# The Naked Scientists Forum

### Author Topic: Does Gravity affect Magnetic Fields?  (Read 3611 times)

#### Space Flow

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##### Does Gravity affect Magnetic Fields?
« on: 15/12/2015 04:44:49 »
I mean if you rotate a magnet in a Gravitational Well, would the shape of the field lines change?
Does Gravity have any effect on these Magnetic Field lines?
And if it does, where can I find information about it?
« Last Edit: 15/12/2015 08:21:45 by chris »

#### Space Flow

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #1 on: 23/12/2015 10:20:46 »
Anyone?????

#### puppypower

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #2 on: 23/12/2015 14:06:29 »
If you look at gravity, in term of General Relativity, gravity causes space-time to bend and contract. Relative to energy, the contraction of space-time causes energy to blue shift. What this means is all the energy quanta gain potential; blue shift. Since some photons are connected to the EM force, when these become blue shifted by gravity; gain energy, and then reflect back into the magnetic field they impact the field differently; in a hotter way.

Gravity is integrated to all the forces, by blue shifting the energy coming from all the other forces via space-time. This can alter the forces via the energy change. As an example, say an electron in a hydrogen atom, drops one energy level, and to give off a photon. If gravity was to blue shift this photon, and that hotter photon was to now hit another hydrogen atom, since it is hotter, it will cause the hydrogen atom to go to an even higher energy level. This means the EM force potential is made higher by gravity. This compounding of energy; blue shifting down the space-time well, by gravity, is why the core of the star is the hottest place. The blue shifting down the well keeps raising the energy bar, changing the forces, until the nuke forces see energy.

As we leave the core of the star and climb out of the space-time well, the energy is red shifted. This makes the energy weaker and weaker, as we climb the well, so forces changes from nuke back to EM, which then get weaker and weaker as we reach the surface and beyond.

The earth's magnetic field starts in the core and reaches the beyond the surface into the atmosphere. It then curls back and returns to the core. It is red shifting away from the core and then blue shifting back to the core. It is not clear, but since the magnetic field interacts with the solar wind, which alters its potential in space, the blue shift back to the core of the earth, is now different than when it left the core.
« Last Edit: 23/12/2015 14:14:10 by puppypower »

#### Space Flow

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #3 on: 23/12/2015 21:16:35 »
Thanks for the reply Puppypower. By the way my granddaughter loves your handle.
Although I understand what you have written above, My question is a bit more subtle than that.
I am not interested in how Gravity effects incoming and outgoing EMR.
To maybe make my line of inquiry a bit clearer, consider a permanent magnet. It has around it well defined static magnetic field lines. These field lines can be mapped as to their exact shape and distance from said PM in all directions around it.

What I want to know is if this PM is rotated in a Gravity well, will said Gravity in any way distort the map of those field lines?

For the sake of this thought experiment lets have this permanent magnet in a total vacuum so no particles of any description can be trapped within any part of those field lines. So Gravity has no actual matter to act on, and no traveling EM apart from the static field lines. And no other influences either.

I have been unable so far to find any theoretical or experimental information that addresses this. (Although I think someone somewhere must have looked into it at some stage). All I have found is various people using reasoning, along the lines of your answer and others that skirt the question, but don't address it directly. I find my inability to find this information very frustrating. I expected clear formulae.
If such information exists I would love to see it.

#### evan_au

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #4 on: 23/12/2015 23:42:15 »
Quote from: puppypower
say an electron in a hydrogen atom, drops one energy level, and to give off a photon. If gravity was to blue shift this photon, and that hotter photon was to now hit another hydrogen atom, since it is hotter, it will cause the hydrogen atom to go to an even higher energy level.
Yes, that can happen. But it requires a significant coincidence.

Hydrogen has particular energy levels; when an electron drops down, the energy of the emitted photon is the difference between the electron energy levels.
An electron can also absorb a photon, and jump to a higher energy level - but only certain energy levels are permitted.
So the blue-shifted photon, falling through the gravitational field must gain exactly the right energy to match a transition on the hydrogen atom. If it doesn't match, the hydrogen atom won't absorb it, and the photon will pass right by.

#### evan_au

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #5 on: 24/12/2015 00:23:35 »
Quote from: Space Flow
Does Gravity affect Magnetic Fields? ...I have been unable so far to find any theoretical or experimental information that addresses this.

You won't find a quantum-mechanical explanation of this interaction. I heard a description that went like this (as an introduction to why string theory is needed):
• Quantum theory generates infinities in a few places. But there are well-defined ways to subtract infinity from these infinities, and get results that make very accurate predictions.
• All applications of quantum theory are assumed to take place in zero gravitational field.
• As soon as you try to include gravity, quantum theory generates an infinite number of infinities that don't go away.

So, ignoring quantum theory (because it doesn't generate useful answers) and string theory (because it is too immature), we must fall back on older theories like Maxwell's equations and Einsteins' Relativity.
• In theory, the static magnetic field from a magnet extends to infinity (but gets rapidly weaker with distance, like distance4)
• From geometry, if you rotate the magnet, the farther parts of the static field will be moving faster than nearer parts.
• Special Relativity says that the magnetic field cannot move faster than the speed of light, so the shape of distant parts of it will be distorted.
• Maxwell says that if you accelerate a magnetic field (and rotating it is a form of acceleration), you will produce stable transverse electromagnetic waves that separate from the static field, and continue on to infinity (getting weaker with distance, like distance2). Today we identify these waves with photons.
• General relativity includes gravitation, and says that the path of photons is bent by the curvature of space, and experience time dilation in gravitational wells (which is equivalent to the blue/red shift described by puppypower).
• These gravitational effects are extremely subtle near the Earth, and still hard to spot in the Sun's much deeper gravitational well.
• To see a significant impact on a short-range experiment like a spinning magnetic field, you would need to get very close to the event horizon of a black hole.
• In this environment, the shape of the near-field magnetic field will be distorted by time dilation.
• Some of the emitted photons will go into orbit around the black hole, and some will enter the black hole, never to return.
• But lets face it - a lot of our theories become rather uncertain extrapolations near the event horizon of a black hole!

#### Space Flow

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #6 on: 24/12/2015 01:07:14 »
Evan, thank you for giving this consideration. Unfortunately I don't think I have made my question clear enough yet.
I am not asking about the behavior of a rotating magnetic field.
When I mentioned rotation it was only for the purpose of comparing different static points of the magnetic field lines within a gravitational influence. So I'll try to make the thought experiment a bit more clear.
We have a permanent magnet in the influence of a gravity well, not magnetically (or electromagnetically) interacting with anything.
(As can be shown by say iron filings on a piece of paper, it has non moving magnetic field lines around it).

If we map those static field lines when the magnet has its north pole pointing up, and then compare them to when the same magnet is at 90 degrees, will we see any distortion due to gravity?

Remember there are no iron filings, air molecules, ions of any description or anything with mass occupying the position of those field lines. Nothing material for gravity to act on. Just the magnetic field lines of a permanent magnet.

Can gravity in any way distort those field lines?

When horizontal in relation to gravity, will the field lines over the magnet end up closer to the magnet while the ones underneath end up further away?
I hope I have asked this clearly enough this time..
If not I will probably have to resort to pictures...
« Last Edit: 20/01/2016 07:57:27 by Space Flow »

#### alysdexia

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #7 on: 17/01/2016 14:56:19 »
Sure, why not?

The B field should compress towards the G source.  That is, the line element contracts proportionally to negative potential.

#### Space Flow

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #8 on: 17/01/2016 21:29:21 »
Sure, why not?

The B field should compress towards the G source.  That is, the line element contracts proportionally to negative potential.
Thank you for that answer. That was exactly what I presumed would be the case.
However trying to find anything to confirm this assumption has been a very fruitless and frustrating search. Even to the point that no one seems to know if the event horizon of a Black Hole can stop these fields manifesting. I didn't expect this lack of knowledge or information (whichever applies).

#### Atomic-S

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #9 on: 19/01/2016 08:24:30 »
Quote
The B field should compress towards the G source.  That is, the line element contracts proportionally to negative potential.
I don't know if this is correct or not; however the key to solving this problem is to start with Einstein's principle of equivalence, which says that the effects of gravity are identical to those of an accelerating reference frame. So the first thing to do is to observe the magnet in such a way that gravity is not operating, and then transform the results into a frame in which it is operating. The way to do that is for the observer to be free-falling during the observation.  As the observer falls, to him there is no gravity, and all directions are dynamically equivalent.  But to him, the magnet is accelerating in the opposite direction, so that the problem transforms into the problem of finding the field of an accelerating magnet. Offhand, I am not sure just what the field of an accelerating magnet looks like, but know that it must change with time because the nature of an electromagnetic field varies as the speed between source and observer varies. In particular, the field is no longer simply magnetic. It will also have an electric component.  Another complication is that it may be necessary to take into account the Lorentz contraction and other features of relativistic transformations in order to calculate the field with sufficient accuracy for this problem.  That will result in, among other things, dimensional distortion of both the magnet and the field. There is also the issue of how Einsteinian speed relationships may alter the way the effective currects within the magnet appear to exist, and they may no longer be correctly modeled as simple current loops as we generally understand that term.  Having done this, we are not finished, because the result has to be put back into the original reference frame. So, in view of all this, the answer to me is by no means clear, but I hope the foregoing gives you an indication of what principles they are that you must use.

#### saspinski

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #10 on: 20/01/2016 00:21:27 »
A rod of magnetic material put carefully on the ground so that it is vertical, is compressed by its own weigth. By Hooke's law its length decresases a little bit. As it affects the atomic spacing, I suppose it modifies the magnetic field.
On the other hand, if it is vertical, but hanging from a hook (no pun) in the roof, the same Hooke's law tell us that it is now a little bit longer. So, I think gravity affects the field lines, but it depends not only on the position (vertical or horizontal), but also on the boundary conditions (no displacement at the bottom or at the top).

#### Space Flow

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #11 on: 20/01/2016 01:13:37 »
A rod of magnetic material put carefully on the ground so that it is vertical, is compressed by its own weigth. By Hooke's law its length decresases a little bit. As it affects the atomic spacing, I suppose it modifies the magnetic field.
On the other hand, if it is vertical, but hanging from a hook (no pun) in the roof, the same Hooke's law tell us that it is now a little bit longer. So, I think gravity affects the field lines, but it depends not only on the position (vertical or horizontal), but also on the boundary conditions (no displacement at the bottom or at the top).
OK thinking along good lines here.
What I am really after is not so much the effect of Gravity in modyfying the physical dimensions of our test permanent magnet, therefore causing a modification in the field lines, although you are right that there would be such an effect at some level.
What I would really like to know is if Gravity can have a direct effect on the shape of the field lines themselves, all other considerations accounted for and deducted.

If we accurately mapped and precisely measured the field lines represented in the above image and then turned this same magnet to a horizontal position,

Would those field lines be at all directly effected by Gravity?
Would Gravity in any way directly modify the shape of those lines, apart from any structural changes it may impose on the magnet?
Another way to put it is can enough Gravity stop a permanent magnet establishing magnetic field lines in any direction?

#### alysdexia

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #12 on: 20/01/2016 03:13:03 »
Quote
The B field should compress towards the G source.  That is, the line element contracts proportionally to negative potential.
I don't know if this is correct or not; however the key to solving this problem is to start with Einstein's principle of equivalence, which says that the effects of gravity are identical to those of an accelerating reference frame.

He said a uniform gravitational field couldn't be distinguished from acceleration.  But there is no such thing.

Quote
So the first thing to do is to observe the magnet in such a way that gravity is not operating, and then transform the results into a frame in which it is operating. The way to do that is for the observer to be free-falling during the observation.  As the observer falls, to him there is no gravity, and all directions are dynamically equivalent.  But to him, the magnet is accelerating in the opposite direction, so that the problem transforms into the problem of finding the field of an accelerating magnet.

A body in free fall either varies in r, upon which its g varies, or varies in θ, upon which its a varies.

Quote
Offhand, I am not sure just what the field of an accelerating magnet looks like, but know that it must change with time because the nature of an electromagnetic field varies as the speed between source and observer varies.

This all is rather irrelevant; the field undergoes jerk, the third derivative of motion.  dr shrinks.

Another way to put it is can enough Gravity stop a permanent magnet establishing magnetic field lines in any direction?

Gravity cannot stop any fields.  If you believe in the Schwarzschild metric like other deluded mathemagicians, then you believe that gravity instead stops heat transfer of those fields (conduction, convection, radiation) when the line element equals celerity's displacement, without accounting for the Lorentzian hıperbolic contraction.

#### wolfekeeper

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #13 on: 26/01/2016 02:11:28 »
Would Gravity in any way directly modify the shape of those lines, apart from any structural changes it may impose on the magnet?
Another way to put it is can enough Gravity stop a permanent magnet establishing magnetic field lines in any direction?
No, it's a well established principle of physics that gravity cannot do that. If it did, then it would violate Einstein's equivalence principle.

In the reference frame of the magnet, the field lines are unaffected by gravity (at least over a small region of space, over large areas, variations in gravity can readily cause distortions of electromagnetic fields.)

#### Space Flow

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #14 on: 26/01/2016 03:07:35 »
No, it's a well established principle of physics that gravity cannot do that. If it did, then it would violate Einstein's equivalence principle.
My thinking has always been the same. But I can find no experimental or observational studies or published papers saying so.
So having said that.
If we had a magnetar that gained a bit more mass from a companion and turned into a black hole, to satisfy the above statement, would those magnetic field lines still be there outside the event horizon?

#### puppypower

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #15 on: 28/01/2016 12:39:10 »
Say the magnet was aligned vertically in a space-time well, with the north pole in a reference that has space-time expanded and the south pole is in a reference that is more contracted. The impact will be a north pole field will red shift and a south pole field will blue shift.

Say we extrapolate this to the limit, where the north pole is red shifted to a longer wavelength that we can measure. It will look like a high energy monopole. In this case a south pole monopole.

#### Space Flow

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #16 on: 29/01/2016 00:38:23 »
Say the magnet was aligned vertically in a space-time well, with the north pole in a reference that has space-time expanded and the south pole is in a reference that is more contracted. The impact will be a north pole field will red shift and a south pole field will blue shift.

Say we extrapolate this to the limit, where the north pole is red shifted to a longer wavelength that we can measure. It will look like a high energy monopole. In this case a south pole monopole.
How do you measure red or blue shift on static lines of force?
We are only considering the magnetic force lines not anything traveling within or carried by those lines of force.
As far as I know they are not associated with anything that can be defined as frequency, as the magnet that is associated with them is essentially equivalent to a DC current magnetic field.
No frequency to shift.

#### JeepKeen

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #17 on: 05/03/2016 12:14:19 »
My common sense tells me yes, but still I'm unsure.

#### Space Flow

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #18 on: 06/03/2016 00:12:54 »
My common sense tells me yes, but still I'm unsure.
It would appear that you, me, and everyone else on this planet is in the same boat.
We all analyze this question with common sense, but there does not appear to be any empirical evidence pointing one way or the other.
To the point that no one is actually sure whether the magnetic fields around SMBH that are said to drive Quasar Jets, are generated totally within the accretion disks, or if they are powered by the twisted magnetic field lines originating behind the Event Horizon of a spinning BH.
I don't know how myself, but surely there is some sort of experiment that can be done to resolve this question?

#### chiralSPO

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #19 on: 06/03/2016 04:42:18 »
please note: I am no expert, so take these thoughts with a grain of salt...

1) Forgetting the magnet itself, and just thinking of the magnetic field: the field has an apparent mass, dictated by the energy stored within the field. Therefore, a magnetic field would fall into a gravitational well. I don't think that that the orientation of that magnetic field would have any effect on the attraction it would have to the gravitational well. Although, if there were a very strong gradient in the gravitational field, it is possible that the tidal shear on the magnet would depend on the relative orientation of the magnetic field and gravitational gradient...

2) Gravity distorts spacetime and therefore must affect anything that propagates through space. In the same way that light is diverted by gravitational wells, presumably the field lines would be similarly affected. Does this mean that gravity affects the magnetic field? I am not so sure that, in that it doesn't appear to change anything intrinsic to the magnetic field, it just changes the geometry of the spacetime the magnetic field is in. So again, I don't think that there would be any significant difference between magnetic fields in differing uniform gravitational fields, but comparing magnetic fields in an inhomogeneous (heterogeneous? nonuniform?) gravitational field should reveal differences depending on the orientation of the magnetic field, and comparing a magnetic field in a uniform gravitational field to an identical magnetic field in an inhomogeneous (heterogeneous? nonuniform?) gravitational field...

#### Colin2B

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##### Re: Does Gravity affect Magnetic Fields?
« Reply #20 on: 09/03/2016 08:56:26 »
the field has an apparent mass, dictated by the energy stored within the field. Therefore, a magnetic field would fall into a gravitational well. .........Gravity distorts spacetime and therefore must affect anything that propagates through space. In the same way that light is diverted by gravitational wells, presumably the field lines would be similarly affected.
I'm no expert either, but as the electromagnetic stress tensor contributes to the energy stress tensor then it must have an effect. However, I did see a calc that suggested that the entire earth's mag field results in an equivalent mass of about 100kg, so we are unlikely to see an everyday effect.

#### The Naked Scientists Forum

##### Re: Does Gravity affect Magnetic Fields?
« Reply #20 on: 09/03/2016 08:56:26 »