The magnetic field as dark matter

[kmarinas86]

The magnetic field as "dark matter"

Is it possible that the magnetic field has energy?

If so, how much would that energy be?

Would the energy have an impression on the space-time continuum?

Since they extend infinitely, could the magnetic field of stars have more energy than the stars themselves?

Could magnetic fields be the "dark matter" we are looking for?

 

[Contrapositive]

Magnetic fields, by themselves, cannot do work. So they can't have energy, like say an object orbiting the Earth would have gravitation potential energy.

Would the energy have an impression on the space-time continuum?

Do you mean gravity? Magnetism does not produce gravity.

 

[Jonathan Scott]

Magnetic fields, by themselves, cannot do work. So they can't have energy, like say an object orbiting the Earth would have gravitation potential energy.

Do you mean gravity? Magnetism does not produce gravity.

Magnetic fields do contain energy, which is assumed to have a density proportional to the square of the field strength. They don't do overall work on electric charges, but can change the momentum of a moving charge and can change the energy of a magnetic dipole.

The gravitational effect of the energy of a static magnetic field would be incredibly tiny; I think it would generally be completely negligible compared with the gravitational effect of the masses of the charged particles necessary to give rise to the field.

 

[Contrapositive]

I stand corrected.

 

[Himanshu]

Is it possible that the magnetic field has energy?

Magnetic fields do have energy given by \mu_{B} (the energy density)=\frac{1}{2\mu_{0}}B^{2}.

Magnetic fields, by themselves, cannot do work. So they can't have energy, like say an object orbiting the Earth would have gravitation potential energy.

I would say 'mass' by itself cannot do work but itself has a substantial amount of energy.

Would the energy have an impression on the space-time continuum?

Space-time continnum has energy which is referred to as http://en.wikipedia.org/wiki/Stress-energy_tensor"

 

[kmarinas86]

Magnetic fields do have energy given by \mu_{B} (the energy density)=\frac{1}{2\mu_{0}}B^{2}.
I would say 'mass' by itself cannot do work but itself has a substantial amount of energy.
Space-time continnum has energy which is referred to as http://en.wikipedia.org/wiki/Stress-energy_tensor"

Energy of a 1 nanotesla magnetic field within 1 cubic light year:

http://www.google.com/search?hl=en&...tic+constant+*+1+cubic+light+year&btnG=Search

1/2 (0.000000001 tesla)^2 / magnetic constant * 1 cubic light year

3.3690412*10^35 joules !

Through E=mc^2, this translates into:

3.74856388*10^18 kilograms

And that's just for one cubic light year and for assuming the whole light year is 1 nanotesla, which it probably is not. Does someone know how to model this in a more complex system?

 

[Allday]

The relevant comparison would be energy density, not total energy ; )

 

[kmarinas86]

The relevant comparison would be energy density, not total energy ; )

Energy density of 1 joule per cubic nanometer would be a more signficant extent in a volume of say, 1 billion cubic light years, instead of 1 cubic nanometer.

 

[Allday]

Energy density of 1 joule per cubic nanometer would be a more signficant extent in a volume of say, 1 billion cubic light years, instead of 1 cubic nanometer.

this is true, however magnetic fields are created by currents and so need to be in the vicinity of matter. I think you are suggesting a comparison of the gravitational effect of the matter to the gravitational effect of the mass equivalent of the energy in the magnetic field created by the matter. This will be very small.

If you are considering the effect the magnetic field would have on nearby charged particles then that is a different story, but not what you were asking I think.