Magnets and space...
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12-10-2011, 10:56 PM (This post was last modified: 12-10-2011 11:00 PM by DeepThought.)
RE: Magnets and space...
Simple. Earths gravitational influence on the iron filings will be much stronger than the influence of the magnet only a few cm from most magnets.

If earths gravitational influence were removed what would it look like?
If you had a magnet floating in space with iron dust nearby evenly distributed.

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12-10-2011, 11:13 PM
RE: Magnets and space...
(12-10-2011 10:56 PM)DeepThought Wrote:  Simple. Earths gravitational influence on the iron filings will be much stronger than the influence of the magnet only a few cm from most magnets.

If earths gravitational influence were removed what would it look like?
If you had a magnet floating in space with iron dust nearby evenly distributed.

By the time earths gravataional influence takes over from the magnet, the experiment you propose becomes invalid whether in space or not.

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12-10-2011, 11:19 PM (This post was last modified: 12-10-2011 11:25 PM by DeepThought.)
RE: Magnets and space...
Is there a clear liquid with an equal density to something magnetic like iron?

Maybe if you could get small black plastic pellets containing enough iron to make it have the same density as water. Then put an electromagnet in the water and turn it on. That would partially simulate the conditions in space.
(12-10-2011 11:13 PM)defacto7 Wrote:  By the time earths gravataional influence takes over from the magnet, the experiment you propose becomes invalid whether in space or not.

Why?

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12-10-2011, 11:37 PM
RE: Magnets and space...
(12-10-2011 11:19 PM)DeepThought Wrote:  Is there a clear liquid with an equal density to something magnetic like iron?

Maybe if you could get small black plastic pellets containing enough iron to make it have the same density as water. Then put an electromagnet in the water and turn it on. That would partially simulate the conditions in space.
(12-10-2011 11:13 PM)defacto7 Wrote:  By the time earths gravataional influence takes over from the magnet, the experiment you propose becomes invalid whether in space or not.

Why?

Zate already explained it from his expertise. It's reasonably simple but still not my call. All I am trying to do is help you visualize the vast differences between the fields in question. I just think you aren't seeing the picture of how they are virtually irrelevant to each other. There really isn't more to go with this that I can see. Have fun though. Go ahead and try the pellet idea??? I don't think that answers the original question. It will tell you about pellets and water and magnets I guess.

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13-10-2011, 03:43 AM (This post was last modified: 13-10-2011 03:51 AM by daemonowner.)
RE: Magnets and space...
@Defacto7
Wait? Did you just say that electromagnetism holds atoms together? Correct me if I am wrong, but I thought that was the residual effects of the strong nuclear force?

Or am I thinking of protons and neutrons, not atoms?
Dammit, I think I got it wrong. It's electromagnetism that holds the nucleus and the electrons together, forming the atom. Physics fail. Sorry.

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13-10-2011, 05:42 AM
 
RE: Magnets and space...
The iron filings shown on the image in the OP help us to visualize the magnetic field of the bar magnet because the magnetic field magnetizes the filing particles, turning them into tiny magnetic dipoles. A magnetic dipole in a magnetic field experiences both a force and a torque. It is the torque acting on the dipoles that is important here, because the torque lines up the magnetic dipoles in the direction of the magnetic field, showing us the direction by their orientation. The total force acting on the dipole will be the superposition of the force exerted by the gravitational field and the force exerted on the dipole by the magnetic field and will cause the dipole to accelerate in the direction of the force, but it does not affect the orientation of the magnetic dipole, which is what we need to visualize the field lines of earth's magnetic field. If we use the model of the forces acting between 2 magnetic dipoles that DeepThought linked to, then the force acting on the dipole drops off at the rate of r^(-4), so it will be negligible, compared to the gravitational force (just as DT said, provided that the filings are very far from the Earth's surface, which was an assumption in the model). This means that the iron filings will fall towards Earth as a gravitational free-fall in space (assuming they are outside the atmosphere). However, the alignment of the tiny dipoles will always conform to the direction of the magnetic field lines at any moment, showing the structure of Earth's magnetic field. That is why I said that removing gravity from the picture would not make any difference because when an object is placed in a uniform gravitational field, then the force of gravity produces no torque about the center of mass of the object (the gravitational forces affecting a tiny iron filing can be considered uniform for all practical purposes).
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13-10-2011, 07:24 AM
 
RE: Magnets and space...
(12-10-2011 11:19 PM)DeepThought Wrote:  Is there a clear liquid with an equal density to something magnetic like iron?

Maybe if you could get small black plastic pellets containing enough iron to make it have the same density as water. Then put an electromagnet in the water and turn it on. That would partially simulate the conditions in space.

Walter Lewin of MIT has a wonderful experiment doing something like this (with grass seeds in an electrostatic field). I have a link to a video of the lecture somewhere. If can find it, I will post it later.

I found it here at 42:00 time stamp.
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13-10-2011, 09:38 AM
RE: Magnets and space...
(12-10-2011 02:31 PM)Zatamon Wrote:  Yes, you would have a 3D version of the image posted in the OP.

So let me get this straight. Assuming that the Earth in the video is a small magnet in space, would the iron dust arc out as the orange and blue magnetic fields do as shown? Or would they cluster as close as possible to the poles.

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14-10-2011, 06:16 AM
 
RE: Magnets and space...
(13-10-2011 09:38 AM)NotSoVacuous Wrote:  So let me get this straight. Assuming that the Earth in the video is a small magnet in space, would the iron dust arc out as the orange and blue magnetic fields do as shown? Or would they cluster as close as possible to the poles.

Why would they cluster around the poles? They would need a force to accelerate them in that direction. As I explained before, the only motion they have, a fair distance from Earth, outside the atmosphere, is a gravitational freefall toward the center of Earth, due to the gravitational force. The rate of acceleration depends on their distance from the Earth's surface because the grav. force acting on them is inversely proportionate to the square of their distance. If the particles have any electric charge on them, then the Lorentz force effect kicks in too, because charged particles moving through a magnetic field are forced into a curved path perpendicular to both the magnetic field and the velocity vector of the particle.

The initial conditions of the experiment decide the arcs: the density and distribution of the particles in space around the globe, the initial velocity (if any) relative to Earth, the size and shape of the metal particles. It will not look quite like it does on the video because the solar wind completely distorts the shape of Earth's magnetic field, as it is shown on the Wikipedia article I linked to. But the torques exerted on the particles will make them rotate in space to line them up with the magnetic field everywhere. The particles themselves do not arrange into arcs, their distribution remains the same (except for their motion toward the Earth), it is the alignment with the magnetic field that makes it appear as if they formed arcs (see the Walter Lewin experiment in MIT I linked to). The more elongated the particles are (less like spheres), the stronger the visible effect. That is why they used iron filings on the image you linked to with the bar magnet. The grass seeds in the MIT experiment are also good in that regard.

I hope this helped to clarify things. I won't be around for a while because I suddenly found myself very busy with our fall book-selling/book buying season (we have a small online book business) and I want to finish writing that science book I mentioned before, so I can start sending it out to publishers soon. I will peek once in a while but won't have time for much else. Smile
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