional minimum densities along a line drawn directly between the two (think saddle). Minimum densities means fewer particles, which means less force exerted on each body from those spaces. Meanwhile forces being exerted from the rest of the field are relatively stronger, meaning when the sum of forces from the entire field is applied to each body, it results in a force on each in a direction along that previously established line in the direction of the other body.

This is a lot like those black and white pictures where you either see the image formed by the black or you see the image formed by the white. I've done a lot of thinking about this for myself, but I'm interested to see how far other imaginations can take this concept before it breaks down.

 

[GodlessAstronomer]

I'd really have to think much more deeply about this before giving a detailed response, but here is my first impression:

In a Newtonian world it seems like this idea would be equivalent to the current model. However I am having trouble reconciling this model with general relativity, where gravity is a manifestation of spacetime curvature. You'd need to somehow make space that is void of these hypothetical particles highly curved, and the densest areas would need to be flat. The problem is when an area of space is totally void, curvature would be infinite (essentially a black hole). How do these particles interact with a black hole? If they fall into it, the black hole would evaporate as more repulsive particles entered it. Do these particles respond to gravity themselves?

It's certainly an interesting idea to think about, but does it offer anything that current gravitational theories don't? Does it solve any of the problems in modern science?

 

[silverpig]

I've thought about this before too when I was introduced to the equivalence principle, but it just doesn't quite work out.

 

[firewolfsm]

There is something quite similar which you can look back to.

Some used to think that gravity might not be an attractive force between masses, but (and this was only applied to celestial bodies as far as I know) a force from the outside pushing (for example) the planets into their orbits around the sun. This would have stemmed from a similar field of opposite effect, but the math matches. There were shortcomings and inaccurate results from this math which reaffirmed gravity as a force between masses.

So basically, I don't think modeling gravity as you proposed would work mathematically.

 

[GeorgeKopf]

First, let's make a bunch of unfounded assumptions.

1. The repulsive gravitational force comes from Dark Matter.
2. Dark Matter was created during the big bang (or big inflation) and is still inflating outward today.
3. Mass has the ability to reduce/cancel the presence of Dark Matter.
4. Black Holes are just very massive objects, the next compression of matter after Neutron Star.

What would we observer in this situation?

1. Bodies of mass would be areas of week repulsion and objects would be pushed into them.
2. Two bodies of mass would have greater force from the all directions except the space between them, causing them to move closer to gether, causing the repulsive force to diminish even more, etc.....
3. The center of the big bang would have higher density of Dark Matter and thus would exhibit stronger repulsive force, than the outter fringes of the universe.
4. Galaxies would be accelerating (not decelerating) from each other and the center of the universe, which they appear to be doing.

 

[Fox5]

Originally posted by: GodlessAstronomer
I'd really have to think much more deeply about this before giving a detailed response, but here is my first impression:

In a Newtonian world it seems like this idea would be equivalent to the current model. However I am having trouble reconciling this model with general relativity, where gravity is a manifestation of spacetime curvature. You'd need to somehow make space that is void of these hypothetical particles highly curved, and the densest areas would need to be flat. The problem is when an area of space is totally void, curvature would be infinite (essentially a black hole). How do these particles interact with a black hole? If they fall into it, the black hole would evaporate as more repulsive particles entered it. Do these particles respond to gravity themselves?

It's certainly an interesting idea to think about, but does it offer anything that current gravitational theories don't? Does it solve any of the problems in modern science?

That might be right. I'm not too familiar with general relativity, but apparently it predicts that gravity can be a repulsive force. Something to do with a Higgs field I think.

 

[KIAman]

Originally posted by: GeorgeKopf
First, let's make a bunch of unfounded assumptions.

1. The repulsive gravitational force comes from Dark Matter.
2. Dark Matter was created during the big bang (or big inflation) and is still inflating outward today.
3. Mass has the ability to reduce/cancel the presence of Dark Matter.
4. Black Holes are just very massive objects, the next compression of matter after Neutron Star.

What would we observer in this situation?

1. Bodies of mass would be areas of week repulsion and objects would be pushed into them.
2. Two bodies of mass would have greater force from the all directions except the space between them, causing them to move closer to gether, causing the repulsive force to diminish even more, etc.....
3. The center of the big bang would have higher density of Dark Matter and thus would exhibit stronger repulsive force, than the outter fringes of the universe.
4. Galaxies would be accelerating (not decelerating) from each other and the center of the universe, which they appear to be doing.

I still can't wrap my head around this. How does this explain the logarithmic reduction of gravity (repulsion) which is directly tied to the massive object regardless of any direction. You would think that if an object moved towards a collection of dark matter, that the repulsion would show increased strength.

The final assumption has to be; dark matter is equally distributed across the universe. That part breaks my thoughts on this.

 

[soccerballtux]

yeah I've heard of this, something along the lines of ZPE and the casimir effect, just on a larger scale.

 

[JTsyo]

If you just had 2 bodies and the substance, why would density vary? Given time, wouldn't the bodies just push ALL of the substance away from them?

In the universe at large, the substance would have to be kept at a boundary of some sort where the forces exerted from all the other matter equals the force from the body in question. Now this boundary wouldn't be symmetric since the matter around the body varies in size and distance. Let's take the sun for example, there's much more matter in the galactic plane that is close to the sun than in the other directions, so the boundary should be much closer to the sun in that direction than others. What I don't see is how this would induce orbits. The substance would have to slip in behind the planet to keep an orbit.

 

[goforbass]

Originally posted by: GeorgeKopf
First, let's make a bunch of unfounded assumptions.

1. The repulsive gravitational force comes from Dark Matter.
2. Dark Matter was created during the big bang (or big inflation) and is still inflating outward today.
3. Mass has the ability to reduce/cancel the presence of Dark Matter.
4. Black Holes are just very massive objects, the next compression of matter after Neutron Star.

What would we observer in this situation?

1. Bodies of mass would be areas of week repulsion and objects would be pushed into them.
2. Two bodies of mass would have greater force from the all directions except the space between them, causing them to move closer to gether, causing the repulsive force to diminish even more, etc.....
3. The center of the big bang would have higher density of Dark Matter and thus would exhibit stronger repulsive force, than the outter fringes of the universe.
4. Galaxies would be accelerating (not decelerating) from each other and the center of the universe, which they appear to be doing.

You took this forward a step beyond what I wanted to in my initial post, but I will take it as a cue to proceed further. You labeled my substance as Dark Matter which I am hesitant to do (because I am not intimately familiar with the properties of dark matter even though it may end up being what I am talking about), while I prefer to continue referring to it as something not yet identified. Several posts have indicated that similar ideas have been explored in the past to their ultimate unraveling, but just for curiosity's sake let me append something kinda magical to this concept.

First off, realize that these particles would be small enough to exist all around us. Even though the repelling gravitational force of say Earth forms a relatively less dense field of these particles, the field still extends to the planets surface and likely all the way to the planet's core, field densities continuing to decrease the further in you go. It is the matter itself that repels them, so just as each individual atom has mass, surrounding each atom there would likewise exist a field of diminishing density of these particles.

NOW WHAT IF: What if this substance also has the property of conducting light (that is to say electromagnetic radiation propagates through this and only this as its medium - light is not a particle/wave but instead just a wave). The void of this substance has the perceived effect of insulating against light. 'Perceived' because it is indirect. There would be a certain density of this substance required for a waveform to hold together. Lower concentration results in the individual particles dispersing the wave's energy as they behave more independently and chaotically. The void effectively absorbs or refracts \ the wave as it approaches from a higher concentration, the wave falls apart as the concentration drops too low, and the wave is prevented from propagating onward (similar to waves crashing on a beach - that's not really an accurate analogy though). This minimum concentration property can be a different value for different wavelengths of light because of the different amounts of energy involved. How would this be observed on a macro scale?

Travel through vacuum: Light would clearly be able to move through the vacuum of space or through an artificially created vacuum on the planet's surface (the particles are small enough to pass right through the vacuum's container so particles are actually able to rush in to fill the vacuum in greater density than outside the container) as the particles would act as the uninterrupted medium for the light waves. The absence of matter in these situations would result in relatively higher densities of the substance and so waves propagating through that medium would travel faster through vacuum than say air or water.

Shielding: Light should not be able to travel through certain collections of matter. Take a sheet of some material one atom thick for example. The individual atoms are arrayed close enough together that the field of particles surrounding each atom interact with fields from adjacent atoms. As a wave of light approaches the sheet of matter, some parts of the wave pass into the regions closest to an atom (which either collapses that part of the wave or redirects it), while other parts of the wave pass through the gap regions furthest from any atom. Using different materials, the masses of each atom can be increased to reduce densities in each atom's surrounding fields. Couple this with successive layers of these sheets (as present in 3-dimensional mass) and some materials will be able to reach a critical mass whereupon light waves are stopped entirely by some materials and not in others. This is obviously heavily dependent on other factors like molecular geometry interacting with different wavelengths etc. and individual refractions from each atom's field gradient acting on the wave, but the point is that matter's interaction with light can be expected using this model.

Refracting of light around massive objects: Since super massive objects will have a dramatic effect on the fields of the particles around them, the density gradient surrounding such an object would have refractive properties on light waves passing close by.

Black holes: They say black holes pull in light, but this model would describe black holes as causing particle densities so low that light waves cannot form. That is to say particles are still present inside, just not in densities high enough to support a wave. The perceived effect is much the same.

The following should also be perceived in order for this model to be accurate:

- Different wavelengths of light might see the edge of a black hole at different locations since different wavelengths can be supported by different densities. It could also cause light to move at it's slowest possible speed just outside the black hole's edge as the densities are just high enough for a wave to propagate, but it is the density of the wave's medium that determines speed.

- Shouldn't an object of mass moving through the vacuum of space feel some quantifiable resistance as the particles of this substance it displaces are moved around (granted they are small enough to filter right between the individual atoms of the object, so the displacement distance might not be huge, but it is still happening)?

- Shouldn't light propagate more slowly in a vacuum on Earth's surface than is does through space in our solar system (which would in turn be slower that it travels between solar systems, which is again slower than between galaxies) since the distance from matter results in more and more minimized cumulative repelling force allowing for greater densities of this substance?


I know it flies in the face of so much accepted science, but the similarities in so many behaviors are too striking for me to just quit thinking about this.