# What is a magnetic field exactly?

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According to what I've read about magnetic fields, all they're described as are imaginary lines around the magnet that depict the area where the magnet has effects upon. What exactly is a magnetic field? And how is the attraction caused?

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Okay, since no one's replying to this thinking this as something amateurish, let me rephrase it.

I need someone to explain how the attraction is caused by magnets. What is the 'field'?

We think of magnetic fields as imaginary lines of force (let's say I think of it that way). How is this force caused around the magnet?

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I guess your question is valid for any kind of field.

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I'd like to know the nature of a magnetic field too..the 'stuff' that it's made of but I guess it'll be the same as for light and electric fields..I don't think they know.

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Yeah, I think it's a valid question for any kind of a field. I wonder if anything other than string theory can explain it.

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quantum mechanics explains it quite well with virtual photons although it can be explained classically as well but can be prone to problems.

basically the field(any field) is just the volume and geometry of influence of its source, be that an electro magnet or whatever.

the field is populated by a sea of 'virtual' photons that exchange momentum between the source and the object being influenced.

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quantum mechanics explains it quite well with virtual photons although it can be explained classically as well but can be prone to problems.

basically the field(any field) is just the volume and geometry of influence of its source, be that an electro magnet or whatever.

the field is populated by a sea of 'virtual' photons that exchange momentum between the source and the object being influenced.

I've just read up on virtual photons...i understand that now. Does the magnetic field still exist in the absence of anything to influence or only when something is within range?

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thats a question on the order of 'if a tree falls in the wood and noone is around to hear it does it mae a noise?'.

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Okay I'll give it a whirl. First they are not described as imaginary lines, the lines represent vectors, which shows the direction and magnitude of the magnetic field. To understand the magnetic field you need to understand the electric field.

So lets consider electrostatics, no moving charges. First lets start with one charge, call it q. There is an electric field around this stationary charge, now place another charge, -q, there is an attraction between the two, related by $\mathbf{F} = q\mathbf{E}$. Where q is the charge of one and E is the electric field of the other.

So now we have a relationship for attraction between stationary charges. Now lets speed things up hahah. Let's consider a moving charge, you now have a charge q moving at speed v, this moving charge now has a magnetic field (and still a electric field, but not as simple as when it is stationary). Now place a stationary charge near by this moving charge. The force on the stationary particle is $\mathbf{F} = q\mathbf{v}\times\mathbf{B}$.

Now take this to larger scales, from single charges, to multiple charges (electrons) say in a wire and you get a relationship of current, force and the magnetic field. Now move this to materials, like a metal, that has electrons around a nucleus, causing tiny loops of currents and you get a total magnetic field in that material. Its more complicated to calculate the magnetic field of a material, but its the same concept.

See if that helps.

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According to what I've read about magnetic fields, all they're described as are imaginary lines around the magnet that depict the area where the magnet has effects upon. What exactly is a magnetic field? And how is the attraction caused?

Merged post follows:

Consecutive posts merged

Okay, since no one's replying to this thinking this as something amateurish, let me rephrase it.

I need someone to explain how the attraction is caused by magnets. What is the 'field'?

We think of magnetic fields as imaginary lines of force (let's say I think of it that way). How is this force caused around the magnet?

In order to explain it to you, I have to know what you understand, what does not cause questions to you.

A magnetic field is a quantitative notion. It stands in the charge motion equations and determines the force on a moving charge. It also stands in the magnetic dipole motion equations and determines the external magnetic force.

Magnetic fields are created with magnets and currents. You may safely understand it as an interaction of moving but rather neurtalized charges so the Coulomb interaction is not the main part of the charge interaction.

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Let us start with a stationary charge. The charge field will be 3-D symmetrical about the charge.

A magnetic field will arise when we give a single charge motion or velocity. One thing one might note, the magnetic field turns a mono-charge with spherical symmetry into a binary divided into north and south pole, which has cylindrical symmetry.

One can then simulate the appearance of the magnetic field with negative and positive charges, both stationary.

From this, I would conclude that a magnetic field is a way, using velocity, to split a charge into two entities. This creates a paradox since charge is considered a single entity. This suggests that charge has a north and south pole which can be made manifest via motion.

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All of you guys are perfectly right. My question however, was, in instance of the explanation of the charges, how the charges interact with each other when there's no physical contact between them.

I did do a reading on virtual photons. The concept seems to be clearer. But, considering that they're 'virtual', can we rely on that explanation?

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All of you guys are perfectly right. My question however, was, in instance of the explanation of the charges, how the charges interact with each other when there's no physical contact between them.

I always say that charges are "long-handed". One can consider them as overlapping. Point-likeness of a charge means a simple dependence of the force from distance. But the force is a long-range one. Charges are quite different from neutral atoms that need close contact to interact. Charges are long-handed and sticky.

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I always say that charges are "long-handed". One can consider them as overlapping. Point-likeness of a charge means a simple dependence of the force from distance. But the force is a long-range one. Charges are quite different from neutral atoms that need close contact to interact. Charges are long-handed and sticky.

You've explained that in context with charges. Is it the same with a magnetic field? I read something on wikipedia that the extent of charges' attraction, as an expample, is infinite because virtual photons exist throughout.

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• 1 year later...

"According to what I've read about magnetic fields, all they're described as are imaginary lines around the magnet that depict the area where the magnet has effects upon. What exactly is a magnetic field? And how is the attraction caused?"

I also have some questions about magnetic and electric fields. Answers that invoke Maxwell's vector field equations are only telling us how charges and fields behave, not what they are.

The idea of virtual photons clearly comes from the field of quantum mechanical and particle physics. I'm not qualified to judge the validity of the virtual photon model. Like many aspects of quantum physics, the mathematics may 'work' in the sense that it agrees with experiments but it doesn't give any insights into what the thing 'is'. One of the things I appreciate about the general relativity is that at least there is some indication about what a gravitational field is; namely a distortion of space. You may say that distorted space is still abstract but it is less abstract than quantum mechanics which doesn't even attempt to give insight into what a field is. I look at a magnet levitating above another magnet with a gap of a few centimeters and wonder what the heck is going on in the gap.

I have two questions:

1. Could the idea of distorted space be applied to other force fields? Can a magnetic field, for example, be modeled as a spatial distortion?

2. A pair of force fields are required to create a propagating photon. Might other force carriers (such as the gluon, W and Z particles and graviton) also be formed by multiple interacting fields of types as yet unknown? How would you go about discovering such fields if they existed?

Thanks

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Answers that invoke Maxwell's vector field equations are only telling us how charges and fields behave, not what they are.

That's true in all of physics, if you get down to the right level of discussion. It tells you how things behave, not what they are.

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"According to what I've read about magnetic fields, all they're described as are imaginary lines around the magnet that depict the area where the magnet has effects upon. What exactly is a magnetic field? And how is the attraction caused?"

I also have some questions about magnetic and electric fields. Answers that invoke Maxwell's vector field equations are only telling us how charges and fields behave, not what they are.

The idea of virtual photons clearly comes from the field of quantum mechanical and particle physics. I'm not qualified to judge the validity of the virtual photon model. Like many aspects of quantum physics, the mathematics may 'work' in the sense that it agrees with experiments but it doesn't give any insights into what the thing 'is'. One of the things I appreciate about the general relativity is that at least there is some indication about what a gravitational field is; namely a distortion of space. You may say that distorted space is still abstract but it is less abstract than quantum mechanics which doesn't even attempt to give insight into what a field is. I look at a magnet levitating above another magnet with a gap of a few centimeters and wonder what the heck is going on in the gap.

I have two questions:

1. Could the idea of distorted space be applied to other force fields? Can a magnetic field, for example, be modeled as a spatial distortion?

2. A pair of force fields are required to create a propagating photon. Might other force carriers (such as the gluon, W and Z particles and graviton) also be formed by multiple interacting fields of types as yet unknown? How would you go about discovering such fields if they existed?

Thanks

Unfortunately the notion of a "field" is a mathematical construct that has been shown to make physical predictions that are consistent with experimental results. A field is not "made" of anything.

It is not true that a pair of force fields are needed to create a photon (there is no such thing as a non-propagating photon). A photon in quantum theory is a disturbance in the electromagnetic field. Viewed classically a large number of photons comprise a classical electromagnetic field. That classical field can be resolved into two components -- the electric component and the magnetic component -- but the resolution is dependent on the reference frame of the observer. The electromagnetic field itself, however, is a single invariant entity.

Gravity is not explained by "distorted space". It is the result of curvature (you can call that distortion) of spacetime which is a lot more than space.

Modern physical theories are expressed in terms of mathematics. There is no avoiding that fact. Those theories have been successful in extending into realms in which everyday language simply fails. Thus there are no answers to many questions posed in that everyday language, such as "What are fields made of ?".

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Unfortunately the notion of a "field" is a mathematical construct that has been shown to make physical predictions that are consistent with experimental results. A field is not "made" of anything.

It is not true that a pair of force fields are needed to create a photon (there is no such thing as a non-propagating photon). A photon in quantum theory is a disturbance in the electromagnetic field. Viewed classically a large number of photons comprise a classical electromagnetic field. That classical field can be resolved into two components -- the electric component and the magnetic component -- but the resolution is dependent on the reference frame of the observer. The electromagnetic field itself, however, is a single invariant entity.

Gravity is not explained by "distorted space". It is the result of curvature (you can call that distortion) of space time which is a lot more than space.

Modern physical theories are expressed in terms of mathematics. There is no avoiding that fact. Those theories have been successful in extending into realms in which everyday language simply fails. Thus there are no answers to many questions posed in that everyday language, such as "What are fields made of ?".

Thanks Organism

You are quite correct about non-propagating photons. And I was wrong to omit the 'time' from space time. What I was getting at is that a photon is the result of the interaction of magnetic and electric fields. My question about force fields still stands. However, I am particularly interested in the first question: Is it both valid and useful to model a magnetic or electric field as causing space time curvature for charged particles? I understand that such a curvature would not effect matter without charge.

Thanks

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• 2 weeks later...

Dr Rocket you say "a field is not made of anything".I would disagree and say it is made of energy,in the same way that a wave of energy traverses the surface of water,by the rising and falling of the water against the force of gravity,water does not traverse the surface,only energy is transferred from one place to another.

In a magnetic field the energy is transferred by the creation and annihilation of matter/anti-matter virtual particles,the virtual particles would not move,but just act as a medium for the transfer of energy.

Edited by derek w
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Dr Rocket you say "a field is not made of anything".I would disagree and say it is made of energy,in the same way that a wave of energy traverses the surface of water,by the rising and falling of the water against the force of gravity,water does not traverse the surface,only energy is transferred from one place to another.

In a magnetic field the energy is transferred by the creation and annihilation of matter/anti-matter virtual particles,the virtual particles would not move,but just act as a medium for the transfer of energy.

Energy isn't a substance, so saying something is "made of energy" isn't a useful answer. Energy is a property. A field is a mathematical construct, i.e. an abstraction, to help us solve problems. So is energy, for that matter.

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You say i can't think of energy as a substance.I do not agree with you 100%.I can think of the vacuum of space as negative energy,a very dilute expanse of expanding (negative)anti-matter.Any fluctuations that create matter/anti-matter virtual particles,being effected by the negative vacuum,matter(positive) to the centre/anti-matter(negative) to the circumference.

Atoms(of matter) form with positive energy at centre negative energy at circumference(because the vacuum is negative).

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You say i can't think of energy as a substance.I do not agree with you 100%.I can think of the vacuum of space as negative energy,a very dilute expanse of expanding (negative)anti-matter.Any fluctuations that create matter/anti-matter virtual particles,being effected by the negative vacuum,matter(positive) to the centre/anti-matter(negative) to the circumference.

Atoms(of matter) form with positive energy at centre negative energy at circumference(because the vacuum is negative).

There's a difference between "I can think of X as Y" and "I can build a useful model by thinking of X as Y". I can think of gravity as space pressure holding me down somehow, but somewhere along the line that model is going to fail in a catastrophic way, but in a way that Newtonian gravity is not.

In the models of physics that work over a wide spectrum of situations, energy is not a substance.

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I was thinking of matter/anti-matter as being distortions of space not pressure.

infinite negative as opposed to finite positive and infinite positive as opposed to finite negative.

The universe is going towards an infinite negative 3 dimensional space and finite positive,that's a distortion.

zero energy = zero force

Edited by derek w
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I was thinking of matter/anti-matter as being distortions of space not pressure.

infinite negative as opposed to finite positive and infinite positive as opposed to finite negative.

The universe is going towards an infinite negative 3 dimensional space and finite positive,that's a distortion.

zero energy = zero force

You might want to look into quantum field theory

It describes all matter and energy as oscillations of various fields, which sort of allows for relativity to takes place with out all of this mucking about with things having to be solid and act like spheres or bundles.

Matter and anti-matter can be described as two different types of oscillations within the same type of field, so that when they are added, the net oscillation equals 0, as can be demonstrated by finding the sum of two sine waves of opposite signs.

Edited by questionposter
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annihilation of matter/anti-matter = an output of energy

creation of matter/anti-matter = an input of energy

to conserve energy annihilation in one place = creation at same rate in another place:-

therefore energy can be transferred from one place to another as a wave.

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You say i can't think of energy as a substance.I do not agree with you 100%.I can think of the vacuum of space as negative energy,a very dilute expanse of expanding (negative)anti-matter.Any fluctuations that create matter/anti-matter virtual particles,being effected by the negative vacuum,matter(positive) to the centre/anti-matter(negative) to the circumference.

Atoms(of matter) form with positive energy at centre negative energy at circumference(because the vacuum is negative).

This is nonsense, word salad. You need to learn some physics.

Edited by DrRocket

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