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Seiryuu
2008-Oct-05, 08:51 AM
I have a question about these parallels (http://en.wikipedia.org/wiki/Electric_field#Parallels_between_electrostatics_an d_gravity).

In my thought experiment thread I was wondering if there could exist a gravitational equivalent to magnetism to explain orbits. People pointed out to me this is very unlikely as no observations indicate this.

However, could it be possible that the gravitional pull as we know and measure it is the effect of not one but two forces at work? If so, instead of trying to add a force to counter the gravitational pull, the gravitational pull itself might be split up into two forces. I reckon this would explain the difference in behaviour and open up new possibilities to account for the similarities, while at the same time acknowledging the differences.

My question is though, is this possible at all or are we really sure that only one force is behind all of this?

Neverfly
2008-Oct-05, 09:51 AM
I'm going to inject a thought experiment of my own....:

Imagine you go on a sailing trip. Without air resistance, your huge ship won't move. That is a lot of force.
Now imagine that upon getting home, your child wants to ride the swingset and asks you to push. The air resistance will not prevent him from moving through it.

What is powerful in one regard can be negligible in another.

The equations don't change.
Even parallels don't change.

But factors can overwhelm eachother.
Gravity greatly overwhelms electricity or expansion at the galactic scale.

When you calculate how much force you need to apply to push the child on the swing, you could leave air resistance out of the equation as negligible and still have fairly accurate results.

Seiryuu
2008-Oct-05, 10:05 AM
Agreed. However, in that thought experiment gravity overwhelms another force, making the other force negligible.

What I'm proposing is different in the sense that I would split up gravity itself as the product of two forces, rather than just one. In other words, nothing will change to the result as the split happens within the force, rather than by influence of outside forces.

My question is, is this possible?

Seiryuu
2008-Oct-05, 10:43 AM
In terms of math, can the following equation

F=G(Mm/r^)

be considered as:

F=(4Πε0G) x [(1/4Πε0)(Mm/r^)]

Where the first part would make up for a force and the second part the other.

PraedSt
2008-Oct-05, 11:10 AM
Sorry Seiryuu, just want a clarification. Do you mean splitting gravity into 2

Like electromagnetism into electricity and magnetism?
Or like positive and negative charges?

Anyway, I think what you suggest might be possible. You'd have to do the usual though: observations, working model, predictions, experiments, blah, blah.

Also, thanks for your link.
I followed it to the concept of negative mass:
http://en.wikipedia.org/wiki/Negative_mass#Negative_mass
Which then led me to the diametric drive:
http://en.wikipedia.org/wiki/Breakthrough_Propulsion_Physics_Program#Diametric_ drive

Niiiice.. :)

Seiryuu
2008-Oct-05, 11:17 AM
Sorry Seiryuu, just want a clarification. Do you mean splitting gravity into 2

Yes


Like electromagnetism into electricity and magnetism?

This one. The total force we measure would be the effect that gravity (the part equivalent to electricity) and levity (the part equivalent to magnetism) have upon eachother. It would also give the total force an attracting and repulsing component, which would explain it's overall perception of a gravity as a weak force.


Anyway, I think what you suggest might be possible. You'd have to do the usual though: observations, working model, predictions, experiments, blah, blah.

I had hoped to be lazy and match it somehow with GR, so that the current model does all the work for me. :p


Also, thanks for your link.

You're welcome. :p

PraedSt
2008-Oct-05, 01:05 PM
:)

Still not clarified!

Electric and magnetic fields are perpendicular to one another.
You used the terms gravity and levity....which do seem like you mean the second example...positive/negative charges, a source and a sink for the same field.
I'm wrong, aren't I? :)

Ok..if you want something like electricity and magnetism, you mean two perpendicular fields. Help me conceptualise that!

Oh...hang on..I just saw your formula post...give me a few minutes!

Seiryuu
2008-Oct-05, 01:09 PM
Er, I'm confused and have no idea which one it is then :P

But in my theory, masses do have a charge, although a gravitational one instead of an electric one if that helps to clarify.

The lighter mass would experience an attractive force due the gravitational field of the heavier mass and a repulsing force due to levitational field. They would indeed be perpendicular to one another, hence the phenomenon of orbits. The combined effect would be what we currently measure as gravity only.

Does this help to clarify?

We probably shouldn't continue this conversation in this topic though, as now it becomes speculation... :p

PraedSt
2008-Oct-05, 01:26 PM
Yeah! We'll be accused of ATM! They're strict on that over here :)

Am still looking at your formula. Sorry; I'm conceptually ok, but mathematically weak. Heh

Seiryuu
2008-Oct-05, 01:28 PM
That's something we have in common then. :p

Ken G
2008-Oct-05, 01:46 PM
By the way, there is a magnetic equivalent to gravity in general relativity, called gravito-magnetic forces. However, they are extremely small in the solar system-- they require rotation speeds approaching light to be significant. Note that the electrons that make current, and magnetism, often do move at speeds that are quite fast, but it's much harder to get big masses to do that.

Seiryuu
2008-Oct-05, 01:50 PM
Yeah, I think that is what Neverfly was describing too. :)

Ken G
2008-Oct-05, 02:37 PM
Actually, I believe Neverfly was comparing gravity to actual electromagnetic forces, because on small scales it is generally the electromagnetic forces that dominate, and on large scales, it's gravity (since electromagnetic charges tend to cancel on large scales). But gravity itself has a magnetic component, which is very much like saying it is 2 forces-- but just as with electricity and magnetism, the magnetic part is generally quite small unless the speeds are quite fast. Electrons do move and spin fast-- planets and stars don't.

PraedSt
2008-Oct-05, 02:45 PM
But gravity itself has a magnetic component, which is very much like saying it is 2 forces

Seiryuu, that's your answer, isn't it?

Thanks Ken. Was unaware of that. Am reading about it now.

Seiryuu
2008-Oct-05, 02:50 PM
I see. Although I'm not sure, I think this is still not the same as what I'm trying to do, since for me the magnetic component would be found in the gravitational constant of G, which is a very strong factor.

Also planets and stars move quite slow relative to eachother, but the systems they're in move as well at faster speeds, don't they?

Thanks for pointing this out indeed though.

mugaliens
2008-Oct-05, 03:06 PM
In terms of math, can the following equation

F=G(Mm/r^)

be considered as:

F=(4Πε0G) x [(1/4Πε0)(Mm/r^)]

Where the first part would make up for a force and the second part the other.

I'm not sure what your purpose is behind your introducing what is essentially a "1 x" factor. Now, if you'd subsituted G with, say, c3[lP2/hbar, we'd be getting somewhere...

But not really, as all you're doing is substituting one known constant (G) for two known constants (lP2 and hbar), which gains no additional understanding into G, as they're known constants, not two hidden components of G.

Ken G
2008-Oct-05, 03:08 PM
Also planets and stars move quite slow relative to eachother, but the systems they're in move as well at faster speeds, don't they?Yes, but relative speed is what counts-- this is relativity, after all. Magnetic-like effects tend to fall off even faster with distance than the more regular aspects of gravity, so if you have to cross vast distances to find large relative speeds, the gravito-magnetic effects won't be that important. Also, I would expect that gravito-magnetic effects are more sensitive to shearing motions than to expanding motions, so it doesn't play much role in cosmology.

Seiryuu
2008-Oct-05, 03:26 PM
I'm not sure what your purpose is behind your introducing what is essentially a "1 x" factor. Now, if you'd subsituted G with, say, c3[lP2/hbar, we'd be getting somewhere...

But not really, as all you're doing is substituting one known constant (G) for two known constants (lP2 and hbar), which gains no additional understanding into G, as they're known constants, not two hidden components of G.

I agree that it gives no additional understanding into G and the reason why I split them up like that is probably due to a misconception of mine, so never mind that. The concept is important though. :)


Yes, but relative speed is what counts-- this is relativity, after all. Magnetic-like effects tend to fall off even faster with distance than the more regular aspects of gravity, so if you have to cross vast distances to find large relative speeds, the gravito-magnetic effects won't be that important. Also, I would expect that gravito-magnetic effects are more sensitive to shearing motions than to expanding motions, so it doesn't play much role in cosmology.

Point taken. :p

cjameshuff
2008-Oct-05, 03:35 PM
By the way, there is a magnetic equivalent to gravity in general relativity, called gravito-magnetic forces. However, they are extremely small in the solar system-- they require rotation speeds approaching light to be significant. Note that the electrons that make current, and magnetism, often do move at speeds that are quite fast, but it's much harder to get big masses to do that.

This is what I meant in that there are no magnetism-like effects that can explain orbits. The effects *do* exist, but it takes an extraordinary amount of effort to measure the effects produced by something the size of Earth. (Gravity Probe B hopefully gathered enough data to measure these effects in Earth orbit, but just barely.)

Attractive forces, even with simple Newtonian mechanics, explain orbits extremely well. I doubt it is even possible to get anything that resembles them with a magnetism-like effect. You should also consider the fact that retrograde and polar orbits are just as possible as prograde ones, the only difference between them being the direction and plane the majority of objects are orbiting in. Also, objects that are not in orbit, but are either falling straight in or being supported by other means (rockets, buoyancy or dynamic lift in air or water, the solid ground), follow ballistic trajectories or experience acceleration consistent with a simple attractive force.

Seiryuu
2008-Oct-05, 03:41 PM
That's the point: you wouldn't have to come up with anything new, as it would already be included in the equation for the total force that we call gravity.

The only thing that changes is the point of view as to whether you consider it one force or not, just like you can consider EM as one force or as the combined effect of both electricity and magnetism. Looking at it this way would make Mm/r^ the attractive force and G the repulsive one.

I also realise that doing this has no practical use whatsoever, but that's why it's all conceptual :p