Field Energy - my own curiosity

Throughout this week not only I have I observed the teachers going through different thought processes about energy, but I've also been watching myself having very similar ideas as well. On Wednesday at lunch I was pretty much ready to give up the idea of forms of energy and just say there is one kind of "energy" (whatever that may mean) and it acts in different ways and is stored in different ways (the same thought that Heather came to, which I blogged about here). More or less, I was ready to just say there is potential energy and kinetic energy.

At lunch Rachel asked about light energy and where that would fit. She mentioned the idea of field energy as a third kind of energy. I was intrigued but also had no idea what field energy could possibly mean. In fact, over the course of the day and evening I decided that field energy sounded less and less like a good idea. Kinetic energy and potential energy seem very intertwined: energy is either active and going around doing stuff or it is perched and ready to strike at any moment. Where could there possibly be a third option between those two? Clearly, I needed to find out more about field energy.

I remembered reading about the energy stored in the theoretical inflaton field which would (theoretically) trigger the inflation that happened right after the big bang. So I went back to the book (Brian Greene's The Hidden Reality) and looked up field in the index. The magnetic field, for instance, is defined informally as "a 'mist' or 'essence' that fills space and does the magnet's bidding." Well that didn't seem to be a very revealing definition...

But I kept reading and came to the part about fields carrying energy. Could this be what is meant by "field energy" that Rachel talked about?

"Fields carry energy. Qualitatively, we know this because fields accomplish tasks that require energy, such as causing objects to move. Quantitatively, the equations of quantum field theory show us how, given the numerical value of a field at a particular location, to calculate the amount of energy it contains."

So if fields can carry energy then fields (whatever those are!) seem to just be some kind of medium in which energy can either be stored (potential) or active (kinetic). In that case it seems like it's really not a third kind of energy in the same way that kinetic and potential are. In fact MAYBE field are really the only medium for energy. Greene also talks about all the other kinds of fields that exist (strong, weak, electron, quark, neutrino, etc.) Maybe that's what a field IS: the medium for energy. And maybe that's what energy IS: the thing that lives in fields. At least that's the point I've come to after preliminary research. I still need to understand fields in a more involved way than I can with the informal definition above.