What exactly is energy?

[swansont]

Conservation of energy is a consequence of time translation symmetry.

 

http://en.wikipedia.org/wiki/Noether's_theorem#Example_1:_Conservation_of_energy

[barfbag]

Conservation of energy is a consequence of time translation symmetry.

 

 

 

Yes. I had just said, "The conservation of energy in time just seems freaky."

[Enthalpy]

Take 1 coulomb of charge. As far as i know there is no formula, similar to the mass one, to replace all that charge with a specific quantity of Joules.

 

An electric, magnetic or electromagnetic field can exist far from any charge, and even after the effect of the charge can be felt locally, for instance if the emitting star has become a black hole.

 

This field stores energy: the one that the camera feels when seeing the light emitted by the then alive star.

 

And even before this light is detected, standard physics tells it contains energy, whether an electron feels it or not. It's convenient to say so because the energy lost by the emitter's radiation is retrieved at the absorber. In these cases, the field stores energy (0.5*eps*E², 0.5*B²/mu) without a charged particle to create it nor a charged particle to feel it.

 

Then you have the gravitational effects of light. Negating that the EM field contains energy woud let one run into trouble.

[studiot]

 

 

Enthalpy

studiot, on 31 Jul 2014 - 4:26 PM, said:

Take 1 coulomb of charge. As far as i know there is no formula, similar to the mass one, to replace all that charge with a specific quantity of Joules.

 

 

 

An electric, magnetic or electromagnetic field can exist far from any charge, and even after the effect of the charge can be felt locally, for instance if the emitting star has become a black hole.

 

This field stores energy: the one that the camera feels when seeing the light emitted by the then alive star.

 

And even before this light is detected, standard physics tells it contains energy, whether an electron feels it or not. It's convenient to say so because the energy lost by the emitter's radiation is retrieved at the absorber. In these cases, the field stores energy (0.5*eps*E², 0.5*B²/mu) without a charged particle to create it nor a charged particle to feel it.

 

Then you have the gravitational effects of light. Negating that the EM field contains energy woud let one run into trouble.

 

You are still avoiding the issue.