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How is energy stored in a field?

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I just found something interesting.

Superconducting Magnetic Energy Storage (SMES) systems store energy in the magnetic field created by the flow of direct current in a superconducting coil which has been cryogenically cooled to a temperature below its superconducting critical temperature.https://en.wikipedia.org/wiki/Superconducting_magnetic_energy_storage#Advantages_over_other_energy_storage_methods

Is this a way to store magnetic field energy without adding a body?

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1 hour ago, Itoero said:

I just found something interesting.

Superconducting Magnetic Energy Storage (SMES) systems store energy in the magnetic field created by the flow of direct current in a superconducting coil which has been cryogenically cooled to a temperature below its superconducting critical temperature.https://en.wikipedia.org/wiki/Superconducting_magnetic_energy_storage#Advantages_over_other_energy_storage_methods

Is this a way to store magnetic field energy without adding a body?

And just how many bodies does it take to supply an electric current?

On 22/09/2018 at 12:14 PM, studiot said:

The field is needed because (classically) it is the medium of interaction between two or more bodies.

 

Quote

Your linked Wiki article

The stored energy can be released back to the network by discharging the coil.

So you need one body to supply rhe current in the first palce, the superconducting coil and another body to take the energy out again.

That's three bodies.

And that's not counting all the charge carriers as bodies.

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And where is the second body when the electron and positron have already disappeared by annihilation, two gamma rays propagated, and one electron detects a gamma ray?

Or if you prefer fields with many photons, send a radio wave to the Moon for reflection there, receive it back on Earth two seconds later. In the meantime, you can wrap the emitting antenna in aluminium foil, destroy it somehow, whatever you like. You don't need the emitting item. The receiving item is sensitive to the field that existed after the emitter was made inoperable.

Similarly, the receiving antenna can be extracted from an aluminium foil just prior to receiving the wave.

If light comes from a remote galaxy, our detector didn't even exist when the light was emitted, and the light source may be a black hole when we detect the light.

In such situations, if you want to keep the laws of energy conservation, momentum conservation, you have to accept that fields exist at times when the items that create or sense them are absent.

There is more. As light passes by a massive object and gets deflected, light also pulls the massive object, even by that little bit. This is necessary if momentum conservation works. It happens possibly at a time where both the emitter and the detector are inexistent, and at a time when photons are not created nor destroyed.

Cumulating all this, one has to admit that propagating fields have an existence independently of the items that create or sense them.

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21 minutes ago, Enthalpy said:

And where is the second body when the electron and positron have already disappeared by annihilation, two gamma rays propagated, and one electron detects a gamma ray?

So the source is destroyed whilst a field is still at least partially intact.

So what?

You would not have the field without the source and youadd another body as a detector.

 

It's been a long time since we learned that source and effect are not instantaneous in a field.

Edited by studiot

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12 hours ago, Enthalpy said:

And where is the second body when the electron and positron have already disappeared by annihilation, two gamma rays propagated, and one electron detects a gamma ray?

Or if you prefer fields with many photons, send a radio wave to the Moon for reflection there, receive it back on Earth two seconds later. In the meantime, you can wrap the emitting antenna in aluminium foil, destroy it somehow, whatever you like. You don't need the emitting item. The receiving item is sensitive to the field that existed after the emitter was made inoperable.

Similarly, the receiving antenna can be extracted from an aluminium foil just prior to receiving the wave.

If light comes from a remote galaxy, our detector didn't even exist when the light was emitted, and the light source may be a black hole when we detect the light.

In such situations, if you want to keep the laws of energy conservation, momentum conservation, you have to accept that fields exist at times when the items that create or sense them are absent.

There is more. As light passes by a massive object and gets deflected, light also pulls the massive object, even by that little bit. This is necessary if momentum conservation works. It happens possibly at a time where both the emitter and the detector are inexistent, and at a time when photons are not created nor destroyed.

Cumulating all this, one has to admit that propagating fields have an existence independently of the items that create or sense them.

Photons do not have a static field, which is what was implied in the OP. Classical, static fields.

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